Minor change and documentation

src/filterGenerator.mjs

@@ -7,8 +7,9 @@ import asyncWrap from './asyncWrap.mjs'
 /**
  * Produces a an async iterator that will return each value or `iterable` which pass an asynchronous truth test.
  *
- * The iterator will try to consume as fast as possible the values from `iterable` and will performs the call
- * to `iteratee` in a queue. This allows to limit the concurrency of the calls to `iteratee`.
+ * The iterator will perform the calls to `iteratee` in a queue. This allows to limit the concurrency of
+ * the calls to `iteratee`. The iterator will consume values from `iterable` only if slots are available in the
+ * queue.
  *
  * If the returned iterator is not fully consumed it will stop consuming new values from `iterable` and scheduling
  * new calls to `iteratee` in the queue, but already scheduled tasks will still be executed.

src/mapGenerator.mjs

@@ -9,8 +9,9 @@ import Queue from './Queue.mjs'
  * Produces a an async iterator that will return each value or `iterable` after having processed them through
  * the `iteratee` function.
  *
- * The iterator will try to consume as fast as possible the values from `iterable` and will performs the call
- * to `iteratee` in a queue. This allows to limit the concurrency of the calls to `iteratee`.
+ * The iterator will perform the calls to `iteratee` in a queue. This allows to limit the concurrency of
+ * the calls to `iteratee`. The iterator will consume values from `iterable` only if slots are available in the
+ * queue.
  *
  * If the returned iterator is not fully consumed it will stop consuming new values from `iterable` and scheduling
  * new calls to `iteratee` in the queue, but already scheduled tasks will still be executed.
@@ -178,7 +179,7 @@ async function * mapGenerator (iterable, iteratee, concurrencyOrQueue = 1, order
       hasFetchedValue = false
       fetchedValue = null
     }
-    if (!fetching && !exhausted && !shouldStop && scheduledCount <= queue.concurrency + 1) {
+    if (!fetching && !exhausted && !shouldStop && scheduledCount <= queue.concurrency) {
       fetch()
     }
   }