Migration Guide for PMD 7

Before you update

Before updating to PMD 7, you should first update to the latest PMD 6 version 6.55.0 and try to fix all deprecation warnings.

There are a couple of deprecated things in PMD 6, you might encounter:

• Properties: In order to define property descriptors, you should use PropertyFactory now. This factory can create properties of any type. E.g. instead of StringProperty.named(...) use PropertyFactory.stringProperty(...).

  Also note, that uiOrder is gone. You can just remove it.

  See also Defining rule properties

• When reporting a violation, you might see a deprecation of the addViolation methods. These methods have been moved to RuleContext. E.g. instead of addViolation(data, node, ...) use asCtx(data).addViolation(node, ...).

• When you are calling PMD from CLI, you need to stop using deprecated CLI params, e.g.
  • -no-cache ➡️ --no-cache
  • -failOnViolation ➡️ --fail-on-violation
  • -reportfile ➡️ --report-file
  • -language ➡️ --use-version
• If you have written custom XPath rule, look out for warnings about deprecated XPath attributes. These warnings might look like

  WARNING: Use of deprecated attribute 'VariableId/@Image' by XPath rule 'VariableNaming' (in ruleset 'VariableNamingRule'), please use @Name instead
  

  and often already suggest an alternative.

• If you still reference rulesets or rules the old way which has been deprecated since 6.46.0:
  • <lang-name>-<ruleset-name>, eg java-basic, which resolves to rulesets/java/basic.xml
  • the internal release number, eg 600, which resolves to rulesets/releases/600.xml

  Such usages produce deprecation warnings that should be easy to spot, e.g.

  Ruleset reference 'java-basic' uses a deprecated form, use 'rulesets/java/basic.xml' instead
  

  Use the explicit forms of these references to be compatible with PMD 7.

  Note: Since PMD 6, all rules are sorted into categories (such as “Best Practices”, “Design”, “Error Prone”) and the old rulesets like basic.xml have been deprecated and have been removed with PMD 7. It is about time to create a custom ruleset.

Approaching 7.0.0

After that, migrate to the release candidates, and fix any problems you encounter. Start with 7.0.0-rc1 via 7.0.0-rc2, 7.0.0-rc3 and 7.0.0-rc4 until you finally use 7.0.0.

You might encounter additionally the following types of problems:

• If you use any programmatic API of PMD, first avoid any usage of deprecated or internal classes/methods. These are marked with one of these annotations: @Deprecated, @DeprecatedUtil700, @InternalApi.
  • Some of these classes are available until 7.0.0-rc4 but are finally removed with 7.0.0.
  • See API changes for details.
• Some rules have been removed, because they have been deprecated. See Removed Rules.
• Some rule properties have been removed or changed. See Changed Rules.
• The filenames of the assets of a release (the “binary distribution zip file”) have changed, see Release downloads.
• Some CLI options have been removed, because they have been deprecated. See CLI Changes for details.
• If you call CPD programmatically, the API has changed, see New Programmatic API for CPD.
• If you use Visualforce, then you need to change “vf” to “visualforce”, e.g. category/vf/security.xml ➡️ category/visualforce/security.xml
• If you use Velocity, then you need to change “vm” to “velocity”, e.g. category/vm/... ➡️ category/velocity/...

The following topics describe well known migration challenges in more detail.

Use cases

I’m using only built-in rules

When you are using only built-in rules, then you should check, whether you use any deprecated rule. With PMD 7 many deprecated rules are finally removed. You can see a complete list of the removed rules in the release notes for PMD 7. The release notes also mention the replacement rule, that should be used instead. For some rules, there is no replacement.

Then many rules have been changed or improved. New properties have been added to make them more versatile or properties have been removed, if they are not necessary anymore. See changed rules in the release notes for PMD 7.

All properties which accept multiple values now use a comma (,) as a delimiter. The previous default was a pipe character (|). The delimiter is not configurable anymore. If needed, the comma can be escaped with a backslash. This affects the following rules: AvoidUsingHardCodedIP, LooseCoupling, UnusedPrivateField, UnusedPrivateMethod, AtLeastOneConstructor, CommentDefaultAccessModifier, FieldNamingConventions, LinguisticNaming, UnnecessaryConstructor, CyclomaticComplexity, NcssCount, SingularField, AvoidBranchingStatementAsLastInLoop, CloseResource.

A handful of rules are new to PMD 7. You might want to check these out: new rules.

Once you have reviewed your ruleset(s), you can switch to PMD 7.

I’m using custom rules

Testing

Ideally, you have written good tests already for your custom rules - see Testing your rules. This helps to identify problems early on.

The base test classes PmdRuleTst and SimpleAggregatorTst have been moved out of package net.sourceforge.pmd.testframework. You’ll need to adjust your imports.

Ruleset XML

The <rule> tag, that defines your custom rule, is required to have a language attribute now. This was always the case for XPath rules, but is now a requirement for Java rules.

XPath rules

If you have XPath based rules, the first step will be to migrate to XPath 2.0 and then to XPath 3.1. XPath 2.0 is available in PMD 6 already and can be used right away. PMD 7 will use by default XPath 3.1 and won’t support XPath 1.0 anymore. The difference between XPath 2.0 and XPath 3.1 is not big, so your XPath 2.0 can be expected to work in PMD 7 without any further changes. So the migration path is to simply migrate to XPath 2.0.

After you have migrated your XPath rules to XPath 2.0, remove the “version” property, since that has been removed with PMD 7. PMD 7 by default uses XPath 3.1. See below XPath for details.

Then change the class attribute of your rule to net.sourceforge.pmd.lang.rule.xpath.XPathRule - because the class XPathRule has been moved into subpackage net.sourceforge.pmd.lang.rule.xpath.

There are some general changes for AST nodes regarding the @Image attribute. See below General AST Changes to avoid @Image.

Additional infos:

• The custom XPath function typeOf has been removed (deprecated since 6.4.0). Use the function pmd-java:typeIs or pmd-java:typeIsExactly instead. See PMD extension functions for available functions.

Java rules

If you have Java based rules, and you are using rulechain, this works a bit different now. The RuleChain API has changed, see [core] Simplify the rulechain (#2490) for the full details. But in short, you don’t call addRuleChainVisit(...) in the rule’s constructor anymore. Instead, you override the method buildTargetSelector:

    protected RuleTargetSelector buildTargetSelector() {
        return RuleTargetSelector.forTypes(ASTVariableId.class);
    }

Java AST changes

The API to navigate the AST also changed significantly:

• Tree traversal using Node API
• Consider using the new NodeStream API to navigate with null-safety. This is optional.

Additionally, if you have created rules for Java - regardless whether it is a XPath based rule or a Java based rule - you might need to adjust your queries or visitor methods. The Java AST has been refactored substantially. The easiest way is to use the PMD Rule Designer to see the structure of the AST. See the section Java AST below for details.

I’ve extended PMD with a custom language…

The guides for Adding a new language with JavaCC and Adding a new CPD language have been updated.

Most notable changes are:

• As an alternative, PMD 7 now supports ANTLR in addition to JavaCC: Adding a new language with ANTLR.
• There is a shared ant script that wraps the calls to javacc: javacc-wrapper.xml. This should be used now.
• PMD’s parser adapter for JavaCC generated parsers is called now JjtreeParserAdapter. This is the class that needs to be implemented now.
• There is no need anymore to write a custom TokenManager - we have now a common base class for JavaCC generated token managers. This base class is AbstractTokenManager.
• A rule violation factory is not needed anymore. For language specific information on rule violations, there is now a ViolationDecorator that a language can implement. These ViolationDecorators are called when a violation is reported and they can provide the additional information. This information can be used by renderers via RuleViolation#getAdditionalInfo.
• A parser visitor adapter is not needed anymore. The visitor interface now provides a default implementation. Instead, a base visitor for the language should be created, which extends AstVisitorBase.
• A rule chain visitor is not needed anymore. PMD provides a common implementation that fits all languages.

I’ve extended PMD with a custom feature…

In that case we can’t provide a general guide unless we know the specific custom feature. If you are having difficulties finding your way around the PMD source code and javadocs and you don’t see the aspect of PMD documented you are using, we are probably missing documentation. Please reach out to us by opening a discussion. We then can enhance the documentation and/or the PMD API.

Special topics

Release downloads

• The asset filenames of PMD on GitHub Releases are now pmd-dist-<version>-bin.zip, pmd-dist-<version>-src.zip and pmd-dist-<version>-doc.zip. Keep that in mind, if you have an automated download script.
• The structure inside the ZIP files stay the same, e.g. we still provide inside the binary distribution ZIP file the base directory pmd-bin-<version>.

CLI Changes

The CLI has been revamped completely (see Release Notes: Revamped Command Line Interface).

Most notable changes:

• Unified start script on all platforms for all commands (PMD, CPD, Designer). Instead of run.sh and pmd.bat, we now have pmd only (technically on Windows, there is still a pmd.bat, but it behaves the same).
  • Executing PMD from CLI now means: run.sh pmd / pmd.bat ➡️ pmd check
  • Executing CPD: run.sh cpd / cpd.bat ➡️ pmd cpd
  • Executing Designer: run.sh designer / designer.bat ➡️ pmd designer
  • Executing CPD GUI: run.sh cpd-gui / cpdgui.bat ➡️ pmd cpd-gui
• There are some changes to the CLI arguments:

  • --fail-on-violation false ➡️ --no-fail-on-violation

    If you don’t replace this argument, then “false” will be interpreted as a file to analyze. You might see then an error message such as [main] ERROR net.sourceforge.pmd.cli.commands.internal.PmdCommand - No such file false.

