fix: await optional file database saves

src/features/ConfigSync/CmdConfigSync.completion.unit.spec.ts

@@ -0,0 +1,220 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+
+vi.mock("@/deps.ts", () => ({
+    addIcon: vi.fn(),
+    diff_match_patch: class DiffMatchPatch {},
+    normalizePath: vi.fn((path: string) => path),
+    parseYaml: vi.fn(),
+    Platform: {},
+}));
+vi.mock("./PluginDialogModal.ts", () => ({
+    PluginDialogModal: class PluginDialogModal {},
+}));
+vi.mock("@/features/HiddenFileCommon/JsonResolveModal.ts", () => ({
+    JsonResolveModal: class JsonResolveModal {},
+}));
+vi.mock("@/modules/features/InteractiveConflictResolving/ConflictResolveModal.ts", () => ({
+    ConflictResolveModal: class ConflictResolveModal {},
+}));
+// The readiness helpers come from the real LiveSyncCommands, so only its log view dependency is replaced.
+vi.mock("@/modules/features/ModuleLog.ts", () => ({
+    MARK_DONE: "",
+}));
+vi.mock("@/common/types.ts", () => ({
+    ICXHeader: "ix:",
+    PERIODIC_PLUGIN_SWEEP: 60,
+}));
+vi.mock("@/common/utils.ts", () => ({
+    cancelTask: vi.fn(),
+    EVEN: Symbol("even"),
+    isCustomisationSyncMetadata: vi.fn(),
+    isPluginMetadata: vi.fn(),
+    scheduleTask: vi.fn(),
+}));
+vi.mock("@/common/PeriodicProcessor.ts", () => ({
+    PeriodicProcessor: class PeriodicProcessor {},
+}));
+vi.mock("@/common/events.ts", () => ({
+    EVENT_REQUEST_OPEN_PLUGIN_SYNC_DIALOG: "open-plugin-sync",
+    eventHub: {
+        onEvent: vi.fn(),
+    },
+}));
+vi.mock("@/common/translation", () => ({
+    $msg: vi.fn((message: string) => message),
+}));
+vi.mock("@/common/obsidianCommunityPlugins.ts", () => ({
+    getObsidianCommunityPluginManager: vi.fn(),
+}));
+
+import type { FilePath } from "@vrtmrz/livesync-commonlib/compat/common/types";
+import { getDocData } from "@vrtmrz/livesync-commonlib/compat/common/utils";
+import { ConfigSync } from "./CmdConfigSync";
+import { createOptionalFileSyncDatabase } from "../../../test/fixtures/optionalFileSyncDatabase";
+
+const path = ".obsidian/snippets/test.css" as FilePath;
+const fixtures: Awaited<ReturnType<typeof createOptionalFileSyncDatabase>>[] = [];
+
+async function createConfigSync(useV2 = false) {
+    const fixture = await createOptionalFileSyncDatabase();
+    fixtures.push(fixture);
+    fixture.settings.usePluginSyncV2 = useV2;
+    const files = new Map<string, { content: string; mtime: number }>([
+        [path, { content: "body { color: red; }", mtime: 2000 }],
+    ]);
+    const storageAccess = {
+        statHidden: vi.fn(async (file: string) => {
+            const entry = files.get(file);
+            return entry
+                ? { type: "file" as const, ctime: 1000, mtime: entry.mtime, size: entry.content.length }
+                : null;
+        }),
+        readHiddenFileBinary: vi.fn(async (file: string) => {
+            const entry = files.get(file);
+            if (!entry) throw new Error(`Missing fixture: ${file}`);
+            return new TextEncoder().encode(entry.content).buffer;
+        }),
+    };
+    const services = {
+        ...fixture.services,
+        appLifecycle: { isReady: () => false, isSuspended: () => true },
+        database: { ...fixture.services.database, isDatabaseReady: vi.fn(() => true) },
+        path: {
+            ...fixture.services.path,
+            isMarkedAsSameChanges: vi.fn(),
+            markChangesAreSame: vi.fn(),
+        },
+    };
+    const config = Object.create(ConfigSync.prototype) as ConfigSync;
+    Object.assign(config, {
+        core: { settings: fixture.settings, localDatabase: fixture.localDatabase, storageAccess, services },
+        _log: vi.fn(),
+        updatePluginList: vi.fn(async () => undefined),
+        updatePluginListV2: vi.fn(async () => undefined),
+        recentProcessedInternalFiles: [],
+    });
+    const databasePath = useV2 ? config.filenameWithUnifiedKey(path) : config.filenameToUnifiedKey(path);
+    return { fixture, config, files, services, storageAccess, databasePath };
+}
+
+afterEach(async () => {
+    vi.restoreAllMocks();
+    for (const fixture of fixtures.splice(0)) await fixture.dispose();
+});
+
+describe("Customisation Sync optional save completion", () => {
+    const flush = { whenFlushRequested: Promise.resolve() };
+
+    it("waits for the database write while the application is suspended or still starting", async () => {
+        const { fixture, config } = await createConfigSync();
+        let release!: () => void;
+        const gate = new Promise<void>((resolve) => {
+            release = resolve;
+        });
+        const put = fixture.localDatabase.putDBEntry.bind(fixture.localDatabase);
+        const spy = vi.spyOn(fixture.localDatabase, "putDBEntry").mockImplementation(async (...args) => {
+            await gate;
+            return await put(...args);
+        });
+        let completed = false;
+        const result = config._processOptionalFileEventWithResult(path, flush).then((outcome) => {
+            completed = true;
+            return outcome;
+        });
+        await vi.waitFor(() => expect(spy).toHaveBeenCalledOnce());
+        expect(completed).toBe(false);
+        release();
+        await expect(result).resolves.toEqual({ kind: "completed" });
+    });
+
+    it.each([false, true])("confirms identical contents and stores a same-time edit (V2: %s)", async (useV2) => {
