Fix edge case with trailing comments in arrow chains (#10543)

* Fix edge case with trailing comments in arrow chains

* Remove handling of args.needsSemi from printComments

changelog_unreleased/javascript/9992.md

@@ -1,4 +1,4 @@
-#### Refine formatting of curried arrow functions (#9992 by @sosukesuzuki and @thorn0)
+#### Refine formatting of curried arrow functions (#9992, #10543 by @sosukesuzuki & @thorn0)
 
 <!-- prettier-ignore -->
 ```js

src/language-js/print/function.js

@@ -1,8 +1,13 @@
 "use strict";
 
+/** @typedef {import("../../document/doc-builders").Doc} Doc */
+
 /** @type {import("assert")} */
 const assert = require("assert");
-const { printDanglingComments, printComments } = require("../../main/comments");
+const {
+  printDanglingComments,
+  printCommentsSeparately,
+} = require("../../main/comments");
 const {
   getNextNonSpaceNonCommentCharacterIndex,
 } = require("../../common/util");
@@ -246,15 +251,20 @@ function printArrowChain(
 
 function printArrowFunctionExpression(path, options, print, args) {
   let node = path.getValue();
+  /** @type {Doc[]} */
   const signatures = [];
-  let body;
+  const body = [];
   let chainShouldBreak = false;
 
   (function rec(path) {
     const doc = printArrowFunctionSignature(path, options, print, args);
-    signatures.push(
-      signatures.length === 0 ? doc : printComments(path, doc, options)
-    );
+    if (signatures.length === 0) {
+      signatures.push(doc);
+    } else {
+      const { leading, trailing } = printCommentsSeparately(path, options);
+      signatures.push([leading, doc]);
+      body.unshift(trailing);
+    }
 
     chainShouldBreak =
       chainShouldBreak ||
@@ -267,7 +277,7 @@ function printArrowFunctionExpression(path, options, print, args) {
       node.body.type !== "ArrowFunctionExpression" ||
       (args && args.expandLastArg)
     ) {
-      body = path.call((bodyPath) => print(bodyPath, args), "body");
+      body.unshift(path.call((bodyPath) => print(bodyPath, args), "body"));
     } else {
       node = node.body;
       path.call(rec, "body");

src/language-js/printer-estree.js

@@ -113,18 +113,18 @@ function genericPrint(path, options, print, args) {
   }
 
   const printedDecorators = printDecorators(path, options, print);
-  // Nodes with decorators can't have parentheses
+  // Nodes with decorators can't have parentheses and don't need leading semicolons
   if (printedDecorators) {
     return group([...printedDecorators, printed]);
   }
 
   const needsParens = pathNeedsParens(path, options);
 
   if (!needsParens) {
-    return printed;
+    return args && args.needsSemi ? [";", printed] : printed;
   }
 
-  const parts = ["(", printed];
+  const parts = [args && args.needsSemi ? ";(" : "(", printed];
 
   if (hasFlowShorthandAnnotationComment(node)) {
     const [comment] = node.trailingComments;

src/main/ast-to-doc.js

@@ -57,7 +57,7 @@ function printAstToDoc(ast, options, alignmentSize = 0) {
     ) {
       // printComments will call the plugin print function and check for
       // comments to print
-      doc = printComments(path, doc, options, args && args.needsSemi);
+      doc = printComments(path, doc, options);
     }
 
     if (shouldCache) {

src/main/comments.js

@@ -540,23 +540,18 @@ function printDanglingComments(path, options, sameIndent, filter) {
   return indent([hardline, join(hardline, parts)]);
 }
 
-function prependCursorPlaceholder(path, options, printed) {
-  if (path.getNode() === options.cursorNode && path.getValue()) {
-    return [cursor, printed, cursor];
-  }
-  return printed;
-}
-
-function printComments(path, printed, options, needsSemi) {
+function printCommentsSeparately(path, options) {
   const value = path.getValue();
-  const comments = value && value.comments;
+  const hasComments = isNonEmptyArray(value && value.comments);
+  const isCursorNode = Boolean(value && value === options.cursorNode);
 
-  if (!isNonEmptyArray(comments)) {
-    return prependCursorPlaceholder(path, options, printed);
+  if (!hasComments) {
+    const maybeCursor = isCursorNode ? cursor : "";