  • PMD tries to display a progress bar. If you don’t want this (e.g. on a CI build server), you can disable this with --no-progress.
  • --no-ruleset-compatibility has been removed without replacement.
  • --stress (or -stress) has been removed without replacement.

Custom distribution packages

When creating a custom distribution which only integrates the languages you need, there are some changes to apply:

• In addition to the language dependencies you want, you also need add a dependency to net.sourceforge.pmd:pmd-cli in order to get the CLI classes.
• When fetching the scripts for the CLI with “maven-dependency-plugin”, you need to additionally fetch the logging configuration. That means, the line <includes>scripts/**,LICENSE</includes> needs to be changed to <includes>scripts/**,LICENSE,conf/**</includes>.
• Since the assembly descriptor pmd-bin includes now optionally also a BOM (bill of material). If you want to create this for your custom distribution, simply add the following plugin configuration:

     <plugin>
        <groupId>org.cyclonedx</groupId>
        <artifactId>cyclonedx-maven-plugin</artifactId>
        <version>2.7.11</version>
        <configuration>
          <outputName>pmd-${project.version}-cyclonedx</outputName>
        </configuration>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>makeAggregateBom</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
  

• The artifact name for PMD Designer has been renamed, you need to use now net.sourceforge.pmd:pmd-designer instead of “pmd-ui”.

Rule tests are now using JUnit5

When you have custom rules, and you have written rule tests according to the guide Testing your rules, you might want to consider upgrading your other tests to JUnit 5. The tests in PMD 7 have been migrated to JUnit5 - including the rule tests for the built-in rules.

When executing the rule tests, you need to make sure to have JUnit5 on the classpath - which you automatically get when you depend on net.sourceforge.pmd:pmd-test. If you also have JUnit4 tests, you need to make sure to have a junit-vintage-engine as well on the test classpath, so that all tests are executed. That means, you might need to add now a dependency to JUnit4 explicitly if needed.

CPD: Reported endcolumn is now exclusive

In PMD 6, the reported position of the duplicated tokens in CPD where always including, e.g. the following described a duplication of length 4 in PMD 6: beginLine=1, endLine=1, beginColumn=1, endColumn=4 - these are the first 4 character in the first line. With PMD 7, the endColumn is now excluding. The same duplication will be reported in PMD 7 as: beginLine=1, endLine=1, beginColumn=1, endColumn=5.

The reported positions in a file follow now the usual meaning: line numbering starts from 1, begin line and end line are inclusive, begin column is inclusive and end column is exclusive. This is the usual behavior of the most common text editors and the PMD part already used that meaning in RuleViolations for a long time in PMD 6 already.

This only affects the XML report format as the others don’t provide column information.

Node API

Starting from one node in the AST, you can navigate to children or parents with the following methods. This is the “traditional” way for simple cases. For more complex cases, consider to use the new NodeStream API.

Many methods available in PMD 6 have been deprecated and removed for a slicker API with consistent naming, that also integrates tightly with the NodeStream API.

• getNthParent(n) ➡️ ancestors().get(n - 1)
• getFirstParentOfType(parentType) ➡️ ancestors(parentType).first()
• getParentsOfType(parentType) ➡️ ancestors(parentType).toList()
• findChildrenOfType(childType) ➡️ children(childType).toList()
• findDescendantsOfType(targetType) ➡️ descendants(targetType).toList()
• getFirstChildOfType(childType) ➡️ firstChild(childType)
• getFirstDescendantOfType(descendantType) ➡️ descendants(descendantType).first()
• hasDescendantOfType(type) ➡️ descendants(type).nonEmpty()

Unchanged methods that work as before:

• getParent
• getChild
• getNumChildren
• getIndexInParent

New methods:

• getFirstChild
• getLastChild
• getPreviousSibling
• getNextSibling
• getRoot

New methods that integrate with NodeStream:

• children - returns a NodeStream containing all the children of this node. Note: in PMD 6, this method returned an Iterable
• descendants
• descendantsOrSelf
• ancestors
• ancestorsOrSelf
• children
• firstChild
• descendants
• ancestors

Methods removed completely:

• getFirstParentOfAnyType(parentTypes):️ There is no direct replacement, but something along the lines:

        ancestors()
                .filter(n -> Arrays.stream(classes)
                        .anyMatch(c -> c.isInstance(n)))
                .first();
  

• findChildNodesWithXPath: Has been removed, because it is very inefficient. Use NodeStream instead.
• hasDescendantMatchingXPath: Has been removed, because it is very inefficient. Use NodeStream instead.
• jjt* like jjtGetParent. These methods were implementation specific. Use the equivalent methods like getParent().

See Node for the details.

NodeStream API

In java rule implementations, you often need to navigate the AST to find the interesting nodes. In PMD 6, this was often done by calling jjtGetChild(int) or jjtGetParent(int) and then checking the node type with instanceof. There are also helper methods available, like getFirstChildOfType(Class) or findDescendantsOfType(Class). These methods might return null and you need to check this for every level.

The new NodeStream API provides easy to use methods that follow the Java Stream API (java.util.stream).

Many complex predicates about nodes can be expressed by testing the emptiness of a node stream. E.g. the following tests if the node is a variable declarator id initialized to the value 0:

Example:

     NodeStream.of(someNode)                           // the stream here is empty if the node is null
               .filterIs(ASTVariableId.class)          // the stream here is empty if the node was not a variable id
               .followingSiblings()                    // the stream here contains only the siblings, not the original node
               .children(ASTNumericLiteral.class)
               .filter(ASTNumericLiteral::isIntLiteral)
               .filterMatching(ASTNumericLiteral::getValueAsInt, 0)
               .nonEmpty(); // If the stream is non empty here, then all the pipeline matched

See NodeStream for the details. Note: This was implemented via PR #1622 [core] NodeStream API

XPath: Migrating from 1.0 to 2.0

XPath 1.0 and 2.0 have some incompatibilities. The XPath 2.0 specification describes them precisely. Those are however mostly corner cases and XPath rules usually don’t feature any of them.

The incompatibilities that are most relevant to migrating your rules are not caused by the specification, but by the different engines we use to run XPath 1.0 and 2.0 queries. Here’s a list of known incompatibilities:

• The namespace prefixes fn: and string: should not be mentioned explicitly. In XPath 2.0 mode, the engine will complain about an undeclared namespace, but the functions are in the default namespace. Removing the namespace prefixes fixes it.
  • fn:substring("Foo", 1) → substring("Foo", 1)
• Conversely, calls to custom PMD functions like typeIs must be prefixed with the namespace of the declaring module (pmd-java).
  • typeIs("Foo") → pmd-java:typeIs("Foo")
• Boolean attribute values on our 1.0 engine are represented as the string values "true" and "false". In 2.0 mode though, boolean values are truly represented as boolean values, which in XPath may only be obtained through the functions true() and false(). If your XPath 1.0 rule tests an attribute like @Private="true", then it just needs to be changed to @Private=true() when migrating. A type error will warn you that you must update the comparison. More is explained on issue #1244.
  • "true", 'true' → true()
  • "false", 'false' → false()
• In XPath 1.0, comparing a number to a string coerces the string to a number. In XPath 2.0, a type error occurs. Like for boolean values, numeric values are represented by our 1.0 implementation as strings, meaning that @BeginLine > "1" worked —that’s not the case in 2.0 mode.
  • @ArgumentCount > '1' → @ArgumentCount > 1
• In XPath 1.0, the expression /Foo matches the children of the root named Foo. In XPath 2.0, that expression matches the root, if it is named Foo. Consider the following tree:

  Foo
  └─ Foo
  └─ Foo
  

  Then /Foo will match the root in XPath 2.0, and the other nodes (but not the root) in XPath 1.0. See e.g. an issue caused by this in Apex, with nested classes.

• The custom function “pmd:matches” which checks a regular expression against a string has been removed, since there is a built-in function available since XPath 2.0 which can be used instead. If you use “pmd:matches” simply remove the “pmd:” prefix.

General AST Changes to avoid @Image

An abstract syntax tree should be abstract, but in the same time, should not be too abstract. One of the base interfaces for PMD’s AST for all languages is Node, which provides the methods getImage and hasImageEqualTo. However, these methods don’t necessarily make sense for all nodes in all contexts. That’s why getImage() often returns just null. Also, the name is not very describing. AST nodes should try to use more specific names, such as getValue() or getName().

For PMD 7, most languages have been adapted. And when writing XPath rules, you need to replace @Image with whatever is appropriate now (e.g. @Name). See below for details.

Apex and Visualforce

There are many usages of @Image. These will be refactored after PMD 7 is released by deprecating the attribute and providing alternatives.

See also issue Deprecate getImage/@Image #4787.

Html

• ASTHtmlTextNode: @Image ➡️ @Text, @NormalizedText ➡️ @Text, @Text ➡️ @WholeText.

Java

There are still many usages of @Image which are not refactored yet. This will be done after PMD 7 is released by deprecating the attribute and providing alternatives.

See also issue Deprecate getImage/@Image #4787.