+        const { fixture, config, databasePath, files } = await createConfigSync(useV2);
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({ kind: "completed" });
+        const first = await fixture.database.get(databasePath);
+        await config._processOptionalFileEventWithResult(path, flush);
+        expect((await fixture.database.get(databasePath))._rev).toBe(first._rev);
+        files.get(path)!.content = "body { color: tan; }";
+        await config._processOptionalFileEventWithResult(path, flush);
+        expect((await fixture.database.get(databasePath))._rev).not.toBe(first._rev);
+    });
+
+    it.each([
+        { useV2: false, throws: false },
+        { useV2: true, throws: false },
+        { useV2: false, throws: true },
+        { useV2: true, throws: true },
+    ])("rejects a failed write and permits the unchanged notification to retry: %j", async ({ useV2, throws }) => {
+        const { fixture, config, databasePath } = await createConfigSync(useV2);
+        const failure = new Error("temporary write failure");
+        const put = vi.spyOn(fixture.localDatabase, "putDBEntry");
+        if (throws) put.mockRejectedValueOnce(failure);
+        else put.mockResolvedValueOnce(false);
+        const failed = config._processOptionalFileEventWithResult(path, flush);
+        if (throws) await expect(failed).rejects.toBe(failure);
+        else await expect(failed).rejects.toThrow("Could not save customisation");
+        await expect(fixture.localDatabase.getDBEntry(databasePath)).resolves.toBe(false);
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({ kind: "completed" });
+        expect(put).toHaveBeenCalledTimes(2);
+        expect(await fixture.localDatabase.getDBEntry(databasePath)).not.toBe(false);
+    });
+
+    it.each([false, true])("confirms deletion and treats a repeated deletion as complete (V2: %s)", async (useV2) => {
+        const { fixture, config, databasePath, files } = await createConfigSync(useV2);
+        await config._processOptionalFileEventWithResult(path, flush);
+        files.delete(path);
+        const put = vi.spyOn(fixture.localDatabase, "putRaw");
+        put.mockResolvedValueOnce({ ok: false, id: "failed", rev: "" });
+        await expect(config._processOptionalFileEventWithResult(path, flush)).rejects.toThrow(
+            "Could not delete customisation"
+        );
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({ kind: "completed" });
+        const deleted = await fixture.database.get(databasePath);
+        expect("deleted" in deleted && deleted.deleted).toBe(true);
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({ kind: "completed" });
+        expect((await fixture.database.get(databasePath))._rev).toBe(deleted._rev);
+    });
+
+    it("distinguishes a different owner and unmet prerequisites", async () => {
+        const { config, services, storageAccess } = await createConfigSync();
+        await expect(config._processOptionalFileEventWithResult("notes.md" as FilePath, flush)).resolves.toEqual({
+            kind: "not-applicable",
+        });
+        services.database.isDatabaseReady.mockReturnValue(false);
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({
+            kind: "veto",
+            value: "database-not-ready",
+        });
+        services.database.isDatabaseReady.mockReturnValue(true);
+        vi.spyOn(services.setting, "getDeviceAndVaultName").mockReturnValue("");
+        await expect(config._processOptionalFileEventWithResult(path, flush)).resolves.toEqual({
+            kind: "veto",
+            value: "device-name-not-configured",
+        });
+        expect(storageAccess.readHiddenFileBinary).not.toHaveBeenCalled();
+    });
+
+    it("preserves every V2 file when neighbouring plug-in files arrive together", async () => {
+        const { fixture, config, files } = await createConfigSync(true);
+        const main = ".obsidian/plugins/example/main.js" as FilePath;
+        const style = ".obsidian/plugins/example/styles.css" as FilePath;
+        files.set(main, { content: "module.exports = {};", mtime: 3000 });
+        files.set(style, { content: "body {}", mtime: 3000 });
+        await Promise.all([
+            config._processOptionalFileEventWithResult(main, flush),
+            config._processOptionalFileEventWithResult(style, flush),
+        ]);
+        expect(await fixture.localDatabase.getDBEntry(config.filenameWithUnifiedKey(main))).not.toBe(false);
+        expect(await fixture.localDatabase.getDBEntry(config.filenameWithUnifiedKey(style))).not.toBe(false);
+    });
+
+    it("does not acknowledge a database deletion which was not accepted", async () => {
+        const { fixture, config, databasePath } = await createConfigSync();
+        await config.storeCustomizationFiles(path);
+        const original = await fixture.localDatabase.getDBEntry(databasePath);
+        expect(original).not.toBe(false);
+        vi.spyOn(fixture.localDatabase, "putRaw").mockResolvedValueOnce({ ok: false, id: "failed", rev: "" });
+        await expect(config.deleteConfigOnDatabase(databasePath)).resolves.toBe(false);
+        const unchanged = await fixture.localDatabase.getDBEntry(databasePath);
+        expect(unchanged && getDocData(unchanged.data)).toBe(original && getDocData(original.data));
+    });
+});

