Track exact source locations on evaluated items

src/Build.OM.UnitTests/Instance/ProjectItemInstance_Tests.cs

@@ -79,6 +79,37 @@ public void AccessorsWithoutMetadata()
             Assert.False(item.Metadata.GetEnumerator().MoveNext());
         }
 
+        [Fact]
+        public void LocationTracksOriginatingItemElement()
+        {
+            using ProjectRootElementFromString projectRootElementFromString = new(
+                """
+                <Project>
+                  <ItemGroup>
+                    <i Include="i1" />
+                  </ItemGroup>
+                </Project>
+                """);
+
+            ProjectRootElement xml = projectRootElementFromString.Project;
+            ProjectItemElement itemElement = xml.Items.Single();
+            ProjectItemInstance item = new ProjectInstance(xml).GetItems("i").Single();
+
+            TaskItemLocation? itemLocation = item.Location;
+            Assert.True(itemLocation.HasValue);
+            TaskItemLocation location = itemLocation.Value;
+            Assert.Equal(itemElement.Location.File, location.File);
+            Assert.Equal(itemElement.Location.Line, location.Line);
+            Assert.Equal(itemElement.Location.Column, location.Column);
+            Assert.Equal(location, ((ITaskItem3)item).Location.Value);
+
+            var copiedItem = new Utilities.TaskItem(item);
+            TaskItemLocation copiedLocation = copiedItem.Location.Value;
+            Assert.Equal(location.File, copiedLocation.File);
+            Assert.Equal(location.Line, copiedLocation.Line);
+            Assert.Equal(location.Column, copiedLocation.Column);
+        }
+
         /// <summary>
         /// Basic ProjectItemInstance with metadata
         /// </summary>

src/Build.UnitTests/Instance/TaskItem_Tests.cs

@@ -50,7 +50,7 @@ public class TaskItem_Tests
         [Fact]
         public void Serialization()
         {
-            TaskItem item = new TaskItem("foo", "bar.proj");
+            TaskItem item = new TaskItem("foo", "bar.proj", sourceLineNumber: 12, sourceColumnNumber: 34);
             item.SetMetadata("a", "b");
 
             TranslationHelpers.GetWriteTranslator().Translate(ref item, TaskItem.FactoryForDeserialization);
@@ -61,6 +61,7 @@ public void Serialization()
             Assert.Equal(item.MetadataCount, deserializedItem.MetadataCount);
             Assert.Equal(item.GetMetadata("a"), deserializedItem.GetMetadata("a"));
             Assert.Equal(item.GetMetadata(ItemSpecModifiers.DefiningProjectFullPath), deserializedItem.GetMetadata(ItemSpecModifiers.DefiningProjectFullPath));
+            Assert.Equal(item.Location, deserializedItem.Location);
         }
 
         /// <summary>

src/Build.UnitTests/InstanceFromRemote/FakeProjectItemElementLink.cs

@@ -18,11 +18,13 @@ namespace Microsoft.Build.Engine.UnitTests.InstanceFromRemote
     internal sealed class FakeProjectItemElementLink : ProjectItemElementLink
     {
         private readonly string _filePath;
+        private readonly ElementLocation _location;
 
         public FakeProjectItemElementLink(string elementName, string filePath)
         {
             ElementName = elementName ?? throw new ArgumentNullException(nameof(elementName));
             _filePath = filePath ?? throw new ArgumentNullException(nameof(filePath));
+            _location = ElementLocation.Create(filePath, 1, 1);
         }
 
         public override int Count => throw new NotImplementedException();
@@ -45,7 +47,7 @@ public FakeProjectItemElementLink(string elementName, string filePath)
 
         public override ProjectElement NextSibling => throw new NotImplementedException();
 
-        public override ElementLocation Location => throw new NotImplementedException();
+        public override ElementLocation Location => _location;
 
         public override IReadOnlyCollection<XmlAttributeLink> Attributes => throw new NotImplementedException();
 

src/Build/BackEnd/Components/RequestBuilder/IntrinsicTasks/ItemGroupIntrinsicTask.cs

@@ -426,7 +426,10 @@ private List<ProjectItemInstance> ExpandItemIntoItems(
 
             // Split Include on any semicolons, and take each split in turn
             var includeSplits = ExpressionShredder.SplitSemiColonSeparatedList(evaluatedInclude);
-            ProjectItemInstanceFactory itemFactory = new ProjectItemInstanceFactory(Project, originalItem.ItemType);
+            ProjectItemInstanceFactory itemFactory = new ProjectItemInstanceFactory(Project, originalItem.ItemType)
+            {
+                SourceLocation = originalItem.Location,
+            };
 
