Ensure error is logged when Closure fails

[ian-craig]

Fixes #162.

Whenever the compiler process exits with non-zero code, we should be reporting some error back to Webpack.

It looks like the on close for compilerProcess has some custom error (and warning?) handling around parsing stderr, but simply calls reject() with no error at the end. The result is for non-zero exit but no stderr we reject, but never pass an error to Webpack.

I think most cases could be cleaned up by passing the error through reject(error) instead of this.reportErrors(compilation, [error]), but not if the stdout parsing logic found warnings but no errors. Instead I've opted to just add another case here that's handled, but I'm not 100% sure there are no other edge cases here.

[ChadKillingsworth]

What's a good way to trigger this just so I can double check it does what it says?

[ian-craig]

The real scenario I hit was a missing dependency which caused the windows version of Closure to fail to run. I suspect that the error was in Windows or whatever wrapper Closure uses to compile a "native" version from Java, so there wasn't the usual error handling from Closure itself.

As a simple test I override the java exe path and ran with platform ['java'].

ClosureCompiler.prototype.javaPath = "my/script/which/exits/1";
new ClosurePlugin({ platform: ['java'] }, ...);

If you do this before applying this PR fix you should see that Webpack passes with no errors, but the bundle is unminified.

[ChadKillingsworth]

Retriggering CI

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ian-craig / name: Ian Craig (af79925, f548d4a)

[aboktor]

@ian-craig I believe this requires you to sign the CLA

[ian-craig]

Signed, hopefully you're good to go now 🚀
Thanks for the bump @aboktor