Migrate from changelog_entry.yaml to towncrier fragments

.github/bump_version.py

@@ -0,0 +1,77 @@
+"""Infer semver bump from towncrier fragment types and update version."""
+
+import re
+import sys
+from pathlib import Path
+
+
+def get_current_version(pyproject_path: Path) -> str:
+    text = pyproject_path.read_text()
+    match = re.search(r'^version\s*=\s*"(\d+\.\d+\.\d+)"', text, re.MULTILINE)
+    if not match:
+        print("Could not find version in pyproject.toml", file=sys.stderr)
+        sys.exit(1)
+    return match.group(1)
+
+
+def infer_bump(changelog_dir: Path) -> str:
+    fragments = [
+        f
+        for f in changelog_dir.iterdir()
+        if f.is_file() and f.name != ".gitkeep"
+    ]
+    if not fragments:
+        print("No changelog fragments found", file=sys.stderr)
+        sys.exit(1)
+
+    categories = {f.suffix.lstrip(".") for f in fragments}
+    # Also check the second-to-last part for compound extensions
+    # like branch-name.breaking.md
+    for f in fragments:
+        parts = f.stem.split(".")
+        if len(parts) >= 2:
+            categories.add(parts[-1])
+
+    if "breaking" in categories:
+        return "major"
+    if "added" in categories or "removed" in categories:
+        return "minor"
+    return "patch"
+
+
+def bump_version(version: str, bump: str) -> str:
+    major, minor, patch = (int(x) for x in version.split("."))
+    if bump == "major":
+        return f"{major + 1}.0.0"
+    elif bump == "minor":
+        return f"{major}.{minor + 1}.0"
+    else:
+        return f"{major}.{minor}.{patch + 1}"
+
+
+def update_file(path: Path, old_version: str, new_version: str):
+    text = path.read_text()
+    updated = text.replace(
+        f'version = "{old_version}"', f'version = "{new_version}"'
+    )
+    if updated != text:
+        path.write_text(updated)
+        print(f"  Updated {path}")
+
+
+def main():
+    root = Path(__file__).resolve().parent.parent
+    pyproject = root / "pyproject.toml"
+    changelog_dir = root / "changelog.d"
+
+    current = get_current_version(pyproject)
+    bump = infer_bump(changelog_dir)
+    new = bump_version(current, bump)
+
+    print(f"Version: {current} -> {new} ({bump})")
+
+    update_file(pyproject, current, new)
+
+
+if __name__ == "__main__":
+    main()

.github/workflows/pr.yaml

@@ -17,27 +17,20 @@ jobs:
         run: uv sync --extra dev
       - name: Check formatting
         run: uv run black . -l 79 --check
-  check-version:
-    name: Check version
+  check-changelog:
+    name: Check changelog fragment
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-        with:
-          fetch-depth: 100
-          repository: ${{ github.event.pull_request.head.repo.full_name }}
-          ref: ${{ github.event.pull_request.head.ref }}
-      - name: Install uv
-        uses: astral-sh/setup-uv@v5
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: 3.14
-      - name: Install dependencies
+      - name: Check for changelog fragment
         run: |
-          uv pip install -e . --system
-          uv pip install "yaml-changelog>=0.1.7" --system
-      - name: Build changelog
-        run: make changelog
+          FRAGMENTS=$(find changelog.d -type f ! -name '.gitkeep' | wc -l)
+          if [ "$FRAGMENTS" -eq 0 ]; then
+            echo "::error::No changelog fragment found in changelog.d/"
+            echo "Add one with: echo 'Description.' > changelog.d/\$(git branch --show-current).<type>.md"
+            echo "Types: added, changed, fixed, removed, breaking"
+            exit 1
+          fi
   Quick-Feedback:
     name: Quick Feedback (Selective Tests + Coverage)
     runs-on: ubuntu-latest

.github/workflows/push.yaml

@@ -24,9 +24,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
         with:
-          fetch-depth: 100
-          repository: ${{ github.event.pull_request.head.repo.full_name }}
-          ref: ${{ github.event.pull_request.head.ref }}
+          fetch-depth: 0
           token: ${{ secrets.POLICYENGINE_GITHUB }}
       - name: Install uv
         uses: astral-sh/setup-uv@v5
@@ -35,11 +33,12 @@ jobs:
         with:
           python-version: 3.14
       - name: Install dependencies
-        run: uv pip install -e ".[dev]" --system
-      - name: Install dependencies
-        run: uv pip install "yaml-changelog>=0.1.7" --system
-      - name: Build changelog
-        run: make changelog
+        run: uv pip install towncrier --system
+      - name: Bump version and build changelog
+        run: |
+          python .github/bump_version.py
+          VERSION=$(python -c "import re; print(re.search(r'version = \"(.+?)\"', open('pyproject.toml').read()).group(1))")
+          towncrier build --yes --version "$VERSION"
       - name: Update changelog
         uses: EndBug/add-and-commit@v9
         with:

CLAUDE.md

@@ -60,10 +60,19 @@ make documentation
   - **ALWAYS run `make format` before committing** - this ensures code meets style guidelines and is non-negotiable
   - Use `git push` to push changes to the PR branch
 
+## Changelog
+Every PR needs a changelog fragment in `changelog.d/`:
+```bash
+echo "Description of change." > changelog.d/<branch-name>.<type>.md
+```
+Types: `added` (minor bump), `changed` (patch), `fixed` (patch), `removed` (minor), `breaking` (major)
+
+**DO NOT** edit `CHANGELOG.md` directly or use `changelog_entry.yaml` (deprecated).
+
 ## Project Requirements
 - Python >= 3.11, < 3.15
 - Follow GitHub Flow with PRs targeting master branch
-- Every PR needs a changelog entry in changelog_entry.yaml
+- Every PR needs a changelog fragment in `changelog.d/`
 - **ALWAYS run `make format` before every commit** - this is mandatory
 
 ## Project-Specific Gotchas

Makefile

@@ -33,11 +33,8 @@ build:
 	rm policyengine_us/data/storage/*.h5 | true
 	python -m build
 changelog:
-	build-changelog changelog.yaml --output changelog.yaml --update-last-date --start-from 0.0.1 --append-file changelog_entry.yaml
-	build-changelog changelog.yaml --org PolicyEngine --repo policyengine-us --output CHANGELOG.md --template .github/changelog_template.md
-	bump-version changelog.yaml pyproject.toml
-	rm changelog_entry.yaml || true
-	touch changelog_entry.yaml
+	python .github/bump_version.py
+	towncrier build --yes --version $$(python -c "import re; print(re.search(r'version = \"(.+?)\"', open('pyproject.toml').read()).group(1))")
 dashboard:
 	python policyengine_us/data/datasets/cps/enhanced_cps/update_dashboard.py
 calibration:

changelog.d/migrate-to-towncrier.changed.md

@@ -0,0 +1 @@
+Migrated from changelog_entry.yaml to towncrier fragments to eliminate merge conflicts.