Initial support for pattern matching in switches

Fixes google/google-java-format#937, google/google-java-format#880

PiperOrigin-RevId: 589140113

core/src/main/java/com/google/googlejavaformat/java/java21/Java21InputAstVisitor.java

@@ -17,7 +17,12 @@
 import com.google.googlejavaformat.OpsBuilder;
 import com.google.googlejavaformat.java.java17.Java17InputAstVisitor;
 import com.sun.source.tree.CaseTree;
+import com.sun.source.tree.ConstantCaseLabelTree;
+import com.sun.source.tree.DeconstructionPatternTree;
+import com.sun.source.tree.DefaultCaseLabelTree;
 import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.PatternCaseLabelTree;
+import com.sun.source.tree.PatternTree;
 
 /**
  * Extends {@link Java17InputAstVisitor} with support for AST nodes that were added or modified in
@@ -33,4 +38,42 @@ public Java21InputAstVisitor(OpsBuilder builder, int indentMultiplier) {
   protected ExpressionTree getGuard(final CaseTree node) {
     return node.getGuard();
   }
+
+  @Override
+  public Void visitDefaultCaseLabel(DefaultCaseLabelTree node, Void unused) {
+    token("default");
+    return null;
+  }
+
+  @Override
+  public Void visitPatternCaseLabel(PatternCaseLabelTree node, Void unused) {
+    scan(node.getPattern(), null);
+    return null;
+  }
+
+  @Override
+  public Void visitConstantCaseLabel(ConstantCaseLabelTree node, Void aVoid) {
+    scan(node.getConstantExpression(), null);
+    return null;
+  }
+
+  @Override
+  public Void visitDeconstructionPattern(DeconstructionPatternTree node, Void unused) {
+    scan(node.getDeconstructor(), null);
+    builder.open(plusFour);
+    token("(");
+    builder.breakOp();
+    boolean first = true;
+    for (PatternTree pattern : node.getNestedPatterns()) {
+      if (!first) {
+        token(",");
+        builder.breakOp(" ");
+      }
+      first = false;
+      scan(pattern, null);
+    }
+    builder.close();
+    token(")");
+    return null;
+  }
 }

palantir-java-format/src/main/java/com/palantir/javaformat/java/java14/Java14InputAstVisitor.java

@@ -114,12 +114,18 @@ public Void visitBindingPattern(BindingPatternTree node, Void unused) {
     }
 
     private void visitBindingPattern(ModifiersTree modifiers, Tree type, Name name) {
+        builder.open(plusFour);
         if (modifiers != null) {
             builder.addAll(visitModifiers(modifiers, Direction.HORIZONTAL, Optional.empty()));
         }
         scan(type, null);
         builder.breakOp(" ");
-        visit(name);
+        if (name.isEmpty()) {
+            token("_");
+        } else {
+            visit(name);
+        }
+        builder.close();
     }
 
     @Override
@@ -259,6 +265,11 @@ public Void visitCase(CaseTree node, Void unused) {
             labels = node.getExpressions();
             isDefault = labels.isEmpty();
         }
+        builder.open(
+                node.getCaseKind().equals(CaseTree.CaseKind.RULE)
+                                && !node.getBody().getKind().equals(Tree.Kind.BLOCK)
+                        ? plusFour
+                        : ZERO);
         if (isDefault) {
             token("default", plusTwo);
         } else {
@@ -301,15 +312,16 @@ public Void visitCase(CaseTree node, Void unused) {
                 builder.space();
                 token("-");
                 token(">");
-                builder.space();
                 if (node.getBody().getKind() == BLOCK) {
+                    builder.space();
                     // Explicit call with {@link CollapseEmptyOrNot.YES} to handle empty case blocks.
                     visitBlock(
                             (BlockTree) node.getBody(),
                             CollapseEmptyOrNot.YES,
                             AllowLeadingBlankLine.NO,
                             AllowTrailingBlankLine.NO);
                 } else {
+                    builder.breakOp(" ");
                     scan(node.getBody(), null);
                 }
                 builder.guessToken(";");
@@ -318,6 +330,7 @@ public Void visitCase(CaseTree node, Void unused) {
             default:
                 throw new IllegalArgumentException(node.getCaseKind().name());
         }
+        builder.close();
         return null;
     }
 

palantir-java-format/src/main/java/com/palantir/javaformat/java/java21/Java21InputAstVisitor.java

