Allow null parent tag when calling GetTagHelpersGivenParent.

- A `null` parent tag in all of our other API represents "any" parent tag, or in this case "root". Prior to this change we'd expect the caller to do their own verification of the parent and then assume all `TagHelperDescriptor`s are valid; this isn't sufficient because only our code base should have that knowledge. #1188
aspnet · Apr 7, 2017 · 96d97f6 · 96d97f6
1 parent af3cf49
commit 96d97f6
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Showing 2 changed files with 20 additions and 5 deletions.
diff --git a/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs b/src/Microsoft.VisualStudio.LanguageServices.Razor/DefaultTagHelperFactsService.cs
@@ -138,11 +138,6 @@ public override IReadOnlyList<TagHelperDescriptor> GetTagHelpersGivenParent(TagH
                 throw new ArgumentNullException(nameof(documentContext));
             }
 
-            if (parentTag == null)
-            {
-                throw new ArgumentNullException(nameof(parentTag));
-            }
-
             var matchingDescriptors = new List<TagHelperDescriptor>();
             var descriptors = documentContext?.TagHelpers;
             if (descriptors?.Count == 0)

diff --git a/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs b/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultTagHelperFactsServiceTest.cs
@@ -286,6 +286,26 @@ public void GetTagHelpersGivenTag_RestrictsTagHelpersBasedOnParent()
             Assert.Equal(expectedDescriptors, descriptors, TagHelperDescriptorComparer.CaseSensitive);
         }
 
+        [Fact]
+        public void GetTagHelpersGivenParent_AllowsRootParentTag()
+        {
+            // Arrange
+            var documentDescriptors = new[]
+            {
+                ITagHelperDescriptorBuilder.Create("TestType", "TestAssembly")
+                    .TagMatchingRule(rule => rule.RequireTagName("div"))
+                    .Build()
+            };
+            var documentContext = TagHelperDocumentContext.Create(string.Empty, documentDescriptors);
+            var service = new DefaultTagHelperFactsService();
+
+            // Act
+            var descriptors = service.GetTagHelpersGivenParent(documentContext, parentTag: null /* root */);
+
+            // Assert
+            Assert.Equal(documentDescriptors, descriptors, TagHelperDescriptorComparer.CaseSensitive);
+        }
+
         [Fact]
         public void GetTagHelpersGivenParent_AllowsUnspecifiedParentTagHelpers()
         {