PKG -- [fcl] fix block height issue in events subcriber (#1177)

* fix block height issue in events

* update docs for events subcribe

* remove log

* add change set

* Update docs/reference/api.md

Co-authored-by: Greg Santos <greg.santos@dapperlabs.com>

Co-authored-by: Greg Santos <greg.santos@dapperlabs.com>

.changeset/empty-ants-switch.md

@@ -0,0 +1,6 @@
+---
+"@onflow/fcl": patch
+---
+
+- Fix events subcribe block height issue
+- Add polling rate guide to docs

docs/reference/api.md

@@ -1654,8 +1654,11 @@ useEffect(() => fcl.tx(txId).subscribe(setTxStatus));
 A utility function that lets you set the transaction to get subsequent status updates (via polling) and the finalized result once available.
 ⚠️The poll rate is set at `10000ms` and will update at that interval for getting new events.
 
-#### Arguments
 
+Note:
+⚠️`fcl.eventPollRate` value **could** be set to change the polling rate of all events subcribers, check [FCL Configuration](#configuration) for guide.
+
+#### Arguments
 | Name        | Type   | Description         |
 | ----------- | ------ | ------------------- |
 | `eventName` | string | A valid event name. |

packages/fcl/src/events/index.js

@@ -4,7 +4,7 @@ import {
   block,
   getEventsAtBlockHeightRange,
   send,
-  decode
+  decode,
 } from "@onflow/sdk"
 
 const RATE = 10000
@@ -29,10 +29,12 @@ const HANDLERS = {
     } else {
       let next = await block()
       ctx.put(HIGH_WATER_MARK, next)
-      const data = await send([
-        getEventsAtBlockHeightRange(ctx.self(), hwm.height, next.height - 1),
-      ]).then(decode)
-      for (let d of data) ctx.broadcast(UPDATED, d.data)
+      if (hwm.height < next.height) {
+        const data = await send([
+          getEventsAtBlockHeightRange(ctx.self(), hwm.height + 1, next.height),
+        ]).then(decode)
+        for (let d of data) ctx.broadcast(UPDATED, d.data)
+      }
       ctx.put(TICK, await scheduleTick(ctx))
     }
   },