Fix unstable trailing comment in parenthesized sequence or assignment expression (#19263)

Co-authored-by: fisker <lionkay@gmail.com>

changelog_unreleased/javascript/19263.md

@@ -0,0 +1,16 @@
+#### Keep trailing comments inside the parentheses of a sequence or assignment expression (#19263 by @sarathfrancis90)
+
+<!-- prettier-ignore -->
+```jsx
+// Input
+const x = (a, b, c /* comment */);
+const y = (a = b /* comment */);
+
+// Prettier stable
+const x = (a, b, c) /* comment */;
+const y = (a = b) /* comment */;
+
+// Prettier main
+const x = (a, b, c /* comment */);
+const y = (a = b /* comment */);
+```

src/language-js/comments/handle-comments.js

@@ -112,8 +112,7 @@ function handleEndOfLineComment(context) {
     handleLastBinaryOperatorOperand,
     handleTSMappedTypeComments,
     handleArrowExpressionComments,
-    handleArrowBodySequenceExpressionTrailingComment,
-    handleArrowBodyAssignmentExpressionTrailingComment,
+    handleParenthesizedExpressionTrailingComment,
     handlePropertySignatureComments,
     handleBinaryCastExpressionComment,
   ].some((fn) => fn(context));
@@ -136,8 +135,7 @@ function handleRemainingComment(context) {
     handleCommentAfterArrowParams,
     handleFunctionNameComments,
     handleTSFunctionTrailingComments,
-    handleArrowBodySequenceExpressionTrailingComment,
-    handleArrowBodyAssignmentExpressionTrailingComment,
+    handleParenthesizedExpressionTrailingComment,
     handleBinaryCastExpressionComment,
   ].some((fn) => fn(context));
 }
@@ -1075,43 +1073,41 @@ function handleArrowExpressionComments({
   return false;
 }
 
-function handleArrowBodySequenceExpressionTrailingComment({
+function handleParenthesizedExpressionTrailingComment({
   comment,
   enclosingNode,
   precedingNode,
   followingNode,
   text,
 }) {
-  if (
-    !followingNode &&
-    enclosingNode?.type === "ArrowFunctionExpression" &&
-    precedingNode?.type === "SequenceExpression" &&
-    enclosingNode.body === precedingNode &&
-    getNextNonSpaceNonCommentCharacter(text, locEnd(comment)) === ")"
-  ) {
-    addTrailingComment(precedingNode.expressions.at(-1), comment);
-    return true;
-  }
-  return false;
-}
+  if (!followingNode && enclosingNode) {
+    const isSequence = precedingNode?.type === "SequenceExpression";
+    const isAssignment = precedingNode?.type === "AssignmentExpression";
 
-function handleArrowBodyAssignmentExpressionTrailingComment({
-  comment,
-  enclosingNode,
-  precedingNode,
-  followingNode,
-  text,
-}) {
-  if (
-    !followingNode &&
-    enclosingNode?.type === "ArrowFunctionExpression" &&
-    precedingNode?.type === "AssignmentExpression" &&
-    enclosingNode.body === precedingNode &&
-    getNextNonSpaceNonCommentCharacter(text, locEnd(comment)) === ")"
-  ) {
-    addTrailingComment(precedingNode.right, comment);
-    return true;
+    if (
+      (isSequence || isAssignment) &&
+      ((enclosingNode.type === "ArrowFunctionExpression" &&
+        enclosingNode.body === precedingNode) ||
+        (enclosingNode.type === "VariableDeclarator" &&
+          enclosingNode.init === precedingNode) ||
+        (enclosingNode.type === "ReturnStatement" &&
+          enclosingNode.argument === precedingNode) ||
+        (isSequence &&
+          enclosingNode.type === "ExpressionStatement" &&
+          enclosingNode.expression === precedingNode) ||
+        (isSequence &&
+          enclosingNode.type === "AssignmentExpression" &&
+          enclosingNode.right === precedingNode)) &&
+      getNextNonSpaceNonCommentCharacter(text, locEnd(comment)) === ")"
+    ) {
+      addTrailingComment(
+        isSequence ? precedingNode.expressions.at(-1) : precedingNode.right,
+        comment,
+      );
+      return true;
+    }
   }
+
   return false;
 }
 

tests/config/format-test/failed-format-tests.js

@@ -33,6 +33,7 @@ const unstableTests = new Map(
     "typescript/call/callee-comments.ts",
     "js/arrows/arrow-chain-with-trailing-comments.js",
     "typescript/as/comments/18160.ts",
+    "js/sequence-expression/parenthesized-trailing-comment-unstable.js",
   ].map((fixture) => {
     const [file, isUnstable = () => true] = Array.isArray(fixture)
       ? fixture

tests/format/js/sequence-expression/__snapshots__/format.test.js.snap

@@ -127,6 +127,64 @@ console.log(
 ================================================================================
 `;
 
+exports[`parenthesized-trailing-comment.js format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+const x1 = (a, b, c /* comment */);
+const x2 = (a = c /* comment */);
+
+(a, b, c /* comment */);
+// (a = c /* comment */);
+
+assigned = (a, b, c /* comment */);
+// assigned = (a = c /* comment */);
+
+function f() {
+  return (a, b, c /* comment */);
+  return (a = c /* comment */);
+}
+
+=====================================output=====================================
+const x1 = (a, b, c /* comment */);
+const x2 = (a = c /* comment */);
+
+(a, b, c /* comment */);
+// (a = c /* comment */);
+
+assigned = (a, b, c /* comment */);
+// assigned = (a = c /* comment */);
+
+function f() {
+  return (a, b, c /* comment */);
+  return (a = c /* comment */);
+}
+
+================================================================================
+`;
+
+exports[`parenthesized-trailing-comment-unstable.js format 1`] = `
+====================================options=====================================
+parsers: ["babel", "flow", "typescript"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+// TODO: Enable tests in parenthesized-trailing-comment.js when they are stable
+
+(a = c /* comment */);
+
+assigned = (a = c /* comment */);
+
+=====================================output=====================================
+// TODO: Enable tests in parenthesized-trailing-comment.js when they are stable
+
+a = c /* comment */;
+
+assigned = a = c /* comment */;
+
+================================================================================
+`;
+
 exports[`return.js format 1`] = `
 ====================================options=====================================
 parsers: ["babel", "flow", "typescript"]

tests/format/js/sequence-expression/parenthesized-trailing-comment-unstable.js

@@ -0,0 +1,5 @@
+// TODO: Enable tests in parenthesized-trailing-comment.js when they are stable
+
+(a = c /* comment */);
+
+assigned = (a = c /* comment */);

tests/format/js/sequence-expression/parenthesized-trailing-comment.js

@@ -0,0 +1,13 @@
+const x1 = (a, b, c /* comment */);
+const x2 = (a = c /* comment */);
+
+(a, b, c /* comment */);
+// (a = c /* comment */);
+
+assigned = (a, b, c /* comment */);
+// assigned = (a = c /* comment */);
+
+function f() {
+  return (a, b, c /* comment */);
+  return (a = c /* comment */);
+}