Some nodes have already the image attribute (and others) deprecated. These deprecated attributes are removed now:

• ASTAnnotationTypeDeclaration: @Image ➡️ @SimpleName
• ASTAnonymousClassDeclaration: @Image ➡️ @SimpleName
• ASTClassDeclaration (previously “ASTClassOrInterfaceDeclaration”): @Image ➡️ @SimpleName
• ASTEnumDeclaration: @Image ➡️ @SimpleName
• ASTFieldDeclaration: @VariableName ➡️ VariableId/@Name
• ASTMethodDeclaration: @Image ➡️ @Name
• ASTMethodDeclaration: @MethodName ➡️ @Name
• ASTRecordDeclaration: @Image ➡️ @SimpleName
• ASTVariableId (previously “ASTVariableDeclaratorId”): @Image ➡️ @Name
• ASTVariableId (previously “ASTVariableDeclaratorId”): @VariableName ➡️ @Name
• ASTVariableId (previously “ASTVariableDeclaratorId”): @Array ➡️ @ArrayType

JavaScript

• ASTAssignment: @Image ➡️ @Operator
• ASTBigIntLiteral: @Image ➡️ @Value
• ASTBreakStatement: @Image ➡️ Name/@Identifier
• ASTContinueStatement: @Image ➡️ Name/@Identifier
• ASTErrorNode: @Image ➡️ @Message
• ASTFunctionNode: @Image ➡️ Name/@Identifier
• ASTInfixExpression: @Image ➡️ @Operator
• ASTKeywordLiteral: @Image ➡️ @Literal
• ASTLabel: @Image ➡️ @Name
• ASTName: @Image ➡️ @Identifier
• ASTNumberLiteral: @Image ➡️ @Value
• ASTObjectProperty: @Image ➡️ @Operator
• ASTPropertyGet: @Image ➡️ @Operator
• ASTRegExpLiteral: @Image ➡️ @Value
• ASTStringLiteral: @Image ➡️ @Value
• ASTUnaryExpression: @Image ➡️ @Operator
• ASTUpdateExpression: @Image ➡️ @Operator
• ASTXmlDotQuery: @Image ➡️ @Operator
• ASTXmlMemberGet: @Image ➡️ @Operator
• ASTXmlPropRef: @Image ➡️ Name[last()]/@Identifier
• ASTXmlString: @Image ➡️ @Xml

JSP

• ASTAttributeValue: @Image ➡️ @Value
• ASTCData: @Image ➡️ @Content
• ASTCommentTag: @Image ➡️ @Content
• ASTElExpression: @Image ➡️ @Content
• ASTHtmlScript: @Image ➡️ @Content
• ASTJspComment: @Image ➡️ @Content
• ASTJspDeclaration: @Image ➡️ @Content
• ASTJspExpression: @Image ➡️ @Content
• ASTJspExpressionInAttribute: @Image ➡️ @Content
• ASTJspScriptlet: @Image ➡️ @Content
• ASTText: @Image ➡️ @Content
• ASTUnparsedText: @Image ➡️ @Content
• ASTValueBinding: @Image ➡️ @Content

Modelica

• ASTAddOp: @Image ➡️ @Operator
• ASTDerClassSpecifier: @Image ➡️ @SimpleClassName
• ASTEnumerationShortClassSpecifier: @Image ➡️ @SimpleClassName
• ASTExtendingLongClassSpecifier: @Image ➡️ @SimpleClassName
• ASTFactor: @Image ➡️ @Operator
• ASTLanguageSpecification: @Image ➡️ @ExternalLanguage
• ASTMulOp: @Image ➡️ @Operator
• ASTName: @Image ➡️ @Name
• ASTNumberLiteral: @Image ➡️ @Value
• ASTRelOp: @Image ➡️ @Operator
• ASTSimpleLongClassSpecifier: @Image ➡️ @SimpleClassName
• ASTSimpleName: @Image ➡️ @Name
• ASTSimpleShortClassSpecifier: @Image ➡️ @SimpleClassName
• ASTStoredDefinition: @Image ➡️ @Name
• ASTStringComment: @Image ➡️ @Comment
• ASTStringLiteral: @Image ➡️ @Value
• ASTWithinClause: @Image ➡️ @Name

PLSQL

There are many usages of @Image. These will be refactored after PMD 7 is released by deprecating the attribute and providing alternatives.

See also issue Deprecate getImage/@Image #4787.

Scala

• ASTLitBoolean: @Image ➡️ @Value
• ASTLitByte: @Image ➡️ @Value
• ASTLitChar: @Image ➡️ @Value
• ASTLitDouble: @Image ➡️ @Value
• ASTLitFloat: @Image ➡️ @Value
• ASTLitInt: @Image ➡️ @Value
• ASTLitLong: @Image ➡️ @Value
• ASTLitNull: @Image ➡️ @Value
• ASTLitShort: @Image ➡️ @Value
• ASTLitString: @Image ➡️ @Value
• ASTLitSymbol: @Image ➡️ @Value
• ASTLitUnit: @Image ➡️ @Value
• ASTNameAnonymous: @Image ➡️ @Value
• ASTNameIndeterminate: @Image ➡️ @Value
• ASTTermName: @Image ➡️ @Value
• ASTTypeName: @Image ➡️ @Value

XML (and POM)

When using XPathRule, text of text nodes was exposed as @Image of normal element type nodes. Now the attribute is called @Text.

Note: In general, it is recommended to use DomXPathRule instead, which exposes text nodes as real XPath/XML text nodes which conforms to the XPath spec. There is no difference, text of text nodes can be selected using text().

Java AST

The Java grammar has been refactored substantially in order to make it easier to maintain and more correct regarding the Java Language Specification.

Here you can see the most important changes as a comparison between the PMD 6 AST (“Old AST”) and PMD 7 AST (“New AST”) and with some background info about the changes.

When in doubt, it is recommended to use the PMD Designer which can also display the AST.

Renamed classes / interfaces

• AccessNode ➡️ ModifierOwner
• ClassOrInterfaceType ➡️ ClassType (ASTClassType)
• ClassOrInterfaceDeclaration ➡️ ClassDeclaration (ASTClassDeclaration)
• AnyTypeDeclaration ➡️ TypeDeclaration (ASTTypeDeclaration)
• MethodOrConstructorDeclaration ➡️ ExecutableDeclaration (ASTExecutableDeclaration)
• VariableDeclaratorId ➡️ VariableId (ASTVariableId)
• ClassOrInterfaceBody ➡️ ClassBody (ASTClassBody)

Annotations

• What: Annotations are consolidated into a single node. SingleMemberAnnotation, NormalAnnotation and MarkerAnnotation are removed in favour of ASTAnnotation. The Name node is removed, replaced by a ASTClassType.
• Why: Those different node types implement a syntax-only distinction, that only makes semantically equivalent annotations have different possible representations. For example, @A and @A() are semantically equivalent, yet they were parsed as MarkerAnnotation resp. NormalAnnotation. Similarly, @A("") and @A(value="") were parsed as SingleMemberAnnotation resp. NormalAnnotation. This also makes parsing much simpler. The nested ClassOrInterface type is used to share the disambiguation logic.
• Related issue: [java] Use single node for annotations (#2282)

@A

└─ Annotation "A"
   └─ MarkerAnnotation "A"
      └─ Name "A"

└─ Annotation "A"
   └─ ClassOrInterfaceType "A"

@A()

└─ Annotation "A"
   └─ NormalAnnotation "A"
      └─ Name "A"

└─ Annotation "A"
   ├─ ClassType "A"
   └─ AnnotationMemberList

@A(value="v")

└─ Annotation "A"
   └─ NormalAnnotation "A"
      ├─ Name "A"
      └─ MemberValuePairs
         └─ MemberValuePair "value"
            └─ MemberValue
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Literal '"v"'

└─ Annotation "A"
   ├─ ClassType "A"
   └─ AnnotationMemberList
      └─ MemberValuePair "value" [ @Shorthand = false() ]
         └─ StringLiteral '"v"'

@A("v")

└─ Annotation "A"
   └─ SingleMemberAnnotation "A"
      ├─ Name "A"
      └─ MemberValue
         └─ PrimaryExpression
            └─ PrimaryPrefix
               └─ Literal '"v"'

└─ Annotation "A"
   ├─ ClassType "A"
   └─ AnnotationMemberList
      └─ MemberValuePair "value" [ @Shorthand = true() ]
         └─ StringLiteral '"v"'

@A(value="v", on=true)

└─ Annotation "A"
   └─ NormalAnnotation "A"
      ├─ Name "A"
      └─ MemberValuePairs
         ├─ MemberValuePair "value"
         │  └─ MemberValue
         │     └─ PrimaryExpression
         │        └─ PrimaryPrefix
         │           └─ Literal '"v"'
         └─ MemberValuePair "on"
            └─ MemberValue
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Literal
                        └─ BooleanLiteral [ @True = true() ]

└─ Annotation "A"
   ├─ ClassType "A"
   └─ AnnotationMemberList
      ├─ MemberValuePair "value" [ @Shorthand = false() ]
      │  └─ StringLiteral '"v"'
      └─ MemberValuePair "on"
         └─ BooleanLiteral [ @True = true() ]

Annotation nesting

• What: ASTAnnotations are now nested within the node, to which they are applied to. E.g. if a method is annotated, the Annotation node is now a child of a ASTModifierList, inside the ASTMethodDeclaration.
• Why: Fixes a lot of inconsistencies, where sometimes the annotations were inside the node, and sometimes just somewhere in the parent, with no real structure.
• Related issue: [java] Move annotations inside the node they apply to (#1875)

@A
public void set(int x) { }

└─ ClassOrInterfaceBodyDeclaration
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   └─ MethodDeclaration
      ├─ ResultType[ @Void = true ]
      ├─ ...

└─ MethodDeclaration
   ├─ ModifierList
   │  └─ Annotation "A"
   │     └─ ClassType "A"
   ├─ VoidType
   ├─ ...

