feat: viem-to-essential-eth migration codemod CLI

[dawsbot]

🪶 viem → essential-eth Migration Codemod

A zero-dependency CLI tool that scans a codebase for viem imports and rewrites them to use essential-eth where an equivalent utility exists.

Usage

npx tsx scripts/migrate.ts ./src --dry-run   # preview changes
npx tsx scripts/migrate.ts ./src              # apply changes

Migration Map (19 functions)

viem	essential-eth	Notes
formatEther	weiToEther	renamed
parseEther	etherToWei	renamed
formatUnits	formatUnits	same
parseUnits	parseUnits	same
formatGwei	gweiToEther	renamed
parseGwei	etherToGwei	renamed
getAddress	getAddress	same
isAddress	isAddress	same
keccak256	keccak256	same
hashMessage	hashMessage	same
toHex	hexlify	renamed
toBytes	arrayify	renamed
concat	concat	same
pad	zeroPad	renamed
trim	stripZeros	renamed
isHex	isHexString	renamed
isBytes	isBytes	same
namehash	namehash	same
encodePacked	pack	renamed

Example Output (from test fixture)

🪶 essential-eth migration tool (dry run)

Scanning ./scripts/migrate-test-fixture...

✅ bytes.ts
   - toHex → hexlify
   - toBytes → arrayify
   - isHex → isHexString
   - concat → concat (same name)
   - isBytes → isBytes (same name)

⚠️  hashing.ts
   - keccak256 → keccak256 (same name)
   - encodePacked → pack
   - hashMessage → hashMessage (same name)
   ⚠️  createPublicClient — not available in essential-eth
   ⚠️  http — not available in essential-eth

✅ utils.ts
   - formatEther → weiToEther
   - parseEther → etherToWei
   - isAddress → isAddress (same name)
   - getAddress → getAddress (same name)

---
📊 Summary:
   Files scanned: 3
   Files with viem imports: 3
   Imports migrated: 12
   Imports unsupported: 2

Features

• Recursive scanning of .ts, .tsx, .js, .jsx files
• Import splitting — if only some symbols from a viem import are supported, it splits the import: supported → essential-eth, unsupported → stays on viem
• Usage rewriting — renames all usages in the file body (e.g. formatEther(x) → weiToEther(x))
• Dry run mode — --dry-run previews changes without modifying files
• Exit code 1 when unsupported imports remain (CI-friendly)
• Zero external dependencies — only uses Node built-ins

Files Added

• scripts/migrate.ts — the migration CLI
• scripts/migrate-test-fixture/ — 3 test fixture files for verification
• MIGRATION.md — documentation

What is Next

• ethers.js → essential-eth migration support
• npx essential-eth migrate ./src (publish as bin)
• Type alias handling (import type { ... } from "viem")
• Re-export / barrel file support

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Project	Deployment	Actions	Updated (UTC)
essential-eth	Error		Feb 7, 2026 9:48pm