Vishwa Prakash Gayasen

This commit **enables the metadata API** for services hosted on the **`BaseController`** by integrating `thrift-python`'s server-side metadata capabilities. It introduces a `getServiceMetadata` method in `CppServerWrapper.cpp`'s `PythonAsyncProcessor` and implements `get_service_metadata` within `TCppServer.py`'s `_ProcessorAdapter` to retrieve and serialize service introspection data. This **new capability** is a critical **unblocker** for tools like Thrift Fiddle, Thriftdbg, and M2T2, allowing them to access essential service metadata for `BaseController`-based services. Comprehensive unit tests were added to ensure the correct retrieval and serialization of service function information.

This commit **fixes a critical stability issue** within the **Thrift Python client's `OmniClient`** by adjusting the error handling contract for the `getChannelProtocolId` method. Previously, this method was incorrectly marked `noexcept` in `thrift/lib/python/client/OmniClient.h`, despite internal operations that could throw exceptions, leading to client crashes during protocol ID computation. The change **removes the `noexcept` specifier** from the C++ declaration and updates the Cython binding in `thrift/lib/python/client/omni_client.pxd` to `except+`, allowing exceptions to be properly propagated. This **enhances the client's resilience**, enabling callers to catch and handle errors gracefully instead of encountering unexpected termination.

This commit performs **maintenance** by removing lint suppressor comments from the `thrift/lib/python/test/bidi_service.thrift` file. These suppressors were previously in place to bypass lint warnings related to **bidi** functionality in **Python Thrift**. With recent linter updates, these suppressions are no longer needed, allowing the full linting rules to apply. This change signifies that **bidi is now properly supported and available in Python**, ensuring better code quality and consistency for this feature.

This commit introduces the **`ThriftBidiType`** to the **Thrift metadata system**, enabling the accurate representation of bidirectional streaming services. A **new struct** is defined in `metadata.thrift` to capture the properties of these services, such as `firstResponse`, `streamType`, and `sinkType`. The **Python Thrift metadata API** is consequently updated to support this new type, involving extensions to `ThriftKind` and the introduction of `ThriftBidiProxy`. This **new capability** ensures that metadata-aware tools can correctly reflect and process bidirectional streaming service definitions.

This commit **enhances the Python Thrift metadata API** by adding the `__init__` constructor to the `ThriftConstStructProxy` interface in `thrift/lib/python/metadata.pyi`. This **interface update** addresses a limitation where the constructor was not available in the API definition, making it unusable in Pyre strict code. By exposing the `__init__` method, this change ensures that **Thrift constant struct proxies** can be correctly instantiated and type-checked, improving the overall robustness and usability of the **Thrift Python library** in strict type-checking environments.

This commit **removes the `--allow-unreleased-streaming` flag** and associated `streamdev-` prefixes from the **Thrift compiler's test suite and generator specifications**. This **maintenance change** signifies the **graduation of bi-directional streaming** to a stable and released feature in C++, Python, and Rust. By eliminating this complex flag, the commit simplifies codegen scripts and the overall build process, particularly for Hack, enabling broader customer onboarding to this now-standard capability. The changes primarily affect `thrift/compiler/test/compiler_test.cc` and `thrift/compiler/test/fixtures/bidi/cmd`.

Re-buillding fixtures

This commit **enhances the integration test suite** for **bidirectional streaming (bidi)** in **Thrift's Python implementation**. It introduces new test cases in `thrift/lib/python/test/bidi.py` to validate **client cancellation**, **bidi streams with different primitive types**, and **struct-based bidi types**. To support these new tests, the `TestBidiService` in `thrift/lib/python/test/bidi_service.thrift` was extended with new Thrift structs and bidi service methods like `intStream` and `structBidi`. This **testing and feature definition** work improves the **robustness and coverage** of the **Python bidi client and server implementations**, ensuring correct behavior for various complex streaming scenarios.

This commit significantly **improves the stability and correctness** of the **Thrift Python bidirectional streaming server** implementation. It introduces a `BidiCallbackWrapper` in `thrift/lib/python/streaming/bidistream.cpp` to enhance the **lifetime management of bidirectional callbacks**, ensuring proper resource handling and preventing premature deallocation. Furthermore, **exception propagation is fixed** in `bidistream.pyx` to correctly convert Python exceptions into Thrift application exceptions, improving error reporting. Finally, the **Thrift Python compiler templates** are updated to generate more robust server code by removing unnecessary arguments and correcting **type hints** for bidirectional stream handlers, leading to cleaner and more type-safe generated code.

This commit provides a **bug fix** for the **Thrift compiler's Python generator**, specifically addressing an issue in how **bidirectional streaming services** handle their initial response. It **corrects the generated code** in `get_handler_result.mustache` by removing an unnecessary `await` operation on the first response value, as the stream tuple was already awaited. Additionally, it ensures that the first response value is properly assigned within the return struct, preventing data loss or incorrect state. This **code generation correction** improves the reliability and correctness of **Python Thrift services** utilizing bidirectional streams. A new test case (`test_bidi_first_response`) has been added to `thrift/lib/python/test/bidi.py` to validate this corrected behavior.

