README.md

@@ -137,12 +137,12 @@ matters.
 
 ### Exit codes
 
-| Code | Meaning                                                                                                                                                                                                        |
-| ---- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `0`  | The backup is complete: every original is at its save path, and no file failed.                                                                                                                                |
-| `1`  | The run finished with files in `failures.json` or albums it could not decrypt or write (see "Backup layout"), or it stopped on another error, printed as one line `quak: <message>`. The next run tries again. |
-| `2`  | Another backup of the same directory is running. This run sent no request and changed nothing.                                                                                                                 |
-| `3`  | There is no usable session: none is saved, the saved one is corrupt, or the server no longer accepts it. Run `quak login` as the user the cron job runs as.                                                    |
+| Code | Meaning                                                                                                                                                                                                                                         |
+| ---- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `0`  | The backup is complete: every original is at its save path, and no file failed.                                                                                                                                                                 |
+| `1`  | The run finished with files in `failures.json` or albums it could not decrypt or write (see "Backup layout"), and its last line says how many, or it stopped on another error, printed as one line `quak: <message>`. The next run tries again. |
+| `2`  | Another backup of the same directory is running. This run sent no request and changed nothing.                                                                                                                                                  |
+| `3`  | There is no usable session: none is saved, the saved one is corrupt, or the server no longer accepts it. Run `quak login` as the user the cron job runs as.                                                                                     |
 
 `<message>` is the error's message, followed by the message of each error that
 caused it. Under Node, as `yarn quak` runs quak, `fetch` reports every failure
@@ -695,8 +695,31 @@ own directory under the per-user cache path.
 prints on stderr is a log line at one of six levels, from the quietest: fatal,
 error, warning, info, debug and trace. A run prints the lines at its own level
 and at every quieter one. stdout holds only the command's output, at every
-level, and `--json` changes stdout only, so a run with `--json` logs the same
-lines on stderr as one without it.
+level.
+
+- Every command that exits non-zero logs a fatal line saying why, such as
+  `quak: <message>`, `Not logged in`, an invalid ID or a collection that does
+  not exist. A command that exits 1 because files or albums failed logs it last,
+  saying how many failed and where to look: `backup` points to `failures.json`
+  and its `FAILED` lines, `backup-metadata` to the `mlDataError` in the JSON of
+  each such file, and `helper fix-missing-thumbnails` to its `Failed files:`
+  list, or to its JSON with `--json`.
+- An error line reports something that failed: the `FAILED` lines that `backup`
+  and `helper fix-missing-thumbnails` log as they work,
+  `ML data of file <id> could not be read` and
+  `ML data request for <n> file(s) failed` from `backup-metadata`,
+  `Could not check <title>` from both thumbnail helpers, and the `Failed files:`
+  list at the end of `backup` and of `helper fix-missing-thumbnails`.
+- A warning reports something that did not fail but needs your attention: after
+  `logout`, that the cache directory still holds decrypted data.
+- Every other line quak logs by default is info.
+
+With `--json`, a command's result on stdout takes the place of its summary on
+stderr: for `backup`, the lines from `--- Backup complete ---` to the end of its
+`Failed files:` list; for `helper list-missing-thumbnails`,
+`No missing thumbnails found.` or `<n> file(s) with missing thumbnails:`; and
+for `helper fix-missing-thumbnails`, the lines from `--- Done ---` to the end of
+its `Failed files:` list. Every other line is logged as it is without `--json`.
 
 - With neither option the level is info: the lines quak prints as it works, such
   as a refresh's progress, the files a backup fetches, its summary and the files
@@ -709,12 +732,9 @@ lines on stderr as one without it.
   URL of an upload of a thumbnail is logged without its query, which holds the
   upload's signature. More repeats stay at trace, and `--verbose --verbose` is
   `-vv`.
-- `-q` lowers it to fatal: quak prints only the line a command prints as it
-  fails and exits non-zero, such as `quak: <message>`, `Not logged in`, an
-  invalid ID or a collection that does not exist. A file that fails inside
-  `backup` is not fatal: it is in `failures.json` and in the exit code, and
-  nothing is printed for it. The prompts of `login` are not log lines, and `-q`
-  leaves them as they are.
+- `-q` lowers it to fatal: a run that exits 0 prints nothing on stderr, and one
+  that exits non-zero prints only its fatal lines. The prompts of `login` are
+  not log lines, and `-q` leaves them as they are.
 
