Support import clauses.

lib/src/ast/css/import.dart

@@ -5,6 +5,7 @@
 import 'package:source_span/source_span.dart';
 
 import '../../visitor/interface/css.dart';
+import 'media_query.dart';
 import 'node.dart';
 import 'value.dart';
 
@@ -15,9 +16,16 @@ class CssImport extends CssNode {
   /// This includes quotes.
   final CssValue<String> url;
 
+  /// The supports condition attached to this import.
+  final CssValue<String> supports;
+
+  /// The media query attached to this import.
+  final List<CssMediaQuery> media;
+
   final FileSpan span;
 
-  CssImport(this.url, this.span);
+  CssImport(this.url, this.span, {this.supports, Iterable<CssMediaQuery> media})
+      : media = media == null ? null : new List.unmodifiable(media);
 
   /*=T*/ accept/*<T>*/(CssVisitor/*<T>*/ visitor) => visitor.visitImport(this);
 }

lib/src/ast/sass/statement/plain_import_rule.dart

@@ -2,11 +2,14 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import 'package:charcode/charcode.dart';
 import 'package:source_span/source_span.dart';
 
 import '../../../visitor/interface/statement.dart';
 import '../interpolation.dart';
+import '../media_query.dart';
 import '../statement.dart';
+import '../supports_condition.dart';
 
 /// A rule that produces a plain CSS `@import` rule.
 class PlainImportRule implements Statement {
@@ -15,12 +18,28 @@ class PlainImportRule implements Statement {
   /// This already contains quotes.
   final Interpolation url;
 
+  /// The supports condition attached to this import, or `null` if no condition
+  /// is attached.
+  final SupportsCondition supports;
+
+  /// The media query attached to this import, or `null` if no condition is
+  /// attached.
+  final List<MediaQuery> media;
+
   final FileSpan span;
 
-  PlainImportRule(this.url, this.span);
+  PlainImportRule(this.url, this.span,
+      {this.supports, Iterable<MediaQuery> media})
+      : media = media == null ? null : new List.unmodifiable(media);
 
   /*=T*/ accept/*<T>*/(StatementVisitor/*<T>*/ visitor) =>
       visitor.visitPlainImportRule(this);
 
-  String toString() => "@import $url;";
+  String toString() {
+    var buffer = new StringBuffer("@import $url");
+    if (supports != null) buffer.write(" supports($supports)");
+    if (media != null) buffer.write(" $media");
+    buffer.writeCharCode($semicolon);
+    return buffer.toString();
+  }
 }

lib/src/parse/stylesheet.dart

@@ -625,23 +625,29 @@ abstract class StylesheetParser extends Parser {
   ///
   /// [start] should point before the `@`.
   Statement _importRule(LineScannerState start) {
-    // TODO: parse supports clauses, url(), and query lists
     var urlStart = scanner.state;
     var next = scanner.peekChar();
     if (next == $u || next == $U) {
       var url = _dynamicUrl();
+      whitespace();
+      var queries = _tryImportQueries();
       _expectStatementSeparator();
       return new PlainImportRule(
           new Interpolation([url], scanner.spanFrom(urlStart)),
-          scanner.spanFrom(start));
+          scanner.spanFrom(start),
+          supports: queries?.item1,
+          media: queries?.item2);
     }
 
     var url = string();
+    whitespace();
+    var queries = _tryImportQueries();
     if (_isPlainImportUrl(url)) {
       var interpolation = new Interpolation(
           [scanner.substring(urlStart.position)], scanner.spanFrom(urlStart));
       _expectStatementSeparator();
-      return new PlainImportRule(interpolation, scanner.spanFrom(start));
+      return new PlainImportRule(interpolation, scanner.spanFrom(start),
+          supports: queries?.item1, media: queries?.item2);
     } else if (_inControlDirective || _inMixin) {
       _disallowedAtRule(start);
       return null;
@@ -666,6 +672,38 @@ abstract class StylesheetParser extends Parser {
     return url.startsWith("http://") || url.startsWith("https://");
   }
 
+  /// Consumes a supports condition and/or a media query after an `@import`.
+  ///
+  /// Returns `null` if neither type of query can be found.
+  Tuple2<SupportsCondition, List<MediaQuery>> _tryImportQueries() {
+    SupportsCondition supports;
+    if (scanIdentifier("supports", ignoreCase: true)) {
+      scanner.expectChar($lparen);
+      var start = scanner.state;
+      if (scanIdentifier("not", ignoreCase: true)) {
+        whitespace();
+        supports = new SupportsNegation(
+            _supportsConditionInParens(), scanner.spanFrom(start));
+      } else {
+        var name = _expression();
+        scanner.expectChar($colon);
+        whitespace();
+        var value = _expression();
+        supports =
+            new SupportsDeclaration(name, value, scanner.spanFrom(start));
+      }
+      scanner.expectChar($rparen);
+      whitespace();
+    }
+
+    var media =
+        _lookingAtInterpolatedIdentifier() || scanner.peekChar() == $lparen
+            ? _mediaQueryList()
+            : null;
+    if (supports == null && media == null) return null;
+    return new Tuple2(supports, media);
+  }
+
   /// Consumes an `@include` rule.
   ///
   /// [start] should point before the `@`.

lib/src/visitor/perform.dart

@@ -609,7 +609,17 @@ class _PerformVisitor
   }
 
   Value visitPlainImportRule(PlainImportRule node) {
-    _parent.addChild(new CssImport(_interpolationToValue(node.url), node.span));
+    var url = _interpolationToValue(node.url);
+    var supports = node.supports;
+    var resolvedSupports = supports is SupportsDeclaration
+        ? "${supports.name.accept(this).toCssString()}: "
+            "${supports.value.accept(this).toCssString()})"
+        : (supports == null ? null : _visitSupportsCondition(supports));
+    _parent.addChild(new CssImport(url, node.span,
+        supports: resolvedSupports == null
+            ? null
+            : new CssValue(resolvedSupports, node.supports.span),
+        media: node?.media?.map(_visitMediaQuery)));
     return null;
   }
 

lib/src/visitor/serialize.dart

@@ -141,6 +141,17 @@ class _SerializeCssVisitor
     _writeIndentation();
     _buffer.write("@import ");
     _buffer.write(node.url.value);
+
+    if (node.supports != null) {
+      _buffer.writeCharCode($space);
+      _buffer.write(node.supports.value);
+    }
+
+    if (node.media != null) {
+      _buffer.writeCharCode($space);
+      _writeBetween(node.media, ', ', visitMediaQuery);
+    }
+
     _buffer.writeCharCode($semicolon);
   }