overrides with processor works unexpectedly

[JounQin]

Tell us about your environment

• ESLint Version: 7.21.0
• Node Version: v14.16.0
• npm Version: 7.5.6
• Operating System: GNU/Linux 5.4.0-1024-gcp

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using?

Default

Please show your full configuration:

https://github.com/JounQin/test/blob/eslint/.eslintrc.js

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

https://github.com/JounQin/test/blob/eslint/test.cjs

yarn eslint test.cjs

What did you expect to happen?

No error because prettier is intended to be disabled

What actually happened? Please copy-paste the actual, raw output from ESLint.

Oops! Something went wrong! :(

ESLint: 7.21.0

Error: ENOTDIR: not a directory, stat '/workspace/test/test.cjs/0_.cjs'
Occurred while linting /workspace/test/test.cjs/0_.cjs:1
    at Object.statSync (fs.js:1086:3)
    at isTypeSync (/workspace/test/node_modules/prettier/third-party.js:9748:46)
    at getDirectorySync (/workspace/test/node_modules/prettier/third-party.js:9802:62)
    at ExplorerSync.searchSync (/workspace/test/node_modules/prettier/third-party.js:9950:66)
    at _resolveConfig (/workspace/test/node_modules/prettier/index.js:25592:50)
    at Function.resolveConfig.sync (/workspace/test/node_modules/prettier/index.js:25621:42)
    at Program (/workspace/test/node_modules/eslint-plugin-prettier/eslint-plugin-prettier.js:167:40)
    at /workspace/test/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/workspace/test/node_modules/eslint/lib/linter/safe-emitter.js:45:38)

Steps to reproduce this issue:

1. clone https://github.com/JounQin/test/tree/eslint or open https://turquoise-limpet-v0as7arg.ws-us03.gitpod.io/
2. run yarn eslint test.cjs, there will be an error
3. toggle the comment in .eslintrc.js and run yarn eslint test.cjs again, there will be no error, but it is not expected, I want to check test.cjs with prettier but disable it on code block

Are you willing to submit a pull request to fix this bug?

I don't know how to fix it easily.

[mdjermanovic]

I can confirm this behavior.

When preprocess() returns a filename with the same extension as the original file, that virtual file will be linted with the configuration for the original file (except the "processor" option).

eslint/lib/linter/linter.js

Lines 1311 to 1326 in ebd7026

	// Resolve configuration again if the file extension was changed.
	if (configForRecursive && path.extname(blockName) !== originalExtname) {
	debug("Resolving configuration again because the file extension was changed.");
	return this._verifyWithConfigArray(
	blockText,
	configForRecursive,
	{ ...options, filename: blockName }
	);
	}
	// Does lint.
	return this._verifyWithoutProcessors(
	blockText,
	config,
	{ ...options, filename: blockName }
	);

I believe we assumed that if a processor used for *.foo files returns a .foo filename, then it's the same content, and calling this._verifyWithConfigArray again would cause infinite recursion. But, as a side effect of using the same config, overrides for *.foo/*.foo do not apply.

I'm not sure what's the intended behavior in this case. For users, it might make more sense to see this as the original file and thus make a configuration for *.foo (not *.foo/*.foo). On the other hand, it looks inconsistent with the behavior when processors return different extensions.

[JounQin]

I believe we assumed that if a processor used for *.foo files returns a .foo filename, then it's the same content, and calling this._verifyWithConfigArray again would cause infinite recursion.

That's not true for markdown/mdx in markdown/mdx.

[JounQin]

I think we should change the following

eslint/lib/linter/linter.js

Lines 1311 to 1319 in ebd7026

	// Resolve configuration again if the file extension was changed.
	if (configForRecursive && path.extname(blockName) !== originalExtname) {
	debug("Resolving configuration again because the file extension was changed.");
	return this._verifyWithConfigArray(
	blockText,
	configForRecursive,
	{ ...options, filename: blockName }
	);
	}

to

// Resolve configuration again if the file content or extension was changed.
if (configForRecursive && (text !== blockText || path.extname(blockName) !== originalExtname)) {
  debug('Resolving configuration again because the file content or extension was changed.')
  return this._verifyWithConfigArray(blockText, configForRecursive, {
    ...options,
    filename: blockName,
  })
}

@mdjermanovic I'd like to raise a PR if you like it.

[mdjermanovic]

@eslint/eslint-tsc thoughts about this, is it a bug or the intended behavior?

If it's a bug, does the fix in #14227 makes sense, and would it be a breaking change now?

[nzakas]

I think this is a bug. We probably did this for performance reasons, since calculating configs is expensive.

I’m also guessing this use case is fairly uncommon so fixing this bug doesn’t seem like a breaking change to me.

[btmills]

I agree this is a bug that we can fix in a semver-minor change.

[nzakas]

Marking as accepted. There is already a PR open.