From 9615abaf6b653f81d5f1d2ddbb7f9956f8e9d26c Mon Sep 17 00:00:00 2001
From: Matthew Barber <quitesimplymatt@gmail.com>
Date: Wed, 10 Aug 2022 12:40:39 +0100
Subject: [PATCH] Introduce `array_api_stubs.py`

---
 array_api_stubs.py | 173 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 173 insertions(+)
 create mode 100644 array_api_stubs.py

diff --git a/array_api_stubs.py b/array_api_stubs.py
new file mode 100644
index 000000000..19ef3081a
--- /dev/null
+++ b/array_api_stubs.py
@@ -0,0 +1,173 @@
+import sys
+from importlib import import_module
+from importlib.util import find_spec
+from inspect import getmembers, isfunction, signature
+from pathlib import Path
+from types import FunctionType, ModuleType, SimpleNamespace
+from typing import Dict, List, Optional
+from unittest import TestCase
+
+__all__ = ["make_stubs_namespace"]
+
+API_VERSIONS = {"2012.12"}  # TODO: infer released versions dynamically
+
+
+def make_stubs_namespace(api_version: Optional[str] = None) -> SimpleNamespace:
+    """
+    Returns a ``SimpleNamespace`` where
+
+    * ``functions`` (``dict[str, FunctionType]``) maps names of top-level
+      functions to their respective stubs.
+    * ``array_methods`` (``dict[str, FunctionType]``) maps names of array
+      methods to their respective stubs.
+    * ``dtype_methods`` (``dict[str, FunctionType]``) maps names of dtype object
+      methods to their respective stubs.
+    * ``category_to_functions`` (``dict[str, dict[str, FunctionType]]``) maps
+      names of categories to their respective function mappings.
+    * ``extension_to_functions`` (``dict[str, dict[str, FunctionType]]``) maps
+      names of extensions to their respective function mappings.
+
+    Examples
+    --------
+
+    Make a stubs namespace.
+
+        >>> from array_api_stubs import make_stubs_namespace
+        >>> stubs = make_stubs_namespace()
+
+    Access the ``array_api.square()`` stub.
+
+        >>> stubs.functions["square"]
+        <function array_api.square(x: ~array, /) -> ~array>
+
+    Find names of all set functions.
+
+        >>> stubs.category_to_functions["set"].keys()
+        dict_keys(['unique_all', 'unique_counts', 'unique_inverse', 'unique_values'])
+
+    Access the array object's ``__add__`` stub.
+
+        >>> stubs.array_methods["__add__"]
+        <function array_api._Array.__add__(self: 'array', other: 'Union[int, float, array]', /) -> 'array'>
+
+    Access the ``array_api.linalg.cross()`` stub.
+
+        >>> stubs.extension_to_functions["linalg"]["cross"]
+        <function array_api.linalg.cross(x1: ~array, x2: ~array, /, *, axis: int = -1) -> ~array>
+
+    """
+    if api_version is None:
+        api_version = "draft"
+    if api_version in API_VERSIONS or api_version == "latest":
+        raise NotImplementedError("{api_version=} not yet supported")
+    elif api_version != "draft":
+        raise ValueError(
+            f"{api_version=} not 'draft', 'latest', "
+            f"or a released version ({API_VERSIONS})"
+        )
+
+    spec_dir = Path(__file__).parent / "spec" / "API_specification"
+    signatures_dir = spec_dir / "array_api"
+    assert signatures_dir.exists()  # sanity check
+    spec_abs_path: str = str(spec_dir.resolve())
+    sys.path.append(spec_abs_path)
+    assert find_spec("array_api") is not None  # sanity check
+
+    name_to_mod: Dict[str, ModuleType] = {}
+    for path in signatures_dir.glob("*.py"):
+        name = path.name.replace(".py", "")
+        name_to_mod[name] = import_module(f"array_api.{name}")
+
+    array = name_to_mod["array_object"].array
+    array_methods: Dict[str, FunctionType] = {}
+    for name, func in getmembers(array, predicate=isfunction):
+        func.__module__ = "array_api"
+        assert "Alias" not in func.__doc__  # sanity check
+        func.__qualname__ = f"_Array.{func.__name__}"
+        array_methods[name] = func
+
