feat: enable null reference type support (#2146)

* feat: enable NRT

* fix: dereference of a possible null reference

* chore: code cleanup

* chore: convert to conditional expression

* Update src/Microsoft.OpenApi/Models/OpenApiOperation.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* chore: PR feedback

* fix: resolve merge conflict errors

* chore: remove deprecated code and tests; make param required

* chore: code refactor and cleanup

* chore: update public API

* chore: address PR comments

* fix: remove nullable Json node params

* chore: use conditional compilation to make reference a required field

* refactor: apply nullable to new changes

* chore: bad merge

Signed-off-by: Vincent Biret <vibiret@microsoft.com>

* chore: simplifies filtering condition

* Update src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* chore: address more PR feedback

* chore: add check for both null and empty strings

* chore: revert to include check for empty strings

* chore: cleanup

* chore: clean up public API

* Update src/Microsoft.OpenApi/Reader/Services/OpenApiRemoteReferenceCollector.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* fix: resolve PR feedback

* chore: add defensive programming

* chore: resolve merge conflicts

* chore: more refactoring

* Update src/Microsoft.OpenApi/Reader/V2/OpenApiOperationDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V2/OpenApiPathItemDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V31/OpenApiServerVariableDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V31/OpenApiSecurityRequirementDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V2/OpenApiSecurityRequirementDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V3/OpenApiServerVariableDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* Update src/Microsoft.OpenApi/Reader/V3/OpenApiSecurityRequirementDeserializer.cs

Co-authored-by: Vincent Biret <vibiret@microsoft.com>

* chore: another round of refactoring

* chore: clean up nullability of params

* fix: compiler errors

* fix: remove redundant cast and update public API

* chore: fix merge conflict issues

* chore: apply copilot suggestion

* Update src/Microsoft.OpenApi/Services/OpenApiWalker.cs

---------

Signed-off-by: Vincent Biret <vibiret@microsoft.com>
Co-authored-by: Vincent Biret <vibiret@microsoft.com>

Author: MaggieKimani1

src/Microsoft.OpenApi.Hidi/Formatters/PowerShellFormatter.cs

@@ -54,7 +54,7 @@ public override void Visit(IOpenApiSchema schema)
 
         public override void Visit(IOpenApiPathItem pathItem)
         {
-            if (pathItem.Operations.TryGetValue(HttpMethod.Put, out var value) &&
+            if (pathItem.Operations is not null && pathItem.Operations.TryGetValue(HttpMethod.Put, out var value) &&
                 value.OperationId != null)
             {
                 var operationId = value.OperationId;
@@ -150,7 +150,7 @@ private static string RemoveKeyTypeSegment(string operationId, IList<IOpenApiPar
             var segments = operationId.SplitByChar('.');
             foreach (var parameter in parameters)
             {
-                var keyTypeExtension = parameter.Extensions.GetExtension("x-ms-docs-key-type");
+                var keyTypeExtension = parameter.Extensions?.GetExtension("x-ms-docs-key-type");
                 if (keyTypeExtension != null && operationId.Contains(keyTypeExtension, StringComparison.OrdinalIgnoreCase))
                 {
                     segments.Remove(keyTypeExtension);
@@ -179,15 +179,20 @@ private static void ResolveFunctionParameters(IList<IOpenApiParameter> parameter
 
         private void AddAdditionalPropertiesToSchema(IOpenApiSchema schema)
         {
-            if (schema is OpenApiSchema openApiSchema && !_schemaLoop.Contains(schema) && schema.Type.Equals(JsonSchemaType.Object))
+            if (schema is OpenApiSchema openApiSchema 
+                && !_schemaLoop.Contains(schema) 
+                && schema.Type.Equals(JsonSchemaType.Object))
             {
                 openApiSchema.AdditionalProperties = new OpenApiSchema() { Type = JsonSchemaType.Object };
 
