Fixed getChainIdDefault() race condition

.changeset/polite-moons-study.md

@@ -0,0 +1,5 @@
+---
+"@onflow/fcl": patch
+---
+
+Fixed `setChainIdDefault()` race condition, instead run function on accessNode.api value changes

packages/fcl/src/default-config.js

@@ -1,5 +1,5 @@
 import {config} from "@onflow/config"
-import {setChainIdDefault} from "./utils/getChainId"
+import {setChainIdDefault, watchForChainIdChanges} from "./utils"
 
 const isServerSide = () => typeof window === "undefined"
 
@@ -14,9 +14,8 @@ config({
   "fcl.storage.default": SESSION_STORAGE,
 })
 
-// this is an async function but we can't await bc it's run at top level.
-// NOT guaranteed that flow.network.default is set after this call (or at startup)
-setChainIdDefault()
+// Set chain id default on access node change
+watchForChainIdChanges()
 
 export async function configLens(regex) {
   return Object.fromEntries(

packages/fcl/src/utils/chain-id-watcher.js

@@ -0,0 +1,21 @@
+import {config} from "@onflow/config"
+import {setChainIdDefault} from "./get-chain-id"
+
+/**
+ * @description
+ * Watches the config for changes to access node and updates the chain id accordingly
+ *
+ * @returns {Function} A function that unsubscribes the listener
+ *
+ */
+export function watchForChainIdChanges() {
+  return config.subscribe(
+    function configSubscriber(config) {
+      const nextAccessNode = config?.["accessNode.api"]
+      if (this.prevAccessNode !== nextAccessNode) {
+        setChainIdDefault()
+      }
+      this.prevAccessNode = nextAccessNode
+    }.bind({})
+  )
+}

packages/fcl/src/utils/chain-id-watcher.test.js

@@ -0,0 +1,54 @@
+import {watchForChainIdChanges} from "./chain-id-watcher"
+import {config} from "@onflow/config"
+import * as chainIdUtils from "./get-chain-id"
+
+describe("chain-id-watcher", () => {
+  let unsubscribe
+
+  afterEach(() => {
+    jest.restoreAllMocks()
+    unsubscribe && unsubscribe()
+  })
+
+  test("flow.network.default is correctly set on first call", async () => {
+    await config.overload(
+      {"accessNode.api": "https://example.com"},
+      async () => {
+        // Mock the setChainIdDefault function
+        const spy = jest.spyOn(chainIdUtils, "setChainIdDefault")
+        spy.mockImplementation(() => {})
+
+        // Start watching for changes
+        unsubscribe = watchForChainIdChanges()
+
+        // Wait for microtask queue to flush
+        await new Promise(resolve => setTimeout(resolve, 0))
+
+        // Expect only one call at initial setup
+        expect(chainIdUtils.setChainIdDefault).toHaveBeenCalledTimes(1)
+      }
+    )
+  })
+
+  test("flow.network.default is correctly set when changed later", async () => {
+    await config.overload({}, async () => {
+      // Mock the setChainIdDefault function
+      const spy = jest.spyOn(chainIdUtils, "setChainIdDefault")
+      spy.mockImplementation(() => {})
+
+      // Start watching for changes
+      unsubscribe = watchForChainIdChanges()
+
+      // Wait for microtask queue to flush
+      await new Promise(resolve => setTimeout(resolve, 0))
+
+      config.put("accessNode.api", "https://example.com")
+
+      // Wait for microtask queue to flush
+      await new Promise(resolve => setTimeout(resolve, 0))
+
+      // Expect two calls since we changed the access node and there is an initial call
+      expect(chainIdUtils.setChainIdDefault).toHaveBeenCalledTimes(1)
+    })
+  })
+})

packages/fcl/src/utils/getChainId.js → packages/fcl/src/utils/get-chain-id.js

@@ -1,7 +1,7 @@
 import * as sdk from "@onflow/sdk"
 import {config} from "@onflow/config"
 import {log} from "@onflow/util-logger"
-import { invariant } from "@onflow/util-invariant"
+import {invariant} from "@onflow/util-invariant"
 
 async function getChainIdFromAccessNode() {
   const response = await sdk.send([sdk.getNetworkParameters()]).then(sdk.decode)
@@ -10,9 +10,9 @@ async function getChainIdFromAccessNode() {
 
 /**
  * Sets the default chain id to the chain id of the access node
- * 
+ *
  * @returns {string} The chain id of the access node
- * 
+ *
  * @example
  * // returns "testnet"
  * setChainIdDefault()
@@ -26,10 +26,10 @@ export async function setChainIdDefault() {
 /**
  * @description
  * Gets the chain ID if its set, otherwise gets the chain ID from the access node
- * 
+ *
  * @returns {string} The chain ID of the access node
  * @throws {Error} If the chain ID is not found
- * 
+ *
  * @example
  * // returns "testnet"
  * getChainId()

packages/fcl/src/utils/getChainId.test.js → packages/fcl/src/utils/get-chain-id.test.js

@@ -1,6 +1,6 @@
 import {config} from "@onflow/config"
 import assert from "assert"
-import {getChainId} from "./getChainId"
+import {getChainId} from "./get-chain-id"
 
 describe("getChainId", () => {
   it("getChainId assuming it's already in config", async () => {

packages/fcl/src/utils/index.js

@@ -1,4 +1,5 @@
-export {getChainId} from "./getChainId"
+export {getChainId} from "./get-chain-id"
+export {watchForChainIdChanges} from "./chain-id-watcher"
 
 export function isAndroid() {
   return (