@cloudflare/codemod

Internal codemod utilities for the Cloudflare Workers SDK.

Developing Codemods

Writing codemods often requires trial and error. The package ships a dedicated dev workflow so you can iterate on transforms in isolation without writing throw-away scripts.

Commands

Workflow

1. Edit dev-snippets/test.ts — put whatever source code you want to transform into this file. It is the default input used by the dev script. You can add more files under dev-snippets/ and reference them from src/dev.ts.

2. Edit testCodemod() in src/dev.ts — this is your sandbox. Call testTransform() with the path to your snippet and a recast visitor that describes the transform:

   const testCodemod = () => {
   	testTransform("../dev-snippets/test.ts", {
   		visitIdentifier(n) {
   			n.node.name = "MyNewName";
   			return false;
   		},
   	});
   };
   

3. Run pnpm dev — the transformed code is printed to the console and written to dev-snippets-outputs/test.ts (gitignored). Inspect the output file to verify the transform behaves as expected.

Key Files

testTransform(filePath, methods)

Mirrors the production transformFile() API but instead of silently writing in place it:

• Prints the transformed source to the console
• Writes the result to the corresponding path under dev-snippets-outputs/

The filePath argument must point to a file inside dev-snippets/; paths outside that directory are rejected.

Inspecting the AST

src/dev.ts includes a commented-out _printSnippet() helper. Uncomment its call at the bottom of the file to log the AST of an arbitrary snippet to the console — useful when you need to know the exact node shape to target in a visitor:

const _printSnippet = () => {
	const snippet = `if (true) { console.log("potato"); }`;
	const program = parseTs(snippet).program;
	console.log(program.body[0]);
};
_printSnippet(); // uncomment to run

Source: packages/codemod/README.md