[java] Add Java12 support

pmd-java/etc/grammar/Java.jjt

@@ -383,6 +383,15 @@ public class JavaParser {
       throwParseException("Multiple case labels in switch statements are only supported with Java 12");
     }
   }
+  /**
+   * Keeps track during tree construction, whether we are currently building a switch label.
+   * A switch label must not contain a LambdaExpression.
+   * Unfortunately, we have added LambdaExpression as part of PrimaryPrefix, which is wrong.
+   * To keep compatibility, this flag is used, whether a LambdaExpression should be parsed
+   * in PrimaryPrefix.
+   * See also comment at #Expression().
+   */
+  private boolean inSwitchLabel = false;
   private void checkForSwitchRules() {
     if (jdkVersion < 12) {
       throwParseException("Switch rules in switch statements are only supported with Java 12");
@@ -424,6 +433,26 @@ public class JavaParser {
     return getToken(1).kind == IDENTIFIER && getToken(1).image.equals(keyword);
   }
 
+  /**
+   * Semantic lookahead needed to distinguish between switch rules
+   * and switch statement. Using the syntactic lookahead for SwitchLabel()
+   * does not work, during lookahead the javacode is not executed, so
+   * that "->" is already consumed as a LambdaExpression, when it is actually
+   * part of the switch rule. See also #inSwitchLabel.
+   */
+  private boolean switchLabeledRuleLookahead(int maxTokens) {
+    int pos = 0;
+
+    while (pos < maxTokens) {
+        Token token = getToken(pos);
+        pos++;
+
+        if (token.kind == COLON) return false;
+        if (token.kind == LAMBDA) return true;
+    }
+    return false;
+  }
+
   public Map<Integer, String> getSuppressMap() {
     return token_source.getSuppressMap();
   }
@@ -2019,16 +2048,15 @@ void Expression() :
  // separated from the AssignmentExpression production. Their use is restricted
  // to method and constructor argument, cast operand, and the RHS of assignments.
  // https://docs.oracle.com/javase/specs/jls/se9/html/jls-15.html#jls-15.27
+ //
+ // To prevent LambdaExpressions in switch labels, the field #inSwitchLabel is used
+ // as a workaround.
 {}
 {
-  LOOKAHEAD((<IDENTIFIER>|LambdaParameters()) "->" ) LambdaExpression()
-  |
-  (
   ConditionalExpression()
   [
     LOOKAHEAD(2) AssignmentOperator() Expression()
   ]
-  )
 }
 
 void AssignmentOperator() :
@@ -2188,7 +2216,7 @@ void SwitchExpression() :
 {}
 {
     {checkForSwitchExpression();}
-    "switch" "(" Expression() ")" "{" SwitchBlock() "}"
+    "switch" "(" Expression() ")" SwitchBlock()
 }
 
 void PrimaryExpression() :
@@ -2218,9 +2246,9 @@ void PrimaryPrefix() :
   Literal()
 | LOOKAHEAD(2) "this" {jjtThis.setUsesThisModifier();}
 | "super" {jjtThis.setUsesSuperModifier();}
-//| LOOKAHEAD( <IDENTIFIER> "->" ) LambdaExpression()
+| LOOKAHEAD( <IDENTIFIER> "->", {!inSwitchLabel} ) LambdaExpression()
-//| LOOKAHEAD( "(" VariableDeclaratorId() ( "," VariableDeclaratorId() )* ")" "->" ) LambdaExpression()
+| LOOKAHEAD( "(" VariableDeclaratorId() ( "," VariableDeclaratorId() )* ")" "->", {!inSwitchLabel} ) LambdaExpression()
-//| LOOKAHEAD( FormalParameters() "->" ) LambdaExpression()
+| LOOKAHEAD( FormalParameters() "->", {!inSwitchLabel} ) LambdaExpression()
 | LOOKAHEAD(3) "(" Expression() ")"
 | AllocationExpression()
 | LOOKAHEAD( ResultType() "." "class" ) ResultType() "." "class"
@@ -2445,41 +2473,37 @@ void StatementExpression() :
 void SwitchStatement():
 {}
 {
-  "switch" "(" Expression() ")" "{"
+  "switch" "(" Expression() ")" SwitchBlock()
-      SwitchBlock()
-  "}"
 }
 