 `-q` with `-v` is refused with one line,
 `error: option '-q, --quiet' cannot be used with option '-v, --verbose'`, and
@@ -772,7 +792,7 @@ fails, the error is logged, each of its files is written with the reason in an
 `mlDataError` field instead of `mlData`, and the dump goes on. A file whose ML
 data does not decrypt, gunzip or parse is logged and written the same way, with
 why in `mlDataError`. The exit code is non-zero if any file was written with
-`mlDataError`.
+`mlDataError`, and the last line then says how many were.
 
 `helper fix-missing-thumbnails` regenerates thumbnails for JPEG images only,
 because the bundled decoder (`jpeg-js`) decodes only JPEG. A non-JPEG image

TODO.md

@@ -36,7 +36,10 @@ declares one.
   end of each refresh and ML data fetch; trace adds each request, which
   `ApiClient` reports through the new `onRequest`. `--json` no longer keeps the
   progress lines off stderr, so `backup` and `--json` runs log a refresh's
-  progress too.
+  progress too. Every line that reports a failed file or album is at error,
+  which the progress callbacks of `backup`, `backup-metadata` and the thumbnail
+  helpers now say, and a command that exits 1 because files or albums failed
+  ends with one fatal line saying how many and where to look.
 
 - 2026-10-18: `quak files` takes the collection ID as an optional argument
   instead of the `--collection` option, which is gone

src/backup.ts

@@ -101,7 +101,10 @@ import type { MLData } from "./mldata-fetch.js";
 import type { Collection, EnteFile, FileMetadata } from "./model/types.js";
 import { hasTransportCode } from "./retry.js";
 
-export type ProgressCallback = (message: string) => void;
+// Reports one line of the backup's progress. `level` is "error" when the line
+// reports something that failed, such as a file or an album, and is left out
+// for every other line.
+export type ProgressCallback = (message: string, level?: "error") => void;
 
 // The lock in a backup directory, as `lockBackupDirectory` returns it.
 export interface BackupLock {
@@ -654,7 +657,7 @@ const runLockedBackup = async (
     for (const record of lib.undecryptable()) {
         const error = `could not be decrypted: ${record.error}`;
         if (record.fileID === undefined) {
-            log(`FAILED album ${record.collectionID}: ${error}`);
+            log(`FAILED album ${record.collectionID}: ${error}`, "error");
             undecryptableAlbums.push(record.collectionID);
         } else if (scope.has(record.collectionID)) {
             const copies = memberships.get(record.fileID);
@@ -699,6 +702,7 @@ const runLockedBackup = async (
             } catch (err) {
                 log(
                     `FAILED verifying original ${file.metadata.title}: ${describeError(err)}`,
+                    "error",
                 );
                 recordFailure(
                     file.id,
@@ -732,6 +736,7 @@ const runLockedBackup = async (
         } catch (err) {
             log(
                 `FAILED original ${file.metadata.title}: ${describeError(err)}`,
+                "error",
             );
             recordFailure(
                 file.id,
@@ -807,7 +812,7 @@ const runLockedBackup = async (
             await lib.fetchMLData();
         } catch (err) {
             mlDataFailure = err;
-            log(`FAILED ML data: ${describeError(err)}`);
+            log(`FAILED ML data: ${describeError(err)}`, "error");
         }
         for (const file of distinct.values()) {
             if (lock.lost) throw lock.lost;
@@ -868,7 +873,10 @@ const runLockedBackup = async (
             downloadDirectory,
         );
     } catch (err) {
-        log(`FAILED removing old album directories: ${describeError(err)}`);
+        log(
+            `FAILED removing old album directories: ${describeError(err)}`,
+            "error",
+        );
     }
 
     // An album whose folder or JSON cannot be written, such as one whose
@@ -897,6 +905,7 @@ const runLockedBackup = async (
             } catch (err) {
                 log(
                     `FAILED removing old links in ${c.name}: ${describeError(err)}`,
+                    "error",
                 );
             }
 
