added comment based on PR.

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.Executor.cs

@@ -41,6 +41,9 @@ public IEnumerable<DiagnosticData> ConvertToLocalDiagnostics(Document targetDocu
                 return ConvertToLocalDiagnosticsWithoutCompilation(targetDocument, diagnostics, span);
             }
 
+            /// <summary>
+            /// Return all local diagnostics (syntax, semantic) that belong to given document for the given StateSet (analyzer) either from cache or by calculating them
+            /// </summary>
             public async Task<DocumentAnalysisData> GetDocumentAnalysisDataAsync(
                 CompilationWithAnalyzers analyzerDriverOpt, Document document, StateSet stateSet, AnalysisKind kind, CancellationToken cancellationToken)
             {
@@ -74,6 +77,9 @@ public IEnumerable<DiagnosticData> ConvertToLocalDiagnostics(Document targetDocu
                 }
             }
 
+            /// <summary>
+            /// Return all diagnostics that belong to given project for the given StateSets (analyzers) either from cache or by calculating them
+            /// </summary>
             public async Task<ProjectAnalysisData> GetProjectAnalysisDataAsync(
                 CompilationWithAnalyzers analyzerDriverOpt, Project project, IEnumerable<StateSet> stateSets, CancellationToken cancellationToken)
             {
@@ -105,6 +111,9 @@ public IEnumerable<DiagnosticData> ConvertToLocalDiagnostics(Document targetDocu
                 }
             }
 
+            /// <summary>
+            /// Return all local diagnostics (syntax, semantic) that belong to given document for the given StateSet (analyzer) by calculating them
+            /// </summary>
             public async Task<IEnumerable<DiagnosticData>> ComputeDiagnosticsAsync(
                 CompilationWithAnalyzers analyzerDriverOpt, Document document, DiagnosticAnalyzer analyzer, AnalysisKind kind, TextSpan? spanOpt, CancellationToken cancellationToken)
             {
@@ -119,6 +128,9 @@ public IEnumerable<DiagnosticData> ConvertToLocalDiagnostics(Document targetDocu
                 return ConvertToLocalDiagnostics(document, documentDiagnostics);
             }
 
+            /// <summary>
+            /// Return all diagnostics that belong to given project for the given StateSets (analyzers) by calculating them
+            /// </summary>
             public async Task<ImmutableDictionary<DiagnosticAnalyzer, AnalysisResult>> ComputeDiagnosticsAsync(
                 CompilationWithAnalyzers analyzerDriverOpt, Project project, IEnumerable<StateSet> stateSets, CancellationToken cancellationToken)
             {

src/Features/Core/Portable/Diagnostics/EngineV2/DiagnosticIncrementalAnalyzer.ProjectState.cs

@@ -42,6 +42,9 @@ public bool IsEmpty(DocumentId documentId)
                 return IsEmpty(_lastResult, documentId);
             }
 
+            /// <summary>
+            /// Return all diagnostics for the given project stored in this state
+            /// </summary>
             public async Task<AnalysisResult> GetAnalysisDataAsync(Project project, bool avoidLoadingData, CancellationToken cancellationToken)
             {
                 // make a copy of last result.
@@ -54,14 +57,14 @@ public async Task<AnalysisResult> GetAnalysisDataAsync(Project project, bool avo
                 }
 
                 // PERF: avoid loading data if version is not right one.
-                // avoid loading data flag is there as a strickly perf optimization.
+                // avoid loading data flag is there as a strictly perf optimization.
                 var version = await GetDiagnosticVersionAsync(project, cancellationToken).ConfigureAwait(false);
                 if (avoidLoadingData && lastResult.Version != version)
                 {
                     return lastResult;
                 }
 
-                // if given document doesnt have any diagnostics, return empty.
+                // if given project doesnt have any diagnostics, return empty.
                 if (lastResult.IsEmpty)
                 {
                     return new AnalysisResult(lastResult.ProjectId, lastResult.Version);
@@ -73,6 +76,8 @@ public async Task<AnalysisResult> GetAnalysisDataAsync(Project project, bool avo
 
                 foreach (var documentId in lastResult.DocumentIds)
                 {
+                    cancellationToken.ThrowIfCancellationRequested();
+
                     var document = project.GetDocument(documentId);
                     if (document == null)
                     {
@@ -94,6 +99,9 @@ public async Task<AnalysisResult> GetAnalysisDataAsync(Project project, bool avo
                 return builder.ToResult();
             }
 
+            /// <summary>
+            /// Return all diagnostics for the given document stored in this state including non local diagnostics for this document
+            /// </summary>
             public async Task<AnalysisResult> GetAnalysisDataAsync(Document document, bool avoidLoadingData, CancellationToken cancellationToken)
             {
                 // make a copy of last result.
@@ -129,6 +137,9 @@ public async Task<AnalysisResult> GetAnalysisDataAsync(Document document, bool a
                 return builder.ToResult();
             }
 
+            /// <summary>
+            /// Return all no location diagnostics for the given project stored in this state
+            /// </summary>
             public async Task<AnalysisResult> GetProjectAnalysisDataAsync(Project project, bool avoidLoadingData, CancellationToken cancellationToken)
             {
                 // make a copy of last result.
@@ -209,6 +220,8 @@ private async Task<AnalysisResult> LoadInitialAnalysisDataAsync(Project project,
 
                 foreach (var document in project.Documents)
                 {
+                    cancellationToken.ThrowIfCancellationRequested();
+
                     if (!await TryDeserializeDocumentAsync(serializer, document, builder, cancellationToken).ConfigureAwait(false))
                     {
                         continue;