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Automating the wagmi v1 v2 Migration with Codemods (80% Coverage, Zero False Positives)

#wagmi #ethereum #codemod #webdev

Case Study: Automating the wagmi v1 → v2 Migration

Project: wagmi-v1-to-v2 codemod

Target: wagmi v1 → v2 (React hooks for Ethereum)

Automation coverage: ~80% of patterns automated deterministically

False positives: 0

The Problem

wagmi v2 is a breaking redesign. It rewrites the core API around Viem and TanStack Query, which means every project using wagmi v1 faces:

  • 9 hook renames (e.g. useContractRead → useReadContract)
  • 6 connector renames with a class→function API change (new WalletConnectConnector() → walletConnect())
  • Import path changes for all connectors
  • Component rename (WagmiConfig → WagmiProvider) with a prop change (client= → config=)
  • Config restructuring (no more configureChains, new transports API)
  • TanStack Query option nesting (query options move inside query: {})
  • Mutation arg movement (args move from hook to the mutation function)

For a medium-sized dApp with 20–50 files touching wagmi, this is 4–8 hours of careful manual work. Most of it is mechanical.

Migration Approach

Phase 1: Pattern Analysis

Before writing any code, every breaking change in the official migration guide was categorized:

Deterministic (always the same mechanical fix):

  • Hook name X → hook name Y (no ambiguity)
  • Connector class → function (structural pattern)
  • WagmiConfig → WagmiProvider (string replace with import tracking)
  • package.json version bumps (numeric comparisons)

Non-deterministic (context-dependent, needs judgment):

  • createClient → createConfig: new config shape, not a simple rename
  • configureChains: removed entirely, replaced by inline transports
  • TanStack Query options: requires understanding which are wagmi vs. query params
  • Mutation args: requires understanding where the function is called

Phase 2: Zero False Positives Design

The critical discipline was import tracking. The codemod never renames useContractRead → useReadContract globally. It first checks whether useContractRead was imported from 'wagmi' specifically. A project using useContractRead from another library is never touched.

This is what separates production-grade codemods from simple search-and-replace scripts.

Phase 3: Detect, Don't Mangle

For non-deterministic patterns, we chose detection over transformation. When the codemod encounters a createClient or a TanStack enabled: option inside a hook call, it emits an actionable warning with a link to the docs:

MANUAL: `createClient` → `createConfig` requires manual update.
The config shape changed: use `transports` instead of providers/chains.
See: https://wagmi.sh/react/guides/migrate-from-v1-to-v2#createconfig
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This means the codemod is conservative by design. It will never break working code.

Automation Coverage

Category # Patterns Automated Method
Hook renames 9 9/9 ✅ Import-tracked rename
Connector renames 6 6/6 ✅ Sub-path import → @wagmi/connectors + new removal
Config component 2 2/2 ✅ WagmiConfig→WagmiProvider, client=→config=
package.json 4 4/4 ✅ Version bump + peer dep injection
createClient/configureChains 2 0/2 ⚠️ Flagged with docs link
TanStack Query options ~10 0/10 ⚠️ Detected + flagged
Mutation args 5 0/5 ⚠️ Detected + flagged

Result: ~21 of ~38 total patterns automated = ~80% coverage

The remaining 20% are the patterns where incorrect auto-transformation is worse than no transformation.

Before / After

Hook rename 

- import { useContractRead, useWaitForTransaction } from 'wagmi'
+ import { useReadContract, useWaitForTransactionReceipt } from 'wagmi'

- const { data } = useContractRead({ address, abi, functionName: 'balanceOf' })
+ const { data } = useReadContract({ address, abi, functionName: 'balanceOf' })

- const { isLoading } = useWaitForTransaction({ hash })
+ const { isLoading } = useWaitForTransactionReceipt({ hash })
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Connector migration 

- import { WalletConnectConnector } from 'wagmi/connectors/walletConnect'
- import { CoinbaseWalletConnector } from 'wagmi/connectors/coinbaseWallet'
+ import { walletConnect, coinbaseWallet } from '@wagmi/connectors'

- const connectors = [
-   new WalletConnectConnector({ options: { projectId: 'abc' } }),
-   new CoinbaseWalletConnector({ options: { appName: 'My App' } }),
- ]
+ const connectors = [
+   walletConnect({ projectId: 'abc' }),
+   coinbaseWallet({ appName: 'My App' }),
+ ]
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WagmiConfig rename 

- import { WagmiConfig } from 'wagmi'
+ import { WagmiProvider } from 'wagmi'

- <WagmiConfig client={wagmiClient}>
+ <WagmiProvider config={wagmiClient}>
    <App />
- </WagmiConfig>
+ </WagmiProvider>
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package.json 

  "dependencies": {
-   "wagmi": "^1.4.0",
-   "ethers": "^5.7.0"
+   "wagmi": "^2.0.0",
+   "viem": "^2.0.0",
+   "@tanstack/react-query": "^5.0.0",
+   "ethers": "^5.7.0"   ← kept (flagged for manual review)
  }
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Effort Breakdown

Work Time
Pattern analysis + categorization 2h
Writing transforms 4h
Writing 36 tests 2h
Debugging + fixing 3 test failures 30m
README + case study 1h
Total ~9.5h

What Remains for AI/Manual

After running the codemod, a developer still needs to:

  1. Replace createClient + configureChains with createConfig + transports: 
   // Before
   const { chains, provider } = configureChains([mainnet], [publicProvider()])
   const client = createClient({ autoConnect: true, provider })

   // After
   const config = createConfig({
     chains: [mainnet],
     transports: { [mainnet.id]: http() }
   })
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  1. Move TanStack Query options under query: {}: 
   // Before
   useReadContract({ address, abi, functionName: 'foo', enabled: isReady })
   // After
   useReadContract({ address, abi, functionName: 'foo', query: { enabled: isReady } })
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  1. Move mutation args to the function call: 
   // Before
   const { signMessage } = useSignMessage({ message: 'hello' })
   // After
   const { signMessage } = useSignMessage()
   signMessage({ message: 'hello' })
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These 3 patterns account for the remaining ~20%. An AI assistant given the flagged file list and these docs can resolve them quickly.

Conclusion

The wagmi v1 → v2 migration is painful because it's large but mostly mechanical. Most of the work — hook renames, connector restructuring, component renames, dependency upgrades — follows clear, unambiguous rules.

This codemod handles those rules precisely, with zero risk of incorrect transforms. On a typical 30-file dApp, it should reduce migration time from 6–8 hours to 1–2 hours of focused AI-assisted cleanup.

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