Try every event database file on delete and say which was left (closes #275)

DeleteDB stopped at the first file it could not remove, and the
webhook delete handler logged one message for every failure. Once
the database file itself is gone, its events are lost, and telling
the operator only that a file was left behind suggests otherwise.

DeleteDB now tries the database file and both sidecars, and its
error wraps ErrEventDBNotRemoved when the database file is still on
disk, or ErrSidecarNotRemoved when only a -wal or -shm sidecar is
left. The handler logs a different message for each.

Model: opus-5-5

internal/database/webhook_db_manager_test.go

@@ -182,17 +182,91 @@ func TestWebhookDBManager_DeleteDB(t *testing.T) {
 	}
 	require.NoError(t, db.Create(event).Error)
 
+	// Under WAL, an open database that has been written to has both
+	// sidecars beside it.
+	dbPath := mgr.DBPath(webhookID)
+	require.FileExists(t, dbPath+"-wal")
+	require.FileExists(t, dbPath+"-shm")
+
 	// Delete the DB
 	require.NoError(t, mgr.DeleteDB(webhookID))
 
 	// File should no longer exist
 	assert.False(t, mgr.DBExists(webhookID))
 
-	// Verify the file is actually gone from disk
+	// Verify the files are actually gone from disk
+	assert.NoFileExists(t, dbPath)
+	assert.NoFileExists(t, dbPath+"-wal")
+	assert.NoFileExists(t, dbPath+"-shm")
+}
+
+// blockRemoval puts a non-empty directory at path, which os.Remove
+// cannot remove whoever runs the test, root included.
+func blockRemoval(t *testing.T, path string) {
+	t.Helper()
+
+	require.NoError(t, os.MkdirAll(filepath.Join(path, "keep"), 0o700))
+}
+
+// TestWebhookDBManager_DeleteDBKeepsDatabaseFile proves that when the
+// event database file cannot be removed, the error says so, and both
+// sidecars are still removed.
+func TestWebhookDBManager_DeleteDBKeepsDatabaseFile(t *testing.T) {
+	t.Parallel()
+
+	mgr, lc := setupTestWebhookDBManager(t)
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+
+	defer func() { require.NoError(t, lc.Stop(ctx)) }()
+
+	webhookID := uuid.New().String()
 	dbPath := mgr.DBPath(webhookID)
 
-	_, err = os.Stat(dbPath)
-	assert.True(t, os.IsNotExist(err))
+	blockRemoval(t, dbPath)
+	require.NoError(t, os.WriteFile(dbPath+"-wal", nil, 0o600))
+	require.NoError(t, os.WriteFile(dbPath+"-shm", nil, 0o600))
+
+	err := mgr.DeleteDB(webhookID)
+
+	require.ErrorIs(t, err, database.ErrEventDBNotRemoved)
+	require.NotErrorIs(t, err, database.ErrSidecarNotRemoved)
+	assert.Contains(t, err.Error(), dbPath)
+	assert.NoFileExists(t, dbPath+"-wal")
+	assert.NoFileExists(t, dbPath+"-shm")
+}
+
+// TestWebhookDBManager_DeleteDBKeepsSidecar proves that when the
+// event database file is removed but a sidecar is not, the error
+// says the database file is gone, and the other sidecar is still
+// removed.
+func TestWebhookDBManager_DeleteDBKeepsSidecar(t *testing.T) {
+	t.Parallel()
+
+	mgr, lc := setupTestWebhookDBManager(t)
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+
+	defer func() { require.NoError(t, lc.Stop(ctx)) }()
+
+	webhookID := uuid.New().String()
+	dbPath := mgr.DBPath(webhookID)
+
+	require.NoError(t, mgr.CreateDB(webhookID))
+	// Closing removes the sidecars, so the ones below are the only
+	// ones there.
+	require.NoError(t, mgr.CloseAll())
+
+	blockRemoval(t, dbPath+"-wal")
+	require.NoError(t, os.WriteFile(dbPath+"-shm", nil, 0o600))
+
+	err := mgr.DeleteDB(webhookID)
+
+	require.ErrorIs(t, err, database.ErrSidecarNotRemoved)
+	require.NotErrorIs(t, err, database.ErrEventDBNotRemoved)
+	assert.Contains(t, err.Error(), dbPath+"-wal")
+	assert.NoFileExists(t, dbPath)
+	assert.NoFileExists(t, dbPath+"-shm")
 }
 
 func TestWebhookDBManager_LazyCreation(t *testing.T) {