Java 25: Compact source files

rewrite-java-25/src/main/java/org/openrewrite/java/isolated/ReloadableJava25ParserVisitor.java

@@ -21,6 +21,7 @@
 import com.sun.source.util.TreePathScanner;
 import com.sun.tools.javac.code.Flags;
 import com.sun.tools.javac.code.Symbol;
+import com.sun.tools.javac.code.Symtab;
 import com.sun.tools.javac.tree.DocCommentTable;
 import com.sun.tools.javac.tree.EndPosTable;
 import com.sun.tools.javac.tree.JCTree;
@@ -37,10 +38,9 @@
 import org.openrewrite.java.JavaParsingException;
 import org.openrewrite.java.JavaPrinter;
 import org.openrewrite.java.internal.JavaTypeCache;
-import org.openrewrite.java.marker.CompactConstructor;
-import org.openrewrite.java.marker.OmitParentheses;
-import org.openrewrite.java.marker.TrailingComma;
+import org.openrewrite.java.marker.*;
 import org.openrewrite.java.tree.*;
+import org.openrewrite.marker.Marker;
 import org.openrewrite.marker.Markers;
 import org.openrewrite.style.NamedStyles;
 
@@ -397,9 +397,11 @@ public J visitClass(ClassTree node, Space fmt) {
         Map<Integer, JCAnnotation> annotationPosTable = mapAnnotations(node.getModifiers().getAnnotations(),
                 new HashMap<>(node.getModifiers().getAnnotations().size()));
 
+        int saveCursor = cursor;
         ReloadableJava25ModifierResults modifierResults = sortedModifiersAndAnnotations(node.getModifiers(), annotationPosTable);
 
         List<J.Annotation> kindAnnotations = collectAnnotations(annotationPosTable);
+        CompactSourceFile compactSourceFile = null;
 
         J.ClassDeclaration.Kind kind;
         if (hasFlag(node.getModifiers(), Flags.ENUM)) {
@@ -412,10 +414,17 @@ public J visitClass(ClassTree node, Space fmt) {
         } else if (hasFlag(node.getModifiers(), Flags.RECORD)) {
             kind = new J.ClassDeclaration.Kind(randomId(), sourceBefore("record"), Markers.EMPTY, kindAnnotations, J.ClassDeclaration.Kind.Type.Record);
         } else {
-            kind = new J.ClassDeclaration.Kind(randomId(), sourceBefore("class"), Markers.EMPTY, kindAnnotations, J.ClassDeclaration.Kind.Type.Class);
+            Space prefix = whitespace();
+            if (source.startsWith("class", cursor)) {
+                skip("class");
+            } else {
+                compactSourceFile = new CompactSourceFile(randomId());
+                cursor = saveCursor;
+            }
+            kind = new J.ClassDeclaration.Kind(randomId(), prefix, Markers.EMPTY, kindAnnotations, J.ClassDeclaration.Kind.Type.Class);
         }
 
-        J.Identifier name = new J.Identifier(randomId(), sourceBefore(node.getSimpleName().toString()),
+        J.Identifier name = new J.Identifier(randomId(), compactSourceFile != null ? EMPTY : sourceBefore(node.getSimpleName().toString()),
                 Markers.EMPTY, emptyList(), ((JCClassDecl) node).getSimpleName().toString(), typeMapping.type(node), null);
 
         JContainer<J.TypeParameter> typeParams = node.getTypeParameters().isEmpty() ? null : JContainer.build(
@@ -498,7 +507,7 @@ public J visitClass(ClassTree node, Space fmt) {
             );
         }
 
-        Space bodyPrefix = sourceBefore("{");
+        Space bodyPrefix = compactSourceFile != null ? whitespace() : sourceBefore("{");
 
         // enum values are required by the grammar to occur before any ordinary field, constructor, or method members
         List<Tree> jcEnums = new ArrayList<>(node.getMembers().size());
@@ -587,10 +596,13 @@ public J visitClass(ClassTree node, Space fmt) {
         members.addAll(convertStatements(membersMultiVariablesSeparated));
         addPossibleEmptyStatementsBeforeClosingBrace(members);
 
-        J.Block body = new J.Block(randomId(), bodyPrefix, Markers.EMPTY, new JRightPadded<>(false, EMPTY, Markers.EMPTY),
-                members, sourceBefore("}"));
+        J.Block body = new J.Block(randomId(), bodyPrefix, compactSourceFile != null ? Markers.build(List.of(new OmitBraces(randomId()))) : Markers.EMPTY,
+                new JRightPadded<>(false, EMPTY, Markers.EMPTY),
+                members,
+                compactSourceFile != null ? whitespace() : sourceBefore("}"));
 
-        return new J.ClassDeclaration(randomId(), fmt, Markers.EMPTY, modifierResults.getLeadingAnnotations(), modifierResults.getModifiers(), kind, name, typeParams,
+        return new J.ClassDeclaration(randomId(), fmt, compactSourceFile != null ? Markers.build(List.of(compactSourceFile)) : Markers.EMPTY,
+                modifierResults.getLeadingAnnotations(), modifierResults.getModifiers(), kind, name, typeParams,
                 primaryConstructor, extendings, implementings, permitting, body, (JavaType.FullyQualified) typeMapping.type(node));
     }
 
@@ -611,17 +623,21 @@ public J visitCompilationUnit(CompilationUnitTree node, Space fmt) {
         Map<Integer, JCAnnotation> annotationPosTable = mapAnnotations(node.getPackageAnnotations(),
                 new HashMap<>(node.getPackageAnnotations().size()));
         List<J.Annotation> packageAnnotations = collectAnnotations(annotationPosTable);
+        List<Marker> markers = new ArrayList<>(styles);
 
