fix(scripts): disable Rollup externalLiveBindings to fix Jest auto-mocking (#7767)

When the CJS inliner bundles a client, variant files (e.g. runtimeConfig
with react-native counterparts) and their transitive dependencies are
kept as Rollup externals. By default, Rollup re-exports these externals
using lazy Object.defineProperty getters:

  Object.defineProperty(exports, k, {
    enumerable: true,
    get: function () { return external[k]; }
  });

Jest's auto-mock (jest.mock()) snapshots module exports at mock-creation
time. Lazy getters haven't resolved yet at that point, so all re-exported
symbols (models, enums, exceptions) become undefined in tests.

Setting externalLiveBindings: false makes Rollup emit eager assignments:

  exports[k] = external[k];

This is semantically equivalent for CJS (live bindings only matter for
ESM circular imports) and allows Jest to see all exports immediately.

Author: TrevorBurnham

Makefile

@@ -53,6 +53,7 @@ test-schema: bundles
 test-integration: bundles
 	rm -rf ./clients/client-sso/node_modules/\@smithy # todo(yarn) incompatible redundant nesting.
 	node ./scripts/validation/no-generic-byte-arrays.js
+	node ./scripts/compilation/Inliner.spec.js
 	yarn g:vitest run -c vitest.config.integ.mts
 	make test-protocols
 	make test-types

scripts/compilation/Inliner.js

@@ -226,6 +226,7 @@ module.exports = class Inliner {
       format: "cjs",
       exports: "named",
       preserveModules: false,
+      externalLiveBindings: false,
     };
 
     const bundle = await rollup.rollup(inputOptions(variantExternalsForRollup));

scripts/compilation/Inliner.spec.js

@@ -0,0 +1,54 @@
+const assert = require("assert");
+const path = require("path");
+const fs = require("fs");
+
+/**
+ * Verify that the Inliner's Rollup output uses eager bindings
+ * for external re-exports (externalLiveBindings: false).
+ *
+ * When externalLiveBindings is true (the default), Rollup emits:
+ *   Object.defineProperty(exports, k, { enumerable: true, get: function () { return ext[k]; } });
+ *
+ * These lazy getters break Jest's auto-mocking because jest.mock()
+ * snapshots exports at mock-creation time, before the getters resolve.
+ *
+ * With externalLiveBindings: false, Rollup emits:
+ *   exports[k] = ext[k];
+ *
+ * which Jest can auto-mock correctly.
+ *
+ * See: https://github.com/aws/aws-sdk-js-v3/issues/7748
+ */
+
+// Test 1: Verify the Inliner source contains externalLiveBindings: false
+const inlinerSource = fs.readFileSync(path.join(__dirname, "Inliner.js"), "utf-8");
+assert.ok(
+  inlinerSource.includes("externalLiveBindings: false"),
+  "Inliner.js must set externalLiveBindings: false in Rollup outputOptions"
+);
+
+// Test 2: If a built client-dynamodb dist-cjs/index.js exists, verify no lazy getter re-exports
+const dynamoIndexPath = path.join(__dirname, "..", "..", "clients", "client-dynamodb", "dist-cjs", "index.js");
+if (fs.existsSync(dynamoIndexPath)) {
+  const indexContents = fs.readFileSync(dynamoIndexPath, "utf-8");
+
+  // Match the lazy getter pattern Rollup emits with externalLiveBindings: true
+  const lazyGetterPattern = /Object\.defineProperty\(exports,\s*k,\s*\{[^}]*get:\s*function/g;
+  const matches = indexContents.match(lazyGetterPattern);
+
+  assert.strictEqual(
+    matches,
+    null,
+    "dist-cjs/index.js must not contain lazy Object.defineProperty getter re-exports. " +
+      "Found " +
+      (matches?.length ?? 0) +
+      " occurrences. " +
+      "Ensure externalLiveBindings: false is set in Rollup outputOptions."
+  );
+
+  console.log("PASS: dist-cjs/index.js has no lazy getter re-exports.");
+} else {
+  console.log("SKIP: client-dynamodb dist-cjs/index.js not found (not built).");
+}
+
+console.log("PASS: Inliner.js has externalLiveBindings: false.");