From f4acb0e1226b63d789a129b7ae088e8fb5165473 Mon Sep 17 00:00:00 2001
From: Kris Zyp <kriszyp@gmail.com>
Date: Tue, 23 Jan 2024 09:21:08 -0700
Subject: [PATCH] Add support for asynchronous iteration with flatMap

---
 package.json          |  2 +-
 util/RangeIterable.js | 31 ++++++++++++++++++++++++++++---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/package.json b/package.json
index eecd88bf3..f9e08e805 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "lmdb",
   "author": "Kris Zyp",
-  "version": "2.9.3-beta.5-debug",
+  "version": "2.10.0-beta.1",
   "description": "Simple, efficient, scalable, high-performance LMDB interface",
   "license": "MIT",
   "repository": {
diff --git a/util/RangeIterable.js b/util/RangeIterable.js
index ce2bf6fd4..ab1c121d2 100644
--- a/util/RangeIterable.js
+++ b/util/RangeIterable.js
@@ -173,21 +173,46 @@ export class RangeIterable {
 			let isFirst = true;
 			let currentSubIterator;
 			return {
-				next() {
+				next(resolvedResult) {
 					try {
 						do {
 							if (currentSubIterator) {
-								let result = currentSubIterator.next();
+								let result;
+								if (resolvedResult) {
+									result = resolvedResult;
+									resolvedResult = undefined;
+								} else result = currentSubIterator.next();
+								if (result.then) {
+									if (!async) throw new Error('Can not synchronously iterate with asynchronous values');
+									return result.then((result) => this.next(result));
+								}
 								if (!result.done) {
 									return result;
 								}
 							}
-							let result = iterator.next();
+							let result = resolvedResult ?? iterator.next();
+							if (result.then) {
+								if (!async) throw new Error('Can not synchronously iterate with asynchronous values');
+								currentSubIterator = undefined;
+								return result.then((result) => this.next(result));
+							}
 							if (result.done) {
 								if (mappedIterable.onDone) mappedIterable.onDone();
 								return result;
 							}
 							let value = callback(result.value);
+							if (value?.then) {
+								if (!async) throw new Error('Can not synchronously iterate with asynchronous values');
+								return value.then((value) => {
+									if (Array.isArray(value) || value instanceof RangeIterable) {
+										currentSubIterator = value[Symbol.iterator]();
+										return this.next();
+									} else {
+										currentSubIterator = null;
+										return { value };
+									}
+								})
+							}
 							if (Array.isArray(value) || value instanceof RangeIterable)
 								currentSubIterator = value[Symbol.iterator]();
 							else {