Allow empty URI strings in library directives

Fixes #38859

Change-Id: I1698b09bfee367634782f6f7c61f1dbda22edc0a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127600
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

Author: srawlins

pkg/analyzer/lib/src/context/source.dart

@@ -134,9 +134,12 @@ class SourceFactoryImpl implements SourceFactory {
 
   @override
   Source resolveUri(Source containingSource, String containedUri) {
-    if (containedUri == null || containedUri.isEmpty) {
+    if (containedUri == null) {
       return null;
     }
+    if (containedUri.isEmpty) {
+      return containingSource;
+    }
     try {
       // Force the creation of an escaped URI to deal with spaces, etc.
       return _internalResolveUri(containingSource, Uri.parse(containedUri));

pkg/analyzer/lib/src/dart/analysis/library_analyzer.dart

@@ -521,7 +521,8 @@ class LibraryAnalyzer {
         return file.exists;
       }
     }
-    return false;
+    // A library can refer to itself with an empty URI.
+    return source == _library.source;
   }
 
   /**

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -10192,6 +10192,9 @@ abstract class UriBasedDirectiveImpl extends DirectiveImpl
     if (uriContent == null) {
       return UriValidationCode.INVALID_URI;
     }
+    if (uriContent.isEmpty) {
+      return null;
+    }
     if (isImport && uriContent.startsWith(_DART_EXT_SCHEME)) {
       return UriValidationCode.URI_WITH_DART_EXT_SCHEME;
     }

pkg/analyzer/lib/src/summary2/library_builder.dart

@@ -296,7 +296,7 @@ class LibraryBuilder {
       directive.configurations,
       directive.uri.stringValue,
     );
-    if (relativeUriStr == null || relativeUriStr.isEmpty) {
+    if (relativeUriStr == null) {
       return null;
     }
     var relativeUri = Uri.parse(relativeUriStr);

pkg/analyzer/lib/src/summary2/linked_unit_context.dart

@@ -137,7 +137,7 @@ class LinkedUnitContext {
   /// Return the [LibraryElement] referenced in the [node].
   LibraryElement directiveLibrary(UriBasedDirective node) {
     var uriStr = LazyDirective.getSelectedUri(node);
-    if (uriStr == null || uriStr.isEmpty) return null;
+    if (uriStr == null) return null;
     return bundleContext.elementFactory.libraryOfUri(uriStr);
   }
 

pkg/analyzer/test/generated/compile_time_error_code.dart

@@ -2354,31 +2354,6 @@ class A<E> {
     ]);
   }
 
-  test_invalidUri_export() async {
-    await assertErrorsInCode('''
-export 'ht:';
-''', [
-      error(CompileTimeErrorCode.INVALID_URI, 7, 5),
-    ]);
-  }
-
-  test_invalidUri_import() async {
-    await assertErrorsInCode('''
-import 'ht:';
-''', [
-      error(CompileTimeErrorCode.INVALID_URI, 7, 5),
-    ]);
-  }
-
-  test_invalidUri_part() async {
-    await assertErrorsInCode(r'''
-library lib;
-part 'ht:';
-''', [
-      error(CompileTimeErrorCode.INVALID_URI, 18, 5),
-    ]);
-  }
-
   test_isInConstInstanceCreation_restored() async {
     // If ErrorVerifier._isInConstInstanceCreation is not properly restored on
     // exit from visitInstanceCreationExpression, the error at (1) will be

pkg/analyzer/test/src/diagnostics/deferred_import_of_extension_test.dart

@@ -74,9 +74,9 @@ void f() {
 
   test_invalidUri() {
     assertErrorsInCode('''
-import '' deferred as foo;
+import 'ht:' deferred as foo;
 ''', [
-      error(CompileTimeErrorCode.INVALID_URI, 7, 2),
+      error(CompileTimeErrorCode.INVALID_URI, 7, 5),
     ]);
   }
 }

pkg/analyzer/test/src/diagnostics/invalid_uri_test.dart

@@ -0,0 +1,53 @@
+// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analyzer/src/error/codes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import '../dart/resolution/driver_resolution.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(InvalidUriTest);
+  });
+}
+
+@reflectiveTest
+class InvalidUriTest extends DriverResolutionTest {
+  test_emptyUri() async {
+    await assertNoErrorsInCode('''
+import '' as top;
+int x;
+class C {
+  int x;
+  int get y => top.x; // ref
+}
+''');
+    assertElement(findNode.simple('x; // ref'), findElement.topGet('x'));
+  }
+
+  test_invalidScheme_export() async {
+    await assertErrorsInCode('''
+export 'ht:';
+''', [
+      error(CompileTimeErrorCode.INVALID_URI, 7, 5),
+    ]);
+  }
+
+  test_invalidScheme_import() async {
+    await assertErrorsInCode('''
+import 'ht:';
+''', [
+      error(CompileTimeErrorCode.INVALID_URI, 7, 5),
+    ]);
+  }
+
+  test_invalidScheme_part() async {
+    await assertErrorsInCode(r'''
+part 'ht:';
+''', [
+      error(CompileTimeErrorCode.INVALID_URI, 5, 5),
+    ]);
+  }
+}

pkg/analyzer/test/src/diagnostics/test_all.dart

@@ -160,6 +160,7 @@ import 'invalid_required_optional_positional_param_test.dart'
 import 'invalid_required_positional_param_test.dart'
     as invalid_required_positional_param;
 import 'invalid_sealed_annotation_test.dart' as invalid_sealed_annotation;
+import 'invalid_uri_test.dart' as invalid_uri;
 import 'invalid_use_of_covariant_in_extension_test.dart'
     as invalid_use_of_covariant_in_extension;
 import 'invalid_use_of_never_value_test.dart' as invalid_use_of_never_value;
@@ -504,6 +505,7 @@ main() {
     invalid_required_optional_positional_param.main();
     invalid_required_positional_param.main();
     invalid_sealed_annotation.main();
+    invalid_uri.main();
     invalid_use_of_covariant_in_extension.main();
     invalid_use_of_never_value.main();
     invalid_use_of_null_value.main();

pkg/analyzer/test/src/summary/resynthesize_common.dart

@@ -6801,7 +6801,7 @@ Future<dynamic> f;
     allowMissingFiles = true;
     var library = await checkLibrary('''
 @foo
-import '';
+import 'ht:';
 ''');
     checkElementText(library, r'''
 @
@@ -7878,19 +7878,18 @@ class C {
 ''');
   }
 
-  test_invalidUri_part_emptyUri() async {
+  test_part_emptyUri() async {
     allowMissingFiles = true;
     var library = await checkLibrary(r'''
 part '';
 class B extends A {}
 ''');
     checkElementText(library, r'''
-part '<unresolved>';
+part 'test.dart';
+class B {
+}
 class B {
 }
---------------------
-unit: null
-
 ''');
   }