If any response contains octet-stream, make response binary

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed shorthand for refresh option in workspace experience. [#5240](https://github.com/microsoft/kiota/issues/5240)
 - Fixed missing type options in help for plugin commands. [#5230](https://github.com/microsoft/kiota/issues/5230)
 - Removed OpenAI plugins generation since the service does not support them anymore.
+- Redirect status codes documenting an application/octet-stream content type now generate a stream return type. [#5246](https://github.com/microsoft/kiota/issues/5246)
 - Fixed an issue where models would be missing when they had no properties and a single allOf entry. [#5014](https://github.com/microsoft/kiota/issues/5014)
 - Reverts modification of responses in output openApi file when generating plugins [#4945](https://github.com/microsoft/kiota/issues/4945)
 - Expand properties types with null type for Typescript. [#4993](https://github.com/microsoft/kiota-typescript/issues/1188)

src/Kiota.Builder/KiotaBuilder.cs

@@ -1159,7 +1159,9 @@ openApiExtension is OpenApiPrimaryErrorMessageExtension primaryErrorMessageExten
         };
     }
     private const string RequestBodyPlainTextContentType = "text/plain";
-    private static readonly HashSet<string> noContentStatusCodes = new(StringComparer.OrdinalIgnoreCase) { "201", "202", "204", "205", "301", "302", "303", "304", "307" };
+    private const string RequestBodyOctetStreamContentType = "application/octet-stream";
+    private static readonly HashSet<string> redirectStatusCodes = new(StringComparer.OrdinalIgnoreCase) { "301", "302", "303", "307" };
+    private static readonly HashSet<string> noContentStatusCodes = new(redirectStatusCodes, StringComparer.OrdinalIgnoreCase) { "201", "202", "204", "205", "304" };
     private static readonly HashSet<string> errorStatusCodes = new(Enumerable.Range(400, 599).Select(static x => x.ToString(CultureInfo.InvariantCulture))
                                                                                  .Concat([CodeMethod.ErrorMappingClientRange, CodeMethod.ErrorMappingServerRange]), StringComparer.OrdinalIgnoreCase);
     private void AddErrorMappingsForExecutorMethod(OpenApiUrlTreeNode currentNode, OpenApiOperation operation, CodeMethod executorMethod)
@@ -1248,29 +1250,28 @@ private void AddErrorMappingToExecutorMethod(OpenApiUrlTreeNode currentNode, Ope
             }
             else if (modelType is null)
             {
-                string returnType;
-                if (operation.Responses.Any(static x => noContentStatusCodes.Contains(x.Key)))
-                    returnType = VoidType;
-                else if (operation.Responses.Any(static x => x.Value.Content.ContainsKey(RequestBodyPlainTextContentType)))
-                    returnType = "string";
-                else
-                    returnType = "binary";
-                return (new CodeType { Name = returnType, IsExternal = true, }, null);
+                return (GetExecutorMethodDefaultReturnType(operation), null);
             }
             return (modelType, null);
         }
         else
         {
-            string returnType;
-            if (operation.Responses.Any(static x => noContentStatusCodes.Contains(x.Key)))
-                returnType = VoidType;
-            else if (operation.Responses.Any(static x => x.Value.Content.ContainsKey(RequestBodyPlainTextContentType)))
-                returnType = "string";
-            else
-                returnType = "binary";
-            return (new CodeType { Name = returnType, IsExternal = true, }, null);
+            return (GetExecutorMethodDefaultReturnType(operation), null);
         }
     }
+    private static CodeType GetExecutorMethodDefaultReturnType(OpenApiOperation operation)
+    {
+        string returnType;
+        if (operation.Responses.Any(static x => x.Value.Content.ContainsKey(RequestBodyOctetStreamContentType) && redirectStatusCodes.Contains(x.Key)))
+            returnType = "binary";
+        else if (operation.Responses.Any(static x => noContentStatusCodes.Contains(x.Key)))
+            returnType = VoidType;
+        else if (operation.Responses.Any(static x => x.Value.Content.ContainsKey(RequestBodyPlainTextContentType)))
+            returnType = "string";
+        else
+            returnType = "binary";
+        return new CodeType { Name = returnType, IsExternal = true, };
+    }
     private void CreateOperationMethods(OpenApiUrlTreeNode currentNode, OperationType operationType, OpenApiOperation operation, CodeClass parentClass)
     {
         try

tests/Kiota.Builder.Tests/ContentTypeMappingTests.cs

@@ -57,6 +57,7 @@ public void Dispose()
     [InlineData("application/octet-stream", "204", false, "default", "void")]
     [InlineData("application/octet-stream", "200", true, "default", "binary")]
     [InlineData("application/octet-stream", "200", false, "default", "binary")]
+    [InlineData("application/octet-stream", "302", false, "default", "binary")] // on a redirect to a binary content we generate a binary return type for download
     [InlineData("text/html", "204", true, "default", "void")]
     [InlineData("text/html", "204", false, "default", "void")]
     [InlineData("text/html", "200", true, "default", "binary")]