Cannot add chains with empty blockExplorers to MetaMask

[tash-2s]

Describe the bug

When attempting to add the Foundry chain to MetaMask, I encounter the following error:

MetaMask - RPC Error: Expected null or array with at least one valid string HTTPS URL 'blockExplorerUrl'.

I discovered that adding the blockExplorers parameter resolves the issue.

Wagmi configures wallet_addEthereumChain's blockExplorerUrls based on the chain's blockExplorers. The current Wagmi implementation leads to an empty array for blockExplorerUrls when chains lack blockExplorers.

wagmi/packages/core/src/connectors/injected.ts

Lines 373 to 393 in 4ba761d

	const { default: blockExplorer, ...blockExplorers } =
	chain.blockExplorers ?? {}
	let blockExplorerUrls: string[] = []
	if (blockExplorer)
	blockExplorerUrls = [
	blockExplorer.url,
	...Object.values(blockExplorers).map((x) => x.url),
	]
	await provider.request({
	method: 'wallet_addEthereumChain',
	params: [
	{
	chainId: numberToHex(chainId),
	chainName: chain.name,
	nativeCurrency: chain.nativeCurrency,
	rpcUrls: [chain.rpcUrls.default?.http[0] ?? ''],
	blockExplorerUrls,
	},
	],
	})

According to MetaMask documentation, they require "One or more URLs", indicating that the empty array triggers the error.

I propose excluding blockExplorerUrls for chains that do not have blockExplorers.

Link to Minimal Reproducible Example

No response

Steps To Reproduce

Create a project:

pnpm create wagmi@2.0.10 --template vite-vanilla

Apply this diff:

diff --git a/src/main.ts b/src/main.ts
index 257488e..47c0748 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -1,11 +1,17 @@
-import { connect, disconnect, reconnect, watchAccount } from '@wagmi/core'
+import { connect, disconnect, reconnect, watchAccount, switchChain } from '@wagmi/core'
 import { Buffer } from 'buffer'
+import { foundry } from '@wagmi/core/chains'
 
 import './style.css'
 import { config } from './wagmi'
 
 globalThis.Buffer = Buffer
 
+const button = document.createElement('button')
+button.textContent = 'Switch to foundry'
+button.onclick = () => switchChain(config, { chainId: foundry.id })
+document.body.appendChild(button)
+
 document.querySelector<HTMLDivElement>('#app')!.innerHTML = `
   <div>
     <div id="account">
diff --git a/src/wagmi.ts b/src/wagmi.ts
index 3bce606..ebadbf5 100644
--- a/src/wagmi.ts
+++ b/src/wagmi.ts
@@ -1,16 +1,15 @@
-import { coinbaseWallet, injected, walletConnect } from '@wagmi/connectors'
+import { injected } from '@wagmi/connectors'
 import { http, createConfig } from '@wagmi/core'
-import { mainnet, sepolia } from '@wagmi/core/chains'
+import { mainnet, sepolia, foundry } from '@wagmi/core/chains'
 
 export const config = createConfig({
-  chains: [mainnet, sepolia],
+  chains: [mainnet, sepolia, foundry],
   connectors: [
     injected(),
-    coinbaseWallet({ appName: 'Create Wagmi' }),
-    walletConnect({ projectId: import.meta.env.VITE_WC_PROJECT_ID }),
   ],
   transports: {
     [mainnet.id]: http(),
     [sepolia.id]: http(),
+    [foundry.id]: http(),
   },
 })

Run the project, connect MetaMask, and switch to the Foundry chain; then, the following error occurs:

MetaMask - RPC Error: Expected null or array with at least one valid string HTTPS URL 'blockExplorerUrl'.

By modifying as follows:

diff --git a/src/wagmi.ts b/src/wagmi.ts
index ebadbf5..1a91b83 100644
--- a/src/wagmi.ts
+++ b/src/wagmi.ts
@@ -2,8 +2,10 @@ import { injected } from '@wagmi/connectors'
 import { http, createConfig } from '@wagmi/core'
 import { mainnet, sepolia, foundry } from '@wagmi/core/chains'
 
+const f = { ...foundry, blockExplorers: { default: { name: "", url: "https://example.com" } } }
+
 export const config = createConfig({
-  chains: [mainnet, sepolia, foundry],
+  chains: [mainnet, sepolia, f],
   connectors: [
     injected(),
   ],

The error is resolved, and everything works as expected:

Wagmi Version

2.6.5

Viem Version

2.7.16

TypeScript Version

5.3.3

Check existing issues

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

Anything else?

No response

[tmm]

Thanks for the detailed issue @tash-2s! You are welcome to submit a PR (excluding blockExplorerUrls for chains that do not have blockExplorers) if you want credit. Otherwise, will get to this soon.

[tash-2s]

@tmm Thanks for taking a look. Let me try quickly!

[github-actions]

This issue has been locked since it has been closed for more than 14 days.

If you found a concrete bug or regression related to it, please open a new bug report with a reproduction against the latest wagmi version. If you have any other comments you can create a new discussion.