@A class C {}

└─ TypeDeclaration
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   └─ ClassOrInterfaceDeclaration "C"
      └─ ClassOrInterfaceBody

└─ ClassDeclaration
    ├─ ModifierList
    │  └─ Annotation "A"
    │     └─ ClassType "A"
    └─ ClassBody

var x = (@A T.@B S) expr;

└─ CastExpression
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   ├─ Type
   │  └─ ReferenceType
   │     └─ ClassOrInterfaceType "T.S"
   │        └─ Annotation "B"
   │           └─ MarkerAnnotation "B"
   │              └─ Name "B"
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ Name "expr"

└─ CastExpression
   ├─ ClassType "S"
   │  ├─ ClassType "T"
   │  │  └─ Annotation "A"
   │  │     └─ ClassType "A"
   │  └─ Annotation "B"
   │     └─ ClassType "B"
   └─ VariableAccess "expr"

var x = (@A T & S) expr;

└─ CastExpression
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   ├─ Type
   │  └─ ReferenceType
   │     └─ ClassOrInterfaceType "T"
   ├─ ReferenceType
   │  └─ ClassOrInterfaceType "S"
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ Name "expr"

└─ CastExpression
  ├─ IntersectionType
  │  ├─ ClassType "T"
  │  │  └─ Annotation "A"
  │  │     └─ ClassType "A"
  │  └─ ClassType "S"
  └─ VariableAccess "expr"

new @A T()

└─ AllocationExpression
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   ├─ ClassOrInterfaceType "T"
   └─ Arguments

└─ ConstructorCall
   ├─ ClassType "T"
   │  └─ Annotation "A"
   │     └─ ClassType "A"
   └─ ArgumentList

new @A int[0]

└─ AllocationExpression
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   ├─ PrimitiveType "int"
   └─ ArrayDimsAndInits
      └─ Expression
         └─ PrimaryExpression
            └─ PrimaryPrefix
               └─ Literal "0"

└─ ArrayAllocation
   └─ ArrayType
      ├─ PrimitiveType "int"
      │  └─ Annotation "A"
      │     └─ ClassType "A"
      └─ ArrayDimensions
         └─ ArrayDimExpr
            └─ NumericLiteral "0"

@A int @B[] x;

└─ LocalVariableDeclaration
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   ├─ Type[ @ArrayType = true() ]
   │  └─ ReferenceType
   │     ├─ PrimitiveType "int"
   │     └─ Annotation "B"
   │        └─ MarkerAnnotation "B"
   │           └─ Name "B"
   └─ VariableDeclarator
      └─ VariableDeclaratorId "x"

└─ LocalVariableDeclaration
  ├─ ModifierList
  │  └─ Annotation "A"
  │     └─ ClassType "A"
  ├─ ArrayType
  │  ├─ PrimitiveType "int"
  │  └─ ArrayDimensions
  │     └─ ArrayTypeDim
  │        └─ Annotation "B"
  │           └─ ClassType "B"
  └─ VariableDeclarator
     └─ VariableId "x"

<@A T, @B S extends @C Object>

└─ TypeParameters
   ├─ TypeParameter "T"
   │  └─ Annotation "A"
   │     └─ MarkerAnnotation "A"
   │        └─ Name "A"
   └─ TypeParameter "S"
      ├─ Annotation "B"
      │  └─ MarkerAnnotation "B"
      │     └─ Name "B"
      └─ TypeBound
         ├─ Annotation "C"
         │  └─ MarkerAnnotation "C"
         │     └─ Name "C"
         └─ ClassOrInterfaceType "Object"

└─ TypeParameters
   ├─ TypeParameter "T"
   │  └─ Annotation "A"
   │     └─ ClassType "A"
   └─ TypeParameter "S" [ @TypeBound = true() ]
      ├─ Annotation "B"
      │  └─ ClassType "B"
      └─ ClassType "Object"
         └─ Annotation "C"
            └─ ClassType "C"

enum E {
  @A E1, @B E2;
}

└─ EnumBody
  ├─ Annotation "A"
  │  └─ MarkerAnnotation "A"
  │     └─ Name "A"
  ├─ EnumConstant "E1"
  ├─ Annotation "B"
  │  └─ MarkerAnnotation "B"
  │     └─ Name "B"
  └─ EnumConstant "E2"

└─ EnumBody
   ├─ EnumConstant "E1"
   │  ├─ ModifierList
   │  │  └─ Annotation "A"
   │  │     └─ ClassType "A"
   │  └─ VariableId "E1"
   └─ EnumConstant "E2"
      ├─ ModifierList
      │  └─ Annotation "B"
      │     └─ ClassType "B"
      └─ VariableId "E2"

Types

Type and ReferenceType

• What:
  • ASTType and ASTReferenceType have been turned into interfaces, implemented by ASTPrimitiveType, ASTClassType, and the new node ASTArrayType. This reduces the depth of the relevant subtrees, and allows to explore them more easily and consistently.
• Why:
  • some syntactic contexts only allow reference types, other allow any kind of type. If you want to match all types of a program, then matching Type would be the intuitive solution. But in 6.0.x, it wouldn’t have sufficed, since in some contexts, no Type node was pushed, only a ReferenceType
  • Regardless of the original syntactic context, any reference type is a type, and searching for ASTType should yield all the types in the tree.
  • Using interfaces allows to abstract behaviour and make a nicer and safer API.
• Migrating
  • There is currently no way to match abstract types (or interfaces) with XPath, so Type and ReferenceType name tests won’t match anything anymore.
  • Type/ReferenceType/ClassOrInterfaceType ➡️ ClassType
  • Type/PrimitiveType ➡️ PrimitiveType.
  • Type/ReferenceType[@ArrayDepth > 1]/ClassOrInterfaceType ➡️ ArrayType/ClassType.
  • Type/ReferenceType/PrimitiveType ➡️ ArrayType/PrimitiveType.
  • Note that in most cases you should check the type of a variable with e.g. VariableId[pmd-java:typeIs("java.lang.String[]")] because it considers the additional dimensions on declarations like String foo[];. The Java equivalent is TypeHelper.isA(id, String[].class);

// in the context of a variable declaration
List<String> strs;

└─ Type (1)
   └─ ReferenceType
      └─ ClassOrInterfaceType "List"
         └─ TypeArguments
            └─ TypeArgument
               └─ ReferenceType (2)
                  └─ ClassOrInterfaceType "String"

└─ ClassType "List"
   └─ TypeArguments
      └─ ClassType "String"

Array changes

• What: Additional nodes ASTArrayType, ASTArrayTypeDim, ASTArrayDimensions, ASTArrayAllocation.
• Why: Support annotated array types ([java] Java8 parsing corner case with annotated array types (#997))
• Related issue: [java] Simplify array allocation expressions (#1981)

String[][] myArray;

└─ Type[ @ArrayType = true() ]
   └─ ReferenceType
      └─ ClassOrInterfaceType[ @Array = true() ][ @ArrayDepth = 2 ] "String"

└─ ArrayType[ @ArrayDepth = 2 ]
   ├─ ClassType "String"
   └─ ArrayDimensions[ @Size = 2 ]
      ├─ ArrayTypeDim
      └─ ArrayTypeDim

String @Annotation1[] @Annotation2[] myArray;

└─ Type[ @ArrayType = true() ]
   └─ ReferenceType
      ├─ ClassOrInterfaceType[ @Array = true() ][ @ArrayDepth = 2 ] "String"
      ├─ Annotation "Annotation1"
      │  └─ MarkerAnnotation "Annotation1"
      │     └─ Name "Annotation1"
      └─ Annotation "Annotation2"
         └─ MarkerAnnotation "Annotation2"
            └─ Name "Annotation2"

└─ ArrayType[ @ArrayDepth = 2 ]
   ├─ ClassType "String"
   └─ ArrayDimensions[ @Size = 2 ]
      ├─ ArrayTypeDim
      │  └─ Annotation "Annotation1"
      │     └─ ClassType "Annotation1"
      └─ ArrayTypeDim
         └─ Annotation "Annotation2"
            └─ ClassType "Annotation2"

new int[2][];
new @Bar int[3][2];
new Foo[] { f, g };

└─ AllocationExpression
   ├─ PrimitiveType "int"
   └─ ArrayDimsAndInits[ @ArrayDepth = 2 ]
      └─ Expression
         └─ PrimaryExpression
            └─ PrimaryPrefix
               └─ Literal "2"

└─ AllocationExpression
   ├─ Annotation "Bar"
   │  └─ MarkerAnnotation "Bar"
   │     └─ Name "Bar"
   ├─ PrimitiveType "int"
   └─ ArrayDimsAndInits[ @ArrayDepth = 2 ]
      ├─ Expression
      │  └─ PrimaryExpression
      │     └─ PrimaryPrefix
      │        └─ Literal "3"
      └─ Expression
         └─ PrimaryExpression
            └─ PrimaryPrefix
               └─ Literal "2"

└─ AllocationExpression
   ├─ ClassOrInterfaceType "Foo"
   └─ ArrayDimsAndInits[ @ArrayDepth = 1 ]
      └─ ArrayInitializer
         ├─ VariableInitializer
         │  └─ Expression
         │     └─ PrimaryExpression
         │        └─ PrimaryPrefix
         │           └─ Name "f"
         └─ VariableInitializer
            └─ Expression
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Name "g"

