Allow wallet_addEthereumChain for Ethereum networks

[kurushdubash]

With EIP-3085, we're able to programmatically add new networks / chains to metamask which is a great experience for users versus having to manually add a custom RPC.

However, Metamask doesn't allow adding/updating chains programmatically that have a chain id that corresponds to any of the default MetaMask chains (basically the Ethereum networks). Although adding a custom RPC will allow you to add an RPC with any of the default chain ids.

This would be really useful for allowing custom RPCs in a programmatic way or at the least be able to add duplicate Eth networks.

An example to validate:

const params = [{
    chainId: '0x1',
    chainName: 'Ethereum Mainnet (Localhost)',
    nativeCurrency: {
      name: 'Eth',
      symbol: 'Eth',
      decimals: 18
    },
    rpcUrls: ['https://localhost:8000'],
    blockExplorerUrls: ['https://etherscan.io/']
  }]

const args = { 
  method: 'wallet_addEthereumChain', 
  params: params
}
window.ethereum.request(args)

will result in

MetaMask - RPC Error: May not specify default MetaMask chain. {code: -32602, message: 'May not specify default MetaMask chain.'}

Note: I'm not able to create a feature request on community.metamask.io - there does not seem to be a way to post new topics.

[the42]

Just so I understand correctly: With this limitation in place, it is essentially not possible to run a full/light node and connect to it right?

[kurushdubash]

Not programatically - you will have to manually configure the RPC through the Metamask UI.

[the42]

Because of #13168 and #13167 it is actually completely impossible for me to add any local network.

[adonesky1]

This is resolved by #16733