Ignore compiled cshtml DLLs from telemetry (#7212)

## Summary of changes

Adds logic when we report loaded DLLs to telemetry to ignore anything
that is a compiled `.cshtml` DLL as we don't really care about them.
Also ignores `Anonymously Hosted DynamicMethods Assembly` that we found
when attempting to reproduce.

## Reason for change

We don't really want to report them.

## Implementation details

Copied the format from others.

## Test coverage

Added some tests to just validate these cases.

## Other details
<!-- Fixes #{issue} -->

Unsure exactly how to create these DLLs in the first place 🤷 

<!-- ⚠️ Note: where possible, please obtain 2 approvals prior to
merging. Unless CODEOWNERS specifies otherwise, for external teams it is
typically best to have one review from a team member, and one review
from apm-dotnet. Trivial changes do not require 2 reviews. -->

Author: bouwkast

tracer/src/Datadog.Trace/Telemetry/Collectors/DependencyTelemetryCollector.cs

@@ -42,6 +42,7 @@ internal void AssemblyLoaded(AssemblyName assembly, string moduleVersionId)
             if (assemblyName is null or ""
              || assembly.Version is null
              || IsTempPathPattern(assemblyName)
+             || IsCompiledRazorViewPattern(assemblyName)
              || (assemblyName[0] == 'A'
               && (assemblyName.StartsWith("App_Web_", StringComparison.Ordinal)
                || assemblyName.StartsWith("App_Theme_", StringComparison.Ordinal)
@@ -50,7 +51,8 @@ internal void AssemblyLoaded(AssemblyName assembly, string moduleVersionId)
                || assemblyName.StartsWith("App_global.asax.", StringComparison.Ordinal)
                || assemblyName.StartsWith("App_Code.", StringComparison.Ordinal)
                || assemblyName.StartsWith("App_Browsers.", StringComparison.Ordinal)
-               || assemblyName.StartsWith("App_WebReferences.", StringComparison.Ordinal)))
+               || assemblyName.StartsWith("App_WebReferences.", StringComparison.Ordinal)
+               || assemblyName.StartsWith("Anonymously Hosted DynamicMethods Assembly", StringComparison.Ordinal)))
              || assemblyName.StartsWith("CompiledRazorTemplates.Dynamic.RazorEngine_", StringComparison.Ordinal)
              || assemblyName.StartsWith("EntityFrameworkDynamicProxies-", StringComparison.Ordinal)
              || assemblyName.StartsWith("expression_host_", StringComparison.Ordinal)
@@ -125,6 +127,34 @@ private static bool IsTempPathPattern(string assemblyName)
                 && IsBase32Char(assemblyName[11]);
         }
 
+        private static bool IsCompiledRazorViewPattern(string assemblyName)
+        {
+            // Pattern: xxxxxxxx.xxx.cshtml (19 characters total)
+            // e.g. 01234abc.def.cshtml
+            // where "x" is a base32 character (a-z, 0-5) and "." is a literal dot
+            // Note: This is very similar to the temp path pattern, keeping it separate for now though
+            return assemblyName.Length == 19
+                   && assemblyName[8] == '.'
+                   && assemblyName[12] == '.'
+                   && assemblyName[13] == 'c'
+                   && assemblyName[14] == 's'
+                   && assemblyName[15] == 'h'
+                   && assemblyName[16] == 't'
+                   && assemblyName[17] == 'm'
+                   && assemblyName[18] == 'l'
+                   && IsBase32Char(assemblyName[0])
+                   && IsBase32Char(assemblyName[1])
+                   && IsBase32Char(assemblyName[2])
+                   && IsBase32Char(assemblyName[3])
+                   && IsBase32Char(assemblyName[4])
+                   && IsBase32Char(assemblyName[5])
+                   && IsBase32Char(assemblyName[6])
+                   && IsBase32Char(assemblyName[7])
+                   && IsBase32Char(assemblyName[9])
+                   && IsBase32Char(assemblyName[10])
+                   && IsBase32Char(assemblyName[11]);
+        }
+
         private static bool IsZxPattern(string assemblyName)
         {
             // zx_01aab0f40246424bb7ebaaf80635953b

tracer/test/Datadog.Trace.Tests/Telemetry/Collectors/DependencyTelemetryCollectorTests.cs

@@ -111,6 +111,8 @@ public void DoesNotHaveChangesWhenSameAssemblyAddedTwice()
         [InlineData("ℛ*1887feb5-1546-46da-a64e-07cba2cb32fa#112-0")]
         [InlineData("ℛ*bcd9d48c-2728-46f5-bd56-bfb58cb0bb22#1156-0")]
         [InlineData("OK_IM_NO-GUID-BUUT-NOT_-THAT_FAR_OFF")]
+        [InlineData("01234abc.def.cshtml")] // compiled Razor view assembly
+        [InlineData("Anonymously Hosted DynamicMethods Assembly")] // compiled Razor view assembly (maybe)
         public void DoesNotHaveChangesWhenAssemblyNameIsIgnoredAssembly(string assemblyName)
         {
             var ignoredName = CreateAssemblyName(new Version(1, 0), name: assemblyName);
@@ -245,6 +247,24 @@ public void HasChangesWhenAddingSameAssemblyWithDifferentHash()
                 .And.OnlyHaveUniqueItems();
         }
 
+        [Theory]
+        [InlineData("01234abc.def.cshtm")]  // Wrong extension
+        [InlineData("01234abc.de.cshtml")]  // Too short middle section
+        [InlineData("01234abc.defg.cshtml")] // Too long middle section
+        [InlineData("01234abcd.def.cshtml")] // Too long first section
+        [InlineData("01234ab.def.cshtml")]   // Too short first section
+        [InlineData("01234abc-def.cshtml")]  // Wrong separator
+        [InlineData("01234abc.DEF.cshtml")]  // Uppercase (not Base32)
+        public void HasChangesWhenAssemblyNameIsNotValidCompiledRazorViewPattern(string assemblyName)
+        {
+            var validName = CreateAssemblyName(new Version(0, 0, 0, 0), name: assemblyName);
+
+            var collector = new DependencyTelemetryCollector();
+            collector.AssemblyLoaded(validName, "some-guid");
+
+            collector.HasChanges().Should().BeTrue($"{assemblyName} should not be filtered out as it doesn't match the exact Razor view pattern");
+        }
+
         private static AssemblyName CreateAssemblyName(Version version = null, string name = null)
         {
             return new AssemblyName()