@nitely Thanks for the PR - could you add a test for this so we can make sure sourcemaps are never broken again?

Also curious if the gulp built-in sourcemaps aren't working and you're already doing a test for this, if you do a failing test for that I can look into fixing that.

err, I checked the tests and they do test the sourcemaps are generated. I reverted the changes and ran the tests, and they pass (as I remembered).

The sourcemaps are generated, the file property is set. So, I went back to my project to try and reproduce the issue again. I found the only way to reproduce it is to pass the transpile option. Using babel at a later stage works just fine as a workaround, ex: .pipe(babel({presets: ['@babel/preset-env']})).

About the gulp built in sourcemaps, I found the dest function requires to pass { sourcemaps: true } as well, ex: .pipe(dest('output/', { sourcemaps: '.' }) to generate external sourcemaps, or .pipe(dest('output/', { sourcemaps: true })); to geenrate inlined sourcemaps. Otherwise they are not generated. It's in the docs.

@nitely Yeah that is expected - if you use just the gulp sourcemaps does this work or is the PR still needed?

The transpile option doesn't work. It throws the missing file property error when using either the gulp-sourcemaps, or the built-in sourcemaps.

gulp-babel on the other hand works fine with both gulp-sourcemaps and the built-in sourcemaps.

I can add tests for the transpile case, but I'll need to add babel as a devDependency, is that ok?