fix: string `//# sourceMappingURL=` breaking tests

[zanona]

This bug was initially reported on avajs/ava#1595, however, it was confirmed this happened with mocha as well so it might be something happening with nyc.

Expected Behavior

Files containing the string //# sourceMappingURL= to be tested without breaking.

Observed Behavior

Apparently, there's a bug where files containing a string with the initial part of a sourcemap instruction, i.e: //# sourceMappingURL=, will fail to generate code coverage as well as being tested.

Bonus Points! Code (or Repository) that Reproduces Issue

Repro: https://github.com/zanona/ava-sourcemap-fail

Forensic Information

Operating System: the operating system you observed the issue on.
Environment Information: information about your project's environment, see instructions below:

node -e "var os=require('os');console.log('Node.js ' + process.version + '\n' + os.platform() + ' ' + os.release())"
Node.js v8.7.0
darwin 16.7.0
ava --version > 0.23.0
npm --version > 5.5.1

[novemberborn]

I think the source map util used by nyc does a string search for the comment pattern. It doesn't generate an AST for the file.

If it's possible try breaking up the string, e.g. '//# source' + 'MappingURL=' to avoid this problem.

[zanona]

thank @novemberborn. yep, that's why I have done so far to work around it, however, I believe the parser can be improved to only catch '//# sourceMappingURL=' on the beginning of lines, etc.

[novemberborn]

This is an upstream issue though, see thlorenz/convert-source-map#60.

[zanona]

@novemberborn Haha, oh my that's NPM 😜 It feels like "The Twelve Tasks of Asterix".
Thanks for pointing that out.

[zanona]

it seems this has now been fixed at thlorenz/convert-source-map@46a6c17 which sits under 1.5.1, so as long as nyc updates their dependencies, it's all good here as well.

[bcoe]

@zanona thanks for tracking down this upstream bug.