Support #if SNIPPET in snippets (Azure#20391)

CONTRIBUTING.md

@@ -197,12 +197,12 @@ When run, the code regions in the format below (where `<snippetName>` is the nam
 //some sample code
 string snippet = "some snippet code";
 
-// Lines prefixed with the below comment format will be ignored by the snippet updater.
-/*@@*/ string ignored = "this code will not appear in the snippet markdown";
-
-// Lines prefixed with the below comment format will appear in the snippet markdown, but will remain comments in the C#` code.
-// Note: these comments should only be used for non-critical code as it will not be compiled or refactored as the code changes.
-//@@ snippet = "value that would never pass a test but looks good in a sample!";
+// The snippet updater defines the SNIPPET directive while parsing. You can use #if SNIPPET to filter lines in or out of the snippet.
+#if SNIPPET
+snippet = "value that would never pass a test but looks good in a sample!";
+#else
+string ignored = "this code will not appear in the snippet markdown";
+#endif
 
 #endregion
 ```

eng/SnippetGenerator/DirectoryProcessor.cs

@@ -28,6 +28,7 @@ public class DirectoryProcessor
             RegexOptions.Compiled | RegexOptions.Singleline | RegexOptions.CultureInvariant);
 
         private UTF8Encoding _utf8EncodingWithoutBOM;
+        private static string[] _snippetPreprocessorSymbols = new [] {"SNIPPET"};
 
         public DirectoryProcessor(string directory)
         {
@@ -208,7 +209,7 @@ private List<Snippet> GetSnippetsInDirectory(string baseDirectory)
                 {
                     var syntaxTree = CSharpSyntaxTree.ParseText(
                         File.ReadAllText(file),
-                        new CSharpParseOptions(LanguageVersion.Preview),
+                        new CSharpParseOptions(LanguageVersion.Preview, preprocessorSymbols: _snippetPreprocessorSymbols),
                         path: file);
 
                     list.AddRange(GetAllSnippets(syntaxTree));
@@ -225,6 +226,9 @@ private List<Snippet> GetSnippetsInDirectory(string baseDirectory)
         private Snippet[] GetAllSnippets(SyntaxTree syntaxTree)
         {
             var snippets = new List<Snippet>();
+            var newRoot = PreprocessorDirectiveRemover.Instance.Visit(syntaxTree.GetRoot());
+            syntaxTree = syntaxTree.WithRootAndOptions(newRoot, syntaxTree.Options);
+
             var directiveWalker = new DirectiveWalker();
             directiveWalker.Visit(syntaxTree.GetRoot());
 
@@ -251,6 +255,41 @@ private Snippet[] GetAllSnippets(SyntaxTree syntaxTree)
             return snippets.ToArray();
         }
 
+        class PreprocessorDirectiveRemover : CSharpSyntaxRewriter
+        {
+            public static PreprocessorDirectiveRemover Instance = new PreprocessorDirectiveRemover();
+            private PreprocessorDirectiveRemover() : base(visitIntoStructuredTrivia: true)
+            {
+            }
+
+            public override SyntaxTrivia VisitTrivia(SyntaxTrivia trivia)
+            {
+                if (trivia.Kind() == SyntaxKind.DisabledTextTrivia)
+                    return SyntaxFactory.Whitespace("");
+
+                return base.VisitTrivia(trivia);
+            }
+
+            public override SyntaxNode VisitIfDirectiveTrivia(IfDirectiveTriviaSyntax node)
+            {
+                return null;
+            }
+
+            public override SyntaxNode VisitElifDirectiveTrivia(ElifDirectiveTriviaSyntax node)
+            {
+                return null;
+            }
+
+            public override SyntaxNode VisitElseDirectiveTrivia(ElseDirectiveTriviaSyntax node)
+            {
+                return null;
+            }
+
