Add a test for CommonJS caching behavior

Summary: Adds a test demonstrating that identical `require()` calls in the same basic block can return different values in the presence of circular dependencies.

Reviewed By: avp

Differential Revision: D25223184

fbshipit-source-id: 00c823b1f03e9f6f663ba56b089dc8624b1d0ba1

test/hermes/cjs/cjs-caching-1.js

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: %hermes -O0 -commonjs %S/cjs-caching-1.js %S/cjs-caching-2.js %S/cjs-caching-3.js | %FileCheck --match-full-lines %s
+// RUN: %hermes -O -fstatic-require -commonjs %S/cjs-caching-1.js %S/cjs-caching-2.js %S/cjs-caching-3.js | %FileCheck --match-full-lines %s
+// RUN: %hermes -O -commonjs %S/cjs-caching-1.js %S/cjs-caching-2.js %S/cjs-caching-3.js | %FileCheck --match-full-lines %s
+
+const copy1 = require('./cjs-caching-2.js');
+copy1.recreateExports();
+const copy2 = require('./cjs-caching-2.js');
+print('With no dependency cycle:');
+print(copy1 === copy2 ? 'Copies are equal' : 'Copies are different');
+
+// CHECK: With a dependency cycle:
+// CHECK-NEXT: Copies are different
+// CHECK-NEXT: With no dependency cycle:
+// CHECK-NEXT: Copies are equal

test/hermes/cjs/cjs-caching-2.js

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: true
+
+function recreateExports() {
+  module.exports = {recreateExports};
+}
+
+recreateExports();
+
+require('./cjs-caching-3.js');

test/hermes/cjs/cjs-caching-3.js

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// RUN: true
+
+const copy1 = require('./cjs-caching-2.js');
+copy1.recreateExports();
+const copy2 = require('./cjs-caching-2.js');
+print('With a dependency cycle:');
+print(copy1 === copy2 ? 'Copies are equal' : 'Copies are different');