Function compute_search_paths

mypy/modulefinder.py:884–969

Compute the search paths as specified in PEP 561. There are the following 4 members created: - User code (from `sources`) - MYPYPATH (set either via config or environment variable) - installed package directories (which will later be split into stub-only and inline) - typeshed

(
    sources: list[BuildSource], options: Options, data_dir: str, alt_lib_path: str | None = None
)

def compute_search_paths(
    sources: list[BuildSource], options: Options, data_dir: str, alt_lib_path: str | None = None
) -> SearchPaths:
    """Compute the search paths as specified in PEP 561.

    There are the following 4 members created:
    - User code (from `sources`)
    - MYPYPATH (set either via config or environment variable)
    - installed package directories (which will later be split into stub-only and inline)
    - typeshed
    """
    # Determine the default module search path.
    lib_path = collections.deque(
        default_lib_path(
            data_dir, options.python_version, custom_typeshed_dir=options.custom_typeshed_dir
        )
    )

    if options.use_builtins_fixtures:
        # Use stub builtins (to speed up test cases and to make them easier to
        # debug).  This is a test-only feature, so assume our files are laid out
        # as in the source tree.
        # We also need to allow overriding where to look for it. Argh.
        root_dir = os.getenv("MYPY_TEST_PREFIX", None)
        if not root_dir:
            root_dir = os.path.dirname(os.path.dirname(__file__))
        root_dir = os.path.abspath(root_dir)
        lib_path.appendleft(os.path.join(root_dir, "test-data", "unit", "lib-stub"))
    # alt_lib_path is used by some tests to bypass the normal lib_path mechanics.
    # If we don't have one, grab directories of source files.
    python_path: list[str] = []
    if not alt_lib_path:
        for source in sources:
            # Include directory of the program file in the module search path.
            if source.base_dir:
                dir = source.base_dir
                if dir not in python_path:
                    python_path.append(dir)

        # Do this even if running as a file, for sanity (mainly because with
        # multiple builds, there could be a mix of files/modules, so its easier
        # to just define the semantics that we always add the current director
        # to the lib_path
        # TODO: Don't do this in some cases; for motivation see see
        # https://github.com/python/mypy/issues/4195#issuecomment-341915031
        if options.bazel:
            dir = "."
        else:
            dir = os.getcwd()
        if dir not in lib_path:
            python_path.insert(0, dir)

    # Start with a MYPYPATH environment variable at the front of the mypy_path, if defined.
    mypypath = mypy_path()

    # Add a config-defined mypy path.
    mypypath.extend(options.mypy_path)