nyc makes stack traces unreadable

[jantimon]

When adding nyc to my ava test runs I receive wrong file numbers in stack traces
as shown in the following examples:

Without nyc

ava -v

returns:

TypeError: this.getModuleNameById is not a function
      mymodule/index.js:137:52

With nyc

nyc ava -v

returns:

TypeError: this.getModuleNameById is not a function
    mymodule/index.js:9:7575

(my error was neither in line 9 nor in column 7575 but in line 137)

[novemberborn]

Yea, this is a known issue, although looking through the issue list it's not explicitly tracked.

Code coverage works by transforming the original source code. Stack traces need to be translated in order to be accurate. nyc doesn't attempt to do this. It's tricky because AVA does and it's unclear how between the two of them stack trace conversion would interact.

[jantimon]

Could a sourcemap solve this?

[novemberborn]

Yes, and I prototyped a solution in #217. I'm not entirely sure we can get source maps out of istanbul though, and I haven't had the time to research the interaction of multiple source-map-support installations within the same process.

[jantimon]

I see - sounds way more complicated than I thought..

[bcoe]

see also: #137

[bcoe]

CC: @gotwarlost it would be nice to consolidate Istanbul and nyc's source-map handling, and to address issues such as stack traces 💯

[kpdecker]

(Deleted prior comment)
It appears that this was throwing and causing the non-instrumented path to trigger, which then defaulted to the original source map, vs. the new one. Continuing investigation.

[lxe]

If you already use babel, one way to allow error stack traces to work with node-sourcemap-support is to use https://github.com/istanbuljs/babel-plugin-istanbul, and set nyc's "sourceMap" and "instrument" settings to false.

[sompylasar]

#619 (comment)

[bcoe]

closing in favor of #619.