1 files changed, 33 insertions, 0 deletions
diff --git a/lib/internal/loader/ModuleMap.js b/lib/internal/loader/ModuleMap.js
new file mode 100644
index 00000000000..aa238afbaed
--- /dev/null
+++ b/lib/internal/loader/ModuleMap.js
@@ -0,0 +1,33 @@
+'use strict';
+
+const ModuleJob = require('internal/loader/ModuleJob');
+const { SafeMap } = require('internal/safe_globals');
+const debug = require('util').debuglog('esm');
+const errors = require('internal/errors');
+
+// Tracks the state of the loader-level module cache
+class ModuleMap extends SafeMap {
+  get(url) {
+    if (typeof url !== 'string') {
+      throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'url', 'string');
+    }
+    return super.get(url);
+  }
+  set(url, job) {
+    if (typeof url !== 'string') {
+      throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'url', 'string');
+    }
+    if (job instanceof ModuleJob !== true) {
+      throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'job', 'ModuleJob');
+    }
+    debug(`Storing ${url} in ModuleMap`);
+    return super.set(url, job);
+  }
+  has(url) {
+    if (typeof url !== 'string') {
+      throw new errors.TypeError('ERR_INVALID_ARG_TYPE', 'url', 'string');
+    }
+    return super.has(url);
+  }
+}
+module.exports = ModuleMap;