Provide a static method for getting diagnostics given a set of analyzers and a compilation.

***NO_CI***
 (changeset 1367702)

Src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -11,6 +11,7 @@
 using System.Reflection.Metadata;
 using System.Text;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeGen;
 using Microsoft.CodeAnalysis.Collections;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -861,6 +862,35 @@ public INamedTypeSymbol GetTypeByMetadataName(string fullyQualifiedMetadataName)
         /// </summary>
         public abstract ImmutableArray<Diagnostic> GetDiagnostics(CancellationToken cancellationToken = default(CancellationToken));
 
+        /// <summary>
+        /// Returns all diagnostics computed by the analyzers for the compilation.
+        /// </summary>
+        /// <param name="analyzers">The set of analyzers to include in the analysis</param>
+        /// <param name="cancellationToken">A cancellation token that can be used to abort analysis.</param>
+        public Task<ImmutableArray<Diagnostic>> GetDiagnosticsAsync(ImmutableArray<DiagnosticAnalyzer> analyzers, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            return GetDiagnosticsAsync(analyzers, null, cancellationToken);
+        }
+
+        /// <summary>
+        /// Returns all diagnostics computed by the analyzers for the compilation.
+        /// </summary>
+        /// <param name="analyzers">The set of analyzers to include in the analysis</param>
+        /// <param name="options">Options that are passed to analyzers</param>
+        /// <param name="cancellationToken">A cancellation token that can be used to abort analysis.</param>
+        public Task<ImmutableArray<Diagnostic>> GetDiagnosticsAsync(ImmutableArray<DiagnosticAnalyzer> analyzers, AnalyzerOptions options, CancellationToken cancellationToken = default(CancellationToken))
+        {
+            options = options ?? AnalyzerOptions.Empty;
+            Compilation newCompilation = null;
+            var analyzerDriver = AnalyzerDriver.Create(this, analyzers, options, out newCompilation, cancellationToken);
+
+            // We need to generate compiler events in order for the event queue to be populated and the analyzer driver to return diagnostics.
+            // So we'll call GetDiagnostics which will generate all events except for those on emit.
+            newCompilation.GetDiagnostics(cancellationToken);
+
+            return analyzerDriver.GetDiagnosticsAsync();
+        }
+
         internal abstract CommonMessageProvider MessageProvider { get; }
 
         /// <param name="accumulator">Bag to which filtered diagnostics will be added.</param>

Src/Samples/CSharp/AsyncPackage/Test/Backend/DiagnosticVerifier.Helper.cs

@@ -64,10 +64,7 @@ protected static Diagnostic[] GetSortedDiagnosticsFromDocuments(DiagnosticAnalyz
             {
                 var compilation = project.GetCompilationAsync().GetAwaiter().GetResult();
 
-                var driver = AnalyzerDriver.Create(compilation, ImmutableArray.Create(analyzer), null, out compilation, CancellationToken.None);
-
-                var discarded = compilation.GetDiagnostics();
-                var diags = driver.GetDiagnosticsAsync().GetAwaiter().GetResult();
+                var diags = compilation.GetDiagnosticsAsync(ImmutableArray.Create(analyzer)).GetAwaiter().GetResult();
                 foreach (var diag in diags)
                 {
                     if (diag.Location == Location.None || diag.Location.IsInMetadata)