fix: stable format for if expression with trailing comment

closes #592

packages/prettier-plugin-java/src/printers/blocks-and-statements.ts

@@ -3,6 +3,7 @@
 import { builders } from "prettier/doc";
 import { concat, dedent, group, indent, join } from "./prettier-builder";
 import { printTokenWithComments } from "./comments/format-comments";
+import { handleCommentsIfStatement } from "./comments/handle-comments";
 import {
   hasLeadingLineComments,
   hasTrailingLineComments
@@ -192,12 +193,17 @@ export class BlocksAndStatementPrettierVisitor extends BaseCstPrettierPrinter {
   }
 
   ifStatement(ctx: IfStatementCtx) {
+    handleCommentsIfStatement(ctx);
+
     const expression = this.visit(ctx.expression);
 
     const ifStatement = this.visit(ctx.statement[0], {
       allowEmptyStatement: true
     });
-    const ifSeparator = isStatementEmptyStatement(ifStatement) ? "" : " ";
+    const ifStatementCtx = ctx.statement[0].children.statementWithoutTrailingSubstatement?.[0].children;
+    const emptyIfStatement = ifStatementCtx?.emptyStatement !== undefined;
+    const hasIfBlock = ifStatementCtx?.block !== undefined;
+    const ifSeparator = emptyIfStatement ? "" : hasIfBlock ? " " : indent(line);
 
     let elsePart: Doc = "";
     if (ctx.Else !== undefined) {
@@ -208,7 +214,9 @@ export class BlocksAndStatementPrettierVisitor extends BaseCstPrettierPrinter {
 
       const elseOnSameLine =
         hasTrailingLineComments(ctx.statement[0]) ||
-        hasLeadingLineComments(ctx.Else[0])
+        hasLeadingLineComments(ctx.Else[0]) ||
+        emptyIfStatement ||
+        !hasIfBlock
           ? hardline
           : " ";
 
@@ -226,7 +234,7 @@ export class BlocksAndStatementPrettierVisitor extends BaseCstPrettierPrinter {
           ifSeparator
         ])
       ]),
-      ifStatement,
+      hasIfBlock ? ifStatement : indent(ifStatement),
       elsePart
     ]);
   }

packages/prettier-plugin-java/src/printers/comments/handle-comments.ts

@@ -1,5 +1,5 @@
-import { hasLeadingComments } from "./comments-utils";
-import { BinaryExpressionCtx, IToken } from "java-parser";
+import { hasLeadingComments, hasTrailingComments } from "./comments-utils";
+import { BinaryExpressionCtx, IToken, IfStatementCtx } from "java-parser";
 
 export function handleCommentsBinaryExpression(ctx: BinaryExpressionCtx) {
   let unaryExpressionIndex = 1;
@@ -43,3 +43,29 @@ export function handleCommentsBinaryExpression(ctx: BinaryExpressionCtx) {
     });
   }
 }
+
+export function handleCommentsIfStatement(ctx: IfStatementCtx) {
+  const rBrace = ctx.RBrace[0];
+  if (!hasTrailingComments(rBrace)) {
+    return;
+  }
+  const statement = ctx.statement[0].children.statementWithoutTrailingSubstatement?.[0].children;
+  if (!statement) {
+    return;
+  }
+  const inner = [statement.assertStatement, statement.breakStatement, statement.continueStatement, statement.doStatement, statement.emptyStatement, statement.expressionStatement, statement.expressionStatement, statement.returnStatement, statement.switchStatement, statement.synchronizedStatement, statement.throwStatement, statement.tryStatement, statement.yieldStatement].find(s => s)?.[0];
+  const block = statement.block?.[0].children.blockStatements?.[0];
+  const rCurly = statement.block?.[0].children.RCurly[0];
+  const target = inner ?? block ?? rCurly;
+  if (!target) {
+    return;
+  }
+  if (block) {
+    block.location.startLine--;
+  }
+  if (!target.leadingComments) {
+    target.leadingComments = [];
+  }
+  target.leadingComments.unshift(...rBrace.trailingComments);
+  delete ctx.RBrace[0].trailingComments;
+}

packages/prettier-plugin-java/test/unit-test/comments/comments-blocks-and-statements/complex/_output.java

