An album whose folder cannot be made no longer stops the backup (closes #197)

Each album's folder, links and JSON are written inside one try. A failure
prints `FAILED album <name>: <reason>`, lists the album's ID in the new
`failedAlbums` of the result and of `--json`, and makes `quak backup` exit 1;
the other albums and `failures.json` are still written.

An album whose folder would have another album's JSON name, ignoring case,
gets its ID. A name over 255 bytes (250 for a folder, which leaves room for
`.json`) gets the ID and is cut short between two characters by
`shortenToBytes` in `src/filename.ts`. A link's ID goes right before its
extension.

Apart from its call to `uniqueNames`, the album loop is only indented into
the try.

Model: opus-5-5

README.md

@@ -815,11 +815,12 @@ directory would have the name of another collection's JSON, again ignoring case,
 gets its ID added as well: beside an album `x`, whose JSON is `x.json`, an album
 named `x.json` gets the directory `x.json (12)/`. A name too long for a file
 name, which most file systems limit to 255 bytes, gets its ID added too. A name
-with its ID added is cut short between two characters, just far enough that it
-fits: first the part before the ID, and once nothing is left of that, a
-symlink's extension. A collection's directory name also leaves room for the
-`.json` its JSON adds. IDs never change, so a name stays the same from run to
-run until such a clash appears or goes away.
+with its ID added is cut short between two characters in the part before the ID,
+just far enough that it fits. When a symlink's extension alone leaves no room
+for the ID, the extension is cut short and the part before the ID keeps only the
+bytes that cut leaves over. A collection's directory name also leaves room for
+the `.json` its JSON adds. IDs never change, so a name stays the same from run
+to run until such a clash appears or goes away.
 
 A collection whose directory or JSON cannot be written, such as one whose
 directory name is taken by a file you put in `collections/`, does not stop the

src/backup.ts

@@ -276,10 +276,12 @@ const rebuildSymlink = (linkPath: string, target: string): void => {
 // case (two names that differ only in case are one entry on a case-insensitive
 // file system), or it is too long for a file name; then it gets ` (<id>)`,
 // right before the extension when `beforeExtension` is set. To fit, the part
-// before the ID is cut short as far as it must be, and once nothing is left of
-// it, so is the extension. With `withJSON`, each entry also has the JSON file
-// `<name>.json` beside it, as an album does: a name then leaves room for
-// `.json`, and one that is another entry's JSON name gets its ID added too.
+// before the ID is cut short as far as it must be. When the extension alone
+// leaves no room for the ID, the extension is cut short and the part before
+// the ID keeps only the bytes that cut leaves over. With `withJSON`, each
+// entry also has the JSON file `<name>.json` beside it, as an album does: a
+// name then leaves room for `.json`, and one that is another entry's JSON name
+// gets its ID added too.
 // Two names with different IDs added never match, but one can match another
 // entry's own name (`IMG (6).JPG`), so this repeats until no name is shared.
 // IDs are stable, so the names are too.

test/cli/backup.test.ts

@@ -1737,27 +1737,35 @@ describe("backup album folders", () => {
         expect(readLedger(outDir).files["5"]).toMatchObject({ attempts: 1 });
     });
 
-    // The extension of this title is 303 bytes, so it leaves no room for the
-    // ID: nothing is left of the name before the ID, and the extension is cut
-    // short after it. The extension holds a "-", so the original is saved
-    // with `.bin`, a name that fits.
+    // The extensions of these titles leave no room for the ID, so each is cut
+    // short and the name before the ID keeps only the bytes that cut leaves
+    // over. File 1's extension is 303 bytes and is cut to 251, which leaves
+    // none. File 2's is 271 bytes and is cut to 250, since "€" takes three
+    // bytes, which leaves one, for the "a". Neither extension is only letters
+    // and digits, so both originals are saved with `.bin`, a name that fits.
     it("cuts the extension of a title short when it leaves no room for the ID", async () => {
         const outDir = join(root, "backup");
         const lib = libraryOf([
             {
                 collection: collection(10, "Trip"),
-                files: [file(1, 10, `a.${"L".repeat(300)}-x`)],
+                files: [
+                    file(1, 10, `a.${"L".repeat(300)}-x`),
+                    file(2, 10, `a.${"€".repeat(90)}`),
+                ],
             },
         ]);
 
         const result = await runBackup(lib, { downloadDirectory: outDir });
 
         const link = ` (1).${"L".repeat(250)}`;
+        const link2 = `a (2).${"€".repeat(83)}`;
         expect(Buffer.byteLength(link)).toBe(255);
+        expect(Buffer.byteLength(link2)).toBe(255);
         expect(result.failed).toBe(0);
         expect(tree(outDir)).toEqual([
             "Trip/",
             `Trip/${link} -> ${linkTo("1.bin")}`,
+            `Trip/${link2} -> ${linkTo("2.bin")}`,
             "Trip.json",
         ]);
     });