src/features/ConfigSync/CmdConfigSync.ts

@@ -69,6 +69,10 @@ import { LiveSyncError } from "@vrtmrz/livesync-commonlib/compat/common/LSError"
 import type { OptionalSyncFeatureMode } from "@/features/optionalSyncFeatures.ts";
 import { getObsidianCommunityPluginManager } from "@/common/obsidianCommunityPlugins.ts";
 
+import type { HandlerOutcome } from "@vrtmrz/livesync-commonlib/compat/services/lib/HandlerUtils";
+import type { OptionalFileEventOptions } from "@vrtmrz/livesync-commonlib/compat/services/base/IService";
+import { PendingConfigSaves } from "./PendingConfigSaves";
+
 const d = "\u200b";
 const d2 = "\n";
 const UPDATED_CONFIGURATION_NOTICE_KEY = "config-sync:updated-configuration";
@@ -1206,7 +1210,7 @@ export class ConfigSync extends LiveSyncCommands {
     }
 
     recentProcessedInternalFiles = [] as string[];
-    async makeEntryFromFile(path: FilePath): Promise<false | PluginDataExFile> {
+    async makeEntryFromFile(path: FilePath, requireCompletion = false): Promise<false | PluginDataExFile> {
         const stat = await this.core.storageAccess.statHidden(path);
         let version: string | undefined;
         let displayName: string | undefined;
@@ -1240,6 +1244,7 @@ export class ConfigSync extends LiveSyncCommands {
         } catch (ex) {
             this._log(`The file ${path} could not be encoded`);
             this._log(ex, LOG_LEVEL_VERBOSE);
+            if (requireCompletion) throw ex;
             return false;
         }
         const mtime = stat.mtime;
@@ -1254,6 +1259,15 @@ export class ConfigSync extends LiveSyncCommands {
     }
 
