GH-49102: [CI] Add type checking infrastructure and CI workflow for type annotations

.pre-commit-config.yaml

@@ -337,6 +337,7 @@ repos:
           ?^ci/scripts/python_sdist_build\.sh$|
           ?^ci/scripts/python_sdist_test\.sh$|
           ?^ci/scripts/python_wheel_unix_test\.sh$|
+          ?^ci/scripts/python_test_type_annotations\.sh$|
           ?^ci/scripts/r_build\.sh$|
           ?^ci/scripts/r_revdepcheck\.sh$|
           ?^ci/scripts/release_test\.sh$|
@@ -379,6 +380,7 @@ repos:
         # TODO: Remove this when we fix all lint failures
         files: >-
           (
+          ?^ci/scripts/python_test_type_annotations\.sh$|
           ?^dev/release/05-binary-upload\.sh$|
           ?^dev/release/binary-recover\.sh$|
           ?^dev/release/post-03-binary\.sh$|

ci/conda_env_python.txt

@@ -24,6 +24,7 @@ cython>=3.1
 cloudpickle
 fsspec
 hypothesis
+libcst>=1.8.6
 numpy>=1.16.6
 pytest
 pytest-faulthandler

ci/scripts/python_build.sh

@@ -81,6 +81,7 @@ export PYARROW_PARALLEL=${n_jobs}
 : "${CMAKE_PREFIX_PATH:=${ARROW_HOME}}"
 export CMAKE_PREFIX_PATH
 export LD_LIBRARY_PATH=${ARROW_HOME}/lib:${LD_LIBRARY_PATH}
+export DYLD_LIBRARY_PATH=${ARROW_HOME}/lib${DYLD_LIBRARY_PATH:+:${DYLD_LIBRARY_PATH}}
 
 # https://github.com/apache/arrow/issues/41429
 # TODO: We want to out-of-source build. This is a workaround. We copy

ci/scripts/python_test_type_annotations.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+set -ex
+pyarrow_dir=${1}
+
+if [ -n "${ARROW_PYTHON_VENV:-}" ]; then
+  # shellcheck source=/dev/null
+  . "${ARROW_PYTHON_VENV}/bin/activate"
+fi
+
+# Install library stubs. Note some libraries contain their own type hints so they need to be installed.
+pip install fsspec pandas-stubs scipy-stubs types-cffi types-psutil types-requests types-python-dateutil
+
+# Install type checkers
+pip install mypy pyright ty
+
+# Run type checkers
+pushd "${pyarrow_dir}"
+mypy
+pyright
+ty check
+popd

ci/scripts/python_wheel_validate_contents.py

@@ -38,7 +38,7 @@ def validate_wheel(path):
                    for info in f.filelist), \
             f"{filename} is missing from the wheel."
     print(f"The wheel: {wheels[0]} seems valid.")
-
+    # TODO(GH-32609): Validate some docstrings were generated and added.
 
 def main():
     parser = argparse.ArgumentParser()

compose.yaml

@@ -1537,7 +1537,8 @@ services:
         /arrow/ci/scripts/python_build.sh /arrow /build &&
         pip install -e /arrow/dev/archery[numpydoc] &&
         archery numpydoc --allow-rule GL10,PR01,PR03,PR04,PR05,PR10,RT03,YD01 &&
-        /arrow/ci/scripts/python_test.sh /arrow"]
+        /arrow/ci/scripts/python_test.sh /arrow &&
+        /arrow/ci/scripts/python_test_type_annotations.sh /arrow/python"]
 
   conda-python-dask:
     # Possible $DASK parameters:

docs/source/developers/python/development.rst

@@ -101,6 +101,74 @@ The test groups currently include:
 * ``s3``: Tests for Amazon S3
 * ``tensorflow``: Tests that involve TensorFlow
 