└─ ArrayAllocation[ @ArrayDepth = 2 ]
   └─ ArrayType[ @ArrayDepth = 2 ]
      ├─ PrimitiveType "int"
      └─ ArrayDimensions[ @Size = 2]
         ├─ ArrayDimExpr
         │  └─ NumericLiteral "2"
         └─ ArrayTypeDim

└─ ArrayAllocation[ @ArrayDepth = 2 ]
   └─ ArrayType[ @Array Depth = 2 ]
      ├─ PrimitiveType "int"
      │  └─ Annotation "Bar"
      │     └─ ClassType "Bar"
      └─ ArrayDimensions[ @Size = 2 ]
         ├─ ArrayDimExpr
         │  └─ NumericLiteral "3"
         └─ ArrayDimExpr
            └─ NumericLiteral "2"

└─ ArrayAllocation[ @ArrayDepth = 1 ]
   └─ ArrayType[ @ArrayDepth = 1 ]
   │  ├─ ClassType "Foo"
   │  └─ ArrayDimensions[ @Size = 1 ]
   │     └─ ArrayTypeDim
   └─ ArrayInitializer[ @Length = 2 ]
      ├─ VariableAccess "f"
      └─ VariableAccess "g"

ClassType nesting

• What: ASTClassType (formerly ASTClassOrInterfaceType) appears to be left recursive now, and encloses its qualifying type.
• Why: To preserve the position of annotations and type arguments
• Related issue: [java] ClassOrInterfaceType AST improvements (#1150)

Map.Entry<K,V>

└─ ClassOrInterfaceType "Map.Entry"
   └─ TypeArguments
      ├─ TypeArgument
      │  └─ ReferenceType
      │     └─ ClassOrInterfaceType "K"
      └─ TypeArgument
         └─ ReferenceType
            └─ ClassOrInterfaceType "V"

└─ ClassType "Entry"
   ├─ ClassType "Map"
   └─ TypeArguments[ @Size = 2 ]
      ├─ ClassType "K"
      └─ ClassType "V"

First<K>.Second.Third<V>

└─ ClassOrInterfaceType "First.Second.Third"
   ├─ TypeArguments
   │  └─ TypeArgument
   │     └─ ReferenceType
   │        └─ ClassOrInterfaceType "K"
   └─ TypeArguments
      └─ TypeArgument
         └─ ReferenceType
            └─ ClassOrInterfaceType "V"

└─ ClassType "Third"
   ├─  ClassType "Second"
   │   └─ ClassType "First"
   │      └─ TypeArguments[ @Size = 1]
   │         └─ ClassType "K"
   └─ TypeArguments[ @Size = 1 ]
      └─ ClassType "V"

TypeArgument and WildcardType

• What:
  • ASTTypeArgument is removed. Instead, the ASTTypeArguments node contains directly a sequence of ASTType nodes. To support this, the new node type ASTWildcardType captures the syntax previously parsed as a TypeArgument.
  • The ASTWildcardBounds node is removed. Instead, the bound is a direct child of the WildcardType.
• Why: Because wildcard types are types in their own right, and having a node to represent them skims several levels of nesting off.

Entry<String, ? extends Node>

└─ ClassOrInterfaceType "Entry"
   └─ TypeArguments
      ├─ TypeArgument
      │  └─ ReferenceType
      │     └─ ClassOrInterfaceType "String"
      └─ TypeArgument[ @Wildcard = true() ]
         └─ WildcardBounds[ @UpperBound = true() ]
            └─ ReferenceType
               └─ ClassOrInterfaceType "Node"

└─ ClassType "Entry"
   └─ TypeArguments[ @Size = 2 ]
      ├─ ClassType "String"
      └─ WildcardType[ @UpperBound = true() ]
         └─ ClassType "Node"

List<?>

└─ ClassOrInterfaceType "List"
   └─ TypeArguments
      └─ TypeArgument[ @Wildcard = true() ]

└─ ClassType "List"
   └─ TypeArguments[ @Size = 1 ]
      └─ WildcardType[ @UpperBound = true() ]

Declarations

Import and Package declarations

• What: Remove the Name node in imports and package declaration nodes.
• Why: Name is a TypeNode, but it’s equivalent to ASTAmbiguousName in that it describes nothing about what it represents. The name in an import may represent a method name, a type name, a field name… It’s too ambiguous to treat in the parser and could just be the image of the import, or package, or module.
• Related issue: [java] Remove Name nodes in Import- and PackageDeclaration (#1888)

import java.util.ArrayList;
import static java.util.Comparator.reverseOrder;
import java.util.*;

├─ ImportDeclaration
│  └─ Name "java.util.ArrayList"
├─ ImportDeclaration[ @Static=true() ]
│  └─ Name "java.util.Comparator.reverseOrder"
└─ ImportDeclaration[ @ImportOnDemand = true() ]
   └─ Name "java.util"

├─ ImportDeclaration "java.util.ArrayList"
├─ ImportDeclaration[ @Static = true() ] "java.util.Comparator.reverseOrder"
└─ ImportDeclaration[ @ImportOnDemand = true() ] "java.util"

package com.example.tool;

└─ PackageDeclaration
   └─ Name "com.example.tool"

└─ PackageDeclaration "com.example.tool"
   └─ ModifierList

Modifier lists

• What: ModifierOwner (formerly AccessNode) is now based on a node: ASTModifierList. That node represents modifiers occurring before a declaration. It provides a flexible API to query modifiers, both explicit and implicit. All declaration nodes now have such a modifier list, even if it’s implicit (no explicit modifiers).
• Why: ModifierOwner (formerly AccessNode) gave a lot of irrelevant methods to its subtypes. E.g. ASTFieldDeclaration::isSynchronized makes no sense. Now, these irrelevant methods don’t clutter the API. The API of ModifierList is both more general and flexible.
• Related issue: [java] Rework AccessNode (#2259)

@A
public void set(final int x, int y) { }

└─ ClassOrInterfaceBodyDeclaration
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   └─ MethodDeclaration[ @Public = true() ] "set"
      ├─ ResultType[ @Void = true() ]
      └─ MethodDeclarator
         └─ FormalParameters[ @Size = 2 ]
            ├─ FormalParameter[ @Final = true() ]
            │  ├─ Type
            │  │  └─ PrimitiveType "int"
            │  └─ VariableDeclaratorId "x"
            └─ FormalParameter[ @Final = false() ]
               ├─ Type
               │  └─ PrimitiveType "int"
               └─ VariableDeclaratorId "y"

└─ MethodDeclaration[ pmd-java:modifiers() = 'public' ] "set"
   ├─ ModifierList
   │  └─ Annotation "A"
   │     └─ ClassType "A"
   ├─ VoidType
   └─ FormalParameters
      ├─ FormalParameter[ pmd-java:modifiers() = 'final' ]
      │  ├─ ModifierList
      │  └─ VariableId "x"
      └─ FormalParameter[ pmd-java:modifiers() = () ]
         ├─ ModifierList
         └─ VariableId "y"

public @A class C {}

└─ TypeDeclaration
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   └─ ClassOrInterfaceDeclaration[ @Public = true() ] "C"
      └─ ClassOrInterfaceBody

└─ ClassDeclaration[ pmd-java:modifiers() = 'public' ] "C"
   ├─ ModifierList
   │  └─ Annotation "A"
   │     └─ ClassType "A"
   └─ ClassBody

Flattened body declarations

• What: Removes ASTClassOrInterfaceBodyDeclaration, ASTTypeDeclaration, and ASTAnnotationTypeMemberDeclaration. These were unnecessary since annotations are nested (see above Annotation nesting).
• Why: This flattens the tree, makes it less verbose and simpler.
• Related issue: [java] Flatten body declarations (#2300)

public class Flat {
    private int f;
}

└─ CompilationUnit
   └─ TypeDeclaration
      └─ ClassOrInterfaceDeclaration "Flat"
         └─ ClassOrInterfaceBody
            └─ ClassOrInterfaceBodyDeclaration
               └─ FieldDeclaration
                  ├─ Type
                  │  └─ PrimitiveType "int"
                  └─ VariableDeclarator
                     └─ VariableDeclaratorId "f"

└─ CompilationUnit
   └─ ClassDeclaration "Flat"
      ├─ ModifierList
      └─ ClassBody
         └─ FieldDeclaration
            ├─ ModifierList
            ├─ PrimitiveType "int"
            └─ VariableDeclarator
               └─ VariableId "f"

public @interface FlatAnnotation {
    String value() default "";
}

└─ CompilationUnit
   └─ TypeDeclaration
      └─ AnnotationTypeDeclaration "FlatAnnotation"
         └─ AnnotationTypeBody
            └─ AnnotationTypeMemberDeclaration
               └─ AnnotationMethodDeclaration "value"
                  ├─ Type
                  │  └─ ReferenceType
                  │     └─ ClassOrInterfaceType "String"
                  └─ DefaultValue
                     └─ MemberValue
                        └─ PrimaryExpression
                           └─ PrimaryPrefix
                              └─ Literal "\"\""

└─ CompilationUnit
   └─ AnnotationTypeDeclaration "FlatAnnotation"
      ├─ ModifierList
      └─ AnnotationTypeBody
         └─ MethodDeclaration "value"
            ├─ ModifierList
            ├─ ClassType "String"
            ├─ FormalParameters
            └─ DefaultValue
               └─ StringLiteral "\"\""

