eslint-disable directives require C-style comments

[danvk]

🐛 Bug Report

• tslint-to-eslint-config version: 1.0.0
• ESLint version: v7.5.0
• Node version: v12.16.3

Actual Behavior

I had some code like this:

// See https://github.com/mikolalysenko/hash-int
export function hashInt(x: number) {
  // tslint:disable:no-bitwise
  const HASH = new Uint32Array(1);
  HASH[0] = x | 0;
  HASH[0] -= HASH[0] << 6;
  HASH[0] ^= HASH[0] >>> 17;
  HASH[0] -= HASH[0] << 9;
  HASH[0] ^= HASH[0] << 4;
  HASH[0] -= HASH[0] << 3;
  HASH[0] ^= HASH[0] << 10;
  HASH[0] ^= HASH[0] >>> 15;
  return HASH[0];
  // tslint:enable
}

When I migrate with --comments, this becomes:

export function hashInt(x: number) {
  // eslint-disable no-bitwise
  const HASH = new Uint32Array(1);
  HASH[0] = x | 0;
  HASH[0] -= HASH[0] << 6;
  HASH[0] ^= HASH[0] >>> 17;
  HASH[0] -= HASH[0] << 9;
  HASH[0] ^= HASH[0] << 4;
  HASH[0] -= HASH[0] << 3;
  HASH[0] ^= HASH[0] << 10;
  HASH[0] ^= HASH[0] >>> 15;
  return HASH[0];
  // eslint-enable
}

Unfortunately this allows all the no-bitwise errors to surface in eslint.

Expected Behavior

It seems that eslint requires C-style comments for eslint-disable directives:

export function hashInt(x: number) {
  /* eslint-disable no-bitwise */
  const HASH = new Uint32Array(1);
  HASH[0] = x | 0;
  HASH[0] -= HASH[0] << 6;
  HASH[0] ^= HASH[0] >>> 17;
  HASH[0] -= HASH[0] << 9;
  HASH[0] ^= HASH[0] << 4;
  HASH[0] -= HASH[0] << 3;
  HASH[0] ^= HASH[0] << 10;
  HASH[0] ^= HASH[0] >>> 15;
  return HASH[0];
  /* eslint-enable */
}

Note that this doesn't seem to be the case for eslint-disable-line or eslint-disable-next-line.

Reproduction

[KingDarBoja]

Hi @danvk, thanks for reporting this bug, you are correct as stated by the official ESLint docs, those require using code blocks whereas the eslint-disable-next-line and eslint-disable-line uses line comments.

[KingDarBoja]

Hi again @danvk, after some checks and fixing our test suite, I noticed your tslint comments using // instead of /* as stated by TSLint docs. Unfortunately, our logic requires the use of block comments as we use the TypeScript AST to check the comment kind (either Single or MultiLine) as you can see at https://github.com/typescript-eslint/tslint-to-eslint-config/blob/master/src/comments/parseFileComments.ts#L42

[danvk]

Hi @KingDarBoja. So what's the decision here? While it may be an accident that tslint allows //-style comments to disable rules for multiple lines, it's definitely existing behavior that would be nice to convert when migrating comments.

[KingDarBoja]

Let me try again if I can find a way to support that alternative on the linked PR.

EDIT Alright, this was easy to fix, now the PR has the correct behaviour for both cases 🚀