@@ -915,6 +924,7 @@ const runLockedBackup = async (
                 } catch (err) {
                     log(
                         `FAILED symlink ${c.name}/${linkName}: ${describeError(err)}`,
+                        "error",
                     );
                     recordFailure(
                         link.file.id,
@@ -931,7 +941,7 @@ const runLockedBackup = async (
                 metaFiles,
             );
         } catch (err) {
-            log(`FAILED album ${c.name}: ${describeError(err)}`);
+            log(`FAILED album ${c.name}: ${describeError(err)}`, "error");
             failedAlbums.push(c.id);
         }
     }

src/cli-commands.ts

@@ -5,8 +5,9 @@
 // `process.exit`: `bin/quak.ts` wires these to the command line, and `run` in
 // `cli-run.ts` prints a thrown error as one line and exits once output has
 // drained. Output must stay byte-identical (see `cli-output.ts`). Each line on
-// stderr goes through `ctx.log` at its level (see `cli-log.ts`); a line a
-// command prints as it fails with a non-zero exit code is fatal.
+// stderr goes through `ctx.log` at its level (see `cli-log.ts`). Every command
+// that exits non-zero logs a fatal line saying why; one that exits 1 because
+// files or albums failed logs it last, saying how many and where to look.
 
 import {
     copyFileSync,
@@ -414,9 +415,14 @@ export const backupMetadataCommand = async (
         await lib.fresh();
         const result = await runMetadataBackup(lib, client, dir, {
             exif: opts.exif || opts.all,
-            onProgress: (msg) => ctx.log("info", msg),
+            onProgress: (msg, level) => ctx.log(level ?? "info", msg),
         });
-        return result.filesWithMLDataError > 0 ? 1 : 0;
+        if (result.filesWithMLDataError === 0) return 0;
+        ctx.log(
+            "fatal",
+            `quak: the ML data of ${result.filesWithMLDataError} file(s) could not be read; see mlDataError in their JSON in ${dir}`,
+        );
+        return 1;
     } finally {
         await lib.close();
     }
@@ -461,7 +467,7 @@ export const backupCommand = async (
                 downloadDirectory: dir,
                 lock,
                 verify: opts.verify,
-                onProgress: (msg) => ctx.log("info", msg),
+                onProgress: (msg, level) => ctx.log(level ?? "info", msg),
             });
 
             if (opts.json) {
@@ -488,11 +494,14 @@ export const backupCommand = async (
                 }
             }
 
-            return result.failed > 0 ||
-                result.undecryptableAlbums.length > 0 ||
-                result.failedAlbums.length > 0
-                ? 1
-                : 0;
+            const albums =
+                result.undecryptableAlbums.length + result.failedAlbums.length;
+            if (result.failed === 0 && albums === 0) return 0;
+            ctx.log(
+                "fatal",
+                `quak: ${result.failed} file(s) and ${albums} album(s) failed; see ${join(dir, "failures.json")} and the FAILED lines`,
+            );
+            return 1;
         } finally {
             await lib.close();
         }
@@ -513,8 +522,8 @@ export const listMissingThumbnailsCommand = async (
         // Refresh first so files added since the cache was written are
         // checked; a failed refresh throws.
         await lib.fresh();
-        const missing = await listMissingThumbnails(lib, client, (msg) =>
-            ctx.log("info", msg),
+        const missing = await listMissingThumbnails(lib, client, (msg, level) =>
+            ctx.log(level ?? "info", msg),
         );
 
         if (opts.json) {
@@ -561,8 +570,10 @@ export const fixMissingThumbnailsCommand = async (
         await lib.fresh();
         if (fileIDs.length === 0) {
             ctx.log("info", "Scanning for missing thumbnails...");
-            const missing = await listMissingThumbnails(lib, client, (msg) =>
-                ctx.log("info", msg),
+            const missing = await listMissingThumbnails(
+                lib,
+                client,
+                (msg, level) => ctx.log(level ?? "info", msg),
             );
             fileIDs = missing.map((m) => m.fileID);
             if (fileIDs.length === 0) {
@@ -576,9 +587,10 @@ export const fixMissingThumbnailsCommand = async (
             lib,
             client,
             fileIDs,
-            (msg) => ctx.log("info", msg),
+            (msg, level) => ctx.log(level ?? "info", msg),
         );
 
