Fix StaticWebAssets base path prefix detection using path segment comparison

src/StaticWebAssetsSdk/Tasks/ComputeEndpointsForReferenceStaticWebAssets.cs

@@ -24,6 +24,9 @@ public override bool Execute()
 
         var result = CandidateEndpoints;
 
+        var routeSegments = new List<PathTokenizer.Segment>();
+        var basePathSegments = new List<PathTokenizer.Segment>();
+
         for (var i = 0; i < CandidateEndpoints.Length; i++)
         {
             var candidateEndpoint = StaticWebAssetEndpoint.FromTaskItem(CandidateEndpoints[i]);
@@ -35,7 +38,7 @@ public override bool Execute()
                 // destined to be used as a reference by other project are passed to this task.
 
                 var oldRoute = candidateEndpoint.Route;
-                if (oldRoute.StartsWith(asset.BasePath))
+                if (StaticWebAssetEndpoint.RouteHasPathPrefix(oldRoute, asset.BasePath, routeSegments, basePathSegments))
                 {
                     Log.LogMessage(MessageImportance.Low, "Skipping endpoint '{0}' because route '{1}' is already updated.", asset.Identity, oldRoute);
                 }

src/StaticWebAssetsSdk/Tasks/Data/StaticWebAssetEndpoint.cs

@@ -538,4 +538,38 @@ void ITaskItem.CopyMetadataTo(ITaskItem destinationItem)
     IDictionary ITaskItem.CloneCustomMetadata() => ((ITaskItem2)this).CloneCustomMetadataEscaped();
 
     #endregion
+
+    public static bool RouteHasPathPrefix(
+        ReadOnlySpan<char> route,
+        ReadOnlySpan<char> prefix,
+        List<PathTokenizer.Segment> routeSegments,
+        List<PathTokenizer.Segment> prefixSegments)
+    {
+        routeSegments.Clear();
+        prefixSegments.Clear();
+
+        var routeTokenizer = new PathTokenizer(route);
+        var routeSegmentCollection = routeTokenizer.Fill(routeSegments);
+
+        var prefixTokenizer = new PathTokenizer(prefix);
+        var prefixSegmentCollection = prefixTokenizer.Fill(prefixSegments);
+
+        if (prefixSegmentCollection.Count > routeSegmentCollection.Count)
+        {
+            return false;
+        }
+
+        for (var i = 0; i < prefixSegmentCollection.Count; i++)
+        {
+            var prefixSegmentSpan = prefixSegmentCollection[i];
+            var routeSegmentSpan = routeSegmentCollection[i];
+
+            if (!prefixSegmentSpan.Equals(routeSegmentSpan, StringComparison.OrdinalIgnoreCase))
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
 }

test/Microsoft.NET.Sdk.StaticWebAssets.Tests/StaticWebAssets/ComputeEndpointsForReferenceStaticWebAssetsTest.cs

@@ -94,21 +94,95 @@ public void FiltersOutEndpointsForAssetsNotFound()
         task.Endpoints[0].GetMetadata("AssetFile").Should().Be(Path.GetFullPath(Path.Combine("wwwroot", "candidate.js")));
     }
 
