use `astTransformers` for import polyfills wont break cache

[xiejay97]

🐛 Bug Report

I have a custom transformer that add polyfills for all test file.

But after modify transformer and rerun test. The cache not clear, I have to run jest --clearCache and all things as expected.

For example, I write a error path to polyfills, so that all tests should throw error.
But just polyfills test file fail (which top has import '@polyfills';), others passed test.
This behavior really strange.

[ahnpnl]

Ah, this might be because ts-jest didn't load transformer content to create cache key, hence cache key remains the same despite what you changed in your transformer.

[xiejay97]

Ah, this might be because ts-jest didn't load transformer content to create cache key, hence cache key remains the same despite what you changed in your transformer.

thanks for your job 👍