Fix #2298 simplify TagHelperDescriptor hash

The hash code implementation here is exhaustive when it doesn't need to
be. Slimming this down to a much more reasonable set of things for perf
reasons.

src/Microsoft.AspNetCore.Razor.Language/AllowedChildTagDescriptorComparer.cs

@@ -54,20 +54,18 @@ namespace Microsoft.AspNetCore.Razor.Language
                 return false;
             }
 
-            return descriptorX != null &&
+            return
                 string.Equals(descriptorX.Name, descriptorY.Name, _stringComparison) &&
-                string.Equals(descriptorX.DisplayName, descriptorY.DisplayName, StringComparison.Ordinal) &&
+                string.Equals(descriptorX.DisplayName, descriptorY.DisplayName, StringComparison.Ordinal);
-                Enumerable.SequenceEqual(descriptorX.Diagnostics, descriptorY.Diagnostics);
         }
 
         /// <inheritdoc />
         public virtual int GetHashCode(AllowedChildTagDescriptor descriptor)
         {
-            var hashCodeCombiner = HashCodeCombiner.Start();
+            var hash = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(descriptor.Name, _stringComparer);
+            hash.Add(descriptor.Name, _stringComparer);
-            hashCodeCombiner.Add(descriptor.DisplayName, StringComparer.Ordinal);
 
-            return hashCodeCombiner.CombinedHash;
+            return hash.CombinedHash;
         }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/BoundAttributeDescriptorComparer.cs

@@ -50,7 +50,7 @@ namespace Microsoft.AspNetCore.Razor.Language
                 return false;
             }
 
-            return descriptorX != null &&
+            return
                 string.Equals(descriptorX.Kind, descriptorY.Kind, StringComparison.Ordinal) &&
                 descriptorX.IsIndexerStringProperty == descriptorY.IsIndexerStringProperty &&
                 descriptorX.IsEnum == descriptorY.IsEnum &&
@@ -61,7 +61,6 @@ namespace Microsoft.AspNetCore.Razor.Language
                 string.Equals(descriptorX.IndexerTypeName, descriptorY.IndexerTypeName, StringComparison.Ordinal) &&
                 string.Equals(descriptorX.Documentation, descriptorY.Documentation, StringComparison.Ordinal) &&
                 string.Equals(descriptorX.DisplayName, descriptorY.DisplayName, StringComparison.Ordinal) &&
-                Enumerable.SequenceEqual(descriptorX.Diagnostics, descriptorY.Diagnostics) &&
                 Enumerable.SequenceEqual(
                     descriptorX.Metadata.OrderBy(propertyX => propertyX.Key, StringComparer.Ordinal),
                     descriptorY.Metadata.OrderBy(propertyY => propertyY.Key, StringComparer.Ordinal));
@@ -74,19 +73,11 @@ namespace Microsoft.AspNetCore.Razor.Language
                 throw new ArgumentNullException(nameof(descriptor));
             }
 
-            var hashCodeCombiner = HashCodeCombiner.Start();
+            var hash = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(descriptor.Kind);
+            hash.Add(descriptor.Kind);
-            hashCodeCombiner.Add(descriptor.IsIndexerStringProperty);
+            hash.Add(descriptor.Name, _stringComparer);
-            hashCodeCombiner.Add(descriptor.IsEnum);
-            hashCodeCombiner.Add(descriptor.HasIndexer);
-            hashCodeCombiner.Add(descriptor.Name, _stringComparer);
-            hashCodeCombiner.Add(descriptor.IndexerNamePrefix, _stringComparer);
-            hashCodeCombiner.Add(descriptor.TypeName, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.IndexerTypeName, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.Documentation, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.DisplayName, StringComparer.Ordinal);
 
-            return hashCodeCombiner.CombinedHash;
+            return hash.CombinedHash;
         }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/RequiredAttributeDescriptorComparer.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using Microsoft.Extensions.Internal;
 
 namespace Microsoft.AspNetCore.Razor.Language
@@ -58,26 +57,21 @@ namespace Microsoft.AspNetCore.Razor.Language
                 return false;
             }
 