Module declarations

• What: Removes the generic Name node and uses instead ASTClassType where appropriate. Also uses specific node types for different directives (requires, exports, uses, provides).
• Why: Simplify queries, support type resolution
• Related issue: [java] Improve module grammar (#3890)

open module com.example.foo {
    requires com.example.foo.http;
    requires java.logging;
    requires transitive com.example.foo.network;

    exports com.example.foo.bar;
    exports com.example.foo.internal to com.example.foo.probe;

    uses com.example.foo.spi.Intf;

    provides com.example.foo.spi.Intf with com.example.foo.Impl;
}

└─ CompilationUnit
   └─ ModuleDeclaration[ @Image = 'com.example.foo' ][ @Open = true() ]
      ├─ ModuleDirective[ @Type = 'REQUIRES' ]
      │  └─ ModuleName[ @Image = 'com.example.foo.http' ]
      ├─ ModuleDirective[ @Type = 'REQUIRES' ]
      │  └─ ModuleName[ @Image = 'java.logging' ]
      ├─ ModuleDirective[ @Type = 'REQUIRES' ][ @RequiresModifier = 'TRANSITIVE' ]
      │  └─ ModuleName[ @Image = 'com.example.foo.network' ]
      ├─ ModuleDirective[ @Type = 'EXPORTS' ]
      │  └─ Name[ @Image = 'com.example.foo.bar' ]
      ├─ ModuleDirective[ @Type = 'EXPORTS' ]
      │  ├─ Name[ @Image = 'com.example.foo.internal' ]
      │  └─ ModuleName[ @Image = 'com.example.foo.probe' ]
      ├─ ModuleDirective[ @Type = 'USES' ]
      │  └─ Name[ @Image = 'com.example.foo.spi.Intf' ]
      └─ ModuleDirective[ @Type = 'PROVIDES' ]
         ├─ Name[ @Image = 'com.example.foo.spi.Intf' ]
         └─ Name[ @Image = 'com.example.foo.Impl' ]

└─ CompilationUnit
   └─ ModuleDeclaration[ @Name = 'com.example.foo' ][ @Open = true() ]
      ├─ ModuleName[ @Name = 'com.example.foo' ]
      ├─ ModuleRequiresDirective
      │  └─ ModuleName[ @Name = 'com.example.foo.http' ]
      ├─ ModuleRequiresDirective
      │  └─ ModuleName[ @Name = 'java.logging' ]
      ├─ ModuleRequiresDirective[ @Transitive = true ]
      │  └─ ModuleName[ @Name = 'com.example.foo.network' ]
      ├─ ModuleExportsDirective[ @PackageName = 'com.example.foo.bar' ]
      ├─ ModuleExportsDirective[ @PackageName = 'com.example.foo.internal' ]
      │  └─ ModuleName [ @Name = 'com.example.foo.probe' ]
      ├─ ModuleUsesDirective
      │  └─ ClassType[ pmd-java:typeIs("com.example.foo.spi.Intf") ]
      └─ ModuleProvidesDirective
         ├─ ClassType[ pmd-java:typeIs("com.example.foo.spi.Intf") ]
         └─ ClassType[ pmd-java:typeIs("com.example.foo.Impl") ]

Anonymous class declarations

• What: A separate node type ASTAnonymousClassDeclaration is introduced for anonymous classes.
• Why: Unify the AST for type declarations including anonymous class declaration in constructor calls and enums.
• Related issues:
  • [java] Add new node for anonymous class declaration (#905)
  • [java] New expression and type grammar (#1759)

Object anonymous = new Object() {  };

└─ LocalVariableDeclaration
   ├─ Type
   │  └─ ReferenceType
   │     └─ ClassOrInterfaceType[ @Image = 'Object' ]
   └─ VariableDeclarator
      ├─ VariableDeclaratorId "anonymous"
      └─ VariableInitializer
         └─ Expression
            └─ PrimaryExpression
               └─ PrimaryPrefix
                  └─ AllocationExpression
                     ├─ ClassOrInterfaceType[ @AnonymousClass = true() ][ @Image = 'Object' ]
                     ├─ Arguments
                     └─ ClassOrInterfaceBody

└─ LocalVariableDeclaration
   ├─ ModifierList
   ├─ ClassType[ @SimpleName = 'Object' ]
   └─ VariableDeclarator
      ├─ VariableId[ @Name = 'anonymous' ]
      └─ ConstructorCall
         ├─ ClassType[ @SimpleName = 'Object' ]
         ├─ ArgumentList
         └─ AnonymousClassDeclaration
            ├─ ModifierList
            └─ ClassBody

Method and Constructor declarations

Method grammar simplification

• What: Simplify and align the grammar used for method and constructor declarations. The methods in an annotation type are now also method declarations.
• Why: The method declaration had a nested node “MethodDeclarator”, which was not available for constructor declarations. This made it difficult to write rules, that concern both methods and constructors without explicitly differentiate between these two.
• Related issue: [java] Align method and constructor declaration grammar (#2034)

public class Sample {
    public Sample(int arg) throws Exception {
        super();
        greet(arg);
    }
    public void greet(int arg) throws Exception {
        System.out.println("Hello");
    }
}

└─ ClassOrInterfaceBody
   ├─ ClassOrInterfaceBodyDeclaration
   │  └─ ConstructorDeclaration[ @Image = 'Sample' ]
   │     ├─ FormalParameters
   │     │  └─ FormalParameter
   │     │     ├─ ...
   │     ├─ NameList
   │     │  └─ Name[ @Image = 'Exception' ]
   │     ├─ ExplicitConstructorInvocation
   │     │  └─ Arguments
   │     └─ BlockStatement
   │        └─ Statement
   │           └─ ...
   └─ ClassOrInterfaceBodyDeclaration
      └─ MethodDeclaration[ @Name = 'greet' ]
         ├─ ResultType
         ├─ MethodDeclarator[ @Image = 'greet' ]
         │  └─ FormalParameters
         │     └─ FormalParameter
         │        ├─ ...
         ├─ NameList
         │  └─ Name[ @Image = 'Exception' ]
         └─ Block
            └─ BlockStatement
               └─ Statement
                  └─ ...

└─ ClassBody
   ├─ ConstructorDeclaration[ @Name = 'Sample' ]
   │  ├─ ModifierList
   │  ├─ FormalParameters
   │  │  └─ FormalParameter
   │  │     ├─ ...
   │  ├─ ThrowsList
   │  │  └─ ClassType[ @SimpleName = 'Exception' ]
   │  └─ Block
   │     ├─ ExplicitConstructorInvocation
   │     │  └─ ArgumentList
   │     └─ ExpressionStatement
   │        └─ ...
   └─ MethodDeclaration[ @Name = 'greet' ]
      ├─ ModifierList
      ├─ VoidType
      ├─ FormalParameters
      │  └─ FormalParameter
      │     ├─ ...
      ├─ ThrowsList
      │  └─ ClassType[ @SimpleName = 'Exception' ]
      └─ Block
         └─ ExpressionStatement
            └─ ...

public @interface MyAnnotation {
    int value() default 1;
}

└─ AnnotationTypeDeclaration[ @SimpleName = 'MyAnnotation' ]
   └─ AnnotationTypeBody
      └─ AnnotationTypeMemberDeclaration
         └─ AnnotationMethodDeclaration[ @Image = 'value' ]
            ├─ Type ...
            └─ DefaultValue ...

└─ AnnotationTypeDeclaration[ @SimpleName = 'MyAnnotation' ]
   ├─ ModifierList
   └─ AnnotationTypeBody
      └─ MethodDeclaration[ @Name = 'value' ]
         ├─ ModifierList
         ├─ PrimitiveType
         ├─ FormalParameters
         └─ DefaultValue ...

Formal parameters

• What: Use ASTFormalParameter only for method and constructor declaration. Lambdas use ASTLambdaParameter, catch clauses use ASTCatchParameter.
• Why: FormalParameter’s API is different from the other ones.
  • FormalParameter must mention a type node.
  • LambdaParameter can be inferred
  • CatchParameter cannot be varargs
  • CatchParameter can have multiple exception types (a ASTUnionType now)

try {

} catch (@A IOException | IllegalArgumentException e) {

}

└─ TryStatement
   ├─ Block
   └─ CatchStatement
      ├─ FormalParameter
      │  ├─ Annotation[ @AnnotationName = 'A' ]
      │  │  └─ MarkerAnnotation[ @AnnotationName = 'A' ]
      │  │     └─ Name[ @Image = 'A' ]
      │  ├─ Type
      │  │  └─ ReferenceType
      │  │     └─ ClassOrInterfaceType[ @Image = 'IOException' ]
      │  ├─ Type
      │  │  └─ ReferenceType
      │  │     └─ ClassOrInterfaceType[ @Image = 'IllegalArgumentException' ]
      │  └─ VariableDeclaratorId[ @Name = 'e' ]
      └─ Block

└─ TryStatement
   ├─ Block
   └─ CatchClause
      ├─ CatchParameter
      │  ├─ ModifierList
      │  │  └─ Annotation[ @SimpleName = 'A' ]
      │  │     └─ ClassType[ @SimpleName = 'A' ]
      │  ├─ UnionType
      │  │  ├─ ClassType[ @SimpleName = 'IOException' ]
      │  │  └─ ClassType[ @SimpleName = 'IllegalArgumentException' ]
      │  └─ VariableId[ @Name = 'e' ]
      └─ Block

(a, b) -> {};
c -> {};
(@A var d) -> {};
(@A int e) -> {};

└─ StatementExpression
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ LambdaExpression
            ├─ VariableDeclaratorId[ @Name = 'a' ]
            ├─ VariableDeclaratorId[ @Name = 'b' ]
            └─ Block

