fix: add license file and test

docs/_includes/pyproject.md

@@ -7,6 +7,7 @@ The metadata is specified in a [standards-based][metadata] format:
 name = "package"
 description = "A great package."
 readme = "README.md"
+license.file = "LICENSE"
 authors = [
   { name = "My Name", email = "[email protected]" },
 ]

noxfile.py

@@ -8,13 +8,16 @@
 from __future__ import annotations
 
 import difflib
+import email.message
 import json
 import os
 import re
 import shutil
 import stat
 import sys
+import tarfile
 import urllib.request
+import zipfile
 from collections.abc import Callable
 from pathlib import Path
 
@@ -270,6 +273,27 @@ def dist(session: nox.Session, backend: str, vcs: bool) -> None:
 
     session.run("twine", "check", f"{sdist}", f"{wheel}")
 
+    # Check for LICENSE in SDist
+    with tarfile.open(sdist) as tf:
+        names = tf.getnames()
+    if not any(n.endswith("LICENSE") for n in names):
+        msg = f"license file missing from {backend} vcs={vcs}'s sdist. Found: {names}"
+        session.error(msg)
+
+    # Check for LICENSE in wheel
+    with zipfile.ZipFile(wheel) as zf:
+        names = zf.namelist()
+        metadata_path = next(iter(n for n in names if n.endswith("METADATA")))
+        with zf.open(metadata_path) as mfile:
+            txt = mfile.read()
+    license_fields = email.message.EmailMessage(txt).get_all("License", [])
+    if license_fields:
+        msg = f"Should not have anything in the License slot, got {license_fields}"
+        session.error(msg)
+    if not any(n.endswith("LICENSE") for n in names):
+        msg = f"license file missing from {backend} vcs={vcs}'s wheel. Found: {names}"
+        session.error(msg)
+
     dist = DIR / "dist"
     dist.mkdir(exist_ok=True)
     sdist.rename(dist / sdist.stem)

{{cookiecutter.project_name}}/pyproject.toml

@@ -162,6 +162,7 @@ maintainers = [
 {%- endif %}
 description = "{{ cookiecutter.project_short_description }}"
 readme = "README.md"
+license.file = "LICENSE"
 requires-python = ">=3.8"
 classifiers = [
   "Development Status :: 1 - Planning",