Config loading raises exceptions in Jest 27

[Ashley Claasen]

Hello,

I am running into the following error message when using jest-erb-transformer with Jest 27:

TypeError: Cannot read property 'filter' of undefined

      at loadConfig (../node_modules/jest-erb-transformer/index.js:68:48)
      at Object.process (../node_modules/jest-erb-transformer/index.js:129:20)
      at ScriptTransformer.transformSource (../node_modules/@jest/transform/build/ScriptTransformer.js:612:31)
      at ScriptTransformer._transformAndBuildScript (../node_modules/@jest/transform/build/ScriptTransformer.js:758:40)
      at ScriptTransformer.transform (../node_modules/@jest/transform/build/ScriptTransformer.js:815:19)

I have done some digging in the way configs are loaded, and it seems that config object is not approached correctly. On the line raising the exception:

const erbTransformers = jestConfig.transform.filter(e => e[1] === __filename)

changing it to

const erbTransformers = jestConfig.config.transform.filter(e => e[1] === __filename)

fixes the issue.

When I use Jest 26 instead of Jest 27 in my project, this line does not raise an exception and the transformer works as expected.

I don't have enough knowledge or skill to point out the breaking change in Jest 27 with certainty, but I think somewhere in there the way options are passed to transformers has been changed. I think in jestjs/jest#10834?

PR with a hotfix for the issue: #17

Thank you for all of your work, I am very happy with this transformer, and please let me know if I can help in any way!

[Chris Wood]

Hi @rjclaasen,

Yeah looks like they've updated how the config gets passed through in v27, thanks for catching this error and taking the time to make PR 💯

I'll take a look at the PR and update the circleci config to let it pass the CI checks.

Thanks, Chris

[Chris Wood]

@rjclaasen I've merged and released your changes in v1.2.4

Thanks again for spotting this and contributing :)