-            return descriptorX != null &&
+            return
                 descriptorX.NameComparison == descriptorY.NameComparison &&
                 descriptorX.ValueComparison == descriptorY.ValueComparison &&
                 string.Equals(descriptorX.Name, descriptorY.Name, _stringComparison) &&
                 string.Equals(descriptorX.Value, descriptorY.Value, StringComparison.Ordinal) &&
-                string.Equals(descriptorX.DisplayName, descriptorY.DisplayName, StringComparison.Ordinal) &&
+                string.Equals(descriptorX.DisplayName, descriptorY.DisplayName, StringComparison.Ordinal);
-                Enumerable.SequenceEqual(descriptorX.Diagnostics, descriptorY.Diagnostics);
         }
 
         /// <inheritdoc />
         public virtual int GetHashCode(RequiredAttributeDescriptor descriptor)
         {
-            var hashCodeCombiner = HashCodeCombiner.Start();
+            var hash = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(descriptor.NameComparison);
+            hash.Add(descriptor.Name, _stringComparer);
-            hashCodeCombiner.Add(descriptor.ValueComparison);
-            hashCodeCombiner.Add(descriptor.Name, _stringComparer);
-            hashCodeCombiner.Add(descriptor.Value, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.DisplayName, StringComparer.Ordinal);
 
-            return hashCodeCombiner.CombinedHash;
+            return hash.CombinedHash;
         }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/TagHelperDescriptorComparer.cs

@@ -49,7 +49,7 @@ namespace Microsoft.AspNetCore.Razor.Language
 
         public virtual bool Equals(TagHelperDescriptor descriptorX, TagHelperDescriptor descriptorY)
         {
-            if (descriptorX == descriptorY)
+            if (object.ReferenceEquals(descriptorX, descriptorY))
             {
                 return true;
             }
@@ -62,6 +62,7 @@ namespace Microsoft.AspNetCore.Razor.Language
             return descriptorX != null &&
                 string.Equals(descriptorX.Kind, descriptorY.Kind, StringComparison.Ordinal) &&
                 string.Equals(descriptorX.AssemblyName, descriptorY.AssemblyName, StringComparison.Ordinal) &&
+                string.Equals(descriptorX.Name, descriptorY.Name, StringComparison.Ordinal) &&
                 Enumerable.SequenceEqual(
                     descriptorX.BoundAttributes.OrderBy(attribute => attribute.Name, _stringComparer),
                     descriptorY.BoundAttributes.OrderBy(attribute => attribute.Name, _stringComparer),
@@ -94,33 +95,12 @@ namespace Microsoft.AspNetCore.Razor.Language
                 throw new ArgumentNullException(nameof(descriptor));
             }
 
-            var hashCodeCombiner = HashCodeCombiner.Start();
+            var hash = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(descriptor.Kind);
+            hash.Add(descriptor.Kind, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.AssemblyName, StringComparer.Ordinal);
+            hash.Add(descriptor.AssemblyName, StringComparer.Ordinal);
+            hash.Add(descriptor.Name, StringComparer.Ordinal);
 
-            var childTags = descriptor.AllowedChildTags.OrderBy(childTag => childTag.Name, _stringComparer);
+            return hash.CombinedHash;
-            foreach (var childTag in childTags)
-            {
-                hashCodeCombiner.Add(_AllowedChildTagDescriptorComparer.GetHashCode(childTag));
-            }
-
-            var boundAttributes = descriptor.BoundAttributes.OrderBy(attribute => attribute.Name, _stringComparer);
-            foreach (var attribute in boundAttributes)
-            {
-                hashCodeCombiner.Add(_boundAttributeComparer.GetHashCode(attribute));
-            }
-
-            var rules = descriptor.TagMatchingRules.OrderBy(rule => rule.TagName, _stringComparer);
-            foreach (var rule in rules)
-            {
-                hashCodeCombiner.Add(_tagMatchingRuleComparer.GetHashCode(rule));
-            }
-
-            hashCodeCombiner.Add(descriptor.Documentation, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.DisplayName, StringComparer.Ordinal);
-            hashCodeCombiner.Add(descriptor.TagOutputHint, _stringComparer);
-
-            return hashCodeCombiner.CombinedHash;
         }
     }
 }

src/Microsoft.AspNetCore.Razor.Language/TagMatchingRuleDescriptorComparer.cs

@@ -54,12 +54,11 @@ namespace Microsoft.AspNetCore.Razor.Language
                 return false;
             }
 
