fix(lagoon): run deferred:purge and the migrate commands on the app's published database (quick-261106-kt2)

The nightly framework entry deferred:purge failed under serve's worker and
schedule:run with "backpack: duplicate provider for *sql.DB": withDB always
opened and published a second pool. It now reuses the published *gorm.DB and
leaves that pool open; the CLI path (nothing published) is unchanged.

modules/lagoon/commands.go

@@ -483,7 +483,16 @@ func purgeBucket(ctx context.Context, app *backpack.App) (*blob.Bucket, func(),
 	return b, func() { _ = b.Close() }, nil
 }
 
+// withDB runs fn on the app's published database when there is one: an
+// in-process run (the scheduler in serve or schedule:run, through
+// bonfire.Catalog.Call) borrows that pool and leaves it open. Otherwise it
+// opens and publishes a pool for the CLI run and closes it when fn returns.
 func withDB(ctx context.Context, app *backpack.App, fn func(*gorm.DB) error) error {
+	if app != nil {
+		if gdb, ok := app.Lookup[*gorm.DB](); ok && gdb != nil {
+			return fn(gdb)
+		}
+	}
 	sqlDB, gdb, err := OpenFromApp(ctx, app)
 	if err != nil {
 		return err

modules/lagoon/purge_test.go

@@ -501,3 +501,50 @@ func TestPurgeDeferredCommand(t *testing.T) {
 		t.Fatal("the command left the file, its blob or a binding")
 	}
 }
+
+// TestPurgeDeferredCommandPublishedDB runs deferred:purge the way the
+// in-process scheduler does: through bonfire.Call on an app whose pool serve
+// already opened and published. The command used to publish a second pool
+// and fail with "backpack: duplicate provider for *sql.DB"; it now runs on
+// the published handle and leaves that pool open.
+func TestPurgeDeferredCommandPublishedDB(t *testing.T) {
+	e := newPurgeEnv(t, "lagoon_purge_published")
+	f := e.file(t, "")
+	created := e.child(t, "created")
+	e.bind(t, "cover", DeferredFileType, fmt.Sprint(f.ID), nil, 3*day)
+	e.bind(t, "children", "acme_purge_children", fmt.Sprint(created), &DeferredEnvelope{Created: true}, 3*day)
+
+	app := backpack.New(purgeConfig(t, map[string]any{"database.dsn": e.dsn, "app.key": base64.StdEncoding.EncodeToString(bytes.Repeat([]byte{7}, 32))}))
+	sqlDB, gdb, err := OpenFromApp(t.Context(), app)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = sqlDB.Close() })
+	if err := Publish(app, sqlDB, gdb); err != nil {
+		t.Fatal(err)
+	}
+	if err := attach.Publish(app, e.bucket); err != nil {
+		t.Fatal(err)
+	}
+	plugins := []party.Plugin{purgePlugin{models: []any{&purgeChild{}}}}
+	var out bytes.Buffer
+	if err := bonfire.Call(t.Context(), RuntimeCommands(app, plugins), "deferred:purge", []string{"--days", "2"}, &out); err != nil {
+		t.Fatalf("deferred:purge: %v\n%s", err, out.String())
+	}
+	if !strings.Contains(out.String(), "purged 2 deferred bindings older than 2 days (1 files, 1 children, 0 skipped)") {
+		t.Fatalf("output = %q", out.String())
+	}
+	if e.fileExists(t, f.ID) || e.blobExists(t, f) || len(e.bindingIDs(t)) != 0 {
+		t.Fatal("the command left the file, its blob or a binding")
+	}
+	if err := sqlDB.PingContext(t.Context()); err != nil {
+		t.Fatalf("published pool closed by the command: %v", err)
+	}
+	if got, ok := app.Lookup[*gorm.DB](); !ok || got != gdb {
+		t.Fatalf("published *gorm.DB replaced: %p, want %p", got, gdb)
+	}
+	out.Reset()
+	if err := bonfire.Call(t.Context(), RuntimeCommands(app, plugins), "migrate:status", nil, &out); err != nil {
+		t.Fatalf("migrate:status: %v\n%s", err, out.String())
+	}
+}