switchChainAsync throw an error when user approved

[xianchenxc]

Check existing issues

• I checked there isn't already an issue for the bug I encountered.

Describe the bug

What I am doing:

1. Connect MetaMask wallet using the "metaMask" connector.
2. Refresh page
3. Switch to a network (e.g., BSC) that is not yet added to your MetaMask wallet.
4. A popup to switch to BSC appears, click “Approve” and then “Switch Network”.

What I expected:

The network is added and switched without any errors.

What is actually happening:

switchChainAsync throws an error: User rejected the request.
Details: The user rejected the switch after the network was added.
Version: 2.20.0

Link to Minimal Reproducible Example

https://codesandbox.io/p/sandbox/wagmi-switchchain-6m86q5

Steps To Reproduce

Here is the link: https://codesandbox.io/p/sandbox/wagmi-switchchain-6m86q5

Steps to reproduce the issue:

1. Remove BNB Smart Chain from your MetaMask wallet.
2. Click the Connect button.
3. Refresh the page.
4. Click the BNB Smart Chain button.
5. A popup to switch to BSC will appear. Click Approve, then Switch Network.
6. An error message will be displayed below the button.

What Wagmi package(s) are you using?

wagmi

Wagmi Package(s) Version(s)

2.12.7

Viem Version

2.20.0

TypeScript Version

5.5.4

Anything else?

No response

[xianchenxc]

I checked the code in "packages/connectors/src/metaMask.ts", and I believe it needs to wait for the "change" event emitter:

// packages/connectors/src/metaMask.ts
await provider.request({
  method: 'wallet_addEthereumChain',
  params: [addEthereumChain],
})

const currentChainId = await this.getChainId()

It might look something like this：

await Promise.all([
  provider.request({
    method: 'wallet_addEthereumChain',
    params: [addEthereumChain],
  }),
  new Promise<void>((resolve) =>
    config.emitter.once('change', ({ chainId: currentChainId }) => {
      if (currentChainId === chainId) resolve()
    }),
  ),
])

const currentChainId = await this.getChainId()

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