feat: port release-v2 experience improvements from #6582 (audited subset) (#6609)

packages/integrations/src/base/response-contract.ts

@@ -0,0 +1,51 @@
+export type ResponseContractParser<TResult> = (response: { json: () => Promise<unknown> }) => Promise<TResult>;
+
+export interface ResponseContractFixture<TResult> {
+  name: string;
+  payload: unknown;
+  expected?: TResult;
+  rejects?: true;
+}
+
+/**
+ * Runs JSON-like fixtures through the same parser used by an integration.
+ * This keeps contribution fixtures transport-free and deterministic while
+ * still exercising schema validation and response mapping.
+ */
+export const simulateResponseContractAsync = async <TParsed, TResult = TParsed>(
+  parser: ResponseContractParser<TParsed>,
+  fixtures: readonly ResponseContractFixture<TResult>[],
+  map: (parsed: TParsed) => TResult = (parsed) => parsed as unknown as TResult,
+) => {
+  const results: { name: string; passed: boolean; message?: string }[] = [];
+
+  for (const fixture of fixtures) {
+    try {
+      const parsed = await parser({ json: () => Promise.resolve(structuredClone(fixture.payload)) });
+      if (fixture.rejects) {
+        results.push({
+          name: fixture.name,
+          passed: false,
+          message: "Expected parser rejection, but parsing succeeded.",
+        });
+        continue;
+      }
+      const actual = map(parsed);
+      const passed = "expected" in fixture ? isDeepStrictEqual(actual, fixture.expected) : true;
+      results.push({
+        name: fixture.name,
+        passed,
+        message: passed ? undefined : "Parsed output did not match expected.",
+      });
+    } catch (error) {
+      results.push({
+        name: fixture.name,
+        passed: fixture.rejects === true,
+        message: fixture.rejects ? undefined : error instanceof Error ? error.message : String(error),
+      });
+    }
+  }
+
+  return results;
+};
+import { isDeepStrictEqual } from "node:util";