@@ -23,9 +23,8 @@ private void myFunction(
     /* axis y */int arg2,
     /* axis z */int arg3
   ) {
-    if (arg1 == 0 && arg2 == 0 && arg == 3) throw new RuntimeException(
-      "X Y Z cannot be all 0"
-    );
+    if (arg1 == 0 && arg2 == 0 && arg == 3)
+      throw new RuntimeException("X Y Z cannot be all 0");
 
     int /*variable name is of value var */var = arg1 + arg2 + arg3;
     if /*true*/(var == 0) {

packages/prettier-plugin-java/test/unit-test/comments/comments-blocks-and-statements/if-statement/_input.java

@@ -15,6 +15,26 @@ void commentsIfLineComment() {
     if ( // test
     t) {
     }
+
+    if (true) // comment
+      System.out.println("Oops");
+
+    if (true) {
+      // comment
+    }
+
+    if (true) // comment
+    {}
+
+    if (true) // comment
+    {
+      System.out.println("Oops");
+    }
+
+    if (true) // comment
+    {
+      if (true) {}
+    }
   }
 
   void commentsIfBlockComment() {

packages/prettier-plugin-java/test/unit-test/comments/comments-blocks-and-statements/if-statement/_output.java

@@ -14,6 +14,28 @@ void commentsIfLineComment() {
     if ( // test
       t
     ) {}
+
+    if (true)
+      // comment
+      System.out.println("Oops");
+
+    if (true) {
+      // comment
+    }
+
+    if (true) {
+      // comment
+    }
+
+    if (true) {
+      // comment
+      System.out.println("Oops");
+    }
+
+    if (true) {
+      // comment
+      if (true) {}
+    }
   }
 
   void commentsIfBlockComment() {

packages/prettier-plugin-java/test/unit-test/empty_statement/_output.java

@@ -37,23 +37,27 @@ public void forEachWithEmptyStatement(List<String> list) {
   }
 
   public void ifElseWithEmptyStatements() {
-    if (test); else {
+    if (test);
+    else {
       System.out.println("one");
     }
 
     if (test) {
       System.out.println("two");
     } else;
 
-    if (test); else;
+    if (test);
+    else;
   }
 
   public void ifElseWithEmptyStatementsWithComments() {
-    if (test) /*test*/; else {
+    if (test)/*test*/;
+    else {
       System.out.println("one");
     }
 
-    if (test); /*test*/else {
+    if (test);
+    /*test*/else {
       System.out.println("one");
     }
 
@@ -65,9 +69,11 @@ public void ifElseWithEmptyStatementsWithComments() {
       System.out.println("two");
     } else;/*test*/
 
-    if (test); /*test*/else;/*test*/
+    if (test);
+    /*test*/else;/*test*/
 
-    if (test) /*test*/; else /*test*/;
+    if (test)/*test*/;
+    else /*test*/;
   }
 
   public void simpleWhileWithEmptyStatement(boolean one) {

packages/prettier-plugin-java/test/unit-test/sealed/_output.java

@@ -46,11 +46,12 @@ default Shape rotate(double angle) {
   }
 
   default String areaMessage() {
-    if (this instanceof Circle) return "Circle: " + area(); else if (
-      this instanceof Rectangle
-    ) return "Rectangle: " + area(); else if (
-      this instanceof RightTriangle
-    ) return "Triangle: " + area();
+    if (this instanceof Circle)
+      return "Circle: " + area();
+    else if (this instanceof Rectangle)
+      return "Rectangle: " + area();
+    else if (this instanceof RightTriangle)
+      return "Triangle: " + area();
     // :(
     throw new IllegalArgumentException();
   }