+        const failed = results.filter((r) => r.status === "failed").length;
         if (opts.json) {
             ctx.stdout.write(JSON.stringify(results, null, 2) + "\n");
         } else {
@@ -586,7 +598,6 @@ export const fixMissingThumbnailsCommand = async (
             const skipped = results.filter(
                 (r) => r.status === "skipped",
             ).length;
-            const failed = results.filter((r) => r.status === "failed").length;
             ctx.log("info", `\n--- Done ---`);
             ctx.log("info", `  Fixed:   ${fixed}`);
             ctx.log("info", `  Skipped: ${skipped}`);
@@ -605,7 +616,12 @@ export const fixMissingThumbnailsCommand = async (
             }
         }
 
-        return results.some((r) => r.status === "failed") ? 1 : 0;
+        if (failed === 0) return 0;
+        ctx.log(
+            "fatal",
+            `quak: ${failed} file(s) failed; see the "Failed files:" list, or the JSON with --json`,
+        );
+        return 1;
     } finally {
         await lib.close();
     }

src/cli-log.ts

@@ -4,9 +4,12 @@
 // Every line quak prints on stderr is a log line at one of six levels, from
 // the quietest: fatal, error, warning, info, debug, trace. A run prints the
 // lines at its own level and at every quieter one. Its level is info unless
-// `-v` or `-q` asks for another (see "CLI surface" in the README). A fatal line
-// is the one a command prints when it fails and exits non-zero, so even `-q`
-// prints it. stdout carries only a command's output and is not a log.
+// `-v` or `-q` asks for another (see "CLI surface" in the README). Every
+// command that exits non-zero logs a fatal line saying why, so even `-q`, which
+// prints only fatal lines, never leaves a non-zero exit unexplained. An error
+// line reports something that failed, such as a file or an album, and a
+// warning something that did not fail but needs the user's attention. stdout
+// carries only a command's output and is not a log.
 //
 // The library itself writes no lines: its layers report through callbacks, and
 // the CLI logs what they report. `logRequests` gives the API client options
@@ -66,6 +69,15 @@ export const logRequests = (
         ),
 });
 
+// How a log line names each operation the library reports the start and end
+// of.
+const OPERATION_NAMES: Record<RefreshEvent["operation"], string> = {
+    refresh: "Refresh",
+    fetchMLData: "ML data fetch",
+    precacheThumbnails: "Thumbnail precache",
+    precacheOriginals: "Original precache",
+};
+
 // A library `onProgress` that logs, at info, each collection whose files a
 // refresh has fetched, and at debug the start and end of each refresh and ML
 // data fetch, with the error of one that failed.
@@ -80,5 +92,8 @@ export const logRefresh =
             return;
         }
         const error = event.error === undefined ? "" : `: ${event.error}`;
-        log("debug", `${event.operation} ${event.status}${error}`);
+        log(
+            "debug",
+            `${OPERATION_NAMES[event.operation]} ${event.status}${error}`,
+        );
     };

src/metadata-backup.ts

@@ -17,7 +17,10 @@ import {
 } from "./mldata-fetch.js";
 import type { EnteFile } from "./model/types.js";
 
-export type ProgressCallback = (message: string) => void;
+// Reports one line of the dump's progress. `level` is "error" when the line
+// reports ML data that could not be read, and is left out for every other
+// line.
+export type ProgressCallback = (message: string, level?: "error") => void;
 
 export interface MetadataBackupOptions {
     exif?: boolean;
@@ -195,13 +198,17 @@ export const runMetadataBackup = async (
             for (const [id, payload] of payloads) mlDataMap.set(id, payload);
             for (const [id, err] of errors) {
                 const reason = describeError(err);
-                log(`ML data of file ${id} could not be read: ${reason}`);
+                log(
+                    `ML data of file ${id} could not be read: ${reason}`,
+                    "error",
+                );
                 mlDataErrors.set(id, reason);
             }
         } catch (err) {
             const reason = err instanceof Error ? err.message : String(err);
             log(
                 `ML data request for ${batch.length} file(s) failed: ${reason}`,
+                "error",
             );
             for (const id of batch) mlDataErrors.set(id, reason);
         }

src/thumbnails.ts

@@ -49,7 +49,10 @@ export interface ThumbnailFixResult {
     reason?: string;
 }
 
