fix(css): when compiling CSS, leave absolute imports alone

Closes #4592

modules/angular2/src/core/compiler/style_url_resolver.ts

@@ -24,6 +24,11 @@ function extractUrls(resolver: UrlResolver, baseUrl: string, cssText: string, fo
     string {
   return StringWrapper.replaceAllMapped(cssText, _cssImportRe, (m) => {
     var url = isPresent(m[1]) ? m[1] : m[2];
+    var schemeMatch = RegExpWrapper.firstMatch(_urlWithSchemaRe, url);
+    if (isPresent(schemeMatch) && schemeMatch[1] != 'package') {
+      // Do not attempt to resolve non-package absolute URLs with URI scheme
+      return m[0];
+    }
     foundUrls.push(resolver.resolve(baseUrl, url));
     return '';
   });
@@ -50,3 +55,6 @@ var _cssUrlRe = /(url\()([^)]*)(\))/g;
 var _cssImportRe = /@import\s+(?:url\()?\s*(?:(?:['"]([^'"]*))|([^;\)\s]*))[^;]*;?/g;
 var _quoteRe = /['"]/g;
 var _dataUrlRe = /^['"]?data:/g;
+// TODO: can't use /^[^:/?#.]+:/g due to clang-format bug:
+//       https://github.com/angular/angular/issues/4596
+var _urlWithSchemaRe = /^['"]?([a-zA-Z\-\+\.]+):/g;

modules/angular2/src/core/dom/emulated_css.dart

@@ -28,6 +28,8 @@ List<EmulatedCssRule> emulateRules(Iterable<cssv.TreeNode> rules) {
         return new EmulatedCssStyleRule(node);
       } else if (node is cssv.MediaDirective) {
         return new EmulatedCssMedialRule(node);
+      } else if (node is cssv.ImportDirective) {
+        return new EmulatedCssImportRule(node);
       }
     })
     .where((r) => r != null)
@@ -100,3 +102,12 @@ class EmulatedMediaList {
         .map((q) => q.span.text).join(' and ');
   }
 }
+
+/// Emulates [CSSImportRule](https://developer.mozilla.org/en-US/docs/Web/API/CSSImportRule)
+class EmulatedCssImportRule extends EmulatedCssRule {
+  EmulatedCssImportRule(cssv.ImportDirective directive) {
+    this
+      ..type = 3
+      ..cssText = '@${directive.span.text};';
+  }
+}

modules/angular2/test/core/compiler/shadow_css_spec.ts

@@ -154,5 +154,11 @@ export function main() {
       var css = s('x >>> y {}', 'a');
       expect(css).toEqual('x[a] y[a] {}');
     });
+
+    it('should pass through @import directives', () => {
+      var styleStr = '@import url("https://fonts.googleapis.com/css?family=Roboto");';
+      var css = s(styleStr, 'a');
+      expect(css).toEqual(styleStr);
+    });
   });
 }

modules/angular2/test/core/compiler/style_url_resolver_spec.ts

@@ -88,5 +88,26 @@ export function main() {
           .toEqual(['http://ng.io/print1.css', 'http://ng.io/print2.css']);
     });
 
+    it('should leave absolute non-package @import urls intact', () => {
+      var css = `@import url('http://server.com/some.css');`;
+      var styleWithImports = resolveStyleUrls(urlResolver, 'http://ng.io', css);
+      expect(styleWithImports.style.trim()).toEqual(`@import url('http://server.com/some.css');`);
+      expect(styleWithImports.styleUrls).toEqual([]);
+    });
+
+    it('should resolve package @import urls', () => {
+      var css = `@import url('package:a/b/some.css');`;
+      var styleWithImports = resolveStyleUrls(new FakeUrlResolver(), 'http://ng.io', css);
+      expect(styleWithImports.style.trim()).toEqual(``);
+      expect(styleWithImports.styleUrls).toEqual(['fake_resolved_url']);
+    });
+
   });
 }
+
+/// The real thing behaves differently between Dart and JS for package URIs.
+class FakeUrlResolver extends UrlResolver {
+  constructor() { super(); }
+
+  resolve(baseUrl: string, url: string): string { return 'fake_resolved_url'; }
+}

modules_dart/transform/lib/src/transform/common/url_resolver.dart

@@ -59,9 +59,8 @@ Uri toAssetScheme(Uri absoluteUri) {
     return absoluteUri;
   }
   if (absoluteUri.scheme != 'package') {
-    throw new FormatException(
-        'Unsupported URI scheme "${absoluteUri.scheme}" encountered.',
-        absoluteUri);
+    // Pass through URIs with non-package scheme
+    return absoluteUri;
   }
 
   if (absoluteUri.pathSegments.length < 2) {

modules_dart/transform/test/transform/common/url_resolver_tests.dart

@@ -88,9 +88,9 @@ void allTests() {
           .toThrowWith(anInstanceOf: FormatException);
     });
 
-    it('should throw for unsupported schemes', () {
-      expect(() => toAssetScheme(Uri.parse('file:///angular2')))
-          .toThrowWith(anInstanceOf: FormatException);
+    it('should pass through unsupported schemes', () {
+      var uri = 'http://server.com/style.css';
+      expect('${toAssetScheme(Uri.parse(uri))}').toEqual(uri);
     });
 
     it('should throw if passed a null uri', () {

modules_dart/transform/test/transform/stylesheet_compiler/all_tests.dart

@@ -16,6 +16,9 @@ const SIMPLE_CSS = '''
 }
 ''';
 
+const HTTP_IMPORT = 'https://fonts.googleapis.com/css?family=Roboto';
+const CSS_WITH_IMPORT = '@import url(${HTTP_IMPORT});';
+
 main() {
   Html5LibDomAdapter.makeCurrent();
   allTests();
@@ -60,6 +63,20 @@ allTests() {
     expect(transform.outputs[1].id.toString())
         .toEqual('somepackage|lib/style.css.shim.dart');
   });
+
+  it('should compile stylesheets with imports', () async {
+    var cssFile = new Asset.fromString(
+        new AssetId('somepackage', 'lib/style.css'), CSS_WITH_IMPORT);
+    var transform = new FakeTransform()..primaryInput = cssFile;
+    await subject.apply(transform);
+    expect(transform.outputs.length).toBe(2);
+    expect(transform.outputs[0].id.toString())
+        .toEqual('somepackage|lib/style.css.dart');
+    expect(transform.outputs[1].id.toString())
+        .toEqual('somepackage|lib/style.css.shim.dart');
+    expect(await transform.outputs[0].readAsString()).toContain(HTTP_IMPORT);
+    expect(await transform.outputs[1].readAsString()).toContain(HTTP_IMPORT);
+  });
 }
 
 @proxy