-            return ruleX != null &&
+            return
                 string.Equals(ruleX.TagName, ruleY.TagName, _stringComparison) &&
                 string.Equals(ruleX.ParentTag, ruleY.ParentTag, _stringComparison) &&
                 ruleX.TagStructure == ruleY.TagStructure &&
-                Enumerable.SequenceEqual(ruleX.Attributes, ruleY.Attributes, _requiredAttributeComparer) &&
+                Enumerable.SequenceEqual(ruleX.Attributes, ruleY.Attributes, _requiredAttributeComparer);
-                Enumerable.SequenceEqual(ruleX.Diagnostics, ruleY.Diagnostics);
         }
 
         public virtual int GetHashCode(TagMatchingRuleDescriptor rule)
@@ -69,18 +68,10 @@ namespace Microsoft.AspNetCore.Razor.Language
                 throw new ArgumentNullException(nameof(rule));
             }
 
-            var hashCodeCombiner = HashCodeCombiner.Start();
+            var hash = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(rule.TagName, _stringComparer);
+            hash.Add(rule.TagName, _stringComparer);
-            hashCodeCombiner.Add(rule.ParentTag, _stringComparer);
-            hashCodeCombiner.Add(rule.TagStructure);
 
-            var attributes = rule.Attributes.OrderBy(attribute => attribute.Name, _stringComparer);
+            return hash.CombinedHash;
-            foreach (var attribute in attributes)
-            {
-                hashCodeCombiner.Add(_requiredAttributeComparer.GetHashCode(attribute));
-            }
-
-            return hashCodeCombiner.CombinedHash;
         }
     }
 }

src/Microsoft.VisualStudio.Editor.Razor/DefaultTagHelperCompletionService.cs

@@ -29,18 +29,16 @@ namespace Microsoft.VisualStudio.Editor.Razor
             _tagHelperFactsService = tagHelperFactsService;
         }
 
-        /*
+        // This API attempts to understand a users context as they're typing in a Razor file to provide TagHelper based attribute IntelliSense.
-         * This API attempts to understand a users context as they're typing in a Razor file to provide TagHelper based attribute IntelliSense.
+        //
-         * 
+        // Scenarios for TagHelper attribute IntelliSense follows:
-         * Scenarios for TagHelper attribute IntelliSense follows:
+        // 1. TagHelperDescriptor's have matching required attribute names
-         * 1. TagHelperDescriptor's have matching required attribute names
+        //  -> Provide IntelliSense for the required attributes of those descriptors to lead users towards a TagHelperified element.
-         *  -> Provide IntelliSense for the required attributes of those descriptors to lead users towards a TagHelperified element.
+        // 2. TagHelperDescriptor entirely applies to current element. Tag name, attributes, everything is fulfilled.
-         * 2. TagHelperDescriptor entirely applies to current element. Tag name, attributes, everything is fulfilled.
+        //  -> Provide IntelliSense for the bound attributes for the applied descriptors.
-         *  -> Provide IntelliSense for the bound attributes for the applied descriptors.
+        //
-         *  
+        // Within each of the above scenarios if an attribute completion has a corresponding bound attribute we associate it with the corresponding
-         *  Within each of the above scenarios if an attribute completion has a corresponding bound attribute we associate it with the corresponding
+        // BoundAttributeDescriptor. By doing this a user can see what C# type a TagHelper expects for the attribute.
-         *  BoundAttributeDescriptor. By doing this a user can see what C# type a TagHelper expects for the attribute.
-         */
         public override AttributeCompletionResult GetAttributeCompletions(AttributeCompletionContext completionContext)
         {
             if (completionContext == null)