Ensure that we report warning when the argument for #pragma warning disable /...

Ensure that we report warning when the argument for #pragma warning disable / restore is an empty string / string that only contains whitespace.

Also throw exception if someone tries to construct a DiagnosticDescriptor with null / empty string as Id. (changeset 1262338)

Src/Compilers/CSharp/Source/Parser/DirectiveParser.cs

@@ -398,7 +398,11 @@ private DirectiveTriviaSyntax ParsePragmaDirective(SyntaxToken hash, SyntaxToken
                                 {
                                     string value = (string)id.Value;
                                     var messageProvider = MessageProvider.Instance;
-                                    if (value.StartsWith(messageProvider.CodePrefix))
+                                    if (string.IsNullOrWhiteSpace(value))
+                                    {
+                                        id = this.AddError(id, ErrorCode.WRN_BadWarningNumber, value);
+                                    }
+                                    else if (value.StartsWith(messageProvider.CodePrefix))
                                     {
                                         // For diagnostic IDs of the form "CS[0-9]*", verify the error code is that of a warning
                                         int compilerWarningNumber;

Src/Compilers/CSharp/Test/Syntax/Diagnostics/DiagnosticTest.cs

@@ -1519,6 +1519,36 @@ public static void Main()
                 Diagnostic(ErrorCode.WRN_StringOrNumericLiteralExpected, ","));
         }
 
+        [WorkItem(913567)]
+        [Fact]
+        public void PragmaWarningWithErrors_EmptyStrings()
+        {
+            var text = @"
+public class C
+{
+    public static void Main()
+    {
+#pragma warning disable """"
+#pragma warning restore """"
+#pragma warning disable ""  ""
+#pragma warning restore """ + "\t" + @"""
+    }
+}";
+            CreateCompilationWithMscorlib(text).VerifyDiagnostics(
+// (6,25): warning CS1691: '' is not a valid warning number
+// #pragma warning disable ""
+Diagnostic(ErrorCode.WRN_BadWarningNumber, "\"\"").WithArguments("").WithLocation(6, 25),
+// (7,25): warning CS1691: '' is not a valid warning number
+// #pragma warning restore ""
+Diagnostic(ErrorCode.WRN_BadWarningNumber, "\"\"").WithArguments("").WithLocation(7, 25),
+// (8,25): warning CS1691: '  ' is not a valid warning number
+// #pragma warning disable "  "
+Diagnostic(ErrorCode.WRN_BadWarningNumber, "\"  \"").WithArguments("  ").WithLocation(8, 25),
+// (9,25): warning CS1691: '{tab}' is not a valid warning number
+// #pragma warning restore "{tab}"
+Diagnostic(ErrorCode.WRN_BadWarningNumber, "\"\t\"").WithArguments("\t").WithLocation(9, 25));
+        }
+
         [WorkItem(546814, "DevDiv")]
         [Fact]
         public void PragmaWarningAlign_0()

Src/Compilers/Core/Source/CodeAnalysisResources.Designer.cs

@@ -249,6 +249,15 @@ internal class CodeAnalysisResources {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to A DiagnosticDescriptor must have an Id that is neiter null nor an empty string nor a string that only contains white space..
+        /// </summary>
+        internal static string DiagnosticIdCantBeNullOrWhitespace {
+            get {
+                return ResourceManager.GetString("DiagnosticIdCantBeNullOrWhitespace", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Empty or invalid file name.
         /// </summary>

Src/Compilers/Core/Source/CodeAnalysisResources.resx

@@ -363,4 +363,7 @@
   <data name="ChangesMustBeOrderedAndNotOverlapping" xml:space="preserve">
     <value>The changes must be ordered and not overlapping.</value>
   </data>
+  <data name="DiagnosticIdCantBeNullOrWhitespace" xml:space="preserve">
+    <value>A DiagnosticDescriptor must have an Id that is neiter null nor an empty string nor a string that only contains white space.</value>
+  </data>
 </root>
\ No newline at end of file

Src/Compilers/Core/Source/Diagnostic/DiagnosticDescriptor.cs

 // Copyright (c) Microsoft Open Technologies, Inc.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+using System;
 using System.Collections.Generic;
-using Microsoft.CodeAnalysis.Diagnostics;
 
 namespace Microsoft.CodeAnalysis
 {
@@ -59,6 +59,11 @@ public class DiagnosticDescriptor
         /// <param name="customTags">Optional custom tags for the diagnostic. See <see cref="WellKnownDiagnosticTags"/> for some well known tags.</param>
         public DiagnosticDescriptor(string id, string description, string messageFormat, string category, DiagnosticSeverity defaultSeverity, bool isEnabledByDefault, params string[] customTags)
         {
+            if (string.IsNullOrWhiteSpace(id))
+            {
+                throw new ArgumentException(CodeAnalysisResources.DiagnosticIdCantBeNullOrWhitespace, "id");
+            }
+
             this.Id = id;
             this.Description = description;
             this.Category = category;