lib: include cached modules in module.children

`module.children` is supposed to be the list of modules included by this
module but lib/module.js failed to update the list when the included
module was retrieved from `Module._cache`.

Fixes: https://github.com/nodejs/node/issues/7131
PR-URL: https://github.com/nodejs/node/pull/14132
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/test/parallel/test-module-children.js b/test/parallel/test-module-children.js
new file mode 100644
index 0000000000..9eec14fda6
--- /dev/null
+++ b/test/parallel/test-module-children.js
@@ -0,0 +1,13 @@
+// Flags: --no-deprecation
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+
+const dir = path.join(common.fixturesDir, 'GH-7131');
+const b = require(path.join(dir, 'b'));
+const a = require(path.join(dir, 'a'));
+
+assert.strictEqual(a.length, 1);
+assert.strictEqual(b.length, 0);
+assert.deepStrictEqual(a[0].exports, b);