upgrade 3.19 to 4.3.0 - no-multi-spaces - incredibly slow

[jzastrow]

Rule                     |  Time (ms) | Relative
:------------------------|-----------:|--------:
no-multi-spaces          | 128895.239 |    98.8%
indent                   |    572.412 |     0.4%
comma-style              |     87.177 |     0.1%
comma-spacing            |     62.077 |     0.0%
no-regex-spaces          |     51.506 |     0.0%
keyword-spacing          |     50.365 |     0.0%
mocha/no-identical-title |     47.103 |     0.0%
no-control-regex         |     42.972 |     0.0%
key-spacing              |     41.282 |     0.0%
no-useless-escape        |     38.029 |     0.0%

Tell us about your environment

• ESLint Version:4.3
• Node Version:8.1.4
• npm Version:5.3.0

What parser (default, Babel-ESLint, etc.) are you using?

Please show your full configuration:

{
  "root": true,
  "extends": "eslint:recommended",

  "rules": {

    "curly": ["error", "all"],
    "eqeqeq": "error",
    "no-eq-null": "error",
    "vars-on-top": "error",
    "wrap-iife": ["error", "any"],
    "max-params": ["warn", { "max": 5 }],
    "no-console": "error",
    "no-unused-vars": ["error", {
      "vars": "all",
      "args": "none"
    }],
    "semi": ["error", "always"],


    // Structure

    "block-spacing": ["warn", "always"],
    "brace-style": ["warn", "1tbs", { "allowSingleLine": true }],
    "comma-dangle": ["warn", "only-multiline"],
    "comma-spacing": ["warn", { "before": false, "after": true }],
    "comma-style": ["warn", "last"],
    "dot-location": ["warn", "property"],
    "indent": ["warn", "tab"],
    "key-spacing": ["warn", {
      "beforeColon": false,
      "afterColon": true,
      "mode": "minimum"
    }],
    "keyword-spacing": ["warn", { "before": true, "after": true }],
    "linebreak-style": ["warn", "unix"],
    "quotes": ["warn", "double", "avoid-escape"],
    "space-infix-ops": "warn",
    "space-unary-ops": ["warn", { "words": true, "nonwords": false }],


    // Other whitespace

    "eol-last": ["warn", "unix"],
    "newline-after-var": ["warn", "always"],
    "newline-before-return": "warn",
    "no-mixed-spaces-and-tabs": ["warn", "smart-tabs"],
    "no-multiple-empty-lines": ["warn", { "max": 2 }],
    "no-multi-spaces": ["warn"],
    "no-trailing-spaces": ["warn", { "skipBlankLines": true }],
    "padded-blocks": [0, "never"],
    "space-before-blocks": ["warn", "always"],
    "space-before-function-paren": ["warn", { "anonymous": "always", "named": "never" }],
    "space-in-parens": ["warn", "never"],
    "spaced-comment": ["warn", "always"],


    // Misc

    "valid-jsdoc": ["warn", {
      "prefer": {
        "return": "returns"
      },
      "requireReturn": false,
      "requireReturnDescription": false
    }],

	"mocha/no-exclusive-tests": "error",
	"mocha/no-identical-title": "error"
  },

  "parserOptions": {
	"ecmaVersion": 8,
	"sourceType": "module",
	"ecmaFeatures": {
	  "experimentalObjectRestSpread": true
	}
  },

  "env": {
    "node": true
  },

  "globals" : {
    "Promise": true
  },

  "plugins": [
	"mocha"
  ]
}

Configuration

What did you do? Please include the actual source code causing the issue.

eslint src test

What did you expect to happen?

As with eslint 3.19 completing within few seconds

What actually happened? Please include the actual, raw output from ESLint.

[not-an-aardvark]

Thanks for the report. Do you have an example of source code that causes this issue?

One potential way to find the file would be to run

eslint --debug src test

You'll get a bunch of debug messages as ESLint runs on each file. I suspect the problem is only occurring in a particular file, so if the debug messages stop printing for more than a few seconds, you can see which file is taking a long time to lint.

[not-an-aardvark]

Never mind, I figured out the problem. The rule takes 17 seconds to run if the source code is the letter a repeated 200000 times.

$ time node -e 'console.log("a".repeat(200000))' | bin/eslint.js --stdin --no-eslintrc --rule='no-multi-spaces:error'

real	0m17.572s
user	0m17.536s
sys	0m0.110s

Looks like there's a backtracking issue in this regex that causes it to take quadratic time with regard to the maximum line length of a file.

Out of interest, are you running ESLint on minified code? I think this would only be noticeable when there's a line that contains more than 50000 characters or so.