Fix comment placement in assignment-like type aliases (TSTypeAliasDeclaration) (#19410)

Co-authored-by: WhoamiI00 <anktiisop12@gmail.com>
Co-authored-by: fisker <lionkay@gmail.com>

changelog_unreleased/typescript/19410.md

@@ -0,0 +1,22 @@
+#### Preserve comment position after `=` in type alias declarations (#19410 by @WhoamiI00)
+
+<!-- prettier-ignore -->
+```ts
+// Input
+type A =
+  /* 1 */ | /* 2 */ (
+    /* 3 */ | /* 4 */ {
+        key: string;
+      }
+  );
+
+// Prettier stable
+type A /* 2 */ = /* 1 */ /* 3 */ /* 4 */ {
+  key: string;
+};
+
+// Prettier main
+type A = /* 1 */ /* 2 */ /* 3 */ /* 4 */ {
+  key: string;
+};
+```

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

@@ -139,6 +139,7 @@ function handleRemainingComment(context) {
     handleParenthesizedExpressionTrailingComment,
     handleBinaryCastExpressionComment,
     handleUnionTypeLeadingComments,
+    handleAssignmentLikeAnnotationLeadingComments,
   ].some((fn) => fn(context));
 }
 
@@ -782,6 +783,28 @@ function handleVariableDeclaratorComments({
   return false;
 }
 
+function handleAssignmentLikeAnnotationLeadingComments({
+  comment,
+  enclosingNode,
+  followingNode,
+  options,
+}) {
+  if (isAssignmentLikeNode(enclosingNode) && followingNode) {
+    // @ts-expect-error -- Safe
+    const leftSide = enclosingNode.id ?? enclosingNode.left;
+    const equalsTokenIndex = stripComments(options).indexOf(
+      "=",
+      locEnd(leftSide),
+    );
+    if (locStart(comment) >= equalsTokenIndex) {
+      addLeadingComment(followingNode, comment);
+      return true;
+    }
+  }
+
+  return false;
+}
+
 function handleTSFunctionTrailingComments({
   comment,
   enclosingNode,

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

@@ -16,7 +16,6 @@ const unstableTests = new Map(
       (options) => options.proseWrap === "always",
     ],
     "flow/hook/declare-hook.js",
-    "flow/hook/comments-before-arrow.js",
     "flow/hook/hook-type-annotation.js",
     "flow/comments/type_annotations.js",
     "typescript/prettier-ignore/mapped-types.ts",

tests/format/typescript/intersection/__snapshots__/format.test.js.snap

@@ -192,25 +192,25 @@ type A2 = C;
 type A3 = C;
 type A4 = C;
 type A5 = C;
-type A6 /*1*/ = C;
+type A6 = /*1*/ C;
-type A7 /*1*/ = C;
+type A7 = /*1*/ C;
-type A8 /*1*/ = C;
+type A8 = /*1*/ C;
-type A9 /*1*/ = C;
+type A9 = /*1*/ C;
-type A10 /*1*/ = /*2*/ C;
+type A10 = /*1*/ /*2*/ C;
-type A11 /*1*/ = /*2*/ C;
+type A11 = /*1*/ /*2*/ C;
-type A12 /*1*/ = C;
+type A12 = /*1*/ C;
 type A13 = /*1*/ C;
 
 type Aa1 = /*1*/ /*2*/ C & D;
 type Aa2 = /*1*/ /*2*/ C & /*3*/ D;
 type Aa3 = /*1*/ /*2*/ C & /*3*/ D /*4*/;
 
-type C1 /*1*/ = a & b;
+type C1 = /*1*/ a & b;
-type C2 /*1*/ = a & b;
+type C2 = /*1*/ a & b;
-type C3 /*1*/ = a & b;
+type C3 = /*1*/ a & b;
-type C4 /*1*/ = a & b;
+type C4 = /*1*/ a & b;
-type C5 /*1*/ = a & b;
+type C5 = /*1*/ a & b;
-type C6 /*0*/ /*1*/ = a & b;
+type C6 /*0*/ = /*1*/ a & b;
 
 type Ctor = (new () => X) & Y;
 