                 /* Because 'additionalProperties' are now being walked,
                  * we need a way to keep track of visited schemas to avoid
                  * endlessly creating and walking them in an infinite recursion.
                  */
-                _schemaLoop.Push(schema.AdditionalProperties);
+                if (schema.AdditionalProperties is not null)
+                {
+                    _schemaLoop.Push(schema.AdditionalProperties);
+                }
             }
         }
 

src/Microsoft.OpenApi.Hidi/OpenApiService.cs

@@ -94,7 +94,7 @@ public static async Task TransformOpenApiDocumentAsync(HidiOptions options, ILog
                 // Load OpenAPI document
                 var document = await GetOpenApiAsync(options, openApiFormat.GetDisplayName(), logger, options.MetadataVersion, cancellationToken).ConfigureAwait(false);
 
-                if (options.FilterOptions != null)
+                if (options.FilterOptions != null && document is not null)
                 {
                     document = ApplyFilters(options, logger, apiDependency, postmanCollection, document);
                 }
@@ -107,7 +107,11 @@ public static async Task TransformOpenApiDocumentAsync(HidiOptions options, ILog
                     var walker = new OpenApiWalker(powerShellFormatter);
                     walker.Walk(document);
                 }
-                await WriteOpenApiAsync(options, openApiFormat, openApiVersion, document, logger, cancellationToken).ConfigureAwait(false);
+                if (document is not null)
+                {
+                    // Write the OpenAPI document to the output file
+                    await WriteOpenApiAsync(options, openApiFormat, openApiVersion, document, logger, cancellationToken).ConfigureAwait(false);
+                }
             }
             catch (TaskCanceledException)
             {
@@ -172,7 +176,7 @@ private static OpenApiDocument ApplyFilters(HidiOptions options, ILogger logger,
                                                     options.FilterOptions.FilterByTags,
                                                     requestUrls,
                                                     document,
-                                                     logger);
+                                                    logger);
             if (predicate != null)
             {
                 var stopwatch = new Stopwatch();
@@ -210,6 +214,7 @@ private static async Task WriteOpenApiAsync(HidiOptions options, OpenApiFormat o
 
                 var stopwatch = new Stopwatch();
                 stopwatch.Start();
+
                 await document.SerializeAsync(writer, openApiVersion, cancellationToken).ConfigureAwait(false);
                 stopwatch.Stop();
 
@@ -219,9 +224,9 @@ private static async Task WriteOpenApiAsync(HidiOptions options, OpenApiFormat o
         }
 
         // Get OpenAPI document either from OpenAPI or CSDL
-        private static async Task<OpenApiDocument> GetOpenApiAsync(HidiOptions options, string format, ILogger logger, string? metadataVersion = null, CancellationToken cancellationToken = default)
+        private static async Task<OpenApiDocument?> GetOpenApiAsync(HidiOptions options, string format, ILogger logger, string? metadataVersion = null, CancellationToken cancellationToken = default)
         {
-            OpenApiDocument document;
+            OpenApiDocument? document;
             Stream stream;
 
             if (!string.IsNullOrEmpty(options.Csdl))
@@ -242,7 +247,7 @@ private static async Task<OpenApiDocument> GetOpenApiAsync(HidiOptions options,
 
                     document = await ConvertCsdlToOpenApiAsync(filteredStream ?? stream, format, metadataVersion, options.SettingsConfig, cancellationToken).ConfigureAwait(false);
                     stopwatch.Stop();
-                    logger.LogTrace("{Timestamp}ms: Generated OpenAPI with {Paths} paths.", stopwatch.ElapsedMilliseconds, document.Paths.Count);
+                    logger.LogTrace("{Timestamp}ms: Generated OpenAPI with {Paths} paths.", stopwatch.ElapsedMilliseconds, document?.Paths.Count);
                 }
             }
             else if (!string.IsNullOrEmpty(options.OpenApi))
@@ -370,7 +375,7 @@ private static MemoryStream ApplyFilterToCsdl(Stream csdlStream, string entitySe
 
             if (result is null) return null;
 
