Jest 23 --config breaks create-react-app on Windows

[bugzpodder]

I am trying to use Jest 23 in create-react-app@next facebook/create-react-app#4555
In particular I've found windows config to break after the upgrade.
The specific part of config being generated is https://github.com/facebook/create-react-app/blob/next/packages/react-scripts/scripts/utils/createJestConfig.js#L47
In Jest 22.4.3 the regex is [\\\\\\\\\\\\]node_modules[\\\\\\\\\\\\].+\.(js|jsx|mjs)$|^.+\.module\.(css|sass|scss)$/ (12 slashes) in jest-runtime
In Jest 23 the error is Invalid regular expression: /[\\\\\]node_modules[\\\\\].+\.(js|jsx|mjs)$|^.+\.module\.(css|sass|scss)$/

Does not repo on other platforms.

[bugzpodder]

repo case:
different behaviors on Jest 23/22.4.3 on windows:
jest --config={\"transformIgnorePatterns\":[\"[/\\]node_modules[/\\]\"]}
#5941 #2381

I don't know the new behavior is intended (ie the way we were doing transformIgnorePatterns was wrong) or if its a jest 23 regression.
It's not an issue on linux.

[SimenB]

Only regex change I can find in the changelog is #5941. Does reverting that fix it for you?

It'd be awesome if you could put together a unit (or integration) test that passes against jest 22, but fails for jest 23

[bugzpodder]

Yep #5941 is the one that affected me. I can look into putting down a unittest after you guys figure out what the correct resolution is (see my previous comment w/ a small repo case).

[SimenB]

None on the core team uses windows, so we'll have to rely on the community to fix this. But having a test in the repo (skipped on windows) would be great for a potential contributor to jump in :)

[TroySchmidt]

@bugzpodder This is breaking my WallabyJS test running on Windows. Is there something you did to the configuration to override the effects of #5941 on breaking Jest 23?

[bugzpodder]

@TroySchmidt I basically changed:
jest --config={\"transformIgnorePatterns\":[\"[/\\]node_modules[/\\]\"]}
to
jest --config={\"transformIgnorePatterns\":[\"/node_modules/\"]}
I don't know if this is the correct change, hopefully this helps you.

[tshinnic]

Speculating...

jest-config/build/index.js::readConfig() calls normalize() on incoming option values and defaults, including transformIgnorePatterns.

When normalize() sees
options.transformIgnorePatterns: "[/\\]node_modules[/\\].+\.(js|jsx|mjs)$"
it converts that to
value: "[\\\\\]node_modules[\\\\\].+\.(js|jsx|mjs)$"

Note that really is 5 back slashes, 2 each from each incoming back slash and 1 from the forward slash. An odd number of back slashes produces much unhappiness for a later new RegExp().

normalize() uses normalizeUnmockedModulePathPatterns() which uses 'jest-regex-util'. Checking the results returned by that module's code finds:

> "/\\\\".replace(/(\/|\\(?![[\]{}()*+?.^$|]))/g, '\\\\').split('')
          [ '\\', '\\', '\\', '\\', '\\', '\\' ]
> "[/\\\\]".replace(/(\/|\\(?![[\]{}()*+?.^$|]))/g, '\\\\').split('')
          [ '[', '\\', '\\', '\\', '\\', '\\', ']' ]

so path separators are okay unless they happen to have char class delimiters around them. Perhaps the wrong routine is being used? Or rather, that one routine is being called for incompatible uses.

Oh, the rules wrt to '[' and ']' got changed by edd95fc and #5941

You probably do want separate routines...

[SimenB]

@hron thoughts?

[ThakurKarthik]

SyntaxError: Invalid regular expression: /[\\]node_modules[\\].+.(js|jsx|mjs)$/: Unterminated character class
at new RegExp ()

  at shouldTransform (node_modules/jest-runtime/build/script_transformer.js:603:9)