jest.mock() calls underneath the code mangle the stacktraces

[GeeWee]

• Issue

If you place code that is hoisted, such as jest.mock() calls, underneath your tests, the stacktrace line numbers are off.

Issue raised in #239 - more details there.

Workaround is to place the mock calls before any actual test code.

This bug is considered low priority.

[kulshekhar]

This happens because the sourcemaps generated by babel are based on the code as it is after hoisting. Any suggestions/contributions to fix this would be very welcome.

[cspotcode]

Babel supports inputting a sourcemap alongside the input code, right? So if the hoisting process generates a sourcemap, pass it to babel.

inputSourceMap option: https://babeljs.io/docs/usage/api/

[kulshekhar]

Hoisting is done in jest and not in babel (afaik) and jest doesn't update the sourcemap during the hosting process

[cspotcode]

@kulshekhar If that's the case, why does ts-jest have to call babel? Wouldn't jest be doing that after this preprocessor has finished its job? I'm trying to debug this bug so I'm figuring out how everything works.

[kulshekhar]

why does ts-jest have to call babel

iirc, this was needed to do hoisting. #235 has all the related discussion.

Wouldn't jest be doing that after this preprocessor has finished its job?

Jest doesn't directly do hoisting. It uses the babel-jest transformer to do that. Since jest doesn't use babel-jest when using ts-jest, we had to incorporate that bit of functionality directly in here.

This is to the best of my recollection. Please correct if I'm wrong @GeeWee

[GeeWee]

Yeah that's accurate.

Edit: I still think babel should be able to update the sourcemap during the hoisting though - I don't know why it doesn't happen in our case. Would love a PR fixing this, as I'm 90% sure it should be possible.