└─ StatementExpression
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ LambdaExpression
            ├─ VariableDeclaratorId[ @Name = 'c' ]
            └─ Block

└─ StatementExpression
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ LambdaExpression
            ├─ FormalParameters
            │  └─ FormalParameter
            │     ├─ Annotation[ @AnnotationName = 'A' ]
            │     │  └─ MarkerAnnotation[ @AnnotationName = 'A' ]
            │     │     └─ Name[ @Image = 'A' ]
            │     └─ VariableDeclaratorId[ @Name = 'd' ]
            └─ Block

└─ StatementExpression
   └─ PrimaryExpression
      └─ PrimaryPrefix
         └─ LambdaExpression
            ├─ FormalParameters
            │  └─ FormalParameter
            │     ├─ Annotation[ @AnnotationName = 'A' ]
            │     │  └─ MarkerAnnotation[ @AnnotationName = 'A' ]
            │     │     └─ Name[ @Image = 'A' ]
            │     ├─ Type
            │     │  └─ PrimitiveType[ @Image = 'int' ]
            │     └─ VariableDeclaratorId[ @Name = 'e' ]
            └─ Block

└─ ExpressionStatement
   └─ LambdaExpression
      ├─ LambdaParameterList
      │  ├─ LambdaParameter
      │  │  ├─ ModifierList
      │  │  └─ VariableId[ @Name = 'a' ]
      │  └─ LambdaParameter
      │     ├─ ModifierList
      │     └─ VariableId[ @Name = 'b' ]
      └─ Block

└─ ExpressionStatement
   └─ LambdaExpression
      ├─ LambdaParameterList
      │  └─ LambdaParameter
      │     ├─ ModifierList
      │     └─ VariableId[ @Name = 'c' ]
      └─ Block

└─ ExpressionStatement
   └─ LambdaExpression
      ├─ LambdaParameterList
      │  └─ LambdaParameter
      │     ├─ ModifierList
      │     │  └─ Annotation[ @SimpleName = 'A' ]
      │     │     └─ ClassType[ @SimpleName = 'A' ]
      │     └─ VariableId[ @Name = 'd' ]
      └─ Block

└─ ExpressionStatement
   └─ LambdaExpression
      ├─ LambdaParameterList
      │  └─ LambdaParameter
      │     ├─ ModifierList
      │     │  └─ Annotation[ @SimpleName = 'A' ]
      │     │     └─ ClassType[ @SimpleName = 'A' ]
      │     ├─ PrimitiveType[ @Kind = 'int' ]
      │     └─ VariableId[ @Name = 'e' ]
      └─ Block

New node for explicit receiver parameter

• What: A separate node type ASTReceiverParameter is introduced to differentiate it from formal parameters.
• Why: A receiver parameter is not a formal parameter, even though it looks like one: it doesn’t declare a variable, and doesn’t affect the arity of the method or constructor. It’s so rarely used that giving it its own node avoids matching it by mistake and simplifies the API and grammar of the ubiquitous ASTFormalParameter and ASTVariableId.
• Related issue: [java] Separate receiver parameter from formal parameter (#1980)

void myMethod(@A Foo this, Foo other) {}

└─ FormalParameters (1)
   ├─ FormalParameter[ @ExplicitReceiverParameter = true() ]
   │  ├─ Annotation "A"
   │  │  └─ MarkerAnnotation "A"
   │  │     └─ Name "A"
   │  ├─ Type
   │  │  └─ ReferenceType
   │  │     └─ ClassOrInterfaceType "Foo"
   │  └─ VariableDeclaratorId[ @ExplicitReceiverParameter = true() ] "this"
   └─ FormalParameter
      ├─ Type
      │  └─ ReferenceType
      │     └─ ClassOrInterfaceType "Foo"
      └─ VariableDeclaratorId "other"

└─ FormalParameters (1)
   ├─ ReceiverParameter
   │  └─ ClassType "Foo"
   │     └─ Annotation "A"
   │        └─ ClassType "A"
   └─ FormalParameter
      ├─ ModifierList
      ├─ ClassType "Foo"
      └─ VariableId "other"

Varargs

• What: parse the varargs ellipsis as an ASTArrayType.
• Why: this improves regularity of the grammar, and allows type annotations to be added to the ellipsis

void myMethod(int... is) {}

└─ FormalParameter[ @Varargs = true() ]
   ├─ Type
   │  └─ PrimitiveType "int"
   └─ VariableDeclaratorId "is"

└─ FormalParameter[ @Varargs = true() ]
   ├─ ModifierList
   ├─ ArrayType
   │  ├─ PrimitiveType "int"
   │  └─ ArrayDimensions
   │     └─ ArrayTypeDim[ @Varargs = true() ]
   └─ VariableId "is"

void myMethod(int @A ... is) {}

└─ FormalParameter[ @Varargs = true() ]
   ├─ Type
   │  └─ PrimitiveType "int"
   ├─ Annotation "A"
   │  └─ MarkerAnnotation "A"
   │     └─ Name "A"
   └─ VariableDeclaratorId "is"

└─ FormalParameter[ @Varargs = true() ]
   ├─ ModifierList
   ├─ ArrayType
   │  ├─ PrimitiveType "int"
   │  └─ ArrayDimensions
   │     └─ ArrayTypeDim[ @Varargs = true() ]
   │        └─ Annotation "A"
   │           └─ ClassType "A"
   └─ VariableId "is"

void myMethod(int[]... is) {}

└─ FormalParameter[ @Varargs = true() ]
   ├─ Type[ @ArrayType = true() ]
   │  └─ ReferenceType
   │     └─ PrimitiveType "int"
   └─ VariableDeclaratorId "is"

└─ FormalParameter[ @Varargs = true() ]
   ├─ ModifierList
   ├─ ArrayType (2)
   │  ├─ PrimitiveType "int"
   │  └─ ArrayDimensions (2)
   │     ├─ ArrayTypeDim
   │     └─ ArrayTypeDim[ @Varargs = true() ]
   └─ VariableId "is"

Add void type node to replace ResultType

• What: Add a ASTVoidType node to replace ASTResultType.
• Why: This means we don’t need the ResultType wrapper when the method is not void, and the result type node is never null.
• Related issue: [java] Add void type node to replace ResultType (#2715)

void foo();

└─ MethodDeclaration "foo"
   ├─ ResultType[ @Void = true() ]
   └─ MethodDeclarator
      └─ FormalParameters

└─ MethodDeclaration "foo"
   ├─ ModifierList
   ├─ VoidType
   └─ FormalParameters

int foo();

└─ MethodDeclaration "foo"
   ├─ ResultType[ @Void = false() ]
   │  └─ Type
   │     └─ PrimitiveType "int"
   └─ MethodDeclarator
      └─ FormalParameters

└─ MethodDeclaration "foo"
   ├─ ModifierList
   ├─ PrimitiveType "int"
   └─ FormalParameters

Statements

Statements are flattened

• What: Statements are flattened. There are no superfluous BlockStatement and Statement nodes anymore. All children of a ASTBlock are by definition ASTStatements, which is now an interface implemented by all statements.
• Why: This simplifies the tree traversal. The removed nodes BlockStatement and Statement didn’t add any additional information. We only need a Statement abstraction. BlockStatement was used to enforce, that no variable or local class declaration is found alone as the child of e.g. an unbraced if, else, for, etc. This is a parser-only distinction that’s not that useful for analysis later on.
• Related issue: [java] Improve statement grammar (#2164)

int i;
i = 1;

└─ Block
   ├─ BlockStatement
   │  └─ LocalVariableDeclaration
   │     ├─ Type
   │     │  └─ PrimitiveType "int"
   │     └─ VariableDeclarator
   │        └─ VariableDeclaratorId "i"
   └─ BlockStatement
      └─ Statement
         └─ StatementExpression
            ├─ PrimaryExpression
            │  └─ PrimaryPrefix
            │     └─ Name "i"
            ├─ AssignmentOperator "="
            └─ Expression
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Literal "1"

└─ Block
   ├─ LocalVariableDeclaration
   │  ├─ ModifierList
   │  ├─ PrimitiveType "int"
   │  └─ VariableDeclarator
   │     └─ VariableId "i"
   └─ ExpressionStatement
      └─ AssignmentExpression "="
         ├─ VariableAccess "i"
         └─ NumericLiteral "1"

New node for For-each statements

• What: New node for For-each statements: ASTForeachStatement instead of ForStatement.
• Why: This makes it a lot easier to distinguish in the AST between For-loops and For-Each-loops. E.g. some rules only apply to one or the other, and it was complicated to write a rule that works with both different subtrees (for loops have additional children ForInit and ForUpdate)
• Related issue: [java] Improve statement grammar (#2164)

for (String s : List.of("a", "b")) { }

└─ BlockStatement
   └─ Statement
      └─ ForStatement[ @Foreach = true() ]
         ├─ LocalVariableDeclaration
         │  ├─ Type
         │  │  └─ ReferenceType
         │  │     └─ ClassOrInterfaceType "String"
         │  └─ VariableDeclarator
         │     └─ VariableDeclaratorId "s"
         ├─ Expression
         │  └─ PrimaryExpression
         │     ├─ PrimaryPrefix
         │     │  └─ Name "List.of"
         │     └─ PrimarySuffix
         │        └─ Arguments (2)
         │           └─ ArgumentList (2)
         │              ├─ Expression
         │              │  └─ PrimaryExpression
         │              │     └─ PrimaryPrefix
         │              │        └─ Literal[ @StringLiteral = true() ][ @Image = '"a"' ]
         │              └─ Expression
         │                 └─ PrimaryExpression
         │                    └─ PrimaryPrefix
         │                       └─ Literal[ @StringLiteral = true() ][ @Image = '"b"' ]
         └─ Statement
            └─ Block

