fix(sync): retry instead of full sync when the database is unavailable

src/lib/managers/sync.manager.svelte.ts

@@ -1,4 +1,5 @@
 import { getSupportedVersion, syncStream } from '$lib/api/client';
+import { App } from '@capacitor/app';
 import { db } from '$lib/db/database';
 import { syncAck, timetable } from '$lib/db/schema';
 import { TODAY_SQL } from '$lib/db/sql';
@@ -98,6 +99,9 @@ class SyncManager {
   }
 
   async #startUp() {
+    // iOS can take the database file away while suspended, so syncs only run in the foreground.
+    App.addListener('pause', () => this.#retry.cancel());
+    App.addListener('resume', () => this.sync());
     this.#enqueue(() => db.delete(timetable).where(lt(timetable.serviceDate, TODAY_SQL)));
     await this.#checkVersion().catch((error) =>
       appLogger.w(`Version check failed: ${describeError(error)}`),
@@ -131,6 +135,7 @@ class SyncManager {
       await this.#reporter.watch(acks, applyAll(planSync(lines)));
       appLogger.i(`Applied ${lines.length} sync lines`);
     } catch (error) {
+      if (error instanceof SyncApplyError && error.isDatabaseUnavailable) throw error;
       appLogger.w(`Incremental sync failed, running a full sync: ${describeError(error)}`);
       await this.#fullSync();
     }

src/lib/sync/sync-errors.ts

@@ -1,3 +1,5 @@
+import { rootCause } from '$lib/utils/logger';
+
 export class SyncStatusError extends Error {
   constructor(
     readonly status: number,
@@ -9,4 +11,12 @@ export class SyncStatusError extends Error {
 
 export class SyncLineError extends Error {}
 
-export class SyncApplyError extends Error {}
+// SQLite's text for SQLITE_CANTOPEN, which the plugin passes through on every platform.
+const CANT_OPEN_MESSAGE = 'unable to open database file';
+
+export class SyncApplyError extends Error {
+  /** A full sync writes to the same file, so it would fail the same way. */
+  get isDatabaseUnavailable(): boolean {
+    return `${rootCause(this)}`.includes(CANT_OPEN_MESSAGE);
+  }
+}

src/lib/sync/sync-reporter.test.ts

@@ -33,6 +33,31 @@ describe('syncFailureEvent', () => {
   ])('reports %s', (type, error) => {
     expect(syncFailureEvent(error, [])?.type).toBe(type);
   });
+
+  it('reports the SQLite error instead of the query that hit it', () => {
+    const sqliteError = new Error('rc: 14 message: unable to open database file');
+    const query = `Failed query: delete from "timetable"\nparams: ${'id,'.repeat(100)}`;
+    const queryError = new Error(query, { cause: sqliteError });
+    const error = new SyncApplyError('sync apply failed', { cause: queryError });
+
+    expect(syncFailureEvent(error, ACKS)?.payload.message).toBe(`${sqliteError}`);
+  });
+});
+
+describe('SyncApplyError', () => {
+  it.each([
+    [
+      'iOS',
+      'Run: Failed in runSQL :  Error: prepareSQL finalize failed rc: 14 message: unable to open database file',
+      true,
+    ],
+    ['Android', 'unable to open database file (code 14 SQLITE_CANTOPEN)', true],
+    ['a constraint', 'UNIQUE constraint failed: route.id', false],
+  ])('knows when the database was unavailable on %s', (_, message, unavailable) => {
+    const error = new SyncApplyError('sync apply failed', { cause: new Error(message) });
+
+    expect(error.isDatabaseUnavailable).toBe(unavailable);
+  });
 });
 
 describe('SyncFailureReporter', () => {

src/lib/sync/sync-reporter.ts

@@ -1,5 +1,5 @@
 import { report, type ReportEvent } from '$lib/api/client';
-import { appLogger, describeError } from '$lib/utils/logger';
+import { appLogger, describeError, rootCause } from '$lib/utils/logger';
 import { SyncApplyError, SyncLineError, SyncStatusError } from './sync-errors';
 import { SYNC_PROTOCOL_V1 } from './sync-stream';
 
@@ -8,7 +8,8 @@ const FIRST_SERVER_ERROR_STATUS = 500;
 
 /** Returns null for failures not worth reporting, like being offline or the gateway being down. */
 export function syncFailureEvent(error: unknown, acks: string[]): ReportEvent | null {
-  const payload = { protocol: SYNC_PROTOCOL_V1, acks, message: describeError(error) };
+  // The gateway truncates the message, and the failed query's params would push the cause out.
+  const payload = { protocol: SYNC_PROTOCOL_V1, acks, message: `${rootCause(error)}` };
 
   if (error instanceof SyncStatusError && error.status < FIRST_SERVER_ERROR_STATUS) {
     return { type: 'SyncFailedHTTPStatusV1', payload: { ...payload, status: error.status } };

src/lib/utils/logger.ts

@@ -45,3 +45,8 @@ export const appLogger = new Logger('APP', logLevel);
 export function describeError(error: unknown): string {
   return error instanceof Error && error.cause ? `${error} (cause: ${error.cause})` : `${error}`;
 }
+
+export function rootCause(error: unknown): unknown {
+  while (error instanceof Error && error.cause) error = error.cause;
+  return error;
+}