[automated] Merge branch 'release/9.0.1xx' => 'release/9.0.2xx'

src/BuiltInTools/dotnet-watch/HotReload/IncrementalMSBuildWorkspace.cs

@@ -22,8 +22,11 @@ public IncrementalMSBuildWorkspace(IReporter reporter)
     {
         WorkspaceFailed += (_sender, diag) =>
         {
-            // Errors reported here are not fatal, an exception would be thrown for fatal issues.
-            reporter.Verbose($"MSBuildWorkspace warning: {diag.Diagnostic}");
+            // Report both Warning and Failure as warnings.
+            // MSBuildProjectLoader reports Failures for cases where we can safely continue loading projects
+            // (e.g. non-C#/VB project is ignored).
+            // https://github.com/dotnet/roslyn/issues/75170
+            reporter.Warn($"msbuild: {diag.Diagnostic}", "⚠");
         };
 
         _reporter = reporter;

test/dotnet-watch.Tests/HotReload/ApplyDeltaTests.cs

@@ -121,6 +121,27 @@ public async Task BlazorWasm()
             //await App.AssertOutputLineStartsWith(MessageDescriptor.HotReloadSucceeded);
         }
 
+        [Fact]
+        public async Task BlazorWasm_MSBuildWarning()
+        {
+            var testAsset = TestAssets
+                .CopyTestAsset("WatchBlazorWasm")
+                .WithSource()
+                .WithProjectChanges(proj =>
+                {
+                    proj.Root.Descendants()
+                        .Single(e => e.Name.LocalName == "ItemGroup")
+                        .Add(XElement.Parse("""
+                            <AdditionalFiles Include="Pages\Index.razor" />
+                            """));
+                });
+
+            App.Start(testAsset, [], testFlags: TestFlags.MockBrowser);
+
+            await App.AssertOutputLineStartsWith("dotnet watch ⚠ msbuild: [Warning] Duplicate source file");
+            await App.AssertWaitingForChanges();
+        }
+
         // Test is timing out on .NET Framework: https://github.com/dotnet/sdk/issues/41669
         [CoreMSBuildOnlyFact]
         public async Task HandleMissingAssemblyFailure()

test/dotnet-watch.Tests/Watch/Utilities/WatchableApp.cs

@@ -51,12 +51,16 @@ public async Task<string> AssertOutputLineStartsWith(string expectedPrefix, Pred
                 success: line => line.StartsWith(expectedPrefix, StringComparison.Ordinal),
                 failure: failure ?? new Predicate<string>(line => line.Contains(WatchErrorOutputEmoji, StringComparison.Ordinal)));
 
-            if (line == null && failure != null)
+            if (line == null)
             {
-                Assert.Fail($"Failed to find expected text: '{expectedPrefix}'");
+                Assert.Fail(failure != null
+                    ? "Encountered failure condition"
+                    : $"Failed to find expected prefix: '{expectedPrefix}'");
+            }
+            else
+            {
+                Assert.StartsWith(expectedPrefix, line, StringComparison.Ordinal);
             }
-
-            Assert.StartsWith(expectedPrefix, line, StringComparison.Ordinal);
 
             return line.Substring(expectedPrefix.Length);
         }