-export type ProgressCallback = (message: string) => void;
+// Reports one line of progress. `level` is "error" when the line reports a
+// file that could not be checked or fixed, and is left out for every other
+// line.
+export type ProgressCallback = (message: string, level?: "error") => void;
 
 // Enumerate every file the library knows about, newest album first, each file
 // once, and report those whose server-side thumbnail is missing. "Missing" is
@@ -111,6 +114,7 @@ export const listMissingThumbnails = async (
                 } else {
                     log(
                         `[${album.name}] Could not check ${photo.title}: ${err instanceof Error ? err.message : String(err)} (not reported as missing)`,
+                        "error",
                     );
                 }
             }
@@ -359,6 +363,7 @@ export const fixMissingThumbnails = async (
         } catch (err) {
             log(
                 `[${collectionName}] FAILED ${title}: ${err instanceof Error ? err.message : err}`,
+                "error",
             );
             results.push({
                 fileID,

test/cli/backup-undecryptable.test.ts

@@ -371,6 +371,24 @@ describe("quak backup with records it cannot decrypt", () => {
         expect(stderr.text).toContain("  Failed:      2\n");
     });
 
+    // The album is an error line. The last line is fatal and counts the files
+    // and the album, so `-q`, which prints fatal lines only, still says why
+    // the backup exits 1.
+    it("logs the album at error, and ends with one fatal line counting the files and the album", async () => {
+        const ctx = {
+            ...context(brokenAccount()),
+            log: stderrLog(stderr, "error"),
+        };
+        expect(await backupCommand(ctx, backupDir(), {})).toBe(1);
+
+        expect(stderr.text).toMatch(
+            /^FAILED album 2: could not be decrypted: /,
+        );
+        expect(stderr.text.split("\n").at(-2)).toBe(
+            `quak: 2 file(s) and 1 album(s) failed; see ${join(backupDir(), "failures.json")} and the FAILED lines`,
+        );
+    });
+
     it("names each album it cannot decrypt in the --json result", async () => {
         expect(await backup(brokenAccount(), { json: true })).toBe(1);
 

test/cli/commands.test.ts

@@ -913,6 +913,38 @@ describe("backup", () => {
         );
     });
 
+    // A failed file is an error line both where the backup fails it and in
+    // the list at the end. The last line is fatal, so `-q`, which prints
+    // fatal lines only, still says why the backup exits 1.
+    it("logs a failed file at error, and ends with one fatal line counting the failures", async () => {
+        const dir = join(root, "backup");
+        const last = `quak: 1 file(s) and 0 album(s) failed; see ${join(dir, "failures.json")} and the FAILED lines\n`;
+        const ctx = context(fakeClient({ failID: 101 }));
+        expect(
+            await backupCommand(
+                { ...ctx, log: stderrLog(stderr, "error") },
+                dir,
+                {},
+            ),
+        ).toBe(1);
+        expect(stderr.text).toBe(
+            "FAILED original sunset.jpg: HTTP 500 from server\n" +
+                "\nFailed files:\n" +
+                "  [Vacation] sunset.jpg (id 101): HTTP 500 from server\n" +
+                last,
+        );
+
+        stderr.text = "";
+        expect(
+            await backupCommand(
+                { ...ctx, log: stderrLog(stderr, "fatal") },
+                dir,
+                { json: true },
+            ),
+        ).toBe(1);
+        expect(stderr.text).toBe(last);
+    });
+
     // `--json` shapes stdout only: the log lines stay on stderr, and the JSON
     // takes the place of the summary.
     it("prints the result as JSON with --json, still exiting 1 on a failure", async () => {
@@ -1303,6 +1335,34 @@ describe("helper list-missing-thumbnails", () => {
     });
 });
 
