TagHelperCollection Part 4: Rewrite Tag Helper Discovery(!) (#12507)

| [Prelude](#12503) | [Part
1](#12504) | [Part
2](#12505) | [Part
3](#12506) | Part 4 | [Part
5](#12509) |

> [!WARNING]
> This pull request contains breaking changes for the RazorSdk. Once
this is merged and flows to the VMR,
dotnet/dotnet@dc17a09
will need to be cherry-picked to resolve build breaks in
`src/sdk/src/RazorSdk`.

Previously, tag helpers were discovered by
`ITagHelperDescriptorProvider`. Each provider was responsible for
walking a compilation's assemblies and producing `TagHelperDescriptors`
from the types within. This change inverts the tag helper discovery
process by introducing `ITagHelperDiscoveryService` and moving the tag
helper construction logic into a set of `TagHelperProducers`. The
`ITagHelperDiscoveryService` performs a single walk of the compilation
or assembly and calls the producers as needed.

Importantly, the new process allows a more expansive cache to be
maintained. There is now a per-assembly cache that holds onto
`TagHelperCollection` instances. The old cache that was owned by
providers via `TagHelperCollector` has been removed.

To complete this change, `ITagHelperDescriptorProvider` and related
types have been _deleted_.

----
CI Build:
https://dev.azure.com/dnceng/internal/_build/results?buildId=2842196&view=results
Toolset Run:
https://dev.azure.com/dnceng/internal/_build/results?buildId=2842249&view=results

Author: DustinCampbell

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/ViewComponentTagHelperDescriptorProviderTest.cs renamed to src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X/test/ViewComponentTagHelperProducerTest.cs

@@ -9,7 +9,7 @@
 namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version1_X;
 
 // This is just a basic integration test. There are detailed tests for the VCTH visitor and descriptor factory.
-public class ViewComponentTagHelperDescriptorProviderTest
+public class ViewComponentTagHelperProducerTest
 {
     [Fact]
     public void DescriptorProvider_FindsVCTH()
@@ -24,12 +24,13 @@ public class StringParameterViewComponent
 
         var compilation = MvcShim.BaseCompilation.AddSyntaxTrees(CSharpSyntaxTree.ParseText(code));
 
-        var context = new TagHelperDescriptorProviderContext(compilation);
-
-        var provider = new ViewComponentTagHelperDescriptorProvider()
+        var projectEngine = RazorProjectEngine.CreateEmpty(static b =>
         {
-            Engine = RazorProjectEngine.CreateEmpty().Engine,
-        };
+            b.Features.Add(new ViewComponentTagHelperProducer.Factory());
+            b.Features.Add(new TagHelperDiscoveryService());
+        });
+
+        Assert.True(projectEngine.Engine.TryGetFeature(out ITagHelperDiscoveryService? service));
 
         var expectedDescriptor = TagHelperDescriptorBuilder.CreateViewComponent("__Generated__StringParameterViewComponentTagHelper", TestCompilation.AssemblyName)
             .TypeName("__Generated__StringParameterViewComponentTagHelper")
@@ -55,9 +56,9 @@ public class StringParameterViewComponent
             .Build();
 
         // Act
-        provider.Execute(context);
+        var result = service.GetTagHelpers(compilation);
 
         // Assert
-        Assert.Single(context.Results, d => d.Equals(expectedDescriptor));
+        Assert.Single(result, d => d.Equals(expectedDescriptor));
     }
 }

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/test/ViewComponentTagHelperDescriptorProviderTest.cs renamed to src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X/test/ViewComponentTagHelperProducerTest.cs

@@ -9,7 +9,7 @@
 namespace Microsoft.AspNetCore.Mvc.Razor.Extensions.Version2_X;
 
 // This is just a basic integration test. There are detailed tests for the VCTH visitor and descriptor factory.
-public class ViewComponentTagHelperDescriptorProviderTest
+public class ViewComponentTagHelperProducerTest
 {
     [Fact]
     public void DescriptorProvider_FindsVCTH()
@@ -24,12 +24,13 @@ public class StringParameterViewComponent
 
         var compilation = MvcShim.BaseCompilation.AddSyntaxTrees(CSharpSyntaxTree.ParseText(code));
 