 void SwitchBlock() #void :
 {}
 {
+    "{"
         (
-    SwitchLabel()
+            LOOKAHEAD( { switchLabeledRuleLookahead(10) } ) ( SwitchLabeledRule() )+
-    (
-        "->" ( Expression() ";" | Block() | ThrowStatement() )
         |
-        ":" (SwitchLabel() ":")* ( BlockStatement() )*
+            (LOOKAHEAD(3) SwitchLabeledStatementGroup() )* (SwitchLabel() ":")*
         )
-)*
+    "}"
-/*
-    LOOKAHEAD(SwitchLabel() "->") SwitchLabeledRule() ( SwitchLabeledRule() )*
-    |
-    ( SwitchLabeledStatementGroup() )*
-*/
 }
 
 void SwitchLabeledStatementGroup() #void:
 {}
 {
-    SwitchLabel() ":" (SwitchLabel() ":")* ( BlockStatement() )*
+    (SwitchLabel() ":")+ ( BlockStatement() )+
 }
 
 void SwitchLabel() :
 {}
 {
-  "case" ConditionalExpression() ({checkForMultipleCaseLabels();} "," ConditionalExpression())*
+{ inSwitchLabel = true; }
+(
+  "case" ( ConditionalExpression() #Expression ) ({checkForMultipleCaseLabels();} "," ( ConditionalExpression() #Expression ) )*
 |
   "default" {jjtThis.setDefault();}
+)
+{ inSwitchLabel = false; }
 }
 
 void SwitchLabeledRule():

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTSwitchExpression.java

@@ -1,9 +1,13 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
 /* Generated By:JJTree: Do not edit this line. ASTSwitchLabeledRule.java Version 4.3 */
 /* JavaCCOptions:MULTI=true,NODE_USES_PARSER=true,VISITOR=true,TRACK_TOKENS=true,NODE_PREFIX=AST,NODE_EXTENDS=,NODE_FACTORY=,SUPPORT_CLASS_VISIBILITY_PUBLIC=true */
+
 package net.sourceforge.pmd.lang.java.ast;
 
-public
+public class ASTSwitchExpression extends AbstractJavaNode {
-class ASTSwitchExpression extends AbstractJavaNode {
     ASTSwitchExpression(int id) {
         super(id);
     }
@@ -12,8 +16,7 @@ class ASTSwitchExpression extends AbstractJavaNode {
         super(p, id);
     }
 
-
+    @Override
-  /** Accept the visitor. **/
     public Object jjtAccept(JavaParserVisitor visitor, Object data) {
         return visitor.visit(this, data);
     }

pmd-java/src/main/java/net/sourceforge/pmd/lang/java/ast/ASTSwitchLabeledRule.java

@@ -1,9 +1,13 @@
+/**
+ * BSD-style license; for more info see http://pmd.sourceforge.net/license.html
+ */
+
 /* Generated By:JJTree: Do not edit this line. ASTSwitchLabeledRule.java Version 4.3 */
 /* JavaCCOptions:MULTI=true,NODE_USES_PARSER=true,VISITOR=true,TRACK_TOKENS=true,NODE_PREFIX=AST,NODE_EXTENDS=,NODE_FACTORY=,SUPPORT_CLASS_VISIBILITY_PUBLIC=true */
+
 package net.sourceforge.pmd.lang.java.ast;
 
-public
+public class ASTSwitchLabeledRule extends AbstractJavaNode {
-class ASTSwitchLabeledRule extends AbstractJavaNode {
     ASTSwitchLabeledRule(int id) {
         super(id);
     }
@@ -12,8 +16,7 @@ class ASTSwitchLabeledRule extends AbstractJavaNode {
         super(p, id);
     }
 
-
+    @Override
-  /** Accept the visitor. **/
     public Object jjtAccept(JavaParserVisitor visitor, Object data) {
         return visitor.visit(this, data);
     }

pmd-java/src/test/java/net/sourceforge/pmd/LanguageVersionDiscovererTest.java

@@ -26,8 +26,8 @@ public class LanguageVersionDiscovererTest {
         File javaFile = new File("/path/to/MyClass.java");
 
         LanguageVersion languageVersion = discoverer.getDefaultLanguageVersionForFile(javaFile);
-        assertEquals("LanguageVersion must be Java 11 !",
+        assertEquals("LanguageVersion must be Java 12 !",
-                LanguageRegistry.getLanguage(JavaLanguageModule.NAME).getVersion("11"), languageVersion);
+                LanguageRegistry.getLanguage(JavaLanguageModule.NAME).getVersion("12"), languageVersion);
     }
 
