TS5.5-beta injects a random `@ts-expect-error` comment in the generated `.d.ts` files

[nicolo-ribaudo]

🔎 Search Terms

comment 5.5 invalid injected inlined

🕗 Version & Regression Information

• This changed in version 5.5-beta

⏯ Playground Link

No response

💻 Code

1. Clone https://github.com/nicolo-ribaudo/babel/tree/ts-5.5-random-comment
2. Run yarn to install all deps
3. Run make generate-tsconfig to generate all the tsconfig.json files
4. Run yarn tsc -b ./packages/babel-helper-plugin-utils/tsconfig.json

If you ever need to reset the TS state (e.g. delete all .tsbuildinfo and .d.ts files), run make clean-dts.

🙁 Actual behavior

dts/packages/babel-parser/src/plugins/typescript/index.d.ts, line 540 contains a random @ts-expect-error comment:

        parseExprListItem(this: Parser, allowEmpty?: boolean, refExpressionErrors?: ExpressionErrors | null, allowPlaceholder?: boolean | // @ts-expect-error todo(flow->ts) 0121
        null): N.Expression | null;

That parseExprListItem is inlined there from another file, that doesn't have that comment:
https://github.com/nicolo-ribaudo/babel/blob/e5726bde94899149d60706698a0f0a968208bf60/packages/babel-parser/src/parser/expression.ts#L2711-L2728

Instead, that comment is coming from
https://github.com/nicolo-ribaudo/babel/blob/e5726bde94899149d60706698a0f0a968208bf60/packages/babel-parser/src/plugins/typescript/index.ts#L2637-L2642

🙂 Expected behavior

The comment shouldn't be there

[nicolo-ribaudo]

I tried using every-ts bisect, and this regression has been introduced by #58085 (cc @weswigham).

A simple reproduction that doesn't take 20s to run TS is:

1. Clone https://github.com/nicolo-ribaudo/babel/tree/ts-5.5-random-comment
2. Run make generate-tsconfig to generate all the tsconfig.json files
3. Inside ./packages/babel-parser, add the files as defined below.
4. Inside ./packages/babel-parser, run rm tsconfig.tsbuildinfo && rm -rf ./dts-parser && every-ts tsc -b . and check ./dts-parser/src/plugins/typescript/index.d.ts

packages/babel-parser/tsconfig.json

{
  "extends": "../../tsconfig.base.json",
  "include": ["./src/**/*.ts"],
  "compilerOptions": {
    "rootDir": ".",
    "declarationDir": "./dts-parser"
  }
}

packages/babel-parser/src/globals.d.ts

declare module "@babel/helper-validator-identifier" {
  export function isReservedWord(word: string, inModule: boolean): boolean;
  export function isStrictReservedWord(
    word: string,
    inModule: boolean,
  ): boolean;
  export function isStrictBindOnlyReservedWord(word: string): boolean;
  export function isStrictBindReservedWord(
    word: string,
    inModule: boolean,
  ): boolean;
  export function isKeyword(word: string): boolean;
  export function isIdentifierStart(code: number): boolean;
  export function isIdentifierChar(code: number): boolean;
  export function isIdentifierName(name: string): boolean;
}

declare module "@babel/helper-string-parser" {
  export type StringContentsErrorHandlers = EscapedCharErrorHandlers & {
    unterminated(
      initialPos: number,
      initialLineStart: number,
      initialCurLine: number,
    ): void;
  };
  export function readStringContents(
    type: "single" | "double" | "template",
    input: string,
    pos: number,
    lineStart: number,
    curLine: number,
    errors: StringContentsErrorHandlers,
  ):
    | {
        pos: number;
        str: string;
        firstInvalidLoc: { pos: number; lineStart: number; curLine: number };
        lineStart: number;
        curLine: number;
        containsInvalid?: undefined;
      }
    | {
        pos: number;
        str: string;
        firstInvalidLoc: { pos: number; lineStart: number; curLine: number };
        lineStart: number;
        curLine: number;
        containsInvalid: boolean;
      };
  type EscapedCharErrorHandlers = HexCharErrorHandlers &
    CodePointErrorHandlers & {
      strictNumericEscape(
        pos: number,
        lineStart: number,
        curLine: number,
      ): void;
    };
  type HexCharErrorHandlers = IntErrorHandlers & {
    invalidEscapeSequence(
      pos: number,
      lineStart: number,
      curLine: number,
    ): void;
  };
  export type IntErrorHandlers = {
    numericSeparatorInEscapeSequence(
      pos: number,
      lineStart: number,
      curLine: number,
    ): void;
    unexpectedNumericSeparator(
      pos: number,
      lineStart: number,
      curLine: number,
    ): void;
    invalidDigit(
      pos: number,
      lineStart: number,
      curLine: number,
      radix: number,
    ): boolean;
  };
  export function readInt(
    input: string,
    pos: number,
    lineStart: number,
    curLine: number,
    radix: number,
    len: number | undefined,
    forceLen: boolean,
    allowNumSeparator: boolean | "bail",
    errors: IntErrorHandlers,
    bailOnError: boolean,
  ): {
    n: number;
    pos: number;
  };
  export type CodePointErrorHandlers = HexCharErrorHandlers & {
    invalidCodePoint(pos: number, lineStart: number, curLine: number): void;
  };
  export function readCodePoint(
    input: string,
    pos: number,
    lineStart: number,
    curLine: number,
    throwOnInvalid: boolean,
    errors: CodePointErrorHandlers,
  ): {
    code: number;
    pos: number;
  };
}

[dragomirtitian]

Investigating this I found:

• visitExistingNodeTreeSymbols will visit child nodes. Then we get to:

return result === node ? setTextRange(context, factory.cloneNode(result), node) : result; 

• If the node is the same, it is cloned and it's position is set to -1 in setTextRange. The problem is sometimes the node is a different instance but it has been updated by the visitor (because it's children might have changed), the visitor will preserve original position of the node on the updated node.
• This is a problem when we reuse nodes across files, as node emitting considers all nodes that have a !=-1 position as being from the current file and looks for their comment

[dragomirtitian]

Self contained way to reproduce: Workbench