+            public override SyntaxNode VisitEndIfDirectiveTrivia(EndIfDirectiveTriviaSyntax node)
+            {
+                return null;
+            }
+        }
         class DirectiveWalker : CSharpSyntaxWalker
         {
             private Stack<RegionDirectiveTriviaSyntax> _regions = new Stack<RegionDirectiveTriviaSyntax>();

sdk/eventhub/Azure.Messaging.EventHubs.Processor/tests/Snippets/Sample02_EventProcessorConfigurationLiveTests.cs

@@ -445,7 +445,7 @@ public void TryTimeoutConfiguration()
             Assert.That(options, Is.Not.Null);
         }
 
-#if NETCOREAPP3_1 || NET5
+#if NETCOREAPP3_1 || NET5 || SNIPPET
         /// <summary>
         ///   Performs basic smoke test validation of the contained snippet.
         /// </summary>

sdk/eventhub/Azure.Messaging.EventHubs/tests/Snippets/Sample02_EventHubsClientsLiveTests.cs

@@ -299,7 +299,7 @@ public void TryTimeoutConfiguration()
             Assert.That(options, Is.Not.Null);
         }
 
-#if NETCOREAPP3_1 || NET5
+#if NETCOREAPP3_1 || NET5 || SNIPPET
         /// <summary>
         ///   Performs basic smoke test validation of the contained snippet.
         /// </summary>

sdk/monitor/Azure.Monitory.Query/tests/LogsClientSamples.cs

@@ -41,8 +41,11 @@ public async Task QueryLogsAsTablePrintAll()
             #region Snippet:QueryLogsPrintTable
 
             LogsClient client = new LogsClient(new DefaultAzureCredential());
-            /*@@*/string workspaceId = TestEnvironment.WorkspaceId;
-            //@@string workspaceId = "<workspace_id>";
+#if SNIPPET
+            string workspaceId = "<workspace_id>";
+#else
+            string workspaceId = TestEnvironment.WorkspaceId;
+#endif
             Response<LogsQueryResult> response = await client.QueryAsync(workspaceId, "AzureActivity | top 10 by TimeGenerated");
 
             LogsQueryResultTable table = response.Value.PrimaryTable;
@@ -74,8 +77,11 @@ public async Task QueryLogsAsPrimitive()
             #region Snippet:QueryLogsAsPrimitive
 
             LogsClient client = new LogsClient(new DefaultAzureCredential());
-            /*@@*/string workspaceId = TestEnvironment.WorkspaceId;
-            //@@string workspaceId = "<workspace_id>";
+#if SNIPPET
+            string workspaceId = "<workspace_id>";
+#else
+            string workspaceId = TestEnvironment.WorkspaceId;
+#endif
 
             // Query TOP 10 resource groups by event count
             Response<IReadOnlyList<string>> response = await client.QueryAsync<string>(workspaceId,
@@ -95,8 +101,11 @@ public async Task QueryLogsAsModels()
             #region Snippet:QueryLogsAsModels
 
             LogsClient client = new LogsClient(new DefaultAzureCredential());
-            /*@@*/string workspaceId = TestEnvironment.WorkspaceId;
-            //@@string workspaceId = "<workspace_id>";
+#if SNIPPET
+            string workspaceId = "<workspace_id>";
+#else
+            string workspaceId = TestEnvironment.WorkspaceId;
+#endif
 
             // Query TOP 10 resource groups by event count
             Response<IReadOnlyList<MyLogEntryModel>> response = await client.QueryAsync<MyLogEntryModel>(workspaceId,
@@ -116,8 +125,11 @@ public async Task BatchQuery()
             #region Snippet:BatchQuery
 
             LogsClient client = new LogsClient(new DefaultAzureCredential());
-            /*@@*/string workspaceId = TestEnvironment.WorkspaceId;
-            //@@string workspaceId = "<workspace_id>";
+#if SNIPPET
+            string workspaceId = "<workspace_id>";
+#else
+            string workspaceId = TestEnvironment.WorkspaceId;
+#endif
 
             // Query TOP 10 resource groups by event count
             // And total event count