ci: automate PyPI publishing from main

.github/workflows/publish.yml

@@ -0,0 +1,92 @@
+name: Publish to PyPI
+
+on:
+  push:
+    branches:
+      - main
+
+concurrency:
+  group: publish-main
+  cancel-in-progress: false
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    environment:
+      name: pypi
+      url: https://pypi.org/p/nmag-python-3
+    permissions:
+      contents: write
+      id-token: write
+
+    steps:
+      - name: Check out the repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Use the latest main commit
+        run: |
+          git fetch --no-tags origin main
+          git checkout --detach origin/main
+
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.12"
+          cache: pip
+
+      - name: Install development dependencies
+        run: |
+          python -m venv .venv
+          .venv/bin/python -m pip install --upgrade pip
+          .venv/bin/python -m pip install ".[dev]"
+
+      - name: Run verification checks
+        run: ./scripts/verify.sh
+
+      - name: Bump patch version when unchanged
+        id: version
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          current_version="$({ python -c 'import tomllib; print(tomllib.load(open("pyproject.toml", "rb"))["project"]["version"])'; })"
+          previous_version=""
+          if git rev-parse HEAD^ >/dev/null 2>&1; then
+            previous_version="$({ git show HEAD^:pyproject.toml | python -c 'import sys, tomllib; print(tomllib.load(sys.stdin.buffer)["project"]["version"])'; })"
+          fi
+
+          if [[ "$current_version" == "$previous_version" ]]; then
+            new_version="$(python scripts/bump_patch_version.py)"
+            current_version="$new_version"
+            echo "bumped=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "bumped=false" >> "$GITHUB_OUTPUT"
+          fi
+
+          echo "version=${current_version}" >> "$GITHUB_OUTPUT"
+          echo "Publishing version ${current_version}"
+
+      - name: Install build and metadata tools
+        run: .venv/bin/python -m pip install --upgrade build twine
+
+      - name: Build distributions
+        run: .venv/bin/python -m build
+
+      - name: Check distributions
+        run: .venv/bin/python -m twine check dist/*
+
+      - name: Publish distributions to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+
+      - name: Record automatic version bump
+        if: steps.version.outputs.bumped == 'true'
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add pyproject.toml
+          git commit -m "chore: bump version to ${{ steps.version.outputs.version }} [skip ci]"
+          git fetch --no-tags origin main
+          git rebase origin/main
+          git push origin HEAD:main

scripts/bump_patch_version.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python3
+"""Increment the patch component of the project version in pyproject.toml."""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+
+PYPROJECT = Path(__file__).resolve().parents[1] / "pyproject.toml"
+VERSION_PATTERN = re.compile(r'(?m)^(version\s*=\s*")([^"\n]+)("\s*)$')
+
+
+def main() -> None:
+    text = PYPROJECT.read_text(encoding="utf-8")
+    matches = list(VERSION_PATTERN.finditer(text))
+    if len(matches) != 1:
+        raise SystemExit("Expected exactly one project version in pyproject.toml")
+
+    match = matches[0]
+    version = match.group(2)
+    components = version.split(".")
+    if len(components) != 3 or not all(component.isdigit() for component in components):
+        raise SystemExit(f"Patch bump requires a numeric X.Y.Z version, got {version!r}")
+
+    major, minor, patch = (int(component) for component in components)
+    new_version = f"{major}.{minor}.{patch + 1}"
+    updated = text[: match.start(2)] + new_version + text[match.end(2) :]
+    PYPROJECT.write_text(updated, encoding="utf-8")
+    print(new_version)
+
+
+if __name__ == "__main__":
+    main()