ManifestStaticFilesStorage doesn't update JavaScript source map references

[Adam Johnson]

ManifestStaticFilesStorage replaces URL's in CSS files with the hashed equivalents, but doesn't have any other out-of-the-box rules. One common use case for cross-static-file-references is a ​JavaScript source map, a structured comment in a JS file.

I think it would be a reasonable inclusion that Django modifies these too. I got it working (with Whitenoise's subclass of ManifestStaticFilesStorage) with this extra regex pattern:

from whitenoise.storage import CompressedManifestStaticFilesStorage


class SuperStaticFilesStorage(CompressedManifestStaticFilesStorage):
    patterns = CompressedManifestStaticFilesStorage.patterns + (
        (
            "*.js",
            (
                (
                    r"(//# sourceMappingURL=(.*?\.js\.map))$",
                    "//# sourceMappingURL=%s",
                ),
            ),
        ),
    )

Ideally the regex would start with a ^{", which requires the regex mulitline flag, and would NOT be compiled in case-insenstive mode. The current storage implementation forces compiling regexes with only the case insensitive flag.}