-        var context = new TagHelperDescriptorProviderContext(compilation);
-
-        var provider = new ViewComponentTagHelperDescriptorProvider()
+        var projectEngine = RazorProjectEngine.CreateEmpty(static b =>
         {
-            Engine = RazorProjectEngine.CreateEmpty().Engine,
-        };
+            b.Features.Add(new ViewComponentTagHelperProducer.Factory());
+            b.Features.Add(new TagHelperDiscoveryService());
+        });
+
+        Assert.True(projectEngine.Engine.TryGetFeature(out ITagHelperDiscoveryService? service));
 
         var expectedDescriptor = TagHelperDescriptorBuilder.CreateViewComponent("__Generated__StringParameterViewComponentTagHelper", TestCompilation.AssemblyName)
             .TypeName("__Generated__StringParameterViewComponentTagHelper")
@@ -55,9 +56,9 @@ public class StringParameterViewComponent
             .Build();
 
         // Act
-        provider.Execute(context);
+        var result = service.GetTagHelpers(compilation);
 
         // Assert
-        Assert.Single(context.Results, d => d.Equals(expectedDescriptor));
+        Assert.Single(result, d => d.Equals(expectedDescriptor));
     }
 }

src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions/test/ViewComponentTagHelperDescriptorProviderTest.cs renamed to src/Compiler/Microsoft.AspNetCore.Mvc.Razor.Extensions/test/ViewComponentTagHelperProducerTest.cs

@@ -9,7 +9,7 @@
 namespace Microsoft.AspNetCore.Mvc.Razor.Extensions;
 
 // This is just a basic integration test. There are detailed tests for the VCTH visitor and descriptor factory.
-public class ViewComponentTagHelperDescriptorProviderTest
+public class ViewComponentTagHelperProducerTest
 {
     [Fact]
     public void DescriptorProvider_FindsVCTH()
@@ -24,12 +24,13 @@ public class StringParameterViewComponent
 
         var compilation = TestCompilation.Create().AddSyntaxTrees(CSharpSyntaxTree.ParseText(code));
 
-        var context = new TagHelperDescriptorProviderContext(compilation);
-
-        var provider = new ViewComponentTagHelperDescriptorProvider()
+        var projectEngine = RazorProjectEngine.CreateEmpty(static b =>
         {
-            Engine = RazorProjectEngine.CreateEmpty().Engine,
-        };
+            b.Features.Add(new ViewComponentTagHelperProducer.Factory());
+            b.Features.Add(new TagHelperDiscoveryService());
+        });
+
+        Assert.True(projectEngine.Engine.TryGetFeature(out ITagHelperDiscoveryService? service));
 
         var expectedDescriptor = TagHelperDescriptorBuilder.CreateViewComponent("__Generated__StringParameterViewComponentTagHelper", TestCompilation.AssemblyName)
             .TypeName("__Generated__StringParameterViewComponentTagHelper")
@@ -55,9 +56,9 @@ public class StringParameterViewComponent
             .Build();
 
         // Act
-        provider.Execute(context);
+        var result = service.GetTagHelpers(compilation);
 
         // Assert
-        Assert.Single(context.Results, d => d.Equals(expectedDescriptor));
+        Assert.Single(result, d => d.Equals(expectedDescriptor));
     }
 }

src/Compiler/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs

@@ -89,6 +89,7 @@ private static void AssertDefaultFeatures(RazorProjectEngine engine)
             feature => Assert.IsType<InheritsDirectivePass>(feature),
             feature => Assert.IsType<MetadataAttributePass>(feature),
             feature => Assert.IsType<PreallocatedTagHelperAttributeOptimizationPass>(feature),
+            feature => Assert.IsType<TagHelperDiscoveryService>(feature),
             feature => Assert.IsType<ViewCssScopePass>(feature));
     }