Fix comment in union type get duplicated (#18393)

changelog_unreleased/typescript/18393.md

@@ -0,0 +1,13 @@
+#### Fix comment inside union type get duplicated (#18393 by @fisker)
+
+<!-- prettier-ignore -->
+```tsx
+// Input
+type Foo = (/** comment */ a | b) | c;
+
+// Prettier stable
+type Foo = /** comment */ (/** comment */ a | b) | c;
+
+// Prettier main
+type Foo = /** comment */ (a | b) | c;
+```

src/language-js/print/union-type.js

@@ -19,6 +19,7 @@ import {
   hasLeadingOwnLineComment,
   isConditionalType,
   isTypeAlias,
+  isUnionType,
 } from "../utilities/index.js";
 
 // `TSUnionType` and `UnionTypeAnnotation`
@@ -77,7 +78,11 @@ function printUnionType(path, options, print) {
     return printComments(path, printedType, options);
   }, "types");
 
-  const { leading, trailing } = printCommentsSeparately(path, options);
+  const { leading, trailing } =
+    // If it's `types` of union type, parent will print comment for us
+    path.key === "types" && isUnionType(path.parent)
+      ? { leading: "", trailing: "" }
+      : printCommentsSeparately(path, options);
 
   if (shouldHug) {
     return [leading, join(" | ", printed), trailing];

tests/format/typescript/union/comments/18389.ts

@@ -0,0 +1,19 @@
+type A1 =     | /**
+     * octahedralRhinocerosTransformer
+     */
+    a
+    | (b | c);
+
+type A2 =     | /**
+     * hippopotamicKangarooMutator
+     */
+    (a | b)
+    | c;
+
+type A4 =
+  (
+  	A | B // comment 1
+  ) | (
+  	// comment2
+    A | B
+  )

tests/format/typescript/union/comments/__snapshots__/format.test.js.snap

@@ -95,3 +95,52 @@ type A3 =
 
 ================================================================================
 `;
+
+exports[`18389.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript", "flow"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+type A1 =     | /**
+     * octahedralRhinocerosTransformer
+     */
+    a
+    | (b | c);
+
+type A2 =     | /**
+     * hippopotamicKangarooMutator
+     */
+    (a | b)
+    | c;
+
+type A4 =
+  (
+  	A | B // comment 1
+  ) | (
+  	// comment2
+    A | B
+  )
+
+=====================================output=====================================
+type A1 =
+  | /**
+   * octahedralRhinocerosTransformer
+   */
+  a
+  | (b | c);
+
+type A2 =
+  | /**
+   * hippopotamicKangarooMutator
+   */
+  (a | b)
+  | c;
+
+type A4 =
+  | (A | B) // comment 1
+  // comment2
+  | (A | B);
+
+================================================================================
+`;