     async storeCustomisationFileV2(path: FilePath, term: string, force = false) {
+        return await this.storeCustomisationFileV2Core(path, term, force, false);
+    }
+
+    private async storeCustomisationFileV2Core(
+        path: FilePath,
+        term: string,
+        force: boolean,
+        requireCompletion: boolean
+    ) {
         const vf = this.filenameWithUnifiedKey(path, term);
         return await serialized(`plugin-${vf}`, async () => {
             const prefixedFileName = vf;
@@ -1261,7 +1275,8 @@ export class ConfigSync extends LiveSyncCommands {
             const id = await this.path2id(prefixedFileName);
             const stat = await this.core.storageAccess.statHidden(path);
             if (!stat) {
-                return false;
+                if (!requireCompletion) return false;
+                return await this.deleteConfigOnDatabaseCore(vf, force, true);
             }
             const mtime = stat.mtime;
             const content = await this.core.storageAccess.readHiddenFileBinary(path);
@@ -1285,7 +1300,10 @@ export class ConfigSync extends LiveSyncCommands {
                         eden: {},
                     };
                 } else {
-                    if (this.services.path.isMarkedAsSameChanges(prefixedFileName, [old.mtime, mtime + 1]) == EVEN) {
+                    if (
+                        !requireCompletion &&
+                        this.services.path.isMarkedAsSameChanges(prefixedFileName, [old.mtime, mtime + 1]) == EVEN
+                    ) {
                         this._log(
                             `STORAGE --> DB:${prefixedFileName}: (config) Skipped (Already checked the same)`,
                             LOG_LEVEL_DEBUG
@@ -1300,7 +1318,7 @@ export class ConfigSync extends LiveSyncCommands {
                     const dataStart = dataSrc.indexOf(DUMMY_END);
                     const oldContent = dataSrc.substring(dataStart + DUMMY_END.length);
                     const oldContentArray = base64ToArrayBuffer(oldContent);
-                    if (await isDocContentSame(oldContentArray, content)) {
+                    if (!old.deleted && (await isDocContentSame(oldContentArray, content))) {
                         this._log(
                             `STORAGE --> DB:${prefixedFileName}: (config) Skipped (the same content)`,
                             LOG_LEVEL_VERBOSE
@@ -1320,24 +1338,36 @@ export class ConfigSync extends LiveSyncCommands {
                     };
                 }
                 const ret = await this.localDatabase.putDBEntry(saveData);
+                if (requireCompletion && (!ret || !ret.ok))
+                    throw new LiveSyncError(`Could not save customisation: ${path}`);
                 this._log(`STORAGE --> DB:${prefixedFileName}: (config) Done`);
                 fireAndForget(() => this.updatePluginListV2(false, this.filenameWithUnifiedKey(path)));
                 return ret;
             } catch (ex) {
                 this._log(`STORAGE --> DB:${prefixedFileName}: (config) Failed`);
                 this._log(ex, LOG_LEVEL_VERBOSE);
+                if (requireCompletion) throw ex;
                 return false;
             }
         });
     }
     async storeCustomizationFiles(path: FilePath, termOverRide?: string) {
+        return await this.storeCustomizationFilesCore(path, termOverRide, false);
+    }
+
+    private async storeCustomizationFilesCore(
+        path: FilePath,
+        termOverRide: string | undefined,
+        requireCompletion: boolean
+    ) {
         const term = termOverRide || this.services.setting.getDeviceAndVaultName();
         if (term == "") {
             this._log($msg("We have to configure the device name"), LOG_LEVEL_NOTICE);
+            if (requireCompletion) throw new LiveSyncError("The device name is not configured");
             return;
         }
         if (this.useV2) {
-            return await this.storeCustomisationFileV2(path, term);
+            return await this.storeCustomisationFileV2Core(path, term, false, requireCompletion);
         }
         const vf = this.filenameToUnifiedKey(path, term);
         // console.warn(`Storing ${path} to ${bareVF} :--> ${keyedVF}`);
@@ -1378,7 +1408,7 @@ export class ConfigSync extends LiveSyncCommands {
                 fileTargets = ["manifest.json", "theme.css"].map((e) => `${parentPath}/${e}` as FilePath);
             }
             for (const target of fileTargets) {
-                const data = await this.makeEntryFromFile(target);
+                const data = await this.makeEntryFromFile(target, requireCompletion);
                 if (data == false) {
                     this._log(`Config: skipped (Possibly is not exist): ${target} `, LOG_LEVEL_VERBOSE);
                     continue;
@@ -1398,9 +1428,9 @@ export class ConfigSync extends LiveSyncCommands {
             // this._log(`Configuration saving: ${prefixedFileName}`);
             if (dt.files.length == 0) {
                 this._log(`Nothing left: deleting.. ${path}`);
-                await this.deleteConfigOnDatabase(prefixedFileName);
+                const deleted = await this.deleteConfigOnDatabaseCore(prefixedFileName, false, requireCompletion);
                 await this.updatePluginList(false, prefixedFileName);
-                return;
+                return requireCompletion ? deleted : undefined;
             }
 
