fix(cli): an unreadable registry says so instead of crashing

cli/package.json

@@ -36,7 +36,7 @@
     "node": ">=22.12"
   },
   "packageManager": "pnpm@12.3.4",
-  "bundleBudgetKB": 601,
+  "bundleBudgetKB": 603,
   "scripts": {
     "build": "tsup && node scripts/check-bundle-size.mjs",
     "build:check-size": "node scripts/check-bundle-size.mjs",

cli/scripts/check-bundle-size.mjs

@@ -24,6 +24,11 @@ const pkg = JSON.parse(readFileSync(resolve(root, "package.json"), "utf8"));
 // display and the subcommand. It deletes 198 lines from a plugin, which the bundle does
 // not carry either way - the trade is a plugin script that had drifted for bytes that are
 // measured. Same 2.2 KB headroom as the three raises before it.
+// 603 was set when a marketplace registry that cannot be read began saying so: measured
+// 600.7 -> 601.2 KB, +0.5 KB for one guard and the sentence it prints. The smallest raise so
+// far, for the smallest change - and the one that showed the budget had 0.3 KB of headroom
+// left, which is less than a correctness fix costs. Same 2.2 KB headroom as the four raises
+// before it.
 const budgetKB = pkg.bundleBudgetKB ?? 500;
 const budgetBytes = budgetKB * 1024;
 

cli/src/infrastructure/adapters/marketplace-registry-adapter.ts

@@ -16,6 +16,31 @@ interface RegistryFile {
   marketplaces: MarketplaceData[];
 }
 
+/** A registry file that exists but cannot be read as one is never read as an empty
+ * registry. `save()` reads this same list, appends to it and writes the whole file back, so
+ * a silent empty read would not merely hide the marketplaces a person registered - it would
+ * delete them on the very next write. A file that is simply absent is a different answer and
+ * keeps its own: no file, no marketplaces, nothing to lose. */
+function unreadable(path: string, reason: string): Error {
+  return new Error(
+    `Cannot read the marketplace registry at ${path}: ${reason}. Repair the file, or ` +
+      `delete it to start from an empty registry.`
+  );
+}
+
+/** The registry's own list, or the reason the file cannot supply one. */
+function registryEntries(raw: string, path: string): MarketplaceData[] {
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(raw);
+  } catch (error) {
+    throw unreadable(path, error instanceof Error ? error.message : "it is not valid JSON");
+  }
+  const entries = (parsed as Partial<RegistryFile> | null)?.marketplaces;
+  if (!Array.isArray(entries)) throw unreadable(path, "it carries no \`marketplaces\` list");
+  return entries;
+}
+
 export class MarketplaceRegistryAdapter implements MarketplaceRegistry {
   async list(projectRoot: string): Promise<readonly Marketplace[]> {
     const project = await this.read(this.projectPath(projectRoot), "project");
@@ -85,8 +110,7 @@ export class MarketplaceRegistryAdapter implements MarketplaceRegistry {
     } catch {
       return [];
     }
-    const parsed = JSON.parse(raw) as RegistryFile;
-    return parsed.marketplaces.map((m) => Marketplace.fromJSON({ ...m, scope }));
+    return registryEntries(raw, path).map((m) => Marketplace.fromJSON({ ...m, scope }));
   }
 
   private async write(path: string, entries: readonly Marketplace[]): Promise<void> {

cli/tests/infrastructure/adapters/marketplace-registry-adapter.integration.test.ts

@@ -43,6 +43,37 @@ describe("MarketplaceRegistryAdapter", () => {
       expect(result).toEqual([]);
     });
 
+    // A registry file that exists but does not hold the list is not an empty registry, and
+    // reading it as one is how a person loses every marketplace they registered: `save()`
+    // reads this same list, appends to it and writes the whole file back, so one silent
+    // empty read turns into a file with one entry where there were five. Found on a real
+    // `~/.config/aidd/marketplaces.json` holding `{"version":1}`, which crashed
+    // `aidd marketplace list` with "Cannot read properties of undefined (reading 'map')" -
+    // a stack trace naming nothing a person can act on.
+    it("refuses a registry file that carries no list, naming the file rather than crashing", async () => {
+      const userFile = join(homeDir, ".config", "aidd", "marketplaces.json");
+      await mkdir(join(homeDir, ".config", "aidd"), { recursive: true });
+      await writeFile(userFile, '{"version":1}', "utf-8");
+
+      await expect(adapter.list(projectRoot)).rejects.toThrow(userFile);
+    });
+
+    it("refuses a registry file that is not JSON at all, naming the file", async () => {
+      const userFile = join(homeDir, ".config", "aidd", "marketplaces.json");
+      await mkdir(join(homeDir, ".config", "aidd"), { recursive: true });
+      await writeFile(userFile, "not json", "utf-8");
+
+      await expect(adapter.list(projectRoot)).rejects.toThrow(userFile);
+    });
+
+    it("reads a registry file whose list is present and empty as an empty registry", async () => {
+      const userFile = join(homeDir, ".config", "aidd", "marketplaces.json");
+      await mkdir(join(homeDir, ".config", "aidd"), { recursive: true });
+      await writeFile(userFile, '{"version":1,"marketplaces":[]}', "utf-8");
+
+      await expect(adapter.list(projectRoot)).resolves.toEqual([]);
+    });
+
     it("returns project entries first, user entries after", async () => {
       const project = Marketplace.fromJSON(baseData({ name: "p1" }));
       const user = Marketplace.fromJSON(baseData({ name: "u1", scope: "user" }));