Document how to generate stubs without docker

Author: chadrik

docs/quick_start/installation.rst

@@ -565,3 +565,19 @@ The workflow looks like this:
 Note that if you can't (or don't want to) build the stubs locally, you can
 download an artifact containing the wheel and `__init__.pyi` file from any job
 that fails the stub validation.
+
+If you want to bypass the use of docker, you can use the following steps to
+build the python bindings and run the stub generator directly:
+
+```
+python -m venv .venv
+. .venv/bin/activate
+mkdir build
+cd build
+cmake -DPython_EXECUTABLE=$(which python) -DCMAKE_INSTALL_PREFIX=../dist ..
+cmake --build . --target=install
+# extract the deps from the pyproject.toml and install them
+pip install $(yq -r '.tool.cibuildwheel.overrides.[0].test-requires' -oy ../pyproject.toml)
+PY_VER=$(python -c "import sys;print(f'{sys.version_info[0]}.{sys.version_info[1]}')")
+PYTHONPATH=../dist/lib/python$PY_VER/site-packages python ../src/bindings/python/stubs/generate_stubs.py --out-path ../src/bindings/python/stubs/
+```

src/bindings/python/CMakeLists.txt

@@ -258,6 +258,7 @@ install(TARGETS PyOpenColorIO
     LIBRARY DESTINATION ${_PyOpenColorIO_SITE_PACKAGE_DIR}
 )
 
+install(FILES package/__init__.py DESTINATION ${_PyOpenColorIO_SITE_PACKAGE_DIR})
 install(FILES stubs/PyOpenColorIO/__init__.pyi DESTINATION ${_PyOpenColorIO_SITE_PACKAGE_DIR})
 install(FILES stubs/PyOpenColorIO/py.typed DESTINATION ${_PyOpenColorIO_SITE_PACKAGE_DIR})
 

src/bindings/python/stubs/generate_stubs.py

@@ -2,7 +2,7 @@
 Script to generate pyi stubs by patching and calling mypy's stubgen tool.
 
 There are two entry-points which are designed to call this script:
- - `make pystubs` is called during local development to generate the
+ - `cmake --build . --target pystubs` is called during local development to generate the
    stubs and copy them into the git repo to be committed and reviewed.
  - in CI, the cibuildwheel action is used to validate that the stubs match what
    has been committed to the repo.
@@ -117,7 +117,6 @@ def main() -> None:
     parser = argparse.ArgumentParser()
     parser.add_argument(
         "--out-path",
-        default="out",
         help="Directory to write the stubs."
     )
     parser.add_argument(
@@ -127,7 +126,10 @@ def main() -> None:
              "contents differ."
     )
     args = parser.parse_args()
-    out_path = pathlib.Path(args.out_path)
+    if not args.out_path:
+        out_path = pathlib.Path(sys.modules[__name__].__file__).parent
+    else:
+        out_path = pathlib.Path(args.out_path)
     print(f"Stub output directory: {out_path}")
 
     # perform import so we can see the traceback if it fails.