+describe("helper fix-missing-thumbnails", () => {
+    // File 999 is in no album, so fixing it fails. The list of failed files
+    // is at error, and the last line is fatal, so `-q`, which prints fatal
+    // lines only, still says why the command exits 1.
+    it("lists a failed file at error, and ends with one fatal line counting the failures", async () => {
+        const last = `quak: 1 file(s) failed; see the "Failed files:" list, or the JSON with --json\n`;
+        const ctx = { ...context(), log: stderrLog(stderr, "error") };
+        expect(await fixMissingThumbnailsCommand(ctx, { file: ["999"] })).toBe(
+            1,
+        );
+        expect(stderr.text).toBe(
+            "\nFailed files:\n" +
+                "  999\tunknown\tfile not found in any collection\n" +
+                last,
+        );
+
+        stderr.text = "";
+        const quiet = { ...context(), log: stderrLog(stderr, "fatal") };
+        expect(
+            await fixMissingThumbnailsCommand(quiet, {
+                file: ["999"],
+                json: true,
+            }),
+        ).toBe(1);
+        expect(stderr.text).toBe(last);
+    });
+});
+
 describe("backup-metadata --exif", () => {
     // Runs the command and returns what it printed to stderr.
     const backupMetadata = async (opts: { exif?: boolean; all?: boolean }) => {

test/cli/log.test.ts

@@ -173,13 +173,13 @@ const FILES = "100\timage\tbeach.jpg\n";
 // line for the one album whose files it fetched. Debug adds the start and end
 // of the refresh, and trace each request with the status of its answer.
 const INFO = "Fetched the files of 1 of 1 collections\n";
-const DEBUG = "refresh started\n" + INFO + "refresh done\n";
+const DEBUG = "Refresh started\n" + INFO + "Refresh done\n";
 const TRACE =
-    "refresh started\n" +
+    "Refresh started\n" +
     "GET https://api.ente.io/collections/v2?sinceTime=0: HTTP 200\n" +
     "GET https://api.ente.io/collections/v2/diff?collectionID=1&sinceTime=0: HTTP 200\n" +
     INFO +
-    "refresh done\n";
+    "Refresh done\n";
 
 describe("the log level", () => {
     it("is info by default", async () => {
@@ -326,6 +326,7 @@ describe("what the library reports", () => {
         ]);
     });
 
+    // Each operation is named in plain words, as the README names it.
     it("logs a refresh's progress at info, and its start and end at debug", () => {
         const { log, lines } = collect();
         const onProgress = logRefresh(log);
@@ -342,13 +343,15 @@ describe("what the library reports", () => {
             status: "failed",
             error: "HTTP 503",
         });
+        onProgress({ operation: "fetchMLData", status: "started" });
         onProgress({ operation: "fetchMLData", status: "done", fetched: 3 });
 
         expect(lines).toEqual([
-            "debug: refresh started",
+            "debug: Refresh started",
             "info: Fetched the files of 1 of 2 collections",
-            "debug: refresh failed: HTTP 503",
-            "debug: fetchMLData done",
+            "debug: Refresh failed: HTTP 503",
+            "debug: ML data fetch started",
+            "debug: ML data fetch done",
         ]);
     });
 });

test/cli/metadata-backup.test.ts

@@ -47,7 +47,7 @@ import {
     type MetadataBackupOptions,
 } from "../../src/metadata-backup.js";
 import { backupMetadataCommand } from "../../src/cli-commands.js";
-import { stderrLog } from "../../src/cli-log.js";
+import { stderrLog, type LogLevel } from "../../src/cli-log.js";
 import {
     buildAccount,
     buildMetaFetch,
@@ -491,9 +491,12 @@ describe("quak backup-metadata", () => {
 });
 
 describe("quak backup-metadata when a file's ML data cannot be read", () => {
-    // Run the CLI command against `fetch`, the mock unless given, and return
-    // its exit code, stderr and output directory.
-    const runCommand = async (fetch = buildMetaFetch(mock)) => {
+    // Run the CLI command against `fetch`, the mock unless given, logging at
+    // `level`, and return its exit code, stderr and output directory.
+    const runCommand = async (
+        fetch = buildMetaFetch(mock),
+        level: LogLevel = "info",
+    ) => {
         const client = await Client.login({
             email: TEST_EMAIL,
             password: TEST_PASSWORD,
@@ -509,7 +512,7 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
                 stdout: { write: () => true },
                 log: stderrLog(
                     { write: (text: string) => (stderr += text) },
-                    "info",
+                    level,
                 ),
                 sessionDir: testDir,
                 cacheDir: mkdtempSync(join(testDir, "cache-")),
@@ -521,13 +524,16 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
         return { code, stderr, outDir };
     };
 
