gh-91172: Create a workflow for verifying bundled pip and setuptools (GH-31885)

Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

.github/workflows/verify-ensurepip-wheels.yml

+name: Verify bundled pip and setuptools
+
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - 'Lib/ensurepip/_bundled/**'
+      - '.github/workflows/verify-ensurepip-wheels.yml'
+      - 'Tools/scripts/verify_ensurepip_wheels.py'
+  pull_request:
+    paths:
+      - 'Lib/ensurepip/_bundled/**'
+      - '.github/workflows/verify-ensurepip-wheels.yml'
+      - 'Tools/scripts/verify_ensurepip_wheels.py'
+
+permissions:
+  contents: read
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: '3'
+      - name: Compare checksums of bundled pip and setuptools to ones published on PyPI
+        run: ./Tools/scripts/verify_ensurepip_wheels.py

Misc/NEWS.d/next/Tests/2022-03-14-23-28-17.bpo-47016.K-t2QX.rst

+Create a GitHub Actions workflow for verifying bundled pip and setuptools.
+Patch by Illia Volochii and Adam Turner.

Tools/scripts/verify_ensurepip_wheels.py

+#! /usr/bin/env python3
+
+"""
+Compare checksums for wheels in :mod:`ensurepip` against the Cheeseshop.
+
+When GitHub Actions executes the script, output is formatted accordingly.
+https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-a-notice-message
+"""
+
+import hashlib
+import json
+import os
+import re
+from pathlib import Path
+from urllib.request import urlopen
+
+PACKAGE_NAMES = ("pip", "setuptools")
+ENSURE_PIP_ROOT = Path(__file__).parent.parent.parent / "Lib/ensurepip"
+WHEEL_DIR = ENSURE_PIP_ROOT / "_bundled"
+ENSURE_PIP_INIT_PY_TEXT = (ENSURE_PIP_ROOT / "__init__.py").read_text(encoding="utf-8")
+GITHUB_ACTIONS = os.getenv("GITHUB_ACTIONS") == "true"
+
+
+def print_notice(file_path: str, message: str) -> None:
+    if GITHUB_ACTIONS:
+        message = f"::notice file={file_path}::{message}"
+    print(message, end="\n\n")
+
+
+def print_error(file_path: str, message: str) -> None:
+    if GITHUB_ACTIONS:
+        message = f"::error file={file_path}::{message}"
+    print(message, end="\n\n")
+
+
+def verify_wheel(package_name: str) -> bool:
+    # Find the package on disk
+    package_path = next(WHEEL_DIR.glob(f"{package_name}*.whl"), None)
+    if not package_path:
+        print_error("", f"Could not find a {package_name} wheel on disk.")
+        return False
+
+    print(f"Verifying checksum for {package_path}.")
+
+    # Find the version of the package used by ensurepip
+    package_version_match = re.search(
+        f'_{package_name.upper()}_VERSION = "([^"]+)', ENSURE_PIP_INIT_PY_TEXT
+    )
+    if not package_version_match:
+        print_error(
+            package_path,
+            f"No {package_name} version found in Lib/ensurepip/__init__.py.",
+        )
+        return False
+    package_version = package_version_match[1]
+
+    # Get the SHA 256 digest from the Cheeseshop
+    try:
+        raw_text = urlopen(f"https://pypi.org/pypi/{package_name}/json").read()
+    except (OSError, ValueError):
+        print_error(package_path, f"Could not fetch JSON metadata for {package_name}.")
+        return False
+
+    release_files = json.loads(raw_text)["releases"][package_version]
+    for release_info in release_files:
+        if package_path.name != release_info["filename"]:
+            continue
+        expected_digest = release_info["digests"].get("sha256", "")
+        break
+    else:
+        print_error(package_path, f"No digest for {package_name} found from PyPI.")
+        return False
+
+    # Compute the SHA 256 digest of the wheel on disk
+    actual_digest = hashlib.sha256(package_path.read_bytes()).hexdigest()
+
+    print(f"Expected digest: {expected_digest}")
+    print(f"Actual digest:   {actual_digest}")
+
+    if actual_digest != expected_digest:
+        print_error(
+            package_path, f"Failed to verify the checksum of the {package_name} wheel."
+        )
+        return False
+
+    print_notice(
+        package_path,
+        f"Successfully verified the checksum of the {package_name} wheel.",
+    )
+    return True
+
+
+if __name__ == "__main__":
+    exit_status = 0
+    for package_name in PACKAGE_NAMES:
+        if not verify_wheel(package_name):
+            exit_status = 1
+    raise SystemExit(exit_status)