fix(formatter): inconsistent union type output between two runs

Author: Dunqing

crates/oxc_formatter/src/write/union_type.rs

@@ -128,17 +128,24 @@ impl<'a> FormatWrite<'a> for AstNode<'a, TSUnionType<'a>> {
         });
 
         if has_leading_comments {
-            let has_own_line_leading_comment = union_type_at_top.types.len() > 1
-                && leading_comments.iter().any(|comment| f.comments().is_own_line_comment(comment));
-            let is_end_of_line_comment = leading_comments
-                .last()
-                .is_some_and(|comment| f.comments().is_end_of_line_comment(comment));
+            let only_type = union_type_at_top.types.len() == 1;
+            let (has_own_line_comment, has_end_of_line_comment) =
+                leading_comments.iter().fold((false, false), |(own_line, end_of_line), comment| {
+                    (
+                        end_of_line || own_line || f.comments().is_own_line_comment(comment),
+                        end_of_line || f.comments().is_end_of_line_comment(comment),
+                    )
+                });
+
             write!(
                 f,
                 [group(&indent(&format_args!(
-                    has_own_line_leading_comment.then(soft_line_break),
+                    ((has_own_line_comment && !only_type)
+                        || (has_end_of_line_comment && only_type))
+                        .then(soft_line_break),
                     FormatLeadingComments::Comments(leading_comments),
-                    (!is_end_of_line_comment).then(soft_line_break),
+                    (!has_end_of_line_comment && has_own_line_comment && only_type)
+                        .then(soft_line_break),
                     group(&content)
                 )))]
             );

crates/oxc_formatter/tests/fixtures/ts/comments/union.ts

@@ -1,3 +1,25 @@
 interface _KeywordDef {
   type?: JSONType | JSONType[] // data types that keyword applies to
 }
+
+type C1 = | (
+  /* 1 */ /*1*/ | (
+    | (
+          | A
+          // A comment to force break
+          | B
+        )
+  )
+  );
+
+
+type C2 = | (
+  /* 1 */ /*1*/ 
+  /* 1 */ | (
+    | (
+          | A
+          // A comment to force break
+          | B
+        )
+  )
+  );

crates/oxc_formatter/tests/fixtures/ts/comments/union.ts.snap

@@ -6,6 +6,28 @@ interface _KeywordDef {
   type?: JSONType | JSONType[] // data types that keyword applies to
 }
 
+type C1 = | (
+  /* 1 */ /*1*/ | (
+    | (
+          | A
+          // A comment to force break
+          | B
+        )
+  )
+  );
+
+
+type C2 = | (
+  /* 1 */ /*1*/ 
+  /* 1 */ | (
+    | (
+          | A
+          // A comment to force break
+          | B
+        )
+  )
+  );
+
 ==================== Output ====================
 ------------------
 { printWidth: 80 }
@@ -14,11 +36,33 @@ interface _KeywordDef {
   type?: JSONType | JSONType[]; // data types that keyword applies to
 }
 
+type C1 = /* 1 */ /*1*/
+  | A
+  // A comment to force break
+  | B;
+
+type C2 =
+  /* 1 */ /*1*/
+  /* 1 */ | A
+  // A comment to force break
+  | B;
+
 -------------------
 { printWidth: 100 }
 -------------------
 interface _KeywordDef {
   type?: JSONType | JSONType[]; // data types that keyword applies to
 }
 
+type C1 = /* 1 */ /*1*/
+  | A
+  // A comment to force break
+  | B;
+
+type C2 =
+  /* 1 */ /*1*/
+  /* 1 */ | A
+  // A comment to force break
+  | B;
+
 ===================== End =====================

tasks/coverage/snapshots/formatter_typescript.snap

@@ -2,15 +2,13 @@ commit: 669c25c0
 
 formatter_typescript Summary:
 AST Parsed     : 9822/9822 (100.00%)
-Positive Passed: 9814/9822 (99.92%)
+Positive Passed: 9815/9822 (99.93%)
 Mismatch: tasks/coverage/typescript/tests/cases/compiler/amdLikeInputDeclarationEmit.ts
 
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/genericTypeAssertions3.ts
 Unexpected token
 Expect to Parse: tasks/coverage/typescript/tests/cases/compiler/typeAssertionToGenericFunctionType.ts
 Unexpected token
-Mismatch: tasks/coverage/typescript/tests/cases/compiler/unionTypeWithLeadingOperator.ts
-
 Mismatch: tasks/coverage/typescript/tests/cases/conformance/expressions/contextualTyping/parenthesizedContexualTyping2.ts
 
 Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/expressions/elementAccess/letIdentifierInElementAccess01.ts