Make Stop stop: no replay, no restart, immediate feedback

Pressing Stop could look like the scan restarting, and for scheduled jobs
it really did restart the Google stage.

- Scheduler: check the abort flag between stages and never clear the
  Google abort after a Stop (that started a fresh all-users Google scan).
  A stopped job is recorded as "cancelled" and skips email/retention;
  scheduler_done carries cancelled=true.
- SSE: scan_cancelled and file_scan_done now end the current scan like
  scan_done, and sse.replay_messages() never replays a finished scan.
  Previously a stopped M365 scan (and every file scan) stayed "current",
  so each reconnect replayed it and re-showed Stop + progress.
- Frontend: scan_cancelled clears the M365 running flag and only tears
  down the UI when no Google/file scan is still running; scheduler_done /
  scheduler_error clear all running flags.
- run_scan: Stop during collection now ends the scan (checkpoint, finish,
  scan_cancelled) instead of announcing scan_start / "Scanning…".
- Stop button: switches to a disabled "Stopping…" state on click; all
  show/hide goes through _setStopBtnDisplay(), which resets it when hidden
  or when a new scan starts.

Adds tests/test_stop_scan.py (10 tests).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_stop_scan.py

@@ -0,0 +1,218 @@
+"""
+Stop must stop — regressions for "pressing Stop seems to restart the scan".
+
+  - SSE replay: a stopped/finished scan's buffered events are never replayed to
+    a reconnecting browser (that re-showed the Stop button and progress bar).
+  - run_scan: Stop during collection ends the scan (checkpoint + scan_cancelled)
+    instead of announcing scan_start / "Scanning…".
+  - Scheduler: Stop during one stage prevents later stages — in particular the
+    Google stage no longer clears the Google abort flag and scans everyone.
+"""
+from __future__ import annotations
+from unittest.mock import MagicMock
+
+import pytest
+
+import sse
+
+
+@pytest.fixture(autouse=True)
+def clean_scan_state():
+    """Restore SSE globals and abort flags so tests don't leak into each other."""
+    from routes import state
+    saved_buf = list(sse._sse_buffer)
+    saved_id = sse._current_scan_id
+    saved_finished = list(sse._finished_scan_ids)
+    sse._sse_buffer.clear()
+    sse._current_scan_id = ""
+    sse._finished_scan_ids.clear()
+    yield
+    state._scan_abort.clear()
+    state._google_scan_abort.clear()
+    sse._sse_buffer.clear()
+    sse._sse_buffer.extend(saved_buf)
+    sse._current_scan_id = saved_id
+    sse._finished_scan_ids.clear()
+    sse._finished_scan_ids.extend(saved_finished)
+
+
+def _events(msgs: list[str]) -> list[str]:
+    return [m.split("\n", 1)[0].removeprefix("event: ") for m in msgs]
+
+
+# ---------------------------------------------------------------------------
+# SSE replay
+# ---------------------------------------------------------------------------
+
+class TestReplay:
+    def test_running_scan_is_replayed(self):
+        sse._current_scan_id = "scan_1"
+        sse.broadcast("scan_phase", {"phase": "Collecting…"})
+        sse.broadcast("scan_progress", {"pct": 10})
+        assert _events(sse.replay_messages()) == ["scan_phase", "scan_progress"]
+
+    def test_stopped_scan_is_not_replayed(self):
+        sse._current_scan_id = "scan_1"
+        sse.broadcast("scan_phase", {"phase": "Collecting…"})
+        sse.broadcast("scan_start", {"total": 5})
+        sse.broadcast("scan_progress", {"pct": 40})
+        sse.broadcast("scan_cancelled", {"completed": 2})
+        assert sse._current_scan_id == ""
+        assert sse.replay_messages() == []
+
+    def test_completed_scan_is_not_replayed(self):
+        sse._current_scan_id = "scan_1"
+        sse.broadcast("scan_progress", {"pct": 100})
+        sse.broadcast("scan_done", {"total_scanned": 1, "flagged_count": 0})
+        assert sse.replay_messages() == []
+
+    def test_file_scan_done_ends_the_file_scan(self):
+        # Previously only scan_done cleared the id, so every finished file scan
+        # stayed "current" and was replayed on each page load.
+        sse._current_scan_id = "filescan_1"
+        sse.broadcast("scan_phase", {"phase": "Files — Share"})
+        sse.broadcast("file_scan_done", {"total_scanned": 3, "flagged_count": 0})
+        assert sse._current_scan_id == ""
+        assert sse.replay_messages() == []
+
+    def test_untagged_events_still_replayed_after_scan_ends(self):
+        sse._current_scan_id = "scan_1"
+        sse.broadcast("scan_progress", {"pct": 40})
+        sse.broadcast("scan_cancelled", {"completed": 2})
+        sse.broadcast("google_scan_done", {"total_scanned": 7})  # no scan running → untagged
+        assert _events(sse.replay_messages()) == ["google_scan_done"]
+
+    def test_new_scan_replays_only_its_own_events(self):
+        sse._current_scan_id = "scan_1"
+        sse.broadcast("scan_progress", {"pct": 40})
+        sse.broadcast("scan_cancelled", {"completed": 2})
+        sse._current_scan_id = "scan_2"
+        sse.broadcast("scan_phase", {"phase": "Collecting…"})
+        msgs = sse.replay_messages()
+        assert _events(msgs) == ["scan_phase"]
+        assert '"scan_id": "scan_2"' in msgs[0]
+
+
+# ---------------------------------------------------------------------------
+# run_scan: Stop during collection
+# ---------------------------------------------------------------------------
+
+class TestRunScanStopDuringCollection:
+    @pytest.fixture()