+    // The failed request is logged at error, so it is the first line printed
+    // at that level.
     it("writes every file, marks the failed batch's files, and exits 1", async () => {
         const { code, stderr, outDir } = await runCommand(
             buildMetaFetch(mock, 200),
+            "error",
         );
 
         expect(code).toBe(1);
-        expect(stderr).toContain("ML data request for 1 file(s) failed");
+        expect(stderr).toMatch(/^ML data request for 1 file\(s\) failed: /);
 
         const ok = JSON.parse(
             readFileSync(
@@ -550,7 +556,9 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
     });
 
     // The server sends ML data for diagram.png encrypted under a key that is
-    // not the file's, so quak cannot decrypt it.
+    // not the file's, so quak cannot decrypt it. That is logged at error, and
+    // the last line is fatal, so `-q`, which prints fatal lines only, still
+    // says why the command exits 1.
     it("writes the reason for ML data that does not decrypt, and exits 1", async () => {
         const otherKey = sodium.crypto_secretstream_xchacha20poly1305_keygen();
         const { header, ciphertext } = encryptBlob(
@@ -568,12 +576,14 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
                     },
                 },
             }),
+            "error",
         );
 
         expect(code).toBe(1);
         const reason = "secretstream chunk authentication failed";
-        expect(stderr).toContain(
-            `ML data of file 200 could not be read: ${reason}\n`,
+        expect(stderr).toBe(
+            `ML data of file 200 could not be read: ${reason}\n` +
+                `quak: the ML data of 1 file(s) could not be read; see mlDataError in their JSON in ${outDir}\n`,
         );
         const failed = JSON.parse(
             readFileSync(

test/thumbnails/thumbnails.test.ts

@@ -544,11 +544,22 @@ describe("listMissingThumbnails", () => {
         const client = await login(counted.fetch, { ...noWait });
         const lib = await openLib(client);
 
-        const missing = await listMissingThumbnails(lib, client);
+        const errors: string[] = [];
+        const missing = await listMissingThumbnails(
+            lib,
+            client,
+            (msg, level) => {
+                if (level === "error") errors.push(msg);
+            },
+        );
         lib.close();
 
-        // Only the genuinely empty thumbnail is reported.
+        // Only the genuinely empty thumbnail is reported. The file that
+        // could not be checked is reported as an error.
         expect(missing.map((m) => m.fileID)).toEqual([101]);
+        expect(errors).toEqual([
+            expect.stringMatching(/^\[.*\] Could not check file-102\.jpg: /),
+        ]);
         // And the 500 was retried rather than accepted as an answer: four
         // attempts is the library default.
         expect(counted.matched()).toBe(4);
@@ -699,7 +710,15 @@ describe("fixMissingThumbnails", () => {
         const client = await login(buildThumbFetch(fixMock));
         const lib = await openLib(client);
 
-        const results = await fixMissingThumbnails(lib, client, [101, 102]);
+        const errors: string[] = [];
+        const results = await fixMissingThumbnails(
+            lib,
+            client,
+            [101, 102],
+            (msg, level) => {
+                if (level === "error") errors.push(msg);
+            },
+        );
         lib.close();
 
         expect(results.length).toBe(2);
@@ -707,6 +726,10 @@ describe("fixMissingThumbnails", () => {
         const failure = results.find((r) => r.fileID === 102)!;
         expect(success.status).toBe("fixed");
         expect(failure.status).toBe("failed");
+        // The failed file, and only it, is reported as an error.
+        expect(errors).toEqual([
+            expect.stringMatching(/^\[.*\] FAILED file-102\.jpg: /),
+        ]);
     });
 
     it("skips a non-JPEG image and a video as unsupported, not failed (issue #17)", async () => {