Make backup wait for the server refresh and fail when it fails (closes #99)

lib.backup() refreshed through the background loop's refresh, which returns
at once when one is already running and swallows a failure, so a backup
could run on the previous file list, or on an empty cache, and exit 0. It
now uses the refresh fresh() uses: it joins a running refresh or starts
one, and rejects before touching any file when it fails. The CLI's error
wrapper prints that as one line and exits 1.

Model: opus-5-5

TODO.md

@@ -18,6 +18,13 @@ Tag v1.0.0.
 
 # Completed Steps
 
+- 2026-09-23: `quak backup` waits for the server refresh and fails when it fails
+  (issue 99). `lib.backup()` joins a refresh already running or starts one, as
+  `fresh()` does, and rejects before touching any file when it fails, leaving
+  `failures.json` as it was, so `quak backup` prints the error as one line and
+  exits 1 instead of backing up the previous run's file list, or nothing, and
+  exiting 0.
+
 - 2026-09-23: CLI errors print a message instead of a stack trace (issue 102).
   An error a command throws is printed as one `quak: MESSAGE` line on stderr and
   the CLI exits 1 once output has drained. The wrapper that does this moved from

src/backup.ts

@@ -1,9 +1,10 @@
 // The backup command, rebuilt on the library API (issue #51).
 //
-// `lib.backup()` refreshes the library, then, for every file in scope, gets its
-// original bytes onto disk under `downloadDirectory` and rebuilds the derived
-// views (per-file sidecars, per-collection symlink trees, per-collection JSON)
-// from the model. The on-disk layout is the historical one, unchanged:
+// `lib.backup()` waits for a completed refresh of the library (a failed one
+// fails the backup before any file is touched), then, for every file in scope,
+// gets its original bytes onto disk under `downloadDirectory` and rebuilds the
+// derived views (per-file sidecars, per-collection symlink trees,
+// per-collection JSON) from the model. The on-disk layout is the historical one, unchanged:
 //
 //     <downloadDirectory>/
 //         originals/<fileID>.<ext>     the decrypted bytes

src/library/index.ts

@@ -538,11 +538,13 @@ export class Library {
     }
 
     // Back up every in-scope file to `downloadDirectory` in the historical
-    // on-disk layout, with a durable failure ledger (issue #51). Refreshes
-    // first, fetches pending originals (and optional thumbnails) through the
-    // content cache and pools, then rebuilds the derived symlink/JSON views
-    // from the model. Throws before any network work when no download directory
-    // is available or no content cache backs the originals it must fetch.
+    // on-disk layout, with a durable failure ledger (issue #51). Waits for a
+    // completed refresh first, as `fresh()` does, joining one already running,
+    // and rejects before touching any file when it fails. Then fetches pending
+    // originals (and optional thumbnails) through the content cache and pools,
+    // and rebuilds the derived symlink/JSON views from the model. Throws before
+    // any network work when no download directory is available or no content
+    // cache backs the originals it must fetch.
     backup(opts?: BackupOptions): Promise<BackupResult> {
         const downloadDirectory =
             opts?.downloadDirectory ?? this.downloadDirectory;
@@ -566,7 +568,7 @@ export class Library {
         const cache = this.cache;
         return runBackup(
             {
-                refresh: () => this.runRefresh(),
+                refresh: () => this.refreshNow(),
                 listCollections: () => this.store.listCollections(),
                 listFiles: (id) => this.store.listFiles(id),
                 original: (fileID) => cache!.original(fileID),

test/cli/backup.test.ts

@@ -625,6 +625,93 @@ describe("lib.backup", () => {
     });
 });
 
