fix #2814: additional comment-related regressions

CHANGELOG.md

@@ -1,5 +1,19 @@
 # Changelog
 
+## Unreleased
+
+* Fix additional comment-related regressions ([#2814](https://github.com/evanw/esbuild/issues/2814))
+
+    This release fixes more edge cases where the new comment preservation behavior that was added in 0.16.14 could introduce syntax errors. Specifically:
+
+    ```js
+    x = () => (/* comment */ {})
+    for ((/* comment */ let).x of y) ;
+    function *f() { yield (/* comment */class {}) }
+    ```
+
+    These cases caused esbuild to generate code with a syntax error in version 0.16.14 or above. These bugs have now been fixed.
+
 ## 0.16.16
 
 * Fix a regression caused by comment preservation ([#2805](https://github.com/evanw/esbuild/issues/2805))

internal/bundler_tests/bundler_default_test.go

@@ -7684,6 +7684,22 @@ func TestCommentPreservation(t *testing.T) {
 					/*a*/ a ? /*b*/ b : /*c*/ c,
 					a /*a*/ ? b /*b*/ : c /*c*/,
 				)
+
+				for (/*foo*/a;;);
+				for (;/*foo*/a;);
+				for (;;/*foo*/a);
+
+				for (/*foo*/a in b);
+				for (a in /*foo*/b);
+
+				for (/*foo*/a of b);
+				for (a of /*foo*/b);
+
+				if (/*foo*/a);
+				with (/*foo*/a);
+				while (/*foo*/a);
+				do {} while (/*foo*/a);
+				switch (/*foo*/a) {}
 			`,
 		},
 		entryPaths: []string{"/entry.js"},

internal/bundler_tests/snapshots/snapshots_default.txt

@@ -596,6 +596,72 @@ console.log(
   ),
   a ? b : c
 );
+for (
+  /*foo*/
+  a;
+  ;
+)
+  ;
+for (
+  ;
+  /*foo*/
+  a;
+)
+  ;
+for (
+  ;
+  ;
+  /*foo*/
+  a
+)
+  ;
+for (
+  /*foo*/
+  a in b
+)
+  ;
+for (
+  a in
+  /*foo*/
+  b
+)
+  ;
+for (
+  /*foo*/
+  a of b
+)
+  ;
+for (
+  a of
+  /*foo*/
+  b
+)
+  ;
+if (
+  /*foo*/
+  a
+)
+  ;
+with (
+  /*foo*/
+  a
+)
+  ;
+while (
+  /*foo*/
+  a
+)
+  ;
+do {
+} while (
+  /*foo*/
+  a
+);
+switch (
+  /*foo*/
+  a
+) {
+}
 
 ================================================================================
 TestCommentPreservationImportAssertions

internal/js_parser/js_parser.go

@@ -2956,7 +2956,7 @@ func (p *parser) parseParenExpr(loc logger.Loc, level js_ast.L, opts parenExprOp
 			panic(js_lexer.LexerPanic{})
 		}
 		value := js_ast.JoinAllWithComma(items)
-		p.markExprAsParenthesized(value)
+		p.markExprAsParenthesized(value, loc, isAsync)
 		return value
 	}
 
@@ -3137,7 +3137,7 @@ func (p *parser) parsePrefix(level js_ast.L, errors *deferredErrors, flags exprF
 			p.allowIn = true
 
 			value := p.parseExpr(js_ast.LLowest)
-			p.markExprAsParenthesized(value)
+			p.markExprAsParenthesized(value, loc, false)
 			p.lexer.Expect(js_lexer.TCloseParen)
 
 			p.allowIn = oldAllowIn
@@ -6848,7 +6848,7 @@ func (p *parser) parseStmt(opts parseStmtOpts) js_ast.Stmt {
 				badLetRange = logger.Range{}
 				initOrNil = stmt
 			} else {
-				initOrNil = js_ast.Stmt{Loc: initLoc, Data: &js_ast.SExpr{Value: expr}}
+				initOrNil = js_ast.Stmt{Loc: expr.Loc, Data: &js_ast.SExpr{Value: expr}}
 			}
 		}
 
@@ -10309,7 +10309,19 @@ func (p *parser) maybeRelocateVarsToTopLevel(decls []js_ast.Decl, mode relocateV
 	return js_ast.Stmt{Loc: value.Loc, Data: &js_ast.SExpr{Value: value}}, true
 }
 
-func (p *parser) markExprAsParenthesized(value js_ast.Expr) {
+func (p *parser) markExprAsParenthesized(value js_ast.Expr, openParenLoc logger.Loc, isAsync bool) {
+	// Don't lose comments due to parentheses. For example, we don't want to lose
+	// the comment here:
+	//
+	//   ( /* comment */ (foo) );
+	//
+	if !isAsync {
+		if comments, ok := p.exprComments[openParenLoc]; ok {
+			delete(p.exprComments, openParenLoc)
+			p.exprComments[value.Loc] = append(comments, p.exprComments[value.Loc]...)
+		}
+	}
+
 	switch e := value.Data.(type) {
 	case *js_ast.EArray:
 		e.IsParenthesized = true