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64 lines
2.9 KiB
Markdown
64 lines
2.9 KiB
Markdown
# @cloudflare/codemod
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Internal codemod utilities for the Cloudflare Workers SDK.
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## Developing Codemods
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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.
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### Commands
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| Command | Description |
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| --------------- | ---------------------------------------------------------- |
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| `pnpm dev` | Run `src/dev.ts` in watch mode (hot-reloads on every save) |
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| `pnpm dev:once` | Run `src/dev.ts` once without watching |
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### Workflow
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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`.
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2. **Edit `testCodemod()` in `src/dev.ts`** — this is your sandbox. Call `testTransform()` with the path to your snippet and a [`recast` visitor](https://github.com/benjamn/recast) that describes the transform:
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```ts
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const testCodemod = () => {
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testTransform("../dev-snippets/test.ts", {
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visitIdentifier(n) {
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n.node.name = "MyNewName";
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return false;
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},
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});
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};
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```
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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.
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### Key Files
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| File | Purpose |
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| ----------------------- | -------------------------------------------------------------------------------------------- |
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| `src/dev.ts` | Dev entry point; exports `testTransform()` and contains the editable `testCodemod()` sandbox |
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| `dev-snippets/test.ts` | Default sample input — replace its contents freely |
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| `dev-snippets-outputs/` | Auto-generated transform output, gitignored — safe to inspect, never committed |
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### `testTransform(filePath, methods)`
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Mirrors the production `transformFile()` API but instead of silently writing in place it:
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- Prints the transformed source to the console
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- Writes the result to the corresponding path under `dev-snippets-outputs/`
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The `filePath` argument must point to a file inside `dev-snippets/`; paths outside that directory are rejected.
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### Inspecting the AST
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`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:
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```ts
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const _printSnippet = () => {
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const snippet = `if (true) { console.log("potato"); }`;
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const program = parseTs(snippet).program;
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console.log(program.body[0]);
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};
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_printSnippet(); // uncomment to run
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```
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