Enable `TagHelper`s with `[RestrictChildren]` to log errors for no tag name tags when targeted by catch all.

#534

src/Microsoft.AspNet.Razor/Parser/TagHelpers/TagHelperParseTreeRewriter.cs

@@ -325,7 +325,7 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
 
         private void ValidateParentTagHelperAllowsTagHelper(string tagName, Block tagBlock, ErrorSink errorSink)
         {
-            var currentlyAllowedChildren = _currentTagHelperTracker?.AllowedChildren;
+            var currentlyAllowedChildren = _currentTagHelperTracker?.PrefixedAllowedChildren;
 
             if (currentlyAllowedChildren != null &&
                 !currentlyAllowedChildren.Contains(tagName, StringComparer.OrdinalIgnoreCase))
@@ -583,9 +583,11 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
                     var tagHelperPrefix = Builder.Descriptors.First().Prefix;
 
                     AllowedChildren = Builder.Descriptors
+                        .Where(descriptor => descriptor.AllowedChildren != null)
                         .SelectMany(descriptor => descriptor.AllowedChildren)
-                        .Distinct(StringComparer.OrdinalIgnoreCase)
+                        .Distinct(StringComparer.OrdinalIgnoreCase);
-                        .Select(allowedChild => tagHelperPrefix + allowedChild);
+
+                    PrefixedAllowedChildren = AllowedChildren.Select(allowedChild => tagHelperPrefix + allowedChild);
                 }
             }
 
@@ -594,6 +596,8 @@ namespace Microsoft.AspNet.Razor.Parser.TagHelpers.Internal
             public uint OpenMatchingTags { get; set; }
 
             public IEnumerable<string> AllowedChildren { get; }
+
+            public IEnumerable<string> PrefixedAllowedChildren { get; }
         }
     }
 }

test/Microsoft.AspNet.Razor.Test/TagHelpers/TagHelperParseTreeRewriterTest.cs

@@ -747,6 +747,86 @@ namespace Microsoft.AspNet.Razor.Test.TagHelpers
             EvaluateData(descriptorProvider, documentContent, expectedOutput, expectedErrors);
         }
 
+        [Fact]
+        public void Rewrite_UnderstandsNullTagNameWithAllowedChildrenForCatchAll()
+        {
+            // Arrange
+            var documentContent = "<p></</p>";
+            var descriptors = new TagHelperDescriptor[]
+                {
+                    new TagHelperDescriptor
+                    {
+                        TagName = "p",
+                        TypeName = "PTagHelper",
+                        AssemblyName = "SomeAssembly",
+                        AllowedChildren = new[] { "custom" },
+                    },
+                    new TagHelperDescriptor
+                    {
+                        TagName = "*",
+                        TypeName = "CatchAllTagHelper",
+                        AssemblyName = "SomeAssembly",
+                    }
+                };
+            var expectedOutput = new MarkupBlock(
+                new MarkupTagHelperBlock("p",
+                    BlockFactory.MarkupTagBlock("</")));
+            var descriptorProvider = new TagHelperDescriptorProvider(descriptors);
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    RazorResources.FormatTagHelperParseTreeRewriter_CannotHaveNonTagContent("p", "custom"),
+                    absoluteIndex: 3,
+                    lineIndex: 0,
+                    columnIndex: 3,
+                    length: 2)
+            };
+
+            // Act & Assert
+            EvaluateData(descriptorProvider, documentContent, expectedOutput, expectedErrors);
+        }
+
+        [Fact]
+        public void Rewrite_UnderstandsNullTagNameWithAllowedChildrenForCatchAllWithPrefix()
+        {
+            // Arrange
+            var documentContent = "<th:p></</th:p>";
+            var descriptors = new TagHelperDescriptor[]
+                {
+                    new TagHelperDescriptor
+                    {
+                        TagName = "p",
+                        TypeName = "PTagHelper",
+                        AssemblyName = "SomeAssembly",
+                        AllowedChildren = new[] { "custom" },
+                        Prefix = "th:",
+                    },
+                    new TagHelperDescriptor
+                    {
+                        TagName = "*",
+                        TypeName = "CatchAllTagHelper",
+                        AssemblyName = "SomeAssembly",
+                        Prefix = "th:",
+                    }
+                };
+            var expectedOutput = new MarkupBlock(
+                new MarkupTagHelperBlock("th:p",
+                    BlockFactory.MarkupTagBlock("</")));
+            var descriptorProvider = new TagHelperDescriptorProvider(descriptors);
+            var expectedErrors = new[]
+            {
+                new RazorError(
+                    RazorResources.FormatTagHelperParseTreeRewriter_CannotHaveNonTagContent("th:p", "custom"),
+                    absoluteIndex: 6,
+                    lineIndex: 0,
+                    columnIndex: 6,
+                    length: 2)
+            };
+
+            // Act & Assert
+            EvaluateData(descriptorProvider, documentContent, expectedOutput, expectedErrors);
+        }
+
         [Fact]
         public void Rewrite_CanHandleStartTagOnlyTagTagMode()
         {