             const content = createTextBlob(serialize(dt));
@@ -1422,7 +1452,7 @@ export class ConfigSync extends LiveSyncCommands {
                         eden: {},
                     };
                 } else {
-                    if (old.mtime == mtime) {
+                    if (!requireCompletion && old.mtime == mtime) {
                         // this._log(`STORAGE --> DB:${prefixedFileName}: (config) Skipped (Same time)`, LOG_LEVEL_VERBOSE);
                         return true;
                     }
@@ -1443,7 +1473,7 @@ export class ConfigSync extends LiveSyncCommands {
                                     }
                                 });
                             const isSame = (await Promise.all(diffs)).every((e) => e == true);
-                            if (isSame) {
+                            if (isSame && !old.deleted) {
                                 this._log(
                                     `STORAGE --> DB:${prefixedFileName}: (config) Skipped (Same content)`,
                                     LOG_LEVEL_VERBOSE
@@ -1464,16 +1494,51 @@ export class ConfigSync extends LiveSyncCommands {
                     };
                 }
                 const ret = await this.localDatabase.putDBEntry(saveData);
+                if (requireCompletion && (!ret || !ret.ok))
+                    throw new LiveSyncError(`Could not save customisation: ${path}`);
                 await this.updatePluginList(false, saveData.path);
                 this._log(`STORAGE --> DB:${prefixedFileName}: (config) Done`);
                 return ret;
             } catch (ex) {
                 this._log(`STORAGE --> DB:${prefixedFileName}: (config) Failed`);
                 this._log(ex, LOG_LEVEL_VERBOSE);
+                if (requireCompletion) throw ex;
                 return false;
             }
         });
     }
+    private pendingOptionalSaves?: PendingConfigSaves;
+
+    async _processOptionalFileEventWithResult(
+        path: FilePath,
+        options?: OptionalFileEventOptions
+    ): Promise<HandlerOutcome<void, string>> {
+        if (!this.isThisModuleEnabled() || !this.isTargetPath(path)) return { kind: "not-applicable" };
+        const configDir = normalizePath(this.configDir);
+        const handledElsewhere = Object.values(this.settings.pluginSyncExtendedSetting)
+            .filter((entry) => entry.mode !== MODE_SELECTIVE && entry.mode !== MODE_SHINY)
+            .flatMap((entry) => entry.files)
+            .some((file) => `${configDir}/${file}`.toLowerCase().startsWith(path.toLowerCase()));
+        if (handledElsewhere) return { kind: "not-applicable" };
+        if (!this._isDatabaseReady()) return { kind: "veto", value: "database-not-ready" };
+        const term = this.services.setting.getDeviceAndVaultName();
+        if (!term) return { kind: "veto", value: "device-name-not-configured" };
+        const stat = await this.core.storageAccess.statHidden(path);
+        if (stat && stat.type !== "file") return { kind: "not-applicable" };
+
+        // V1 saves a complete file group; V2 persists each file separately.
+        const key = this.useV2 ? this.filenameWithUnifiedKey(path, term) : this.filenameToUnifiedKey(path, term);
+        this.pendingOptionalSaves ??= new PendingConfigSaves();
+        await this.pendingOptionalSaves.enqueue(
+            key,
+            async () => {
+                await this.storeCustomizationFilesCore(path, term, true);
+            },
+            options?.whenFlushRequested
+        );
+        return { kind: "completed" };
+    }
+
     async _anyProcessOptionalFileEvent(path: FilePath): Promise<boolean> {
         return await this.watchVaultRawEventsAsync(path);
     }
@@ -1615,6 +1680,14 @@ export class ConfigSync extends LiveSyncCommands {
     }
 