-            return result.Diagnostic.Errors.Count == 0;
+            return result.Diagnostic?.Errors.Count == 0;
         }
 
         private static async Task<ReadResult> ParseOpenApiAsync(string openApiFile, bool inlineExternal, ILogger logger, Stream stream, CancellationToken cancellationToken = default)
@@ -407,7 +412,7 @@ private static async Task<ReadResult> ParseOpenApiAsync(string openApiFile, bool
         /// </summary>
         /// <param name="csdl">The CSDL stream.</param>
         /// <returns>An OpenAPI document.</returns>
-        public static async Task<OpenApiDocument> ConvertCsdlToOpenApiAsync(Stream csdl, string format, string? metadataVersion = null, IConfiguration? settings = null, CancellationToken token = default)
+        public static async Task<OpenApiDocument?> ConvertCsdlToOpenApiAsync(Stream csdl, string format, string? metadataVersion = null, IConfiguration? settings = null, CancellationToken token = default)
         {
             using var reader = new StreamReader(csdl);
             var csdlText = await reader.ReadToEndAsync(token).ConfigureAwait(false);
@@ -425,7 +430,7 @@ public static async Task<OpenApiDocument> ConvertCsdlToOpenApiAsync(Stream csdl,
         /// </summary>
         /// <param name="document"> The converted OpenApiDocument.</param>
         /// <returns> A valid OpenApiDocument instance.</returns>
-        public static OpenApiDocument FixReferences(OpenApiDocument document, string format)
+        public static OpenApiDocument? FixReferences(OpenApiDocument document, string format)
         {
             // This method is only needed because the output of ConvertToOpenApi isn't quite a valid OpenApiDocument instance.
             // So we write it out, and read it back in again to fix it up.
@@ -584,52 +589,54 @@ private static string GetInputPathExtension(string? openapi = null, string? csdl
 
                 var openApiFormat = options.OpenApiFormat ?? (!string.IsNullOrEmpty(options.OpenApi) ? GetOpenApiFormat(options.OpenApi, logger) : OpenApiFormat.Yaml);
                 var document = await GetOpenApiAsync(options, openApiFormat.GetDisplayName(), logger, null, cancellationToken).ConfigureAwait(false);
-
-                using (logger.BeginScope("Creating diagram"))
+                if (document is not null)
                 {
-                    // If output is null, create a HTML file in the user's temporary directory
-                    var sourceUrl = (string.IsNullOrEmpty(options.OpenApi), string.IsNullOrEmpty(options.Csdl)) switch {
-                        (false, _) => options.OpenApi!,
-                        (_, false) => options.Csdl!,
-                        _ => throw new InvalidOperationException("No input file path or URL provided")
-                    };
-                    if (options.Output == null)
+                    using (logger.BeginScope("Creating diagram"))
                     {
-                        var tempPath = Path.GetTempPath() + "/hidi/";
-                        if (!File.Exists(tempPath))
+                        // If output is null, create a HTML file in the user's temporary directory
+                        var sourceUrl = (string.IsNullOrEmpty(options.OpenApi), string.IsNullOrEmpty(options.Csdl)) switch
                         {
-                            Directory.CreateDirectory(tempPath);
-                        }
-
-                        var fileName = Path.GetRandomFileName();
-
-                        var output = new FileInfo(Path.Combine(tempPath, fileName + ".html"));
-                        using (var file = new FileStream(output.FullName, FileMode.Create))
+                            (false, _) => options.OpenApi!,
+                            (_, false) => options.Csdl!,
+                            _ => throw new InvalidOperationException("No input file path or URL provided")
+                        };
+                        if (options.Output == null)
                         {
-                            using var writer = new StreamWriter(file);
-                            WriteTreeDocumentAsHtml(sourceUrl, document, writer);
+                            var tempPath = Path.GetTempPath() + "/hidi/";
+                            if (!File.Exists(tempPath))
+                            {
+                                Directory.CreateDirectory(tempPath);
+                            }
+
+                            var fileName = Path.GetRandomFileName();
+
+                            var output = new FileInfo(Path.Combine(tempPath, fileName + ".html"));
+                            using (var file = new FileStream(output.FullName, FileMode.Create))
+                            {
+                                using var writer = new StreamWriter(file);
+                                WriteTreeDocumentAsHtml(sourceUrl, document, writer);
+                            }
+                            logger.LogTrace("Created Html document with diagram ");
+
+                            // Launch a browser to display the output html file
+                            using var process = new Process();
+                            process.StartInfo.FileName = output.FullName;
+                            process.StartInfo.UseShellExecute = true;
+                            process.Start();
+
+                            return output.FullName;
                         }
-                        logger.LogTrace("Created Html document with diagram ");
-
-                        // Launch a browser to display the output html file
-                        using var process = new Process();
-                        process.StartInfo.FileName = output.FullName;
-                        process.StartInfo.UseShellExecute = true;
-                        process.Start();
-
-                        return output.FullName;
-                    }
-                    else  // Write diagram as Markdown document to output file
-                    {
-                        using (var file = new FileStream(options.Output.FullName, FileMode.Create))
+                        else  // Write diagram as Markdown document to output file
                         {
+                            using var file = new FileStream(options.Output.FullName, FileMode.Create);
                             using var writer = new StreamWriter(file);
                             WriteTreeDocumentAsMarkdown(sourceUrl, document, writer);
+
+                            logger.LogTrace("Created markdown document with diagram ");
+                            return options.Output.FullName;
                         }
-                        logger.LogTrace("Created markdown document with diagram ");
-                        return options.Output.FullName;
                     }
-                }
+                }                
             }
             catch (TaskCanceledException)
             {
@@ -645,7 +652,7 @@ private static string GetInputPathExtension(string? openapi = null, string? csdl
         private static void LogErrors(ILogger logger, ReadResult result)
         {
             var context = result.Diagnostic;
-            if (context.Errors.Count != 0)
+            if (context is not null && context.Errors.Count != 0)
             {
                 using (logger.BeginScope("Detected errors"))
                 {
@@ -697,7 +704,7 @@ internal static void WriteTreeDocumentAsHtml(string sourceUrl, OpenApiDocument d
                 </style>
                 <body>
                 """);
-            writer.WriteLine("<h1>" + document.Info.Title + "</h1>");
+            writer.WriteLine("<h1>" + document?.Info.Title + "</h1>");
             writer.WriteLine();
             writer.WriteLine($"<h3> API Description: <a href='{sourceUrl}'>{sourceUrl}</a></h3>");
 