     /**
@@ -48,7 +48,7 @@ public class LanguageVersionDiscovererTest {
     public void testLanguageVersionDiscoverer() {
         PMDConfiguration configuration = new PMDConfiguration();
         LanguageVersionDiscoverer languageVersionDiscoverer = configuration.getLanguageVersionDiscoverer();
-        assertEquals("Default Java version", LanguageRegistry.getLanguage(JavaLanguageModule.NAME).getVersion("11"),
+        assertEquals("Default Java version", LanguageRegistry.getLanguage(JavaLanguageModule.NAME).getVersion("12"),
                 languageVersionDiscoverer
                         .getDefaultLanguageVersion(LanguageRegistry.getLanguage(JavaLanguageModule.NAME)));
         configuration

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/Java12Test.java

@@ -34,6 +34,11 @@ public class Java12Test {
         ASTCompilationUnit compilationUnit = ParserTstUtil.parseAndTypeResolveJava("12",
                 loadSource("MultipleCaseLabels.java"));
         Assert.assertNotNull(compilationUnit);
+        ASTSwitchStatement switchStatement = compilationUnit.getFirstDescendantOfType(ASTSwitchStatement.class);
+        Assert.assertTrue(switchStatement.jjtGetChild(0) instanceof ASTExpression);
+        Assert.assertTrue(switchStatement.jjtGetChild(1) instanceof ASTSwitchLabel);
+        ASTSwitchLabel switchLabel = switchStatement.getFirstChildOfType(ASTSwitchLabel.class);
+        Assert.assertEquals(3, switchLabel.findChildrenOfType(ASTExpression.class).size());
     }
 
     @Test(expected = ParseException.class)
@@ -46,6 +51,23 @@ public class Java12Test {
         ASTCompilationUnit compilationUnit = ParserTstUtil.parseAndTypeResolveJava("12",
                 loadSource("SwitchRules.java"));
         Assert.assertNotNull(compilationUnit);
+        ASTSwitchStatement switchStatement = compilationUnit.getFirstDescendantOfType(ASTSwitchStatement.class);
+        Assert.assertTrue(switchStatement.jjtGetChild(0) instanceof ASTExpression);
+        Assert.assertTrue(switchStatement.jjtGetChild(1) instanceof ASTSwitchLabeledRule);
+        ASTSwitchLabeledRule switchLabeledRule = (ASTSwitchLabeledRule) switchStatement.jjtGetChild(1);
+        Assert.assertEquals(2, switchLabeledRule.jjtGetNumChildren());
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(0) instanceof ASTSwitchLabel);
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(1) instanceof ASTExpression);
+
+        switchLabeledRule = (ASTSwitchLabeledRule) switchStatement.jjtGetChild(4);
+        Assert.assertEquals(2, switchLabeledRule.jjtGetNumChildren());
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(0) instanceof ASTSwitchLabel);
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(1) instanceof ASTBlock);
+
+        switchLabeledRule = (ASTSwitchLabeledRule) switchStatement.jjtGetChild(5);
+        Assert.assertEquals(2, switchLabeledRule.jjtGetNumChildren());
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(0) instanceof ASTSwitchLabel);
+        Assert.assertTrue(switchLabeledRule.jjtGetChild(1) instanceof ASTThrowStatement);
     }
 
     @Test(expected = ParseException.class)
@@ -58,6 +80,11 @@ public class Java12Test {
         ASTCompilationUnit compilationUnit = ParserTstUtil.parseAndTypeResolveJava("12",
                 loadSource("SwitchExpressions.java"));
         Assert.assertNotNull(compilationUnit);
+
+        ASTSwitchExpression switchExpression = compilationUnit.getFirstDescendantOfType(ASTSwitchExpression.class);
+        Assert.assertEquals(6, switchExpression.jjtGetNumChildren());
+        Assert.assertTrue(switchExpression.jjtGetChild(0) instanceof ASTExpression);
+        Assert.assertEquals(5, switchExpression.findChildrenOfType(ASTSwitchLabeledRule.class).size());
     }
 
 }

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/jdkversiontests/java12/SwitchRules.java

@@ -14,7 +14,8 @@ public class SwitchRules {
           case MONDAY, FRIDAY, SUNDAY -> System.out.println("  6");
           case TUESDAY                -> System.out.println("  7");
           case THURSDAY, SATURDAY     -> System.out.println("  8");
-          case WEDNESDAY              -> System.out.println("  9");
+          case WEDNESDAY              -> { System.out.println("  9"); }
+          default                     -> throw new IllegalArgumentException();
         }
     }
 }