ENH: add type stubs from numpy-stubs

Add the type stubs and tests from numpy-stubs. Things this entails:

- Copy over the stubs (numpy/__init__.pyi and
  numpy/core/_internal.pyi)
  - The only modification made was removing `ndarray.tostring` since
    it is deprecated
- Update some setup.py files to include pyi files
- Move the tests from numpy-stubs/tests into numpy/tests
  - Skip them if mypy is not installed (planning on setting up CI in a
    future PR)
  - Add a mypy.ini; use it to configure mypy in the tests
    - It tells mypy where to find NumPy in the test env
    - It ignores internal NumPy type errors (since we only want to
      consider errors from the tests cases)
  - Some small edits were made to fix test cases that were emitting
    deprecation warnings
 - Add numpy/py.typed so that the types are picked up in an
   installed version of NumPy

1 files changed, 127 insertions, 0 deletions

diff --git a/numpy/tests/test_typing.py b/numpy/tests/test_typing.py
new file mode 100644
index 000000000..757ea0b52
--- /dev/null
+++ b/numpy/tests/test_typing.py
@@ -0,0 +1,127 @@
+import importlib.util
+import itertools
+import os
+import re
+from collections import defaultdict
+
+import pytest
+try:
+    from mypy import api
+except ImportError:
+    NO_MYPY = True
+else:
+    NO_MYPY = False
+
+TESTS_DIR = os.path.dirname(os.path.abspath(__file__))
+PASS_DIR = os.path.join(TESTS_DIR, "pass")
+FAIL_DIR = os.path.join(TESTS_DIR, "fail")
+REVEAL_DIR = os.path.join(TESTS_DIR, "reveal")
+MYPY_INI = os.path.join(TESTS_DIR, "mypy.ini")
+CACHE_DIR = os.path.join(TESTS_DIR, ".mypy_cache")
+
+
+def get_test_cases(directory):
+    for root, _, files in os.walk(directory):
+        for fname in files:
+            if os.path.splitext(fname)[-1] == ".py":
+                fullpath = os.path.join(root, fname)
+                # Use relative path for nice py.test name
+                relpath = os.path.relpath(fullpath, start=directory)
+
+                yield pytest.param(
+                    fullpath,
+                    # Manually specify a name for the test
+                    id=relpath,
+                )
+
+
+@pytest.mark.skipif(NO_MYPY, reason="Mypy is not installed")
+@pytest.mark.parametrize("path", get_test_cases(PASS_DIR))
+def test_success(path):
+    stdout, stderr, exitcode = api.run([
+        "--config-file",
+        MYPY_INI,
+        "--cache-dir",
+        CACHE_DIR,
+        path,
+    ])
+    assert exitcode == 0, stdout
+    assert re.match(r"Success: no issues found in \d+ source files?", stdout.strip())
+
+
+@pytest.mark.skipif(NO_MYPY, reason="Mypy is not installed")
+@pytest.mark.parametrize("path", get_test_cases(FAIL_DIR))
+def test_fail(path):
+    stdout, stderr, exitcode = api.run([
+        "--config-file",
+        MYPY_INI,
+        "--cache-dir",
+        CACHE_DIR,
+        path,
+    ])
+    assert exitcode != 0
+
+    with open(path) as fin:
+        lines = fin.readlines()
+
+    errors = defaultdict(lambda: "")
+    error_lines = stdout.rstrip("\n").split("\n")
+    assert re.match(
+        r"Found \d+ errors? in \d+ files? \(checked \d+ source files?\)",
+        error_lines[-1].strip(),
+    )
+    for error_line in error_lines[:-1]:
+        error_line = error_line.strip()
+        if not error_line:
+            continue
+
+        lineno = int(error_line.split(":")[1])
+        errors[lineno] += error_line
+
+    for i, line in enumerate(lines):
+        lineno = i + 1
+        if " E:" not in line and lineno not in errors:
+            continue
+
+        target_line = lines[lineno - 1]
+        if "# E:" in target_line:
+            marker = target_line.split("# E:")[-1].strip()
+            assert lineno in errors, f'Extra error "{marker}"'
+            assert marker in errors[lineno]
+        else:
+            pytest.fail(f"Error {repr(errors[lineno])} not found")
+
+
+@pytest.mark.skipif(NO_MYPY, reason="Mypy is not installed")
+@pytest.mark.parametrize("path", get_test_cases(REVEAL_DIR))
+def test_reveal(path):
+    stdout, stderr, exitcode = api.run([
+        "--config-file",
+        MYPY_INI,
+        "--cache-dir",
+        CACHE_DIR,
+        path,
+    ])
+
+    with open(path) as fin:
+        lines = fin.readlines()
+
+    for error_line in stdout.split("\n"):
+        error_line = error_line.strip()
+        if not error_line:
+            continue
+
+        lineno = int(error_line.split(":")[1])
+        assert "Revealed type is" in error_line
+        marker = lines[lineno - 1].split("# E:")[-1].strip()
+        assert marker in error_line
+
+
+@pytest.mark.skipif(NO_MYPY, reason="Mypy is not installed")
+@pytest.mark.parametrize("path", get_test_cases(PASS_DIR))
+def test_code_runs(path):
+    path_without_extension, _ = os.path.splitext(path)
+    dirname, filename = path.split(os.sep)[-2:]
+    spec = importlib.util.spec_from_file_location(f"{dirname}.{filename}", path)
+    test_module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(test_module)