This commit **establishes a new test bidirectional streaming service** within the **Thrift Python library**. It introduces a `TestBidiService` definition in `thrift/lib/python/test/bidi_service.thrift` and provides a Python handler implementation along with new test cases in `thrift/lib/python/test/bidi.py` to validate the functionality of bidirectional streams. Additionally, it includes a **bug fix** in `thrift/lib/python/server/python_async_processor.pyx` to correctly pass arguments for bidirectional stream transformations and a **refactoring** in `thrift/lib/python/streaming/bidistream.pyx` to simplify callback invocation. This work ensures the robustness and correctness of **Thrift's Python bidirectional streaming implementation** by providing a dedicated testing framework.

This commit introduces a **new feature** to the **Python Thrift streaming sink component** to properly handle bidirectional streams. It adds logic within the `sink_final_resp_callback` to set the future result to `None` when the final response type of the stream is `None`. This **enhancement** ensures that **bidirectional streams** without a final response are correctly terminated, preventing potential hangs or incorrect state. The change improves the robustness and correctness of **Thrift stream processing** for scenarios where no final response is expected.

This commit **enhances and refactors the Python Thrift code generation** for **bidirectional stream functions**. It **updates the client return type template** (`client_return_type.mustache`) to **exclude the final sink response type**, streamlining the client's understanding of stream termination. Concurrently, the **function second return type template** (`function_second_return_type.mustache`) is modified to **generate both sink and stream element types**, providing more comprehensive type information for these complex stream interactions. This ensures **generated Python clients** accurately reflect the nature of bidirectional streams, improving type safety and developer experience.

This commit introduces **bidirectional streaming support** to the **Thrift Python code generator**, enabling the automatic generation of both client and server-side code for services utilizing this communication pattern. This **new capability** updates the core C++ generator logic and various Python templates to correctly handle bidirectional stream function types, callbacks, and metadata. Specifically, it adds imports for `BidirectionalStream`, includes `ThriftBidiType` in metadata, defines callback typing signatures, and updates RPC kind generation to `BIDIRECTIONAL_STREAM`. This allows Python developers to define and consume **bidirectional streaming RPCs** in their Thrift services, significantly expanding the communication paradigms available, with the feature enabled via `devmode`.

This commit introduces **codegen support for internal types of bidirectional (bidi) streams** within the **Thrift Python generator**. It modifies the generation of service argument types to correctly handle the unique `RpcKind` of bidi streams, which do not have a final response. Specifically, it adds conditional logic to `service_arg_type_list.mustache` and `service_arg_types.mustache` to include stream/sink element types and exclude the final sink result class for bidi RPCs. This **new capability** ensures accurate type implementation and `pyi` generation for **bidirectional RPCs** in Python, enabling proper type hinting and runtime behavior.

This commit introduces a **new capability** to **Thrift's Python server** by enabling the **binding of Python bidirectional stream handlers to C++ implementations**. It allows Python `async` methods to define stream transformations, which are then executed efficiently in C++ through new components in `thrift/lib/python/streaming/bidistream`. This **feature** significantly enhances the server's ability to handle complex streaming RPCs, supporting both initial responses and pure stream transformations, by bridging Python's async generators with C++ execution. The `python_async_processor.pyx` module is updated to utilize this new binding, allowing Python server handlers to leverage C++ for underlying stream processing.

This commit **introduces support for bidirectional streaming RPC requests** within the **Thrift Python server's asynchronous processor**. It **adds a new feature** by wiring up the necessary logic in `thrift/lib/python/server/PythonAsyncProcessor.cpp`, specifically within the `dispatchRequest` method. This enables the server to handle bidi requests by invoking the `StreamTransformation` factory via `return_bidistream` and dispatching them using `dispatchRequestBidi`. This enhancement allows for more dynamic and interactive communication patterns between clients and the Python Thrift server.

This commit **adds a new C++ API** to the **Thrift Python streaming library** to enable binding C++ `StreamTransformation` objects to Python. It introduces two new functions, `createIOBufStreamTransformation` and `createResponseAndStreamTransformation`, which allow Python to create and utilize C++-backed stream transformations for `IOBuf` and for combined response-and-stream scenarios. This **new capability** significantly enhances interoperability, allowing Python services to leverage high-performance C++ stream processing logic within the Thrift framework.

This commit introduces a **new capability** to the **Thrift Python streaming library** by adding a `Py_promise` helper specifically designed for `PyObject`. It defines and implements the `Promise_PyObject` class and its associated methods in `thrift/lib/python/streaming/py_promise.pxd` and `thrift/lib/python/streaming/py_promise.pyx`, enabling the seamless handling of **Python objects within promise-based streaming operations**. This enhancement is crucial for supporting **bidirectional transformations** and exposes `genNextStreamValue` as a public API, facilitating more complex data flows.

This commit **refactors** the **Thrift Python streaming library** by moving the definition of the `ServerSinkGenerator` class to `thrift/lib/python/streaming/sink.pxd`. This change makes the `ServerSinkGenerator` and its internal attributes, including the `_fbthrift_create` static method, directly accessible and usable within **bidirectional streaming Cython code**. The primary impact is an **enhancement** of interoperability, allowing Cython-based components to leverage this critical server-side sink generator.