     async deleteConfigOnDatabase(prefixedFileName: FilePathWithPrefix, forceWrite = false) {
+        return await this.deleteConfigOnDatabaseCore(prefixedFileName, forceWrite, false);
+    }
+
+    private async deleteConfigOnDatabaseCore(
+        prefixedFileName: FilePathWithPrefix,
+        forceWrite: boolean,
+        requireCompletion: boolean
+    ) {
         // const id = await this.path2id(prefixedFileName);
         const mtime = new Date().getTime();
         return await serialized("file-x-" + prefixedFileName, async () => {
@@ -1640,13 +1713,15 @@ export class ConfigSync extends LiveSyncCommands {
                         type: "newnote",
                     };
                 }
-                await this.localDatabase.putRaw(saveData);
+                const result = await this.localDatabase.putRaw(saveData);
+                if (!result.ok) throw new LiveSyncError(`Could not delete customisation: ${prefixedFileName}`);
                 await this.updatePluginList(false, prefixedFileName);
                 this._log(`STORAGE -x> DB:${prefixedFileName}: (config) Done`);
                 return true;
             } catch (ex) {
                 this._log(`STORAGE -x> DB:${prefixedFileName}: (config) Failed`);
                 this._log(ex, LOG_LEVEL_VERBOSE);
+                if (requireCompletion) throw ex;
                 return false;
             }
         });
@@ -1756,6 +1831,9 @@ export class ConfigSync extends LiveSyncCommands {
     }
     override onBindFunction(core: LiveSyncCore, services: InjectableServiceHub): void {
         services.fileProcessing.processOptionalFileEvent.addHandler(this._anyProcessOptionalFileEvent.bind(this));
+        services.fileProcessing.processOptionalFileEventWithResult?.addHandler(
+            this._processOptionalFileEventWithResult.bind(this)
+        );
         services.conflict.getOptionalConflictCheckMethod.addHandler(this._anyGetOptionalConflictCheckMethod.bind(this));
         services.replication.processVirtualDocument.addHandler(this._anyModuleParsedReplicationResultItem.bind(this));
         services.setting.onRealiseSetting.addHandler(this._everyRealizeSettingSyncMode.bind(this));

src/features/ConfigSync/PendingConfigSaves.ts

@@ -0,0 +1,49 @@
+import { compatGlobal, type CompatTimeoutHandle } from "@vrtmrz/livesync-commonlib/compat/common/coreEnvFunctions";
+
+type PendingSave = {
+    save: () => Promise<void>;
+    completion: Promise<void>;
+    resolve: () => void;
+    reject: (error: unknown) => void;
+    timer?: CompatTimeoutHandle;
+    started: boolean;
+};
+
+/** Owns the quiet-period delay and completion of coalesced customisation saves. */
+export class PendingConfigSaves {
+    private readonly pending = new Map<string, PendingSave>();
+
+    enqueue(key: string, save: () => Promise<void>, whenFlushRequested?: Promise<void>): Promise<void> {
+        let group = this.pending.get(key);
+        if (!group) {
+            let resolve!: () => void;
+            let reject!: (error: unknown) => void;
+            const completion = new Promise<void>((onResolve, onReject) => {
+                resolve = onResolve;
+                reject = onReject;
+            });
+            group = { save, completion, resolve, reject, started: false };
+            this.pending.set(key, group);
+        } else {
+            group.save = save;
+            if (group.timer !== undefined) compatGlobal.clearTimeout(group.timer);
+        }
+        const captured = group;
+        group.timer = compatGlobal.setTimeout(() => this.run(key, captured), 100);
+        // Capture this group: a late flush of an earlier event must not release
+        // a newer group which happens to use the same customisation key.
+        void whenFlushRequested?.then(
+            () => this.run(key, captured),
+            () => {}
+        );
+        return group.completion;
+    }
+
+    private run(key: string, group: PendingSave): void {
+        if (group.started) return;
+        group.started = true;
+        if (group.timer !== undefined) compatGlobal.clearTimeout(group.timer);
+        this.pending.delete(key);
+        void Promise.resolve().then(group.save).then(group.resolve, group.reject);
+    }
+}