└─ Block
   └─ ForeachStatement
      ├─ LocalVariableDeclaration
      │  ├─ ModifierList
      │  ├─ ClassType "String"
      │  └─ VariableDeclarator "s"
      │     └─ VariableId "s"
      ├─ MethodCall "of"
      │  ├─ TypeExpression
      │  │  └─ ClassType "List"
      │  └─ ArgumentList (2)
      │     ├─ StringLiteral[ @Image = '"a"' ]
      │     └─ StringLiteral[ @Image = '"b"' ]
      └─ Block

New nodes for ExpressionStatement, LocalClassStatement

• What: Renamed StatementExpression to ASTExpressionStatement. Added new node ASTLocalClassStatement.
• Why: ExpressionStatement is now a ASTStatement, that can be used as a child in a block. It itself has only one child, which is some kind of ASTExpression, which can be really any kind of expression (like assignment). In order to allow local class declarations as part of a block, we introduced ASTLocalClassStatement which is a statement that carries a type declaration. Now blocks are just a list of statements. This allows us to have two distinct hierarchies for expressions and statements.
• Related issue: [java] Improve statement grammar (#2164)

i++;
class LocalClass {}

└─ Block
   ├─ BlockStatement
   │  └─ Statement
   │     └─ StatementExpression
   │        └─ PostfixExpression "++"
   │           └─ PrimaryExpression
   │              └─ PrimaryPrefix
   │                 └─ Name "i"
   └─ BlockStatement
      └─ ClassOrInterfaceDeclaration[ @Local = true() ] "LocalClass"
         └─ ClassOrInterfaceBody

└─ Block
   ├─ ExpressionStatement
   │  └─ UnaryExpression "++"
   │     └─ VariableAccess "i"
   └─ LocalClassStatement
      └─ ClassDeclaration "LocalClass"
         ├─ ModifierList
         └─ ClassBody

Improve try-with-resources grammar

• What: The AST representation of a try-with-resources statement has been simplified. It uses now ASTLocalVariableDeclaration unless it is a concise try-with-resources.
• Why: Simpler integration try-with-resources into symboltable and type resolution.
• Related issue: [java] Improve try-with-resources grammar (#1897)

try (InputStream in = new FileInputStream(); OutputStream out = new FileOutputStream();) { }

└─ TryStatement
   └─ ResourceSpecification
      └─ Resources
         ├─ Resource
         │  ├─ Type
         │  │  └─ ReferenceType
         │  │     └─ ClassOrInterfaceType "InputStream"
         │  ├─ VariableDeclaratorId "in"
         │  └─ Expression
         │     └─ ...
         └─ Resource
            ├─ Type
            │  └─ ReferenceType
            │     └─ ClassOrInterfaceType "OutputStream"
            ├─ VariableDeclaratorId "out"
            └─ Expression
               └─ ...

└─ TryStatement
   └─ ResourceList[ @TrailingSemiColon = true() ] (2)
      ├─ Resource[ @ConciseResource = false() ] "in"
      │  └─ LocalVariableDeclaration
      │     ├─ ModifierList
      │     ├─ ClassType "InputStream"
      │     └─ VariableDeclarator
      │        ├─ VariableId "in"
      │        └─ ConstructorCall
      │           ├─ ClassType "FileInputStream"
      │           └─ ArgumentList (0)
      └─ Resource[ @ConciseResource = false() ] "out"
         └─ LocalVariableDeclaration
            ├─ ModifierList
            ├─ ClassType "OutputStream"
            └─ VariableDeclarator
               ├─ VariableId "out"
               └─ ConstructorCall
                  ├─ ClassType "FileOutputStream"
                  └─ ArgumentList (0)

InputStream in = new FileInputStream();
try (in) {}

└─ TryStatement
   └─ ResourceSpecification
      └─ Resources
         └─ Resource "in"
            └─ Name "in"

└─ TryStatement
   └─ ResourceList[ @TrailingSemiColon = false() ] (1)
      └─ Resource[ @ConciseResource = true() ] "in"
         └─ VariableAccess "in"

Expressions

• ASTExpression and ASTPrimaryExpression have been turned into interfaces. These added no information to the AST and increased its depth unnecessarily. All expressions implement the first interface. Both of those nodes can no more be found in ASTs.

• Migrating:

  • Basically, Expression/X or Expression/PrimaryExpression/X, just becomes X
  • There is currently no way to match abstract or interface types with XPath, so Expression or PrimaryExpression name tests won’t match anything anymore. However, the axis step *[@Expression=true()] matches any expression.

New nodes for different literals types

• What:
  • ASTLiteral has been turned into an interface.
  • ASTNumericLiteral, ASTCharLiteral, ASTStringLiteral, and ASTClassLiteral are new nodes that implement that interface.
  • ASTLiteral implements ASTPrimaryExpression
• Why: The fact that ASTNullLiteral and ASTBooleanLiteral were nested within it but other literals types were all directly represented by it was inconsistent, and ultimately that level of nesting was unnecessary.
• Related issue: [java] New expression and type grammar (#1759)
• Migrating:
  • Remove all /Literal/ segments from your XPath expressions
  • If you tested several types of literals, you can e.g. do it like /*[self::StringLiteral or self::CharLiteral]/
  • As usual, use the designer to explore the new AST structure

char c = 'c';
boolean b = true;
int i = 1;
double d = 1.0;
String s = "s";
Object n = null;

└─ Literal[ @CharLiteral = true() ] "'c'"
└─ Literal
   └─ BooleanLiteral[ @True = true() ]
└─ Literal[ @IntLiteral = true() ] "1"
└─ Literal[ @DoubleLiteral = true() ] "1.0"
└─ Literal[ @StringLiteral = true() ] "\"s\""
└─ Literal
   └─ NullLiteral

└─ CharLiteral "'c'"
└─ BooleanLiteral[ @True = true() ]
└─ NumericLiteral[ @IntLiteral = true() ] "1"
└─ NumericLiteral[ @DoubleLiteral = true() ] "1.0"
└─ StringLiteral "\"s\""
└─ NullLiteral

Method calls, constructor calls, array allocations

• What: Extra nodes dedicated for method and constructor calls and array allocations
  • ASTConstructorCall
  • ASTMethodCall
  • ASTArrayAllocation
• Why: It was extremely difficult to identify method calls in PMD 6 - these consisted of multiple nodes with primary prefix, suffix and expressions. This was too low level to be easy to be used.
• Related issue: [java] New expression and type grammar (#1759)

o.myMethod("a");
new Object("b");
new int[10];
new int[] { 1, 2, 3 };

└─ PrimaryExpression
   ├─ PrimaryPrefix
   │  └─ Name "o.myMethod"
   └─ PrimarySuffix
      └─ Arguments
         └─ ArgumentList (1)
            └─ Expression
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Literal "\"a\""

└─ PrimaryExpression
   └─ PrimaryPrefix
      └─ AllocationExpression
         ├─ ClassOrInterfaceType "Object"
         └─ Arguments
            └─ ArgumentList
               └─ Expression
                  └─ PrimaryExpression
                     └─ PrimaryPrefix
                        └─ Literal "\"b\""

└─ PrimaryExpression
   └─ PrimaryPrefix
      └─ AllocationExpression
         ├─ PrimitiveType "int"
         └─ ArrayDimsAndInits
            └─ Expression
               └─ PrimaryExpression
                  └─ PrimaryPrefix
                     └─ Literal "10"

└─ PrimaryPrefix
   └─ AllocationExpression
      ├─ PrimitiveType "int"
      └─ ArrayDimsAndInits
         └─ ArrayInitializer
            ├─ VariableInitializer
            │  └─ Expression
            │     └─ PrimaryExpression
            │        └─ PrimaryPrefix
            │           └─ Literal "1"
            ├─ VariableInitializer
            │  └─ Expression
            │     └─ PrimaryExpression
            │        └─ PrimaryPrefix
            │           └─ Literal "2"
            └─ VariableInitializer
               └─ Expression
                  └─ PrimaryExpression
                     └─ PrimaryPrefix
                        └─ Literal "3"

└─ MethodCall "myMethod"
   ├─ VariableAccess "o"
   └─ ArgumentList (1)
      └─ StringLiteral "\"a\""

└─ ConstructorCall
   ├─ ClassType "Object"
   └─ ArgumentList (1)
      └─ StringLiteral "\"b\""

└─ ArrayAllocation[ @ArrayDepth = 1 ]
   └─ ArrayType
      ├─ PrimitiveType "int"
      └─ ArrayDimensions (1)
         └─ ArrayDimExpr
            └─ NumericLiteral "10"

└─ ArrayAllocation[ @ArrayDepth = 1 ]
   ├─ ArrayType
   │  ├─ PrimitiveType "int"
   │  └─ ArrayDimensions (1)
   │     └─ ArrayTypeDim
   └─ ArrayInitializer[ @Length = 3 ]
      ├─ NumericLiteral "1"
      ├─ NumericLiteral "2"
      └─ NumericLiteral "3"

Method call chains are left-recursive

• What: The nodes ASTPrimaryPrefix and ASTPrimarySuffix are removed from the grammar. Subtrees for primary expressions appear to be left-recursive now.
• Why: Allows to reuse abstractions like method calls without introducing a new artificial node (like method chain).
• Related issue: [java] New expression and type grammar (#1759)