@@ -751,7 +758,7 @@ internal static async Task PluginManifestAsync(HidiOptions options, ILogger logg
 
             cancellationToken.ThrowIfCancellationRequested();
 
-            if (options.FilterOptions != null)
+            if (options.FilterOptions != null && document is not null)
             {
                 document = ApplyFilters(options, logger, apiDependency, null, document);
             }
@@ -765,24 +772,31 @@ internal static async Task PluginManifestAsync(HidiOptions options, ILogger logg
             // Write OpenAPI to Output folder
             options.Output = new(Path.Combine(options.OutputFolder, "openapi.json"));
             options.TerseOutput = true;
-            await WriteOpenApiAsync(options, OpenApiFormat.Json, OpenApiSpecVersion.OpenApi3_1, document, logger, cancellationToken).ConfigureAwait(false);
-
-            // Create OpenAIPluginManifest from ApiDependency and OpenAPI document
-            var manifest = new OpenAIPluginManifest(document.Info?.Title ?? "Title", document.Info?.Title ?? "Title", "https://go.microsoft.com/fwlink/?LinkID=288890", document.Info?.Contact?.Email ?? "placeholder@contoso.com", document.Info?.License?.Url.ToString() ?? "https://placeholderlicenseurl.com")
-            {
-                DescriptionForHuman = document.Info?.Description ?? "Description placeholder",
-                Api = new("openapi", "./openapi.json"),
-                Auth = new ManifestNoAuth(),
-            };
-            manifest.NameForModel = manifest.NameForHuman;
-            manifest.DescriptionForModel = manifest.DescriptionForHuman;
-
-            // Write OpenAIPluginManifest to Output folder
-            var manifestFile = new FileInfo(Path.Combine(options.OutputFolder, "ai-plugin.json"));
-            using var file = new FileStream(manifestFile.FullName, FileMode.Create);
-            using var jsonWriter = new Utf8JsonWriter(file, new() { Indented = true });
-            manifest.Write(jsonWriter);
-            await jsonWriter.FlushAsync(cancellationToken).ConfigureAwait(false);
+            if (document is not null)
+            {
+                await WriteOpenApiAsync(options, OpenApiFormat.Json, OpenApiSpecVersion.OpenApi3_1, document, logger, cancellationToken).ConfigureAwait(false);
+
+                // Create OpenAIPluginManifest from ApiDependency and OpenAPI document
+                var manifest = new OpenAIPluginManifest(document.Info.Title ?? "Title",
+                                                        document.Info.Title ?? "Title",
+                                                        "https://go.microsoft.com/fwlink/?LinkID=288890",
+                                                        document.Info?.Contact?.Email ?? "placeholder@contoso.com",
+                                                        document.Info?.License?.Url?.ToString() ?? "https://placeholderlicenseurl.com")
+                {
+                    DescriptionForHuman = document.Info?.Description ?? "Description placeholder",
+                    Api = new("openapi", "./openapi.json"),
+                    Auth = new ManifestNoAuth(),
+                };
+                manifest.NameForModel = manifest.NameForHuman;
+                manifest.DescriptionForModel = manifest.DescriptionForHuman;
+
+                // Write OpenAIPluginManifest to Output folder
+                var manifestFile = new FileInfo(Path.Combine(options.OutputFolder, "ai-plugin.json"));
+                using var file = new FileStream(manifestFile.FullName, FileMode.Create);
+                using var jsonWriter = new Utf8JsonWriter(file, new() { Indented = true });
+                manifest.Write(jsonWriter);
+                await jsonWriter.FlushAsync(cancellationToken).ConfigureAwait(false);
+            }
         }
     }
 }

