Fix #3697 - lookahead error in concise resource spec

docs/pages/release_notes.md

@@ -16,6 +16,9 @@ This is a {{ site.pmd.release_type }} release.
 
 ### Fixed Issues
 
+*   java
+    *   [#3698](https://github.com/pmd/pmd/issues/3697): \[java] Parsing error with try-with-resources and qualified resource
+
 ### API Changes
 
 ### External Contributions

pmd-java/etc/grammar/Java.jjt

@@ -2406,9 +2406,15 @@ void Resources() :
 void Resource() :
 {}
 {
-   LOOKAHEAD(2) ( ( "final" {jjtThis.setFinal(true);} | Annotation() )* LocalVariableType() VariableDeclaratorId() "=" Expression() )
-   |
-   Name() {checkForBadConciseTryWithResourcesUsage();}
+   LOOKAHEAD("this" | Name() ")") (
+       {checkForBadConciseTryWithResourcesUsage();}
+       Name()
+       // replaced with Expression in PMD 7, do the bare minimum
+       | "this" "." Name() // possible pmd6 improvement: add a isThisModifier() or so
+   )
+   | ( "final" {jjtThis.setFinal(true);} | Annotation() )*
+     LocalVariableType() VariableDeclaratorId() "=" Expression()
+
 }
 
 void CatchStatement() :

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

@@ -25,6 +25,7 @@ public class ParserCornersTest {
     private static final String MULTICATCH = "public class Foo { public void bar() { "
         + "try { System.out.println(); } catch (RuntimeException | IOException e) {} } }";
     private final JavaParsingHelper java = JavaParsingHelper.WITH_PROCESSING.withResourceContext(ParserCornersTest.class);
+    private final JavaParsingHelper java9 = java.withDefaultVersion("9");
     private final JavaParsingHelper java8 = java.withDefaultVersion("1.8");
     private final JavaParsingHelper java4 = java.withDefaultVersion("1.4");
     private final JavaParsingHelper java5 = java.withDefaultVersion("1.5");
@@ -90,6 +91,33 @@ public class ParserCornersTest {
         java4.parse(CAST_LOOKAHEAD_PROBLEM);
     }
 
+    @Test
+    public final void testTryWithResourcesConcise() {
+        // https://github.com/pmd/pmd/issues/3697
+        java9.parse("import java.io.InputStream;\n"
+                        + "public class Foo {\n"
+                        + "    public InputStream in;\n"
+                        + "    public void bar() {\n"
+                        + "        Foo f = this;\n"
+                        + "        try (f.in) {\n"
+                        + "        }\n"
+                        + "    }\n"
+                        + "}");
+    }
+
+    @Test
+    public final void testTryWithResourcesThis() {
+        // https://github.com/pmd/pmd/issues/3697
+        java9.parse("import java.io.InputStream;\n"
+                        + "public class Foo {\n"
+                        + "    public InputStream in;\n"
+                        + "    public void bar() {\n"
+                        + "        try (this.in) {\n"
+                        + "        }\n"
+                        + "    }\n"
+                        + "}");
+    }
+
     /**
      * Tests a specific generic notation for calling methods. See:
      * https://jira.codehaus.org/browse/MPMD-139