@@ -409,25 +409,25 @@ type A2 = C
 type A3 = C
 type A4 = C
 type A5 = C
-type A6 /*1*/ = C
+type A6 = /*1*/ C
-type A7 /*1*/ = C
+type A7 = /*1*/ C
-type A8 /*1*/ = C
+type A8 = /*1*/ C
-type A9 /*1*/ = C
+type A9 = /*1*/ C
-type A10 /*1*/ = /*2*/ C
+type A10 = /*1*/ /*2*/ C
-type A11 /*1*/ = /*2*/ C
+type A11 = /*1*/ /*2*/ C
-type A12 /*1*/ = C
+type A12 = /*1*/ C
 type A13 = /*1*/ C
 
 type Aa1 = /*1*/ /*2*/ C & D
 type Aa2 = /*1*/ /*2*/ C & /*3*/ D
 type Aa3 = /*1*/ /*2*/ C & /*3*/ D /*4*/
 
-type C1 /*1*/ = a & b
+type C1 = /*1*/ a & b
-type C2 /*1*/ = a & b
+type C2 = /*1*/ a & b
-type C3 /*1*/ = a & b
+type C3 = /*1*/ a & b
-type C4 /*1*/ = a & b
+type C4 = /*1*/ a & b
-type C5 /*1*/ = a & b
+type C5 = /*1*/ a & b
-type C6 /*0*/ /*1*/ = a & b
+type C6 /*0*/ = /*1*/ a & b
 
 type Ctor = (new () => X) & Y
 
@@ -625,25 +625,25 @@ type A2 = C;
 type A3 = C;
 type A4 = C;
 type A5 = C;
-type A6 /*1*/ = C;
+type A6 = /*1*/ C;
-type A7 /*1*/ = C;
+type A7 = /*1*/ C;
-type A8 /*1*/ = C;
+type A8 = /*1*/ C;
-type A9 /*1*/ = C;
+type A9 = /*1*/ C;
-type A10 /*1*/ = /*2*/ C;
+type A10 = /*1*/ /*2*/ C;
-type A11 /*1*/ = /*2*/ C;
+type A11 = /*1*/ /*2*/ C;
-type A12 /*1*/ = C;
+type A12 = /*1*/ C;
 type A13 = /*1*/ C;
 
 type Aa1 = /*1*/ /*2*/ C & D;
 type Aa2 = /*1*/ /*2*/ C & /*3*/ D;
 type Aa3 = /*1*/ /*2*/ C & /*3*/ D /*4*/;
 
-type C1 /*1*/ = a & b;
+type C1 = /*1*/ a & b;
-type C2 /*1*/ = a & b;
+type C2 = /*1*/ a & b;
-type C3 /*1*/ = a & b;
+type C3 = /*1*/ a & b;
-type C4 /*1*/ = a & b;
+type C4 = /*1*/ a & b;
-type C5 /*1*/ = a & b;
+type C5 = /*1*/ a & b;
-type C6 /*0*/ /*1*/ = a & b;
+type C6 /*0*/ = /*1*/ a & b;
 
 type Ctor = (new () => X) & Y;
 

tests/format/typescript/intersection/consistent-with-flow/__snapshots__/format.test.js.snap

@@ -91,24 +91,135 @@ type B2 = C;
 type B3 = C;
 type B4 = C;
 type B5 = C;
-type B6 /*1*/ = C;
+type B6 = /*1*/ C;
-type B7 /*1*/ = C;
+type B7 = /*1*/ C;
-type B8 /*1*/ = C;
+type B8 = /*1*/ C;
-type B9 /*1*/ = C;
+type B9 = /*1*/ C;
-type B10 /*1*/ = /*2*/ C;
+type B10 = /*1*/ /*2*/ C;
-type B11 /*1*/ = /*2*/ C;
+type B11 = /*1*/ /*2*/ C;
-type B12 /*1*/ = C;
+type B12 = /*1*/ C;
 
 type Bb1 = /*1*/ /*2*/ C & D;
 type Bb2 = /*1*/ /*2*/ C & /*3*/ D;
 type Bb3 = /*1*/ /*2*/ C & /*3*/ D /*4*/;
 
