Handle synchronize webhook and add AMENDED bill status

When new commits are pushed to a PR with an open bill, the bill is now
closed with a new AMENDED status instead of being silently invalidated.
The PullRequestHandler.synchronize() method updates the stored PR SHA
and closes any open bill as amended; draft bills are unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mfosterw

.claude/skills/new-bill-feature/SKILL.md

@@ -48,7 +48,7 @@ The Bill system spans these files. Review each to determine if it needs changes:
 - `config/settings/base.py` — WEBISCITE_* settings (quorum, majority thresholds, voting period, GitHub token/repo)
 
 ## Key patterns to follow
-- Bill status choices: DRAFT, OPEN, APPROVED, REJECTED, FAILED, CLOSED
+- Bill status choices: DRAFT, OPEN, APPROVED, AMENDED, REJECTED, FAILED, CLOSED
 - Votes are M2M through Vote model with unique constraint on (bill, user)
 - Bill.vote() toggles existing votes; raises ClosedBillVoteError if bill not OPEN
 - Constitutional bills need WEBISCITE_SUPERMAJORITY (66.67%), normal need WEBISCITE_NORMAL_MAJORITY (50%)
@@ -62,6 +62,8 @@ The Bill system spans these files. Review each to determine if it needs changes:
 - PullRequest.close() closes both open and draft bills
 - The submit PeriodicTask is created disabled for draft bills; Bill.publish() enables it and resets last_run_at so the voting period starts from publication
 - GitHub's `ready_for_review` webhook action triggers PullRequestHandler.ready_for_review(), which updates the PR and publishes the draft bill
+- GitHub's `synchronize` webhook action (new commits pushed to PR) triggers PullRequestHandler.synchronize(), which updates the PR SHA and closes any open bill with AMENDED status; draft bills are not affected
+- Bill.close() accepts an optional `status` parameter (default Bill.Status.CLOSED) to set a different terminal status (e.g. AMENDED)
 
 ## Steps
 1. Read the relevant files from the checklist above

democrasite/webiscite/migrations/0008_alter_bill_status_alter_historicalbill_status.py

@@ -0,0 +1,23 @@
+# Generated by Django 5.2.11 on 2026-02-24 20:20
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('webiscite', '0007_alter_bill__submit_task'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='bill',
+            name='status',
+            field=models.CharField(choices=[('draft', 'Draft'), ('open', 'Open'), ('approved', 'Approved'), ('amended', 'PR Amended'), ('rejected', 'Rejected'), ('failed', 'Not Enough Votes'), ('closed', 'PR Closed')], default='open', help_text='The current status of the bill', max_length=10),
+        ),
+        migrations.AlterField(
+            model_name='historicalbill',
+            name='status',
+            field=models.CharField(choices=[('draft', 'Draft'), ('open', 'Open'), ('approved', 'Approved'), ('amended', 'PR Amended'), ('rejected', 'Rejected'), ('failed', 'Not Enough Votes'), ('closed', 'PR Closed')], default='open', help_text='The current status of the bill', max_length=10),
+        ),
+    ]

democrasite/webiscite/models.py

@@ -130,6 +130,7 @@ class Status(models.TextChoices):
         DRAFT = "draft", _("Draft")
         OPEN = "open", _("Open")
         APPROVED = "approved", _("Approved")
+        AMENDED = "amended", _("PR Amended")  # PR updated with new commits
         REJECTED = "rejected", _("Rejected")
         FAILED = "failed", _("Not Enough Votes")  # Failed to reach quorum
         # Translators: PR is short for "pull request"
@@ -271,9 +272,9 @@ def _schedule_submit_task(self) -> None:
         super().save()
         self.log("Scheduled %s", self._submit_task.name)
 