src/features/ConfigSync/PendingConfigSaves.unit.spec.ts

@@ -0,0 +1,84 @@
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { PendingConfigSaves } from "./PendingConfigSaves";
+
+function deferred() {
+    let resolve!: () => void;
+    let reject!: (error: unknown) => void;
+    const promise = new Promise<void>((onResolve, onReject) => {
+        resolve = onResolve;
+        reject = onReject;
+    });
+    return { promise, resolve, reject };
+}
+
+afterEach(() => vi.useRealTimers());
+
+describe("pending customisation saves", () => {
+    it("retains the quiet period and completes every coalesced notification after the actual save", async () => {
+        vi.useFakeTimers();
+        const pending = new PendingConfigSaves();
+        const save = deferred();
+        const firstSave = vi.fn(async () => {});
+        const lastSave = vi.fn(() => save.promise);
+        const first = pending.enqueue("plugin", firstSave);
+        await vi.advanceTimersByTimeAsync(80);
+        const second = pending.enqueue("plugin", lastSave);
+        let completed = false;
+        const all = Promise.all([first, second]).then(() => {
+            completed = true;
+        });
+        await vi.advanceTimersByTimeAsync(99);
+        expect(lastSave).not.toHaveBeenCalled();
+        await vi.advanceTimersByTimeAsync(1);
+        expect(firstSave).not.toHaveBeenCalled();
+        expect(lastSave).toHaveBeenCalledOnce();
+        expect(completed).toBe(false);
+        save.resolve();
+        await all;
+        expect(completed).toBe(true);
+    });
+
+    it("flushes the captured group without waiting for or releasing later notifications", async () => {
+        vi.useFakeTimers();
+        const pending = new PendingConfigSaves();
+        const flush = deferred();
+        const lateFlush = deferred();
+        const firstSave = deferred();
+        const work = vi.fn(() => firstSave.promise);
+        const first = pending.enqueue("plugin", work, flush.promise);
+        const coalesced = pending.enqueue("plugin", work, lateFlush.promise);
+        flush.resolve();
+        await vi.advanceTimersByTimeAsync(0);
+        expect(work).toHaveBeenCalledOnce();
+        const nextWork = vi.fn(async () => {});
+        const later = pending.enqueue("plugin", nextWork);
+        lateFlush.resolve();
+        await vi.advanceTimersByTimeAsync(0);
+        expect(nextWork).not.toHaveBeenCalled();
+        firstSave.resolve();
+        await Promise.all([first, coalesced]);
+        expect(nextWork).not.toHaveBeenCalled();
+        await vi.advanceTimersByTimeAsync(100);
+        await later;
+        expect(nextWork).toHaveBeenCalledOnce();
+    });
+
+    it("rejects every coalesced notification with the original failure and permits a later retry", async () => {
+        vi.useFakeTimers();
+        const pending = new PendingConfigSaves();
+        const failure = new Error("database write failed");
+        const save = async () => {
+            throw failure;
+        };
+        const first = pending.enqueue("plugin", save);
+        const second = pending.enqueue("plugin", save);
+        const outcomes = Promise.allSettled([first, second]);
+        await vi.advanceTimersByTimeAsync(100);
+        expect(await outcomes).toEqual([
+            { status: "rejected", reason: failure },
+            { status: "rejected", reason: failure },
+        ]);
+        const retry = pending.enqueue("plugin", async () => {}, Promise.resolve());
+        await retry;
+    });
+});