-type D1 /*1*/ = a & b;
+type D1 = /*1*/ a & b;
-type D2 /*1*/ = a & b;
+type D2 = /*1*/ a & b;
-type D3 /*1*/ = a & b;
+type D3 = /*1*/ a & b;
-type D4 /*1*/ = a & b;
+type D4 = /*1*/ a & b;
-type D5 /*1*/ = a & b;
+type D5 = /*1*/ a & b;
-type D6 /*0*/ /*1*/ = a & b;
+type D6 /*0*/ = /*1*/ a & b;
+
+================================================================================
+`;
+
+exports[`single-member.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript", "flow"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+// https://github.com/oxc-project/oxc/pull/21915
+
+// export type aType = & // Comment
+// "VALUE";
+
+export type bType = &
+// Comment
+"VALUE";
+
+export type cType = & /* Comment */
+"VALUE";
+
+export type dType = /* Comment */
+& "VALUE";
+
+// export type eType = // Comment
+// & "VALUE";
+
+export type fType = &
+/* Comment */
+"VALUE";
+
+export type gType = &
+// Comment
+// Comment
+"VALUE";
+
+export type hType = &
+"VALUE";
+
+export type iType = /* Comment */ /* Comment */ & "VALUE";
+
+export type jType = /* Comment */
+/* Comment */ & "VALUE";
+
+export type kType = /* Comment */
+&
+// Comment
+"VALUE";
+
+export type lType = /* Comment */ &
+// Comment
+"VALUE";
+
+export type mType = & "VALUE" /* Comment */;
+
+export type nType = // Comment
+& /* Comment */
+"VALUE";
+
+// type oType = // Comment
+// & // Comment
+// "VALUE"
+
+=====================================output=====================================
+// https://github.com/oxc-project/oxc/pull/21915
+
+// export type aType = & // Comment
+// "VALUE";
+
+export type bType =
+  // Comment
+  "VALUE";
+
+export type cType = /* Comment */ "VALUE";
+
+export type dType = /* Comment */ "VALUE";
+
+// export type eType = // Comment
+// & "VALUE";
+
+export type fType =
+  /* Comment */
+  "VALUE";
+
+export type gType =
+  // Comment
+  // Comment
+  "VALUE";
+
+export type hType = "VALUE";
+
+export type iType = /* Comment */ /* Comment */ "VALUE";
+
+export type jType = /* Comment */ /* Comment */ "VALUE";
+
+export type kType =
+  /* Comment */
+  // Comment
+  "VALUE";
+
+export type lType =
+  /* Comment */ // Comment
+  "VALUE";
+
+export type mType = "VALUE"; /* Comment */
+
+export type nType = /* Comment */ "VALUE"; // Comment
+
+// type oType = // Comment
+// & // Comment
+// "VALUE"
 
 ================================================================================
 `;

tests/format/typescript/intersection/consistent-with-flow/single-member.ts

@@ -0,0 +1,53 @@
+// https://github.com/oxc-project/oxc/pull/21915
+
+// export type aType = & // Comment
+// "VALUE";
+
+export type bType = &
+// Comment
+"VALUE";
+
+export type cType = & /* Comment */
+"VALUE";
+
+export type dType = /* Comment */
+& "VALUE";
+
+// export type eType = // Comment
+// & "VALUE";
+
+export type fType = &
+/* Comment */
+"VALUE";
+
+export type gType = &
+// Comment
+// Comment
+"VALUE";
+
+export type hType = &
+"VALUE";
+
+export type iType = /* Comment */ /* Comment */ & "VALUE";
+
+export type jType = /* Comment */
+/* Comment */ & "VALUE";
+
+export type kType = /* Comment */
+&
+// Comment
+"VALUE";
+
+export type lType = /* Comment */ &
+// Comment
+"VALUE";
+
+export type mType = & "VALUE" /* Comment */;
+
+export type nType = // Comment
+& /* Comment */
+"VALUE";
+
+// type oType = // Comment
+// & // Comment
+// "VALUE"

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

@@ -567,13 +567,13 @@ type A2 = C;
 type A3 = C;
 type A4 = C;
 type A5 = C;
-type A6 /*1*/ = C;
+type A6 = /*1*/ C;
-type A7 /*1*/ = C;
+type A7 = /*1*/ C;
-type A8 /*1*/ = C;
+type A8 = /*1*/ C;
-type A9 /*1*/ = C;
+type A9 = /*1*/ C;
-type A10 /*1*/ = /*2*/ C;
+type A10 = /*1*/ /*2*/ C;
-type A11 /*1*/ = /*2*/ C;
+type A11 = /*1*/ /*2*/ C;
-type A12 /*1*/ = C;
+type A12 = /*1*/ C;
 type A13 = /*1*/ C;
 