+// Every refresh fails, as with an expired session or no network.
+class FailingClient extends MockClient {
+    override async collectionsSince(): Promise<CollectionsPage> {
+        throw new Error("HTTP 401 from server");
+    }
+}
+
+// Holds its refresh open until `release()` is called, then reports a third
+// album, so a backup can be started while that refresh is still running.
+class HeldClient extends MockClient {
+    release!: () => void;
+    private held = new Promise<void>((resolve) => {
+        this.release = resolve;
+    });
+    override async collectionsSince(): Promise<CollectionsPage> {
+        await this.held;
+        return {
+            collections: [collection(3, "Later")],
+            deleted: [],
+            cursor: 2,
+        };
+    }
+    override async filesSince(args: {
+        collectionID: number;
+    }): Promise<FilesPage> {
+        if (args.collectionID !== 3) return super.filesSince(args);
+        return { files: [file(300, 3, "late.jpg")], deleted: [], cursor: 2 };
+    }
+}
+
+// Fill the library cache on disk, so the next open starts its refresh in the
+// background instead of waiting for it.
+const fillCache = async (): Promise<void> => {
+    const lib = await openLibrary(stubSource());
+    await lib.close();
+};
+
+describe("the refresh before a backup", () => {
+    it("waits for a refresh already running and backs up what it found", async () => {
+        await fillCache();
+        const client = new HeldClient();
+        const lib = await openLibrary(stubSource(), client);
+        const outDir = join(root, "backup");
+
+        const backup = lib.backup({ downloadDirectory: outDir });
+        client.release();
+        const result = await backup;
+
+        expect(result.totalFiles).toBe(4);
+        expect(existsSync(join(outDir, "originals", "300.jpg"))).toBe(true);
+        await lib.close();
+    });
+
+    it("fails before any download when the refresh fails, leaving failures.json as it was", async () => {
+        await fillCache();
+        const outDir = join(root, "backup");
+        seedLedger(outDir, 100, "beach.jpg");
+        const ledgerPath = join(outDir, "failures.json");
+        const ledgerBefore = readFileSync(ledgerPath, "utf-8");
+        const source = stubSource();
+        const lib = await openLibrary(source, new FailingClient());
+
+        await expect(lib.backup({ downloadDirectory: outDir })).rejects.toThrow(
+            "HTTP 401 from server",
+        );
+
+        expect(source.originalCalls).toBe(0);
+        expect(readFileSync(ledgerPath, "utf-8")).toBe(ledgerBefore);
+        expect(existsSync(join(outDir, "originals"))).toBe(false);
+        await lib.close();
+    });
+
+    it("fails when the refresh fails on an empty cache, instead of backing up nothing", async () => {
+        const source = stubSource();
+        const lib = await openLibrary(source, new FailingClient());
+        const outDir = join(root, "backup");
+
+        await expect(lib.backup({ downloadDirectory: outDir })).rejects.toThrow(
+            "HTTP 401 from server",
+        );
+
+        expect(source.originalCalls).toBe(0);
+        expect(existsSync(outDir)).toBe(false);
+        await lib.close();
+    });
+});
+
 // The album folders under collections/, driven through `runBackup` with a
 // stand-in library whose albums a test changes between runs.
 describe("backup album folders", () => {

test/cli/commands.test.ts

@@ -20,6 +20,7 @@ import {
 } from "node:fs";
 import { join } from "node:path";
 import { tmpdir } from "node:os";
+import { PassThrough } from "node:stream";
 import { describe, it, expect, beforeAll, beforeEach, afterEach } from "vitest";
 
 import {
@@ -34,6 +35,7 @@ import {
     backupCommand,
     listMissingThumbnailsCommand,
 } from "../../src/cli-commands.js";
+import { run } from "../../src/cli-run.js";
 import { loadSession } from "../../src/cli-session.js";
 import type { Client, ClientSnapshot } from "../../src/client.js";
 import type { ContentSource } from "../../src/library/content.js";
@@ -430,6 +432,34 @@ describe("backup", () => {
         expect(result.errors[0].fileID).toBe(101);
         expect(stderr.text).toBe("Starting backup...\n");
     });
+
+    it("exits 1 with the error on one line when the refresh fails", async () => {
+        const client = {
+            ...fakeClient(),
+            collectionsSince: async () => {
+                throw new Error("HTTP 401 from server");
+            },
+        } as unknown as Client;
+        const dir = join(root, "backup");
+        // Through `run`, as `bin/quak.ts` does, which prints a thrown error.
+        const runStderr = new PassThrough();
+        let runText = "";
+        runStderr.on("data", (chunk: Buffer) => {
+            runText += chunk.toString();
+        });
+        const code = await new Promise<number>((resolve) => {
+            void run(
+                backupCommand(context(client), dir, {}),
+                new PassThrough(),
+                runStderr,
+                resolve,
+            );
+        });
+        expect(code).toBe(1);
+        expect(runText).toBe("quak: HTTP 401 from server\n");
+        expect(stderr.text).toBe("Starting backup...\nRefreshing library...\n");
+        expect(existsSync(join(dir, "originals"))).toBe(false);
+    });
 });
 
 describe("helper list-missing-thumbnails", () => {