Use the full file path as the target path when it's missing

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/SourceGenerators/RazorSourceGenerator.RazorProviders.cs

@@ -94,8 +94,9 @@ private static (SourceGeneratorProjectItem?, Diagnostic?) ComputeProjectItems((A
             }
             else
             {
-                // If the TargetPath is not provided, we effectively assume its in the root of the project.
-                relativePath = Path.GetFileName(additionalText.Path);
+                // If the TargetPath is not provided, it could be a Misc Files situation, or just a project that isn't using the
+                // Web or Razor SDK. In this case, we just use the physical path.
+                relativePath = additionalText.Path;
             }
 
             options.TryGetValue("build_metadata.AdditionalFiles.CssScope", out var cssScope);

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/TextDocumentExtensions.cs

@@ -28,8 +28,7 @@ public static bool TryComputeHintNameFromRazorDocument(this TextDocument razorDo
         var filePath = razorDocument.FilePath.AsSpanOrDefault();
         if (string.IsNullOrEmpty(razorDocument.Project.FilePath))
         {
-            var fileName = filePath[filePath.LastIndexOfAny(['/', '\\'])..].TrimStart(['/', '\\']);
-            hintName = RazorSourceGenerator.GetIdentifierFromPath(fileName);
+            hintName = RazorSourceGenerator.GetIdentifierFromPath(filePath);
             return hintName is not null;
         }
 

src/Razor/test/Microsoft.VisualStudioCode.RazorExtension.Test/Endpoints/Shared/ComputedTargetPathTest.cs

@@ -0,0 +1,133 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.VisualStudioCode.RazorExtension.Test.Endpoints.Shared;
+
+public class ComputedTargetPathTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+{
+    [Fact]
+    public async Task GetHintName()
+    {
+        // Creating a misc files project will mean that there is no globalconfig created, so no target paths will be set
+        var document = CreateProjectAndRazorDocument("");
+
+        _ = await document.Project.GetCompilationAsync(DisposalToken);
+
+        Assert.True(document.TryComputeHintNameFromRazorDocument(out var hintName));
+        var generatedDocument = await document.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName, DisposalToken);
+        Assert.NotNull(generatedDocument);
+    }
+
+    [Fact]
+    public async Task NoGlobalConfig_WithProjectFilePath()
+    {
+        var doc1Path = FilePath(@"Pages\Index.razor");
+
+        var document = CreateProjectAndRazorDocument("");
+
+        var doc1 = document.Project.AddAdditionalDocument(
+            doc1Path,
+            SourceText.From("""
+                <div>This is a page</div>
+                """),
+            filePath: doc1Path);
+
+        var project = doc1.Project.RemoveAnalyzerConfigDocument(doc1.Project.AnalyzerConfigDocuments.First().Id);
+
+        _ = await project.GetCompilationAsync(DisposalToken);
+
+        doc1 = project.GetAdditionalDocument(doc1.Id).AssumeNotNull();
+
+        Assert.True(doc1.TryComputeHintNameFromRazorDocument(out var hintName));
+        var generatedDocument = await doc1.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName, DisposalToken);
+        Assert.NotNull(generatedDocument);
+    }
+
+    [Fact]
+    public async Task NoGlobalConfig_NoProjectFilePath()
+    {
+        var doc1Path = FilePath(@"Pages\Index.razor");
+
+        // Creating a misc files project will mean that there is no globalconfig created, so no target paths will be set
+        var document = CreateProjectAndRazorDocument("", miscellaneousFile: true);
+
+        var doc1 = document.Project.AddAdditionalDocument(
+            doc1Path,
+            SourceText.From("""
+                <div>This is a page</div>
+                """),
+            filePath: doc1Path);
+
+        _ = await doc1.Project.GetCompilationAsync(DisposalToken);
+
+        Assert.True(doc1.TryComputeHintNameFromRazorDocument(out var hintName));
+        var generatedDocument = await doc1.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName, DisposalToken);
+        Assert.NotNull(generatedDocument);
+    }
+
+    [Fact]
+    public async Task NoGlobalConfig_MultipleFilesWithTheSameName()
+    {
+        var doc1Path = FilePath(@"Pages\Index.razor");
+        var doc2Path = FilePath(@"Components\Index.razor");
+
+        // Creating a misc files project will mean that there is no globalconfig created, so no target paths will be set
+        var document = CreateProjectAndRazorDocument("", miscellaneousFile: true);
+
+        var doc1 = document.Project.AddAdditionalDocument(
+            doc1Path,
+            SourceText.From("""
+                <div>This is a page</div>
+                """),
+            filePath: doc1Path);
+        var doc2 = doc1.Project.AddAdditionalDocument(
+            doc2Path,
+            SourceText.From("""
+                <div>This is a component</div>
+                """),
+            filePath: doc2Path);
+
+        // Make sure we have a doc1 from the final project
+        doc1 = doc2.Project.GetAdditionalDocument(doc1.Id).AssumeNotNull();
+
+        Assert.True(doc1.TryComputeHintNameFromRazorDocument(out var hintName1));
+        var generatedDocument = await doc1.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName1, DisposalToken);
+        Assert.NotNull(generatedDocument);
+
+        Assert.True(doc2.TryComputeHintNameFromRazorDocument(out var hintName2));
+        generatedDocument = await doc2.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName2, DisposalToken);
+        Assert.NotNull(generatedDocument);
+    }
+
+    [Fact]
+    public async Task NotAllFilesHaveTargetPaths()
+    {
+        var doc1Path = FilePath(@"Pages\Index.razor");
+
+        // This will create a project with a globalconfig, and target paths for a single razor file
+        var document = CreateProjectAndRazorDocument("""
+            <div>This is a normal file with a target path
+            """);
+
+        // Now add a file without updating the globalconfig
+        var doc1 = document.Project.AddAdditionalDocument(
+            doc1Path,
+            SourceText.From("""
+                <div>This is an extra document</div>
+                """),
+            filePath: doc1Path);
+
+        Assert.True(doc1.TryComputeHintNameFromRazorDocument(out var hintName));
+        var generatedDocument = await doc1.Project.TryGetSourceGeneratedDocumentFromHintNameAsync(hintName, DisposalToken);
+        Assert.NotNull(generatedDocument);
+    }
+}