fix: stop search if files names are undefined

[emuraton]

Summary

Files names seems to be undefined on certain cases for Window

      names.forEach(file => {
            ^

TypeError: Cannot read property 'forEach' of undefined
    at fs.readdir (C:\Users\timbault\talend-ui\ui\node_modules\jest-haste-map\build\crawlers\node.js:36:13)
    at go$readdir$cb (C:\Users\timbault\talend-ui\ui\node_modules\graceful-fs\graceful-fs.js:149:14)
    at FSReqWrap.oncomplete (fs.js:135:15)
error Command failed with exit code 1.

I'm not sure why this variable is undefined, but I added defensive code to return earlier more gracefuly.

Test plan

Added an unit test to confirm we return early if names is undefined.

fixes: #6715

[codecov-io]

Codecov Report

Merging #6761 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6761      +/-   ##
==========================================
- Coverage   66.98%   66.98%   -0.01%     
==========================================
  Files         250      250              
  Lines       10360    10363       +3     
  Branches        3        3              
==========================================
+ Hits         6940     6942       +2     
- Misses       3419     3420       +1     
  Partials        1        1

Impacted Files	Coverage Δ
packages/jest-haste-map/src/crawlers/node.js	98.78% <ø> (-1.22%)	⬇️

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[thymikee]

How about going a bit more idiomatic Node.js with if (err) {?

[SimenB]

Yeah, if that's what happens (unhandled error) that's the correct fix. @emuraton do you have a reproduction case for your error?

[emuraton]

@SimenB I did not suceed to replicate the issue case of @timbault.
But from the stack trace, callback doesnt return an error @thymikee, just names undefined.
I can add both check if you think its better (if( err || !names))

Doest it make sense?

[thymikee]

If it returns undefined names, but null err, it's a bug in Node imho and you should also file it there

[SimenB]

Agreed, the docs says you should always get an array: https://nodejs.org/api/fs.html#fs_fs_readdir_path_options_callback

[emuraton]

Sorry for the late answer, after double thought I think you were right before actually. Checking err should be enough.
If I find a bit of time today, I'll try to replicate to see if its a bug from Node or if your first comments were right

[thymikee]

Thanks, looking forward to it!

[emuraton]

After few tests cases, I always got something following this shape. So I think checking err, as you suggested, should be enough.

      { Error: ENOTDIR: not a directory, scandir '/Users/emilienmuraton/Code/jest/packages/jest-haste-map/src/__tests__/index.test.js'
        errno: -20,
        code: 'ENOTDIR',
        syscall: 'scandir',
        path: '/Users/emilienmuraton/Code/jest/packages/jest-haste-map/src/__tests__/index.test.js' }
      }
  { names: undefined }

[SimenB]

Could you update the changelog as well? :)

[thymikee]

You'll need to rebase/merge master, as this CHANGELOG is outdated (latest Jest release is 23.5.0)

[thymikee]

nvm, fixed that for you :)

[emuraton]

Thanks 👍

[github-actions]

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