+    return { leading: maybeCursor, trailing: maybeCursor };
   }
 
   const leadingParts = [];
-  const trailingParts = [needsSemi ? ";" : "", printed];
+  const trailingParts = [];
 
   path.each((commentPath) => {
     const comment = commentPath.getValue();
@@ -583,10 +578,20 @@ function printComments(path, printed, options, needsSemi) {
     }
   }, "comments");
 
-  return prependCursorPlaceholder(path, options, [
-    ...leadingParts,
-    ...trailingParts,
-  ]);
+  if (isCursorNode) {
+    leadingParts.unshift(cursor);
+    trailingParts.push(cursor);
+  }
+
+  return { leading: leadingParts, trailing: trailingParts };
+}
+
+function printComments(path, doc, options) {
+  const { leading, trailing } = printCommentsSeparately(path, options);
+  if (!leading && !trailing) {
+    return doc;
+  }
+  return [leading, doc, trailing];
 }
 
 function ensureAllCommentsPrinted(astComments) {
@@ -609,6 +614,7 @@ function ensureAllCommentsPrinted(astComments) {
 module.exports = {
   attach,
   printComments,
+  printCommentsSeparately,
   printDanglingComments,
   getSortedChildNodes,
   ensureAllCommentsPrinted,

tests/js/arrows/__snapshots__/jsfmt.spec.js.snap

@@ -164,6 +164,82 @@ a = b => {
 ================================================================================
 `;
 
+exports[`arrow-chain-with-trailing-comments.js - {"arrowParens":"always"} format 1`] = `
+====================================options=====================================
+arrowParens: "always"
+parsers: ["babel", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+x = (bifornCringerMoshedPerplexSawder) => ((askTrovenaBeenaDependsRowans, glimseGlyphsHazardNoopsTieTie) => (f00) => {
+  averredBathersBoxroomBuggyNurl();
+} // BOOM
+)
+
+x2 = (a) => ((askTrovenaBeenaDependsRowans1, askTrovenaBeenaDependsRowans2, askTrovenaBeenaDependsRowans3) => {
+  c();
+} /* ! */ // KABOOM
+)
+
+=====================================output=====================================
+x =
+  (bifornCringerMoshedPerplexSawder) =>
+  (askTrovenaBeenaDependsRowans, glimseGlyphsHazardNoopsTieTie) =>
+  (f00) => {
+    averredBathersBoxroomBuggyNurl();
+  }; // BOOM
+
+x2 =
+  (a) =>
+  (
+    askTrovenaBeenaDependsRowans1,
+    askTrovenaBeenaDependsRowans2,
+    askTrovenaBeenaDependsRowans3
+  ) => {
+    c();
+  } /* ! */; // KABOOM
+
+================================================================================
+`;
+
+exports[`arrow-chain-with-trailing-comments.js - {"arrowParens":"avoid"} format 1`] = `
+====================================options=====================================
+arrowParens: "avoid"
+parsers: ["babel", "typescript"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+x = (bifornCringerMoshedPerplexSawder) => ((askTrovenaBeenaDependsRowans, glimseGlyphsHazardNoopsTieTie) => (f00) => {
+  averredBathersBoxroomBuggyNurl();
+} // BOOM
+)
+
+x2 = (a) => ((askTrovenaBeenaDependsRowans1, askTrovenaBeenaDependsRowans2, askTrovenaBeenaDependsRowans3) => {
+  c();
+} /* ! */ // KABOOM
+)
+
+=====================================output=====================================
+x =
+  bifornCringerMoshedPerplexSawder =>
+  (askTrovenaBeenaDependsRowans, glimseGlyphsHazardNoopsTieTie) =>
+  f00 => {
+    averredBathersBoxroomBuggyNurl();
+  }; // BOOM
+
+x2 =
+  a =>
+  (
+    askTrovenaBeenaDependsRowans1,
+    askTrovenaBeenaDependsRowans2,
+    askTrovenaBeenaDependsRowans3
+  ) => {
+    c();
+  } /* ! */; // KABOOM
+
+================================================================================
+`;
+
 exports[`assignment-chain-with-arrow-chain.js - {"arrowParens":"always"} format 1`] = `
 ====================================options=====================================
 arrowParens: "always"

tests/js/arrows/arrow-chain-with-trailing-comments.js

@@ -0,0 +1,9 @@
+x = (bifornCringerMoshedPerplexSawder) => ((askTrovenaBeenaDependsRowans, glimseGlyphsHazardNoopsTieTie) => (f00) => {
+  averredBathersBoxroomBuggyNurl();
+} // BOOM
+)
+
+x2 = (a) => ((askTrovenaBeenaDependsRowans1, askTrovenaBeenaDependsRowans2, askTrovenaBeenaDependsRowans3) => {
+  c();
+} /* ! */ // KABOOM
+)