add test to actually reproduce python#5784

mypy/test/testpep561.py

@@ -32,6 +32,11 @@
 alpha_func(2)
 """
 
+C_EXT_PROGRAM = """
+from typedpkg_c_ext.foo import speak
+from typedpkg_c_ext.hello import helloworld
+"""
+
 
 class NamespaceProgramImportStyle(Enum):
     from_import = """\
@@ -166,12 +171,14 @@ def setUp(self) -> None:
             create_namespace_program_source(NamespaceProgramImportStyle.from_import))
         self.regular_import_namespace_example_program = ExampleProgram(
             create_namespace_program_source(NamespaceProgramImportStyle.from_import))
+        self.c_ext_example_program = ExampleProgram(C_EXT_PROGRAM)
 
     def tearDown(self) -> None:
         self.simple_example_program.cleanup()
         self.from_namespace_example_program.cleanup()
         self.import_as_namespace_example_program.cleanup()
         self.regular_import_namespace_example_program.cleanup()
+        self.c_ext_example_program.cleanup()
 
     def test_get_pkg_dirs(self) -> None:
         """Check that get_package_dirs works."""
@@ -302,6 +309,17 @@ def test_nested_and_namespace_regular_import(self) -> None:
                 venv_dir=venv_dir,
             )
 
+    def test_c_ext_from_import(self) -> None:
+        self.c_ext_example_program.init()
+        with self.virtualenv() as venv:
+            venv_dir, python_executable = venv
+            self.install_package('typedpkg_c_ext', python_executable)
+            self.c_ext_example_program.check_mypy_run(
+                python_executable,
+                [],
+                venv_dir=venv_dir,
+            )
+
 
 if __name__ == '__main__':
     main()

test-data/packages/typedpkg_c_ext/hello.c

@@ -0,0 +1,31 @@
+#include <Python.h>
+
+// Function 1: A simple 'hello world' function
+static PyObject* helloworld(PyObject* self, PyObject* args)
+{
+    printf("Hello World\n");
+    return Py_None;
+}
+
+// Our Module's Function Definition struct
+// We require this `NULL` to signal the end of our method
+// definition
+static PyMethodDef myMethods[] = {
+    { "helloworld", helloworld, METH_NOARGS, "Prints Hello World" },
+    { NULL, NULL, 0, NULL }
+};
+
+// Our Module Definition struct
+static struct PyModuleDef myModule = {
+    PyModuleDef_HEAD_INIT,
+    "hello",
+    "Test Module",
+    -1,
+    myMethods
+};
+
+// Initializes our module using our above struct
+PyMODINIT_FUNC PyInit_hello(void)
+{
+    return PyModule_Create(&myModule);
+}

test-data/packages/typedpkg_c_ext/setup.py

@@ -0,0 +1,12 @@
+from setuptools import setup, Extension
+
+setup(
+    name='typedpkg_c_ext',
+    version='1.0',
+    packages=['typedpkg_c_ext'],
+    ext_modules=[Extension('typedpkg_c_ext.hello', ['hello.c'])],
+    zip_safe=False,
+    package_data={
+        'typedpkg_c_ext': ['py.typed']
+    },
+)

test-data/packages/typedpkg_c_ext/typedpkg_c_ext/foo.py

@@ -0,0 +1,5 @@
+from . import hello
+
+
+def speak() -> None:
+    hello.helloworld()