-    def close(self) -> None:
+    def close(self, status: "Bill.Status" = Status.CLOSED) -> None:
         """Close the bill and disable its submit task"""
-        self.status = self.Status.CLOSED
+        self.status = status
         self.save()
         self.log("Closed")
 

democrasite/webiscite/tests/test_models.py

@@ -207,6 +207,17 @@ def test_close(self, bill: Bill):
         assert bill._submit_task is not None  # noqa: SLF001
         assert bill._submit_task.enabled is False  # noqa: SLF001
 
+    def test_close_amended(self, bill: Bill):
+        assert bill._submit_task is not None  # noqa: SLF001
+        assert bill._submit_task.enabled is True  # noqa: SLF001
+
+        bill.close(status=Bill.Status.AMENDED)
+
+        bill.refresh_from_db()
+        assert bill.status == Bill.Status.AMENDED
+        assert bill._submit_task is not None  # noqa: SLF001
+        assert bill._submit_task.enabled is False  # noqa: SLF001
+
 
 class TestBillPublish:
     def test_publish(self):

democrasite/webiscite/tests/test_webhooks.py

@@ -217,3 +217,25 @@ def test_closed(self, mock_close, pr_handler: PullRequestHandler, bill: Bill):
 
         assert response == (bill.pull_request, mock_close.return_value)
         mock_close.assert_called_once()
+
+    def test_synchronize(self, pr_handler: PullRequestHandler):
+        bill = BillFactory.create(status=Bill.Status.OPEN)
+        pr = GithubPullRequestFactory.create(bill=bill)
+
+        pull_request, amended_bill = pr_handler.synchronize(pr)
+
+        assert pull_request is not None
+        assert amended_bill is not None
+        amended_bill.refresh_from_db()
+        assert amended_bill.status == Bill.Status.AMENDED
+        assert amended_bill._submit_task is not None  # noqa: SLF001
+        assert amended_bill._submit_task.enabled is False  # noqa: SLF001
+
+    def test_synchronize_no_open_bill(self, pr_handler: PullRequestHandler):
+        # Default GithubPullRequestFactory creates a closed bill (no active bill)
+        pr = GithubPullRequestFactory.create()
+
+        pull_request, bill = pr_handler.synchronize(pr)
+
+        assert pull_request is not None
+        assert bill is None

democrasite/webiscite/webhooks.py

@@ -115,6 +115,29 @@ def ready_for_review(
         bill.publish()
         return (pull_request, bill)
 
+    def synchronize(self, pr: dict[str, Any]) -> tuple[PullRequest, Bill | None]:
+        """Handle new commits pushed to an open pull request.
+
+        Updates the pull request with the new SHA and closes any active bill
+        as amended, since votes on the old version no longer apply.
+
+        Args:
+            pr: The parsed JSON object representing the pull request
+
+        Returns:
+            A tuple containing the updated pull request and the closed bill, if any
+        """
+        pull_request = PullRequest.objects.create_from_github(pr)
+
+        try:
+            bill: Bill = pull_request.bill_set.get(status=Bill.Status.OPEN)
+        except Bill.DoesNotExist:
+            pull_request.log("No open bill found")
+            return (pull_request, None)
+
+        bill.close(status=Bill.Status.AMENDED)
+        return (pull_request, bill)
+
     def closed(self, pr: dict[str, Any]) -> tuple[PullRequest | None, Bill | None]:
         """Disables the open bill associated with the pull request
 

docs/webiscite.rst

@@ -41,5 +41,12 @@ If the votes for the Bill pass the threshold, the pull request is merged into
 the master branch on Github and automatically deployed, officially making it
 part of Democrasite.
 
+If new commits are pushed to a pull request while a Bill is open for voting,
+GitHub sends a ``synchronize`` event.
+:meth:`~democrasite.webiscite.webhooks.PullRequestHandler.synchronize`
+updates the stored pull request with the new SHA and closes the open Bill
+with an ``AMENDED`` status, since the votes no longer reflect the current
+code. Draft bills are not affected by synchronize events.
+
 .. _GitHub: https://github.com/mfosterw/cookiestocracy
 .. _webhook: https://docs.github.com/en/developers/webhooks-and-events/webhooks/about-webhooks