@@ -19,7 +19,13 @@
 import com.palantir.javaformat.OpsBuilder;
 import com.palantir.javaformat.java.java14.Java14InputAstVisitor;
 import com.sun.source.tree.CaseTree;
+import com.sun.source.tree.ConstantCaseLabelTree;
+import com.sun.source.tree.DeconstructionPatternTree;
+import com.sun.source.tree.DefaultCaseLabelTree;
 import com.sun.source.tree.ExpressionTree;
+import com.sun.source.tree.PatternCaseLabelTree;
+import com.sun.source.tree.PatternTree;
+
 /**
  * Extends {@link Java14InputAstVisitor} with support for AST nodes that were added or modified in
  * Java 21.
@@ -33,4 +39,42 @@ public Java21InputAstVisitor(OpsBuilder builder, int indentMultiplier) {
     protected ExpressionTree getGuard(final CaseTree node) {
         return node.getGuard();
     }
+
+    @Override
+    public Void visitDefaultCaseLabel(DefaultCaseLabelTree node, Void unused) {
+        token("default");
+        return null;
+    }
+
+    @Override
+    public Void visitPatternCaseLabel(PatternCaseLabelTree node, Void unused) {
+        scan(node.getPattern(), null);
+        return null;
+    }
+
+    @Override
+    public Void visitConstantCaseLabel(ConstantCaseLabelTree node, Void aVoid) {
+        scan(node.getConstantExpression(), null);
+        return null;
+    }
+
+    @Override
+    public Void visitDeconstructionPattern(DeconstructionPatternTree node, Void unused) {
+        scan(node.getDeconstructor(), null);
+        builder.open(plusFour);
+        token("(");
+        builder.breakOp();
+        boolean first = true;
+        for (PatternTree pattern : node.getNestedPatterns()) {
+            if (!first) {
+                token(",");
+                builder.breakOp(" ");
+            }
+            first = false;
+            scan(pattern, null);
+        }
+        builder.close();
+        token(")");
+        return null;
+    }
 }

palantir-java-format/src/test/java/com/palantir/javaformat/java/FileBasedTests.java

@@ -50,7 +50,7 @@ public final class FileBasedTests {
                     .putAll(15, "I603")
                     .putAll(16, "I588")
                     .putAll(17, "I683", "I684", "I696")
-                    .putAll(21, "SwitchGuardClause")
+                    .putAll(21, "SwitchGuardClause", "SwitchRecord", "SwitchDouble", "SwitchUnderscore", "I880")
                     .build();
 
     private final Class<?> testClass;

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/I880.input

@@ -0,0 +1,19 @@
+class I880 {
+  public String f(int i) {
+    return switch (i) {
+      case 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 -> "looooooooooooooooooooooooooooooooooooooooong expression";
+      default -> "looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong expression";
+    };
+  }
+
+  public boolean test(int i) {
+    return switch (i) {
+      case 0 -> // zero
+      false;
+      case 1 -> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa".length()
+          == 0;
+      default -> // otherwise
+      true;
+    };
+  }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/I880.output

@@ -0,0 +1,18 @@
+class I880 {
+    public String f(int i) {
+        return switch (i) {
+            case 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 -> "looooooooooooooooooooooooooooooooooooooooong expression";
+            default -> "looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong expression";
+        };
+    }
+
+    public boolean test(int i) {
+        return switch (i) {
+            case 0 -> // zero
+                false;
+            case 1 -> "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa".length() == 0;
+            default -> // otherwise
+                true;
+        };
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchDouble.input

@@ -0,0 +1,7 @@
+class SwitchDouble {
+  void x(Object o) {
+    switch (o) {
+      case null, default:
+    }
+  }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchDouble.output

@@ -0,0 +1,7 @@
+class SwitchDouble {
+    void x(Object o) {
+        switch (o) {
+            case null, default:
+        }
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchRecord.input

@@ -0,0 +1,21 @@
+record SwitchRecord(int i) {
+  int x(Object o) {
+    return switch (o) {
+      case SwitchRecord(int i) -> i;
+      default -> 0;
+    };
+  }
+  int f(Object o) {
+    return switch (o) {
+      case SwitchRecord(int one, int two, int three, int four, int five, int six, int seven, int eight, int nine) -> nine;
+      default -> 0;
+    };
+  }
+  int g(Object o) {
+    return switch (o) {
+      case SwitchRecord(int one, int two, int three, int four, int five, int six, int seven, int eight, int nine) -> 
+      System.err.println("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.");
+      default -> 0;
+    };
+  }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchRecord.output

@@ -0,0 +1,44 @@
+record SwitchRecord(int i) {
+    int x(Object o) {
+        return switch (o) {
+            case SwitchRecord(int i) -> i;
+            default -> 0;
+        };
+    }
+
+    int f(Object o) {
+        return switch (o) {
+            case SwitchRecord(
+                    int one,
+                    int two,
+                    int three,
+                    int four,
+                    int five,
+                    int six,
+                    int seven,
+                    int eight,
+                    int nine) -> nine;
+            default -> 0;
+        };
+    }
+
+    int g(Object o) {
+        return switch (o) {
+            case SwitchRecord(
+                    int one,
+                    int two,
+                    int three,
+                    int four,
+                    int five,
+                    int six,
+                    int seven,
+                    int eight,
+                    int nine) -> System.err.println(
+                    "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor"
+                            + " incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis"
+                            + " nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo"
+                            + " consequat.");
+            default -> 0;
+        };
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchUnderscore.input

@@ -0,0 +1,8 @@
+public class SwitchUnderscore {
+  void x(Object o) {
+    switch (o) {
+      case String _:
+      default:
+    }
+  }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/SwitchUnderscore.output

@@ -0,0 +1,8 @@
+public class SwitchUnderscore {
+    void x(Object o) {
+        switch (o) {
+            case String _:
+            default:
+        }
+    }
+}