Introduce a version of the circular import test

tests/test_circular_imports.py

@@ -0,0 +1,110 @@
+"""Tests for circular imports in all local packages and modules.
+
+This ensures all internal packages can be imported right away without
+any need to import some other module before doing so.
+
+This module is based on an idea that pytest uses for self-testing:
+* https://github.com/aio-libs/aiohttp/blob/91108c9/tests/test_circular_imports.py
+* https://github.com/sanitizers/octomachinery/blob/be18b54/tests/circular_imports_test.py
+* https://github.com/pytest-dev/pytest/blob/d18c75b/testing/test_meta.py
+* https://twitter.com/codewithanthony/status/1229445110510735361
+"""
+
+from __future__ import annotations
+
+import os
+import pkgutil
+import subprocess
+import sys
+from collections.abc import Iterator
+from itertools import chain
+from pathlib import Path
+from types import ModuleType
+
+import pytest
+
+import piptools
+from piptools.utils import PIP_VERSION
+
+
+def _find_all_importables(pkg: ModuleType) -> list[str]:
+    """Find all importables in the project.
+
+    Return them in order.
+    """
+    return sorted(
+        set(
+            chain.from_iterable(
+                _discover_path_importables(Path(p), pkg.__name__) for p in pkg.__path__
+            ),
+        ),
+    )
+
+
+def _discover_path_importables(pkg_pth: Path, pkg_name: str) -> Iterator[str]:
+    """Yield all importables under a given path and package."""
+    for dir_path, _d, file_names in os.walk(pkg_pth):
+        pkg_dir_path = Path(dir_path)
+
+        if pkg_dir_path.parts[-1] == "__pycache__":
+            continue
+
+        if all(Path(_).suffix != ".py" for _ in file_names):
+            continue
+
+        rel_pt = pkg_dir_path.relative_to(pkg_pth)
+        pkg_pref = ".".join((pkg_name,) + rel_pt.parts)
+        yield from (
+            pkg_path
+            for _, pkg_path, _ in pkgutil.walk_packages(
+                (str(pkg_dir_path),),
+                prefix=f"{pkg_pref}.",
+            )
+        )
+
+
+def _allowed_deprecation_warning_filters() -> list[str]:
+    """
+    Yield filters which allow for deprecation warnings based on the current
+    test environment.
+    """
+    # note that we can't use regex syntax in filters as of yet, only literals
+    # https://github.com/python/cpython/pull/138149 allows regex usage, but is not
+    # yet supported on all Python versions we support
+    flags: list[str] = []
+    if PIP_VERSION[:2] < (25, 3):
+        flags.extend(
+            ("-W", "ignore:pkg_resources is deprecated as an API.:DeprecationWarning:")
+        )
+    if PIP_VERSION[:2] <= (22, 2):
+        flags.extend(
+            (
+                "-W",
+                (
+                    "ignore:path is deprecated. Use files() instead."
+                    ":DeprecationWarning:"
+                ),
+                "-W",
+                (
+                    "ignore:Creating a LegacyVersion has been deprecated "
+                    "and will be removed in the next major release"
+                    ":DeprecationWarning:"
+                ),
+            )
+        )
+    return flags
+
+
+@pytest.mark.parametrize("import_path", _find_all_importables(piptools))
+def test_no_warnings(import_path: str) -> None:
+    """Verify that each importable name can be independently imported.
+
+    This is seeking for any import errors including ones caused
+    by circular imports.
+    """
+    import_statement = f"import {import_path!s}"
+    # On lower pip versions, we need to allow certain deprecation warnings.
+    flags = ("-W", "error", *_allowed_deprecation_warning_filters())
+    command = (sys.executable, *flags, "-c", import_statement)
+
+    subprocess.check_call(command)