Add parser support for using a URI in a part-of directive

pkg/analyzer/lib/src/task/dart.dart

Index: pkg/analyzer/lib/src/task/dart.dart
diff --git a/pkg/analyzer/lib/src/task/dart.dart b/pkg/analyzer/lib/src/task/dart.dart
index 8821bc4d93011afe13a43f09ec1f6d5b239a5396..09a5803c4c8ef1f60f4feb8d6bb283ed4e36a3e8 100644
--- a/pkg/analyzer/lib/src/task/dart.dart
+++ b/pkg/analyzer/lib/src/task/dart.dart
@@ -1551,28 +1551,43 @@ class BuildLibraryElementTask extends SourceBasedAnalysisTask {
           // name as the library.
           //
           if (context.exists(partSource)) {
-            String partLibraryName =
-                _getPartLibraryName(partSource, partUnit, directivesToResolve);
-            if (partLibraryName == null) {
+            _NameOrSource nameOrSource = _getPartLibraryNameOrUri(
+                context, partSource, partUnit, directivesToResolve);
+            if (nameOrSource == null) {
               errors.add(new AnalysisError(
                   librarySource,
                   partUri.offset,
                   partUri.length,
                   CompileTimeErrorCode.PART_OF_NON_PART,
                   [partUri.toSource()]));
-            } else if (libraryNameNode == null) {
-              if (partsLibraryName == _UNKNOWN_LIBRARY_NAME) {
-                partsLibraryName = partLibraryName;
-              } else if (partsLibraryName != partLibraryName) {
-                partsLibraryName = null;
+            } else {
+              String name = nameOrSource.name;
+              if (name != null) {
+                if (libraryNameNode == null) {
+                  if (partsLibraryName == _UNKNOWN_LIBRARY_NAME) {
+                    partsLibraryName = name;
+                  } else if (partsLibraryName != name) {
+                    partsLibraryName = null;
+                  }
+                } else if (libraryNameNode.name != name) {
+                  errors.add(new AnalysisError(
+                      librarySource,
+                      partUri.offset,
+                      partUri.length,
+                      StaticWarningCode.PART_OF_DIFFERENT_LIBRARY,
+                      [libraryNameNode.name, name]));
+                }
+              } else {
+                Source source = nameOrSource.source;
+                if (source != librarySource) {
+                  errors.add(new AnalysisError(
+                      librarySource,
+                      partUri.offset,
+                      partUri.length,
+                      StaticWarningCode.PART_OF_DIFFERENT_LIBRARY,
+                      [librarySource.uri.toString(), source.uri.toString()]));
+                }
               }
-            } else if (libraryNameNode.name != partLibraryName) {
-              errors.add(new AnalysisError(
-                  librarySource,
-                  partUri.offset,
-                  partUri.length,
-                  StaticWarningCode.PART_OF_DIFFERENT_LIBRARY,
-                  [libraryNameNode.name, partLibraryName]));
             }
           }
           if (entryPoint == null) {
@@ -1679,7 +1694,10 @@ class BuildLibraryElementTask extends SourceBasedAnalysisTask {
    * Return the name of the library that the given part is declared to be a
    * part of, or `null` if the part does not contain a part-of directive.
    */
-  String _getPartLibraryName(Source partSource, CompilationUnit partUnit,
+  _NameOrSource _getPartLibraryNameOrUri(
+      AnalysisContext context,
+      Source partSource,
+      CompilationUnit partUnit,
       List<Directive> directivesToResolve) {
     NodeList<Directive> directives = partUnit.directives;
     int length = directives.length;
@@ -1689,7 +1707,15 @@ class BuildLibraryElementTask extends SourceBasedAnalysisTask {
         directivesToResolve.add(directive);
         LibraryIdentifier libraryName = directive.libraryName;
         if (libraryName != null) {
-          return libraryName.name;
+          return new _NameOrSource(libraryName.name, null);
+        }
+        String uri = directive.uri?.stringValue;
+        if (uri != null) {
+          Source librarySource =
+              context.sourceFactory.resolveUri(partSource, uri);
+          if (librarySource != null) {
+            return new _NameOrSource(null, librarySource);
+          }
         }
       }
     }
@@ -4021,6 +4047,7 @@ class ParseDartTask extends SourceBasedAnalysisTask {
     parser.parseFunctionBodies =
         options.analyzeFunctionBodiesPredicate(_source);
     parser.parseGenericMethodComments = options.strongMode;
+    parser.enableUriInPartOf = options.enableUriInPartOf;
     CompilationUnit unit = parser.parseCompilationUnit(tokenStream);
     unit.lineInfo = lineInfo;
 
@@ -6380,6 +6407,18 @@ class _ImportSourceClosureTaskInput extends TaskInputImpl<List<Source>> {
 }
 
 /**
+ * An object holding either the name or the source associated with a part-of
+ * directive.
+ */
+class _NameOrSource {
+  final String name;
+
+  final Source source;
+
+  _NameOrSource(this.name, this.source);
+}
+
+/**
  * The kind of the source closure to build.
  */
 enum _SourceClosureKind { IMPORT, EXPORT, IMPORT_EXPORT }