fix(ci): accept empty successful promotion responses

scripts/deploy-vercel.mjs

@@ -5,7 +5,7 @@ import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
 import { randomUUID } from "node:crypto";
-import { activateDeployment, findDeployment, waitForDeployment } from "./deployment-status.mjs";
+import { activateDeployment, findDeployment, readProviderResult, waitForDeployment } from "./deployment-status.mjs";
 
 const root = path.resolve(import.meta.dirname, "..");
 const localStaging = process.argv.includes("--local-staging");
@@ -70,9 +70,7 @@ async function providerApi(endpoint, cwd, project, token, label, method = "GET")
     ...(method === "POST" ? { body: "{}" } : {}),
     signal: AbortSignal.timeout(30_000),
   });
-  if (!response.ok) throw new Error(`${label} provider lookup failed (${response.status}).`);
-  if (response.status === 204) return {};
-  return response.json();
+  return readProviderResult(response, label, { empty: method === "POST" });
 }
 
 async function confirmReady(cwd, project, token, label, commit, run) {

scripts/deployment-status.mjs

@@ -1,4 +1,12 @@
 /** Confirm provider state instead of trusting the CLI's deployment snapshot. */
+export async function readProviderResult(response, label, { empty = false } = {}) {
+  if (!response.ok) throw new Error(`${label} provider request failed (${response.status}).`);
+  // Promotion returns a successful empty 200 response, not a JSON document.
+  if (empty || response.status === 204) return {};
+  try { return await response.json(); }
+  catch { throw new Error(`${label} provider returned invalid JSON.`); }
+}
+
 export async function activateDeployment(id, {
   project, label, read, promote, maxAttempts = 30, intervalMs = 2000,
   sleep = ms => new Promise(resolve => setTimeout(resolve, ms)),

scripts/deployment-status.test.mjs

@@ -1,10 +1,18 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { activateDeployment, findDeployment, waitForDeployment } from "./deployment-status.mjs";
+import { activateDeployment, findDeployment, readProviderResult, waitForDeployment } from "./deployment-status.mjs";
 
 const id = "dpl_test123";
 const options = { label: "Backend", intervalMs: 0, maxAttempts: 3 };
 
+test("successful empty promotion responses are accepted while lookups require JSON", async () => {
+  assert.deepEqual(await readProviderResult(new Response(null, { status: 200 }), "Promotion", { empty: true }), {});
+  assert.deepEqual(await readProviderResult(new Response(null, { status: 204 }), "Promotion"), {});
+  assert.deepEqual(await readProviderResult(Response.json({ id }), "Lookup"), { id });
+  await assert.rejects(readProviderResult(new Response(null, { status: 200 }), "Lookup"), /invalid JSON/);
+  await assert.rejects(readProviderResult(new Response(null, { status: 403 }), "Promotion", { empty: true }), /request failed \(403\)/);
+});
+
 test("already-current production builds do not request a conflicting promotion", async () => {
   await activateDeployment(id, { ...options, project: "project", read: async () => ({ id: "project", targets: { production: { id } } }),
     promote: async () => assert.fail("already-current deployments must not be promoted again") });