+    dtype_eq = name_to_mod["data_types"].__eq__
+    assert isinstance(dtype_eq, FunctionType)  # for mypy
+    dtype_eq.__module__ = "array_api"
+    dtype_eq.__qualname__ = "_DataType.__eq__"
+    dtype_methods: Dict[str, FunctionType] = {"__eq__": dtype_eq}
+
+    functions: Dict[str, FunctionType] = {}
+    category_to_functions: Dict[str, Dict[str, FunctionType]] = {}
+    for name, mod in name_to_mod.items():
+        if name.endswith("_functions"):
+            category = name.replace("_functions", "")
+            name_to_func = {}
+            for name in mod.__all__:
+                func = getattr(mod, name)
+                assert isinstance(func, FunctionType)  # sanity check
+                func.__module__ = "array_api"
+                name_to_func[name] = func
+            functions.update(name_to_func)
+            category_to_functions[category] = name_to_func
+
+    extensions: List[str] = ["linalg"]  # TODO: infer on runtime
+    extension_to_functions: Dict[str, Dict[str, FunctionType]] = {}
+    for ext in extensions:
+        mod = name_to_mod[ext]
+        name_to_func = {name: getattr(mod, name) for name in mod.__all__}
+        name_to_func = {}
+        for name in mod.__all__:
+            func = getattr(mod, name)
+            assert isinstance(func, FunctionType)  # sanity check
+            assert func.__doc__ is not None  # for mypy
+            if "Alias" in func.__doc__:
+                func.__doc__ = functions[name].__doc__
+            func.__module__ = f"array_api.{ext}"
+            name_to_func[name] = func
+        extension_to_functions[ext] = name_to_func
+
+    return SimpleNamespace(
+        functions=functions,
+        array_methods=array_methods,
+        dtype_methods=dtype_methods,
+        category_to_functions=category_to_functions,
+        extension_to_functions=extension_to_functions,
+    )
+
+
+class TestMakeStubsNamespace(TestCase):
+    def setUp(self):
+        self.stubs = make_stubs_namespace()
+
+    def test_attributes(self):
+        assert isinstance(self.stubs, SimpleNamespace)
+        for attr in ["functions", "array_methods", "dtype_methods"]:
+            mapping = getattr(self.stubs, attr)
+            assert isinstance(mapping, dict)
+            assert all(isinstance(k, str) for k in mapping.keys())
+            assert all(isinstance(v, FunctionType) for v in mapping.values())
+        for attr in ["category_to_functions", "extension_to_functions"]:
+            mapping = getattr(self.stubs, attr)
+            assert isinstance(mapping, dict)
+            assert all(isinstance(k, str) for k in mapping.keys())
+            for sub_mapping in mapping.values():
+                assert isinstance(sub_mapping, dict)
+                assert all(isinstance(k, str) for k in sub_mapping.keys())
+                assert all(isinstance(v, FunctionType) for v in sub_mapping.values())
+
+    def test_function_meta(self):
+        toplevel_stub = self.stubs.functions["matmul"]
+        assert toplevel_stub.__module__ == "array_api"
+        extension_stub = self.stubs.extension_to_functions["linalg"]["matmul"]
+        assert extension_stub.__module__ == "array_api.linalg"
+        assert extension_stub.__doc__ == toplevel_stub.__doc__
+
+    def test_array_method_meta(self):
+        stub = self.stubs.array_methods["__add__"]
+        assert stub.__module__ == "array_api"
+        assert stub.__qualname__ == "_Array.__add__"
+        first_arg = next(iter(signature(stub).parameters.values()))
+        assert first_arg.name == "self"
+
+    def test_dtype_method_meta(self):
+        stub = self.stubs.dtype_methods["__eq__"]
+        assert stub.__module__ == "array_api"
+        assert stub.__qualname__ == "_DataType.__eq__"
+        first_arg = next(iter(signature(stub).parameters.values()))
+        assert first_arg.name == "self"

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