src/Microsoft.OpenApi.Readers/Microsoft.OpenApi.Readers.csproj

@@ -11,6 +11,7 @@
         <!-- https://github.com/dotnet/sourcelink/blob/main/docs/README.md#embeduntrackedsources -->
         <EmbedUntrackedSources>true</EmbedUntrackedSources>
         <NoWarn>NU5048</NoWarn>
+        <Nullable>enable</Nullable>
         <PackageReadmeFile>README.md</PackageReadmeFile>
     </PropertyGroup>
 

src/Microsoft.OpenApi.Readers/OpenApiYamlReader.cs

@@ -84,11 +84,11 @@ public static ReadResult Read(JsonNode jsonNode, OpenApiReaderSettings settings)
         }
 
         /// <inheritdoc/>
-        public T ReadFragment<T>(MemoryStream input,
+        public T? ReadFragment<T>(MemoryStream input,
                                  OpenApiSpecVersion version,
                                  OpenApiDocument openApiDocument,
                                  out OpenApiDiagnostic diagnostic,
-                                 OpenApiReaderSettings settings = null) where T : IOpenApiElement
+                                 OpenApiReaderSettings? settings = null) where T : IOpenApiElement
         {
             if (input is null) throw new ArgumentNullException(nameof(input));
             JsonNode jsonNode;
@@ -110,7 +110,7 @@ public T ReadFragment<T>(MemoryStream input,
         }
 
         /// <inheritdoc/>
-        public static T ReadFragment<T>(JsonNode input, OpenApiSpecVersion version, OpenApiDocument openApiDocument, out OpenApiDiagnostic diagnostic, OpenApiReaderSettings settings = null) where T : IOpenApiElement
+        public static T? ReadFragment<T>(JsonNode input, OpenApiSpecVersion version, OpenApiDocument openApiDocument, out OpenApiDiagnostic diagnostic, OpenApiReaderSettings? settings = null) where T : IOpenApiElement
         {
             return _jsonReader.ReadFragment<T>(input, version, openApiDocument, out diagnostic, settings);
         }

src/Microsoft.OpenApi/Exceptions/OpenApiException.cs

@@ -33,7 +33,7 @@ public OpenApiException(string message)
         /// </summary>
         /// <param name="message">The plain text error message for this exception.</param>
         /// <param name="innerException">The inner exception that is the cause of this exception to be thrown.</param>
-        public OpenApiException(string message, Exception innerException)
+        public OpenApiException(string message, Exception? innerException)
             : base(message, innerException)
         {
         }
@@ -46,6 +46,6 @@ public OpenApiException(string message, Exception innerException)
         /// a text/plain pointer as defined in https://tools.ietf.org/html/rfc5147
         /// Currently only line= is provided because using char= causes tests to break due to CR/LF and LF differences
         /// </summary>
-        public string Pointer { get; set; }
+        public string? Pointer { get; set; }
     }
 }