+Type Checking
+=============
+
+PyArrow provides type stubs (``*.pyi`` files) for static type checking. These
+stubs are located in the ``pyarrow-stubs/`` directory and are automatically
+included in the distributed wheel packages.
+
+Running Type Checkers
+---------------------
+
+We support multiple type checkers. Their configurations are in
+``pyproject.toml``.
+
+**mypy**
+
+To run mypy on the PyArrow codebase:
+
+.. code-block::
+
+   $ cd arrow/python
+   $ mypy
+
+The mypy configuration is in the ``[tool.mypy]`` section of ``pyproject.toml``.
+
+**pyright**
+
+To run pyright:
+
+.. code-block::
+
+   $ cd arrow/python
+   $ pyright
+
+The pyright configuration is in the ``[tool.pyright]`` section of ``pyproject.toml``.
+
+**ty**
+
+To run ty (note: currently only partially configured):
+
+.. code-block::
+
+   $ cd arrow/python
+   $ ty check
+
+Maintaining Type Stubs
+-----------------------
+
+Type stubs for PyArrow are maintained in the ``pyarrow-stubs/``
+directory. These stubs mirror the structure of the main ``pyarrow/`` package.
+
+When adding or modifying public APIs:
+
+1. **Update the corresponding ``.pyi`` stub file** in ``pyarrow-stubs/``
+   to reflect the new or changed function/class signatures.
+
+2. **Include type annotations** where possible. For Cython modules or
+   dynamically generated APIs such as compute kernels add the corresponding
+   stub in ``pyarrow-stubs/``.
+
+3. **Run type checkers** to ensure the stubs are correct and complete.
+
+The stub files are automatically copied into the built wheel during the build
+process and will be included when users install PyArrow, enabling type checking
+in downstream projects and for users' IDEs.
+
+Note: ``py.typed`` marker file in the ``pyarrow/`` directory indicates to type
+checkers that PyArrow supports type checking according to :pep:`561`.
+
 Doctest
 =======
 

python/MANIFEST.in

@@ -4,6 +4,7 @@ include ../NOTICE.txt
 
 global-include CMakeLists.txt
 graft pyarrow
+graft pyarrow-stubs
 graft cmake_modules
 
 global-exclude *.so

python/pyarrow-stubs/pyarrow/__init__.pyi

@@ -0,0 +1,29 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+"""Type stubs for PyArrow.
+
+This is a placeholder stub file.
+Complete type annotations will be added in subsequent PRs.
+"""
+
+from typing import Any
+
+# TODO(GH-48970): remove __getattr__ before release as this
+# will annotate non-existing attributes as Any.
+# https://github.com/apache/arrow/issues/48970
+def __getattr__(name: str) -> Any: ...

python/pyarrow/py.typed

@@ -0,0 +1,16 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.

python/pyproject.toml

@@ -18,6 +18,8 @@
 [build-system]
 requires = [
     "cython >= 3.1",
+    # Needed for build-time stub docstring extraction
+    "libcst>=1.8.6",
     "numpy>=1.25",
     # configuring setuptools_scm in pyproject.toml requires
     # versions released after 2022
@@ -88,11 +90,47 @@ include = ["pyarrow"]
 namespaces = false
 
 [tool.setuptools.package-data]
-pyarrow = ["*.pxd", "*.pyx", "includes/*.pxd"]
+pyarrow = ["*.pxd", "*.pyi", "*.pyx", "includes/*.pxd", "py.typed"]
 
 [tool.setuptools_scm]
 root = '..'
 version_file = 'pyarrow/_generated_version.py'
 version_scheme = 'guess-next-dev'
 git_describe_command = 'git describe --dirty --tags --long --match "apache-arrow-[0-9]*.*"'
 fallback_version = '24.0.0a0'
+
+# TODO: Enable type checking once stubs are merged
+[tool.mypy]
+files = ["pyarrow-stubs"]
+mypy_path = "$MYPY_CONFIG_FILE_DIR/pyarrow-stubs"
+exclude = [
+    "^pyarrow/",
+    "^benchmarks/",
+    "^examples/",
+    "^scripts/",
+]
+
+# TODO: Enable type checking once stubs are merged
+[tool.pyright]
+pythonPlatform = "All"
+pythonVersion = "3.10"
+include = ["pyarrow-stubs"]
+exclude = [
+    "pyarrow",
+    "benchmarks",
+    "examples",
+    "scripts",
+    "build",
+]
+stubPath = "pyarrow-stubs"
+typeCheckingMode = "basic"
+
+# TODO: Enable type checking once stubs are merged
+[tool.ty.src]
+include = ["pyarrow-stubs"]
+exclude = [
+    "pyarrow",
+    "benchmarks",
+    "examples",
+    "scripts",
+]

python/requirements-build.txt

@@ -1,4 +1,5 @@
 cython>=3.1
+libcst>=1.8.6
 numpy>=1.25
 setuptools_scm>=8
 setuptools>=77

python/requirements-wheel-build.txt

@@ -1,5 +1,7 @@
 build
 cython>=3.1
+# Needed for build-time stub docstring extraction
+libcst>=1.8.6
 numpy>=2.0.0
 setuptools_scm
 setuptools>=77