         J.Package packageDecl = null;
         if (cu.getPackageName() != null) {
-            Space packagePrefix = sourceBefore("package");
-            packageDecl = new J.Package(randomId(), packagePrefix, Markers.EMPTY,
+            packageDecl = new J.Package(randomId(), sourceBefore("package"), Markers.EMPTY,
                     convert(cu.getPackageName()), packageAnnotations);
+        } else if (cu.getPackageName() == null &&
+                   cu.modle.equals(Symtab.instance(context).unnamedModule) &&
+                   cu.packge.equals(Symtab.instance(context).unnamedModule.unnamedPackage)) {
+            int saveCursor = cursor;
         }
         return new J.CompilationUnit(
                 randomId(),
                 fmt,
-                Markers.build(styles),
+                Markers.build(markers),
                 sourcePath,
                 fileAttributes,
                 charset.name(),

rewrite-java-tck/src/main/java/org/openrewrite/java/tree/ClassDeclarationTest.java

@@ -16,12 +16,14 @@
 package org.openrewrite.java.tree;
 
 import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.openrewrite.Issue;
 import org.openrewrite.java.JavaIsoVisitor;
 import org.openrewrite.java.MinimumJava17;
+import org.openrewrite.java.MinimumJava25;
 import org.openrewrite.test.RewriteTest;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -276,4 +278,134 @@ class A {
           )
         );
     }
+
+    @Issue("https://openjdk.org/jeps/512")
+    @MinimumJava25
+    @Nested
+    class ImplicitClasses implements RewriteTest {
+
+        @Test
+        void implicitClassWithMainMethod() {
+            rewriteRun(
+              java(
+                """
+                  void main() {
+                      System.out.println("Hello from implicit class!");
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassWithAbundantSpacing() {
+            rewriteRun(
+              java(
+                """
+
+                  void main() {
+
+                      System.out.println("Hello from implicit class!");
+
+                  }
+
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassWithMultipleMethods() {
+            rewriteRun(
+              java(
+                """
+                  void main() {
+                      greet("World");
+                  }
+
+                  void greet(String name) {
+                      System.out.println("Hello, " + name + "!");
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassWithFields() {
+            rewriteRun(
+              java(
+                """
+                  String greeting = "Hello";
+
+                  void main() {
+                      System.out.println(greeting + ", World!");
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassUtilizingJavaBase() {
+            rewriteRun(
+              java(
+                """
+                  void main() {
+                      List<String> names = new ArrayList<>();
+                      names.add("Alice");
+                      names.add("Bob");
+                      System.out.println(names);
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassWithConstructor() {
+            rewriteRun(
+              java(
+                """
+                  private String name;
+
+                  Main(String name) {
+                      this.name = name;
+                  }
+
+                  void main() {
+                      System.out.println("Name: " + name);
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+
+        @Test
+        void implicitClassWithInnerClass() {
+            rewriteRun(
+              java(
+                """
+                  void main() {
+                      Helper helper = new Helper();
+                      helper.help();
+                  }
+
+                  class Helper {
+                      void help() {
+                          System.out.println("Helping!");
+                      }
+                  }
+                  """,
+                spec -> spec.path("com/example/Main.java")
+              )
+            );
+        }
+    }
 }

rewrite-java-tck/src/main/java/org/openrewrite/java/tree/MethodDeclarationTest.java

@@ -15,7 +15,10 @@
  */
 package org.openrewrite.java.tree;
 
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
+import org.openrewrite.Issue;
+import org.openrewrite.java.MinimumJava25;
 import org.openrewrite.test.RewriteTest;
 
 import static org.openrewrite.java.Assertions.java;
@@ -116,4 +119,91 @@ public void foo() { }/*Comments*/
         );
     }
 
+    @Issue("https://openjdk.org/jeps/512")
+    @MinimumJava25
+    @Nested
+    class InstanceMainMethods implements RewriteTest {
+
+        @Test
+        void instanceMainMethodWithNoParameters() {
+            rewriteRun(
+              java(
+                """
+                  class HelloWorld {
+                      void main() {
+                          System.out.println("Hello, World!");
+                      }
+                  }
+                  """
+              )
+            );
+        }
+
+        @Test
+        void instanceMainMethodWithStringArrayParameter() {
+            rewriteRun(
+              java(
+                """
+                  class HelloWorld {
+                      void main(String[] args) {
+                          System.out.println("Hello, World!");
+                      }
+                  }
+                  """
+              )
+            );
+        }
+
+        @Test
+        void instanceMainMethodWithInstanceFields() {
+            rewriteRun(
+              java(
+                """
+                  class Counter {
+                      private int count = 0;
+
+                      void main() {
+                          count++;
+                          System.out.println("Count: " + count);
+                      }
+                  }
+                  """
+              )
+            );
+        }
+
+        @Test
+        void instanceMainMethodCallingInstanceMethods() {
+            rewriteRun(
+              java(
+                """
+                  class Greeter {
+                      void main() {
+                          greet("World");
+                      }
+
+                      void greet(String name) {
+                          System.out.println("Hello, " + name + "!");
+                      }
+                  }
+                  """
+              )
+            );
+        }
+
+        @Test
+        void staticMainMethodStillSupported() {
+            rewriteRun(
+              java(
+                """
+                  class TraditionalMain {
+                      public static void main(String[] args) {
+                          System.out.println("Traditional main method");
+                      }
+                  }
+                  """
+              )
+            );
+        }
+    }
 }