             // EngineFileUtilities.GetFileListEscaped api invocation evaluates excludes by default.
             // If the code process any expression like "@(x)", we need to handle excludes explicitly using EvaluateExcludePaths().
@@ -473,7 +476,9 @@ private List<ProjectItemInstance> ExpandItemIntoItems(
                             null,
                             null,
                             originalItem.Location.File,
-                            useItemDefinitionsWithoutModification: false));
+                            useItemDefinitionsWithoutModification: false,
+                            originalItem.Location.Line,
+                            originalItem.Location.Column));
                     }
                 }
             }

src/Build/BackEnd/Components/RequestBuilder/TaskBuilder.cs

@@ -1223,7 +1223,10 @@ private void InferTaskOutputs(
                     // This is an output item.
                     // Expand only with properties first, so that expressions like Include="@(foo)" will transfer the metadata of the "foo" items as well, not just their item specs.
                     var outputItemSpecs = bucket.Expander.ExpandIntoStringListLeaveEscaped(taskParameterAttribute, ExpanderOptions.ExpandPropertiesAndMetadata, taskItemInstance.TaskParameterLocation);
-                    ProjectItemInstanceFactory itemFactory = new ProjectItemInstanceFactory(_buildRequestEntry.RequestConfiguration.Project, itemName);
+                    ProjectItemInstanceFactory itemFactory = new ProjectItemInstanceFactory(_buildRequestEntry.RequestConfiguration.Project, itemName)
+                    {
+                        SourceLocation = taskItemInstance.Location,
+                    };
 
                     foreach (string outputItemSpec in outputItemSpecs)
                     {

src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs

@@ -1801,7 +1801,7 @@ private void GatherTaskItemOutputs(bool outputTargetIsItem, string outputTargetN
                             {
                                 // The common case -- all items involved are Microsoft.Build.Execution.ProjectItemInstance.TaskItems.
                                 // Furthermore, because that is true, we know by definition that they also implement ITaskItem2.
-                                newItem = new ProjectItemInstance(_projectInstance, outputTargetName, outputAsProjectItem.IncludeEscaped, parameterLocationEscaped);
+                                newItem = new ProjectItemInstance(_projectInstance, outputTargetName, outputAsProjectItem.IncludeEscaped, parameterLocationEscaped, parameterLocation.Line, parameterLocation.Column);
 
                                 newItem.SetMetadata(outputAsProjectItem.MetadataCollection); // copy-on-write!
                             }
@@ -1810,7 +1810,7 @@ private void GatherTaskItemOutputs(bool outputTargetIsItem, string outputTargetN
                                 if (output is ITaskItem2 outputAsITaskItem2)
                                 {
                                     // Probably a Microsoft.Build.Utilities.TaskItem.  Not quite as good, but we can still preserve escaping.
-                                    newItem = new ProjectItemInstance(_projectInstance, outputTargetName, outputAsITaskItem2.EvaluatedIncludeEscaped, parameterLocationEscaped);
+                                    newItem = new ProjectItemInstance(_projectInstance, outputTargetName, outputAsITaskItem2.EvaluatedIncludeEscaped, parameterLocationEscaped, parameterLocation.Line, parameterLocation.Column);
 
                                     // If found, directly pass the backing copy-on-write dictionary.
                                     // Otherwise, retrieve a cloned dictionary from the task item.
@@ -1830,7 +1830,7 @@ private void GatherTaskItemOutputs(bool outputTargetIsItem, string outputTargetN
                                 {
                                     // Not a ProjectItemInstance.TaskItem or even a ITaskItem2, so we have to fake it.
                                     // Setting an item spec expects the escaped value, as does setting metadata.
-                                    newItem = new ProjectItemInstance(_projectInstance, outputTargetName, EscapingUtilities.Escape(output.ItemSpec), parameterLocationEscaped);
+                                    newItem = new ProjectItemInstance(_projectInstance, outputTargetName, EscapingUtilities.Escape(output.ItemSpec), parameterLocationEscaped, parameterLocation.Line, parameterLocation.Column);
 
                                     newItem.SetMetadataOnTaskOutput(EnumerateMetadata(output.CloneCustomMetadata()));
 
@@ -1948,7 +1948,7 @@ private void GatherArrayStringAndValueOutputs(bool outputTargetIsItem, string ou
                         // attempting to put an empty string into an item is a no-op.
                         if (output?.Length > 0)
                         {
-                            _batchBucket.Lookup.AddNewItem(new ProjectItemInstance(_projectInstance, outputTargetName, EscapingUtilities.Escape(output), EscapingUtilities.Escape(parameterLocation.File)));
+                            _batchBucket.Lookup.AddNewItem(new ProjectItemInstance(_projectInstance, outputTargetName, EscapingUtilities.Escape(output), EscapingUtilities.Escape(parameterLocation.File), parameterLocation.Line, parameterLocation.Column));
                         }
                     }
 

src/Build/Instance/ProjectInstance.cs

@@ -3537,7 +3537,9 @@ private ProjectItemInstance InstantiateProjectItemInstance(ProjectItem item)
                 directMetadata,
                 inheritedItemDefinitions,
                 item.Xml.ContainingProject.EscapedFullPath,
-                useItemDefinitionsWithoutModification: false);
+                useItemDefinitionsWithoutModification: false,
+                item.Xml.Location.Line,
+                item.Xml.Location.Column);
 
             return instance;
         }
@@ -3597,7 +3599,9 @@ private static ProjectItemInstance InstantiateProjectItemInstanceFromImmutablePr
                 directMetadata,
                 inheritedItemDefinitions,
                 item.Xml.ContainingProject.EscapedFullPath,
-                useItemDefinitionsWithoutModification: true);
+                useItemDefinitionsWithoutModification: true,
+                item.Xml.Location.Line,
+                item.Xml.Location.Column);
             return instance;
         }