+    def engine(self, monkeypatch):
+        import scan_engine
+        from routes import state
+        sent: list[tuple[str, dict]] = []
+        checkpoints: list = []
+        monkeypatch.setattr(scan_engine, "broadcast", lambda ev, data: sent.append((ev, data)))
+        monkeypatch.setattr(scan_engine, "DB_OK", False)
+        monkeypatch.setattr(scan_engine, "_load_checkpoint", lambda key, **kw: None)
+        monkeypatch.setattr(scan_engine, "_save_checkpoint", lambda *a, **kw: checkpoints.append(a))
+        monkeypatch.setattr(scan_engine, "_clear_checkpoint", lambda **kw: None)
+        conn = MagicMock()
+        conn.is_app_mode = True
+        monkeypatch.setattr(state, "connector", conn)
+        monkeypatch.setattr(state, "flagged_items", [])
+        opts = {"sources": [], "user_ids": [{"id": "u1", "displayName": "User"}], "options": {}}
+        return scan_engine, sent, checkpoints, opts
+
+    def test_stop_before_processing_does_not_announce_scan_start(self, engine):
+        scan_engine, sent, checkpoints, opts = engine
+        from routes import state
+        state._scan_abort.set()
+        scan_engine.run_scan(opts)
+        names = [e for e, _ in sent]
+        assert "scan_cancelled" in names
+        assert "scan_start" not in names
+        assert not any(e == "scan_phase" and "Scanning" in d.get("phase", "") for e, d in sent)
+        assert "scan_done" not in names
+        assert len(checkpoints) == 1  # resumable
+
+    def test_without_stop_scan_runs_to_done(self, engine):
+        scan_engine, sent, _, opts = engine
+        scan_engine.run_scan(opts)
+        names = [e for e, _ in sent]
+        assert "scan_start" in names and "scan_done" in names
+        assert "scan_cancelled" not in names
+
+
+# ---------------------------------------------------------------------------
+# Scheduler: Stop ends the whole job
+# ---------------------------------------------------------------------------
+
+class TestSchedulerStop:
+    JOB = {"id": "j1", "name": "Nightly", "profile_id": "", "enabled": True,
+           "auto_email": True, "auto_retention": True, "retention_years": 5}
+    OPTIONS = {"sources": ["email", "gmail"], "user_ids": [], "options": {},
+               "file_sources": [{"id": "f1", "path": "/srv/share", "label": "Share"}],
+               "google_sources": ["gmail"]}
+
+    @pytest.fixture()
+    def job(self, monkeypatch):
+        import gdpr_scanner
+        import scan_scheduler
+        import routes.google_scan as google_scan
+        from routes import state
+
+        sent: list[tuple[str, dict]] = []
+        monkeypatch.setattr(scan_scheduler, "load_jobs", lambda: [dict(self.JOB)])
+        monkeypatch.setattr(gdpr_scanner, "_get_db", lambda *a, **kw: None)
+        monkeypatch.setattr(gdpr_scanner, "broadcast", lambda ev, data: sent.append((ev, data)))
+        conn = MagicMock()
+        conn.is_authenticated.return_value = True
+        monkeypatch.setattr(state, "connector", conn)
+        monkeypatch.setattr(state, "google_connector", MagicMock())
+        monkeypatch.setattr(state, "flagged_items", [{"id": "found"}])
+
+        mocks = {
+            "run_scan": MagicMock(),
+            "run_file_scan": MagicMock(),
+            "google": MagicMock(),
+        }
+        monkeypatch.setattr(gdpr_scanner, "run_scan", mocks["run_scan"])
+        monkeypatch.setattr(gdpr_scanner, "run_file_scan", mocks["run_file_scan"])
+        monkeypatch.setattr(google_scan, "_run_google_scan", mocks["google"])
+
+        sched = scan_scheduler.ScanScheduler()
+        monkeypatch.setattr(sched, "_build_options", lambda cfg: {
+            k: (list(v) if isinstance(v, list) else dict(v) if isinstance(v, dict) else v)
+            for k, v in self.OPTIONS.items()})
+        mocks["email"] = MagicMock()
+        mocks["retention"] = MagicMock()
+        monkeypatch.setattr(sched, "_send_email_report", mocks["email"])
+        monkeypatch.setattr(sched, "_run_retention", mocks["retention"])
+        return sched, mocks, sent
+
+    def test_stop_during_m365_stage_skips_file_and_google(self, job):
+        from routes import state
+        sched, mocks, sent = job
+
+        def _user_presses_stop(opts):  # what POST /api/scan/stop does mid-scan
+            state._scan_abort.set()
+            state._google_scan_abort.set()
+        mocks["run_scan"].side_effect = _user_presses_stop
+
+        sched._execute_scan("j1")
+
+        mocks["run_scan"].assert_called_once()
+        mocks["run_file_scan"].assert_not_called()
+        mocks["google"].assert_not_called()
+        assert state._google_scan_abort.is_set(), "Google abort must not be cleared after Stop"
+        run = sched._last_runs["j1"]
+        assert run["status"] == "cancelled"
+        mocks["email"].assert_not_called()
+        mocks["retention"].assert_not_called()
+        done = [d for e, d in sent if e == "scheduler_done"]
+        assert done and done[0]["cancelled"] is True
+
+    def test_uninterrupted_job_runs_every_stage(self, job):
+        sched, mocks, sent = job
+        sched._execute_scan("j1")
+        mocks["run_scan"].assert_called_once()
+        mocks["run_file_scan"].assert_called_once()
+        mocks["google"].assert_called_once()
+        assert sched._last_runs["j1"]["status"] == "completed"
+        mocks["email"].assert_called_once()
+        mocks["retention"].assert_called_once()
+        done = [d for e, d in sent if e == "scheduler_done"]
+        assert done and done[0]["cancelled"] is False