feat: look up local row ids by sync id for the sync plugin (Plugin-Sync#4)

src/backend/sync/host.ts

@@ -38,6 +38,7 @@ import { hosts, sshCredentials } from "../database/db/schema.js";
 import {
   createResolvers,
   deleteStoredRow,
+  findStoredIds,
   listStoredRows,
   loadWireRow,
   loadWireRows,
@@ -271,6 +272,11 @@ export function createSyncHost(): PluginSyncHost {
       ensureCore: () => ensureCoreEntities(),
       onChanged: (listener) => onEntitiesChanged(listener),
       onLocalWrite: (listener) => onLocalWrite(listener),
+      idsOf: async (type, userId, syncIds) => {
+        const entity = getEntity(type);
+        if (!entity || entity.load) return {};
+        return findStoredIds(entity, userId, syncIds);
+      },
     },
 
     replica: {

src/backend/sync/store.ts

@@ -112,6 +112,21 @@ export async function findStoredRow(
   return row ?? null;
 }
 
+/** The local ids of the user's own rows, by sync id. Unknown ones are left out. */
+export async function findStoredIds(
+  entity: RegisteredSyncEntity,
+  userId: string,
+  syncIds: string[],
+): Promise<Record<string, number>> {
+  const ids: Record<string, number> = {};
+  if (entity.singleton || !entity.table) return ids;
+  for (const syncId of new Set(syncIds)) {
+    const row = await findStoredRow(entity, userId, syncId);
+    if (row && typeof row.id === "number") ids[syncId] = row.id;
+  }
+  return ids;
+}
+
 /** Gives an old row with no syncId one, so it can take part. */
 async function ensureSyncId(
   entity: RegisteredSyncEntity,

src/backend/tests/sync/host.test.ts

@@ -8,6 +8,8 @@ const mocks = vi.hoisted(() => ({
   getLink: vi.fn(),
   generateJWTToken: vi.fn(),
   revokeSession: vi.fn(),
+  getEntity: vi.fn(),
+  findStoredIds: vi.fn(),
 }));
 
 vi.mock("../../utils/auth-manager.js", () => ({
@@ -28,7 +30,7 @@ vi.mock("../../utils/app-version.js", () => ({
 vi.mock("../../notify/core-notify.js", () => ({ sendCoreAlert: vi.fn() }));
 vi.mock("../../plugins/index.js", () => ({ getPluginRuntime: vi.fn() }));
 vi.mock("../../plugins/sync-registry.js", () => ({
-  getEntity: vi.fn(),
+  getEntity: mocks.getEntity,
   listEntities: () => [{ type: "hosts", owner: "core", order: 10 }],
   onEntitiesChanged: vi.fn(),
 }));
@@ -55,7 +57,9 @@ vi.mock("../../utils/permission-manager.js", () => ({
 vi.mock("../../sync/entities.js", () => ({
   registerCoreSyncEntities: vi.fn(),
 }));
-vi.mock("../../sync/store.js", () => ({}));
+vi.mock("../../sync/store.js", () => ({
+  findStoredIds: mocks.findStoredIds,
+}));
 vi.mock("../../sync/wire.js", () => ({}));
 vi.mock("../../sync/records.js", () => ({
   listChanges: mocks.listChanges,
@@ -215,3 +219,22 @@ describe("host.links", () => {
     });
   });
 });
+
+describe("host.entities.idsOf", () => {
+  it("maps sync ids to the user's own row ids", async () => {
+    const entity = { type: "snippets", table: {} };
+    mocks.getEntity.mockReturnValue(entity);
+    mocks.findStoredIds.mockResolvedValue({ a: 3 });
+    expect(
+      await createSyncHost().entities.idsOf!("snippets", "u", ["a", "b"]),
+    ).toEqual({ a: 3 });
+    expect(mocks.findStoredIds).toHaveBeenCalledWith(entity, "u", ["a", "b"]);
+  });
+
+  it("answers nothing for an unknown or built type", async () => {
+    mocks.getEntity.mockReturnValue(undefined);
+    expect(await createSyncHost().entities.idsOf!("x", "u", ["a"])).toEqual({});
+    mocks.getEntity.mockReturnValue({ type: "y", load: vi.fn() });
+    expect(await createSyncHost().entities.idsOf!("y", "u", ["a"])).toEqual({});
+  });
+});