 type Aa1 = /*1*/ /*2*/ C | D;
@@ -583,7 +583,7 @@ type Aa3 = /*1*/ /*2*/ C | /*3*/ D /*4*/;
 type C1 = /*1*/ a | b;
 type C2 = /*1*/ a | b;
 type C3 = /*1*/ a | b;
-type C4 /*1*/ = a | b;
+type C4 = /*1*/ a | b;
 type C5 = /*1*/ a | b;
 type C6 /*0*/ = /*1*/ a | b;
 

tests/format/typescript/union/single-type/__snapshots__/format.test.js.snap

@@ -1,5 +1,34 @@
 // Jest Snapshot v1, https://jestjs.io/docs/snapshot-testing
 
+exports[`comments.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+// https://github.com/prettier/prettier/issues/18834
+type A1 = /* 1 */ | T1;
+type A2 = /* 1 */ | (T2);
+type A3 = (/* 1 */ | T3);
+type A4 = /* 1 */ | /* 2 */ T4;
+type A5 = /* 1 */ | (/* 2 */ T5);
+type A6 = /* 0 */ /* 1 */ | /* 2 */ T6;
+type A7 = /* 0 */ | /* 1 */ T7;
+type A8 /* = */ /* 1:before */ = /* 2 */ | /* 3 */ T7;
+
+=====================================output=====================================
+// https://github.com/prettier/prettier/issues/18834
+type A1 = /* 1 */ T1;
+type A2 = /* 1 */ T2;
+type A3 = /* 1 */ T3;
+type A4 = /* 1 */ /* 2 */ T4;
+type A5 = /* 1 */ /* 2 */ T5;
+type A6 = /* 0 */ /* 1 */ /* 2 */ T6;
+type A7 = /* 0 */ /* 1 */ T7;
+type A8 /* = */ /* 1:before */ = /* 2 */ /* 3 */ T7;
+
+================================================================================
+`;
+
 exports[`single-type.ts format 1`] = `
 ====================================options=====================================
 parsers: ["typescript"]
@@ -13,9 +42,51 @@ type A1 =
   );
 
 =====================================output=====================================
-type A1 /* 2 */ = /* 1 */ /* 3 */ /* 4 */ {
+type A1 = /* 1 */ /* 2 */ /* 3 */ /* 4 */ {
   key: string;
 };
 
 ================================================================================
 `;
+
+exports[`single-type-2.ts format 1`] = `
+====================================options=====================================
+parsers: ["typescript"]
+                                                      printWidth: 80 (default) |
+=====================================input======================================
+// https://github.com/oxc-project/oxc/pull/21915
+export type myType = | // Comment
+  "A";
+
+// Block comment same-line after pipe
+type BlockComment = | /* block */
+  "B";
+
+// Same-line comment then own-line comment
+type Mixed = | // first
+  // second
+  "C";
+
+// Long line comment that exceeds printWidth on the \`=\` line
+type LongType = | // This is a really long comment that might exceed the print width limit
+  "A";
+
+=====================================output=====================================
+// https://github.com/oxc-project/oxc/pull/21915
+export type myType = // Comment
+  "A";
+
+// Block comment same-line after pipe
+type BlockComment = /* block */ "B";
+
+// Same-line comment then own-line comment
+type Mixed = // first
+  // second
+  "C";
+
+// Long line comment that exceeds printWidth on the \`=\` line
+type LongType = // This is a really long comment that might exceed the print width limit
+  "A";
+
+================================================================================
+`;

tests/format/typescript/union/single-type/comments.ts

@@ -0,0 +1,9 @@
+// https://github.com/prettier/prettier/issues/18834
+type A1 = /* 1 */ | T1;
+type A2 = /* 1 */ | (T2);
+type A3 = (/* 1 */ | T3);
+type A4 = /* 1 */ | /* 2 */ T4;
+type A5 = /* 1 */ | (/* 2 */ T5);
+type A6 = /* 0 */ /* 1 */ | /* 2 */ T6;
+type A7 = /* 0 */ | /* 1 */ T7;
+type A8 /* = */ /* 1:before */ = /* 2 */ | /* 3 */ T7;

tests/format/typescript/union/single-type/single-type-2.ts

@@ -0,0 +1,16 @@
+// https://github.com/oxc-project/oxc/pull/21915
+export type myType = | // Comment
+  "A";
+
+// Block comment same-line after pipe
+type BlockComment = | /* block */
+  "B";
+
+// Same-line comment then own-line comment
+type Mixed = | // first
+  // second
+  "C";
+
+// Long line comment that exceeds printWidth on the `=` line
+type LongType = | // This is a really long comment that might exceed the print width limit
+  "A";