1 files changed, 46 insertions, 0 deletions
diff --git a/js/promise_util.ts b/js/promise_util.ts
new file mode 100644
index 000000000..a550bc388
--- /dev/null
+++ b/js/promise_util.ts
@@ -0,0 +1,46 @@
+import { PromiseRejectEvent } from "./libdeno";
+
+/* tslint:disable-next-line:no-any */
+const rejectMap = new Map<Promise<any>, string>();
+// For uncaught promise rejection errors
+
+/* tslint:disable-next-line:no-any */
+const otherErrorMap = new Map<Promise<any>, string>();
+// For reject after resolve / resolve after resolve errors
+
+export function promiseRejectHandler(
+  error: Error | string,
+  event: PromiseRejectEvent,
+  /* tslint:disable-next-line:no-any */
+  promise: Promise<any>
+) {
+  switch (event) {
+    case "RejectWithNoHandler":
+      rejectMap.set(promise, (error as Error).stack || "RejectWithNoHandler");
+      break;
+    case "HandlerAddedAfterReject":
+      rejectMap.delete(promise);
+      break;
+    default:
+      // error is string here
+      otherErrorMap.set(promise, `Promise warning: ${error as string}`);
+  }
+}
+
+// Return true when continue, false to die on uncaught promise reject
+export function promiseErrorExaminer(): boolean {
+  if (otherErrorMap.size > 0) {
+    for (const msg of otherErrorMap.values()) {
+      console.log(msg);
+    }
+    otherErrorMap.clear();
+  }
+  if (rejectMap.size > 0) {
+    for (const msg of rejectMap.values()) {
+      console.log(msg);
+    }
+    rejectMap.clear();
+    return false;
+  }
+  return true;
+}