+    [Fact]
+    public void AppliesBasePathWhenRouteStartsWithBasePathButNotAsPathSegment()
+    {
+        // This test verifies the fix for a bug where routes like "App1.styles.css"
+        // were incorrectly skipped because they start with the BasePath "App1".
+        // The correct behavior is that the base path should only be considered
+        // "already applied" if the route starts with "App1/" (as a path segment),
+        // not just any string starting with "App1".
+        var errorMessages = new List<string>();
+        var buildEngine = new Mock<IBuildEngine>();
+        buildEngine.Setup(e => e.LogErrorEvent(It.IsAny<BuildErrorEventArgs>()))
+            .Callback<BuildErrorEventArgs>(args => errorMessages.Add(args.Message));
+
+        // Create an asset with BasePath "App1" and a route "App1.styles.css"
+        // The route starts with "App1" but NOT "App1/", so the base path should still be applied
+        var task = new ComputeEndpointsForReferenceStaticWebAssets
+        {
+            BuildEngine = buildEngine.Object,
+            Assets = [CreateCandidate(
+                Path.Combine("obj", "scopedcss", "bundle", "App1.styles.css"),
+                "App1",
+                "Project",
+                "App1.styles.css",
+                "All",
+                "CurrentProject",
+                basePath: "App1")],
+            CandidateEndpoints = [CreateCandidateEndpoint("App1.styles.css", Path.Combine("obj", "scopedcss", "bundle", "App1.styles.css"))]
+        };
+
+        // Act
+        var result = task.Execute();
+
+        // Assert
+        result.Should().Be(true);
+        task.Endpoints.Should().ContainSingle();
+        // The route should be "App1/App1.styles.css", not just "App1.styles.css"
+        task.Endpoints[0].ItemSpec.Should().Be("App1/App1.styles.css");
+    }
+
+    [Fact]
+    public void SkipsBasePathApplicationWhenRouteAlreadyHasBasePathAsPathSegment()
+    {
+        // This test verifies that routes already starting with "BasePath/" are correctly skipped
+        var errorMessages = new List<string>();
+        var buildEngine = new Mock<IBuildEngine>();
+        buildEngine.Setup(e => e.LogErrorEvent(It.IsAny<BuildErrorEventArgs>()))
+            .Callback<BuildErrorEventArgs>(args => errorMessages.Add(args.Message));
+
+        var task = new ComputeEndpointsForReferenceStaticWebAssets
+        {
+            BuildEngine = buildEngine.Object,
+            Assets = [CreateCandidate(
+                Path.Combine("wwwroot", "css", "app.css"),
+                "App1",
+                "Discovered",
+                "css/app.css",
+                "All",
+                "All",
+                basePath: "App1")],
+            // Route already has the base path as a path segment
+            CandidateEndpoints = [CreateCandidateEndpoint("App1/css/app.css", Path.Combine("wwwroot", "css", "app.css"))]
+        };
+
+        // Act
+        var result = task.Execute();
+
+        // Assert
+        result.Should().Be(true);
+        task.Endpoints.Should().ContainSingle();
+        // Should remain "App1/css/app.css", not become "App1/App1/css/app.css"
+        task.Endpoints[0].ItemSpec.Should().Be("App1/css/app.css");
+    }
+
     private static ITaskItem CreateCandidate(
         string itemSpec,
         string sourceId,
         string sourceType,
         string relativePath,
         string assetKind,
-        string assetMode)
+        string assetMode,
+        string basePath = "base")
     {
         var result = new StaticWebAsset()
         {
             Identity = Path.GetFullPath(itemSpec),
             SourceId = sourceId,
             SourceType = sourceType,
             ContentRoot = Directory.GetCurrentDirectory(),
-            BasePath = "base",
+            BasePath = basePath,
             RelativePath = relativePath,
             AssetKind = assetKind,
             AssetMode = assetMode,

test/Microsoft.NET.Sdk.StaticWebAssets.Tests/StaticWebAssets/StaticWebAssetEndpointTest.cs

@@ -0,0 +1,63 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#nullable disable
+
+using Microsoft.AspNetCore.StaticWebAssets.Tasks;
+
+namespace Microsoft.NET.Sdk.StaticWebAssets.Tests;
+
+public class StaticWebAssetEndpointTest
+{
+    [Theory]
+    [InlineData("App1/css/app.css", "App1")]
+    [InlineData("App1", "App1")]
+    [InlineData("App1/css/styles/app.css", "App1/css")]
+    [InlineData("App1/css/app.css", "")]
+    [InlineData("", "")]
+    [InlineData("App1\\css\\app.css", "App1")]
+    [InlineData("App1/css\\app.css", "App1")]
+    [InlineData("App1/App1.lib.module.js", "App1")]
+    [InlineData("app1/css/app.css", "App1")]
+    [InlineData("APP1/css/app.css", "app1")]
+    public void RouteHasPathPrefix_ReturnsTrue_WhenRouteStartsWithPrefixAsPathSegment(string route, string prefix)
+    {
+        var routeSegments = new List<PathTokenizer.Segment>();
+        var prefixSegments = new List<PathTokenizer.Segment>();
+
+        var result = StaticWebAssetEndpoint.RouteHasPathPrefix(route, prefix, routeSegments, prefixSegments);
+
+        result.Should().BeTrue();
+    }
+
+    [Theory]
+    [InlineData("App1.styles.css", "App1")]
+    [InlineData("App1", "App1/css/app.css")]
+    [InlineData("App1/js/app.js", "App1/css")]
+    [InlineData("App12/css/app.css", "App1")]
+    [InlineData("App1Bundle/app.js", "App1")]
+    [InlineData("App1.lib.module.js", "App1")]
+    public void RouteHasPathPrefix_ReturnsFalse_WhenRouteDoesNotStartWithPrefixAsPathSegment(string route, string prefix)
+    {
+        var routeSegments = new List<PathTokenizer.Segment>();
+        var prefixSegments = new List<PathTokenizer.Segment>();
+
+        var result = StaticWebAssetEndpoint.RouteHasPathPrefix(route, prefix, routeSegments, prefixSegments);
+
+        result.Should().BeFalse();
+    }
+
+    [Fact]
+    public void RouteHasPathPrefix_ReusesSegmentLists()
+    {
+        var routeSegments = new List<PathTokenizer.Segment>();
+        var prefixSegments = new List<PathTokenizer.Segment>();
+
+        StaticWebAssetEndpoint.RouteHasPathPrefix("a/b/c", "a", routeSegments, prefixSegments);
+        StaticWebAssetEndpoint.RouteHasPathPrefix("x/y/z", "x/y", routeSegments, prefixSegments);
+
+        var result = StaticWebAssetEndpoint.RouteHasPathPrefix("App1/css/app.css", "App1", routeSegments, prefixSegments);
+
+        result.Should().BeTrue();
+    }
+}