scripts-blender/addons/blender_kitsu/wheels/__init__.py

@@ -0,0 +1,135 @@
+"""External dependencies loader."""
+
+import contextlib
+import importlib
+from pathlib import Path
+import sys
+import logging
+from types import ModuleType
+from typing import Iterator, Iterable
+
+_my_dir = Path(__file__).parent
+_log = logging.getLogger(__name__)
+
+
+def load_wheel(module_name: str, submodules: Iterable[str]) -> list[ModuleType]:
+    """Loads modules from a wheel file 'module_name*.whl'.
+
+    Loads `module_name`, and if submodules are given, loads
+    `module_name.submodule` for each of the submodules. This allows loading all
+    required modules from the same wheel in one session, ensuring that
+    inter-submodule references are correct.
+
+    Returns the loaded modules, so [module, submodule, submodule, ...].
+    """
+
+    fname_prefix = _fname_prefix_from_module_name(module_name)
+    wheel = _wheel_filename(fname_prefix)
+
+    loaded_modules: list[ModuleType] = []
+    to_load = [module_name] + [f"{module_name}.{submodule}" for submodule in submodules]
+
+    # Load the module from the wheel file. Keep a backup of sys.path so that it
+    # can be restored later. This should ensure that future import statements
+    # cannot find this wheel file, increasing the separation of dependencies of
+    # this add-on from other add-ons.
+    with _sys_path_mod_backup(wheel):
+        for modname in to_load:
+            try:
+                module = importlib.import_module(modname)
+            except ImportError as ex:
+                raise ImportError(
+                    "Unable to load %r from %s: %s" % (modname, wheel, ex)
+                ) from None
+            assert isinstance(module, ModuleType)
+            loaded_modules.append(module)
+            _log.info("Loaded %s from %s", modname, module.__file__)
+
+    assert len(loaded_modules) == len(
+        to_load
+    ), f"expecting to load {len(to_load)} modules, but only have {len(loaded_modules)}: {loaded_modules}"
+    return loaded_modules
+
+
+def load_wheel_global(module_name: str, fname_prefix: str = "") -> ModuleType:
+    """Loads a wheel from 'fname_prefix*.whl', unless the named module can be imported.
+
+    This allows us to use system-installed packages before falling back to the shipped wheels.
+    This is useful for development, less so for deployment.
+
+    If `fname_prefix` is the empty string, it will use the first package from `module_name`.
+    In other words, `module_name="pkg.subpkg"` will result in `fname_prefix="pkg"`.
+    """
+
+    if not fname_prefix:
+        fname_prefix = _fname_prefix_from_module_name(module_name)
+
+    try:
+        module = importlib.import_module(module_name)
+    except ImportError as ex:
+        _log.debug("Unable to import %s directly, will try wheel: %s", module_name, ex)
+    else:
+        _log.debug(
+            "Was able to load %s from %s, no need to load wheel %s",
+            module_name,
+            module.__file__,
+            fname_prefix,
+        )
+        return module
+
+    wheel = _wheel_filename(fname_prefix)
+
+    wheel_filepath = str(wheel)
+    if wheel_filepath not in sys.path:
+        sys.path.insert(0, wheel_filepath)
+
+    try:
+        module = importlib.import_module(module_name)
+    except ImportError as ex:
+        raise ImportError(
+            "Unable to load %r from %s: %s" % (module_name, wheel, ex)
+        ) from None
+
+    _log.debug("Globally loaded %s from %s", module_name, module.__file__)
+    return module
+
+
+@contextlib.contextmanager
+def _sys_path_mod_backup(wheel_file: Path) -> Iterator[None]:
+    """Temporarily inserts a wheel onto sys.path.
+
+    When the context exits, it restores sys.path and sys.modules, so that
+    anything that was imported within the context remains unimportable by other
+    modules.
+    """
+    old_syspath = sys.path[:]
+    old_sysmod = sys.modules.copy()
+
+    try:
+        sys.path.insert(0, str(wheel_file))
+        yield
+    finally:
+        # Restore without assigning a new list instance. That way references
+        # held by other code will stay valid.
+        sys.path[:] = old_syspath
+        sys.modules.clear()
+        sys.modules.update(old_sysmod)
+
+
+def _wheel_filename(fname_prefix: str) -> Path:
+    path_pattern = "%s*.whl" % fname_prefix
+    wheels: list[Path] = list(_my_dir.glob(path_pattern))
+    if not wheels:
+        raise RuntimeError("Unable to find wheel at %r" % path_pattern)
+
+    # If there are multiple wheels that match, load the last-modified one.
+    # Alphabetical sorting isn't going to cut it since BAT 1.10 was released.
+    def modtime(filepath: Path) -> float:
+        return filepath.stat().st_mtime
+
+    wheels.sort(key=modtime)
+    return wheels[-1]
+
+
+def _fname_prefix_from_module_name(module_name: str) -> str:
+    return module_name.split(".", 1)[0]