Fix unhandled exception in /getItem and /getTargetResult for items with illegal path characters

src/MSBuild.UnitTests/XMake_Tests.cs

@@ -888,6 +888,38 @@ public void GetStarOutputsToFileIfRequested(string extraSwitch, string result)
             result.ShouldContain("MSB1068");
         }
 
+        /// <summary>
+        /// Regression test for issue where getTargetResult/getItem would throw an unhandled exception
+        /// when the item spec contained illegal path characters (e.g. compiler command line flags).
+        /// </summary>
+        [Theory]
+        [InlineData("-getTargetResult:GetCompileCommands", "\"Result\": \"Success\"")]
+        [InlineData("-getItem:CompileCommands", "\"Identity\":")]
+        public void GetTargetResultWithIllegalPathCharacters(string extraSwitch, string expectedContent)
+        {
+            using TestEnvironment env = TestEnvironment.Create();
+            // Create a project that mimics the ClangTidy target - it outputs items with illegal path characters
+            // (compiler command line flags) as the item spec.
+            TransientTestFile project = env.CreateFile("testProject.csproj", @"
+<Project>
+  <ItemGroup>
+    <CompileCommands Include=""/c /nologo /W3 /WX- /diagnostics:column /Od /D _DEBUG"" />
+  </ItemGroup>
+
+  <Target Name=""GetCompileCommands"" Returns=""@(CompileCommands)"">
+    <ItemGroup>
+      <CompileCommands Include=""/c /fp:precise /permissive- /Fa&quot;Debug\\&quot; /Fo&quot;Debug\\&quot; /Gd --target=amd64-pc-windows-msvc /TP"" />
+    </ItemGroup>
+  </Target>
+</Project>
+");
+            string results = RunnerUtilities.ExecMSBuild($" {project.Path} /t:GetCompileCommands {extraSwitch}", out bool success);
+            // The build should succeed instead of throwing an unhandled exception
+            success.ShouldBeTrue(results);
+            // The output should contain the expected content
+            results.ShouldContain(expectedContent);
+        }
+
         [Theory]
         [InlineData(true)]
         [InlineData(false)]

src/MSBuild/JsonOutputFormatter.cs

@@ -67,7 +67,7 @@ internal void AddItemInstancesInJsonFormat(string[] itemNames, ProjectInstance p
                             continue;
                         }
 
-                        jsonItem[metadatumName] = item.GetMetadataValue(metadatumName);
+                        jsonItem[metadatumName] = TryGetMetadataValue(item, metadatumName);
                     }
 
                     itemArray.Add(jsonItem);
@@ -108,7 +108,7 @@ internal void AddItemsInJsonFormat(string[] itemNames, Project project)
                             continue;
                         }
 
-                        jsonItem[metadatumName] = item.GetMetadataValue(metadatumName);
+                        jsonItem[metadatumName] = TryGetMetadataValue(item, metadatumName);
                     }
 
                     itemArray.Add(jsonItem);
@@ -147,7 +147,7 @@ internal void AddTargetResultsInJsonFormat(string[] targetNames, BuildResult res
                             continue;
                         }
 
-                        jsonItem[metadatumName] = item.GetMetadata(metadatumName);
+                        jsonItem[metadatumName] = TryGetMetadata(item, metadatumName);
                     }
 
                     outputArray.Add(jsonItem);
@@ -159,5 +159,62 @@ internal void AddTargetResultsInJsonFormat(string[] targetNames, BuildResult res
 
             _topLevelNode["TargetResults"] = targetResultsNode;
         }
+
+        /// <summary>
+        /// Attempts to get metadata from an ITaskItem. If the metadata is a built-in metadata
+        /// (like FullPath, Directory, etc.) and the item spec contains illegal path characters,
+        /// this will catch the InvalidOperationException and return an empty string.
+        /// </summary>
+        private static string TryGetMetadata(ITaskItem item, string metadataName)
+        {
+            try
+            {
+                return item.GetMetadata(metadataName);
+            }
+            catch (InvalidOperationException)
+            {
+                // Built-in metadata like FullPath, Directory, etc. require path computation.
+                // If the item spec contains illegal path characters, return empty string.
+                return string.Empty;
+            }
+        }
+
+        /// <summary>
+        /// Attempts to get metadata value from a ProjectItemInstance. If the metadata is a built-in metadata
+        /// (like FullPath, Directory, etc.) and the item spec contains illegal path characters,
+        /// this will catch the InvalidOperationException and return an empty string.
+        /// </summary>
+        private static string TryGetMetadataValue(ProjectItemInstance item, string metadataName)
+        {
+            try
+            {
+                return item.GetMetadataValue(metadataName);
+            }
+            catch (InvalidOperationException)
+            {
+                // Built-in metadata like FullPath, Directory, etc. require path computation.
+                // If the item spec contains illegal path characters, return empty string.
+                return string.Empty;
+            }
+        }
+
+        /// <summary>
+        /// Attempts to get metadata value from a ProjectItem. If the metadata is a built-in metadata
+        /// (like FullPath, Directory, etc.) and the item spec contains illegal path characters,
+        /// this will catch the InvalidOperationException and return an empty string.
+        /// </summary>
+        private static string TryGetMetadataValue(ProjectItem item, string metadataName)
+        {
+            try
+            {
+                return item.GetMetadataValue(metadataName);
+            }
+            catch (InvalidOperationException)
+            {
+                // Built-in metadata like FullPath, Directory, etc. require path computation.
+                // If the item spec contains illegal path characters, return empty string.
+                return string.Empty;
+            }
+        }
     }
 }