canonicalize method

Future<AsyncCanonicalizeResult?> canonicalize(Uri url, { AsyncImporter? baseImporter, Uri? baseUrl, bool forImport = false, })

Canonicalizes url according to one of this cache's importers.

The baseUrl should be the canonical URL of the stylesheet that contains the load, if it exists.

Returns the importer that was used to canonicalize url, the canonical URL, and the URL that was passed to the importer (which may be resolved relative to baseUrl if it's passed).

If baseImporter is non-null, this first tries to use baseImporter to canonicalize url (resolved relative to baseUrl if it's passed).

If any importers understand url, returns that importer as well as the canonicalized URL and the original URL (resolved relative to baseUrl if applicable). Otherwise, returns null.

Implementation

Future<AsyncCanonicalizeResult?> canonicalize(Uri url,
    {AsyncImporter? baseImporter,
    Uri? baseUrl,
    bool forImport = false}) async {
  if (isBrowser &&
      (baseImporter == null || baseImporter is NoOpImporter) &&
      _importers.isEmpty) {
    throw "Custom importers are required to load stylesheets when compiling "
        "in the browser.";
  }

  if (baseImporter != null && url.scheme == '') {
    var relativeResult = await putIfAbsentAsync(
        _relativeCanonicalizeCache,
        (
          url,
          forImport: forImport,
          baseImporter: baseImporter,
          baseUrl: baseUrl
        ),
        () => _canonicalize(baseImporter, baseUrl?.resolveUri(url) ?? url,
            baseUrl, forImport));
    if (relativeResult != null) return relativeResult;
  }

  return await putIfAbsentAsync(
      _canonicalizeCache, (url, forImport: forImport), () async {
    for (var importer in _importers) {
      if (await _canonicalize(importer, url, baseUrl, forImport)
          case var result?) {
        return result;
      }
    }

    return null;
  });
}