robotrix

Several useful TypeScript transpilation transformers.

Getting started

Install the library:

yarn add robotrix

Transformers

Node Env Transformer

Replaces process.env.[PARAM] expressions with string literals, using provided env.

import { createNodeEnvTransformer } from 'robotrix'
import { transpileModule } from 'typescript'

const nodeEnvTransformer = createNodeEnvTransformer(process.env)

const transpileOutput = transpileModule(code, { transformers: { before: [nodeEnvTransformer] } })

React Dev Transformer

Adds meta-data which is used by React for development error messages.

It adds the following attributes to all JSX elements:

• __self={this}
• __source={{ fileName: __jsxFileName, lineNumber: [jsx line number] }}

if __source was added, the following declaration is prepended to source file: const __jsxFileName = [absolute file path]

import { reactDevTransformer } from 'robotrix'
import { transpileModule } from 'typescript'

const transpileOutput = transpileModule(code, { transformers: { before: [reactDevTransformer] } })

Dead Ifs Transformer

Detects and removes dead if branches. Checks the expression of every if statement, and cancels out always falsy branches.

It detects true, false, and basic string equality comparison (==, ===, !=, !==).

import { deadIfsTransformer } from 'robotrix'
import { transpileModule } from 'typescript'

const transpileOutput = transpileModule(code, { transformers: { before: [deadIfsTransformer] } })

CommonJS to ESM Transformer

Transforms CommonJS calls/exports to ESM syntax. If a source file is identified as using require, module, or exports, it is wrapped with the following:

[generated imports]

let exports = {}, module = { exports }

[original code]

export default module.exports

Each require(...) call with a string request is converted to a generated import statement with a unique identifier.

import { createCjsToEsmTransformer } from 'robotrix'
import { transpileModule } from 'typescript'

const cjsToEsmTransformer = createCjsToEsmTransformer()
const transpileOutput = transpileModule(code, { transformers: { before: [cjsToEsmTransformer] } })

createCjsToEsmTransformer() also accepts an optional options object, where one can currently specify shouldTransform to control whether to transform require(...) calls based on their target.

const blacklisted = new Set(['fs', 'another', 'etc'])

// doesn't convert any require(...) calls that target items in blacklisted
const cjsToEsmTransformer = createCjsToEsmTransformer({
    shouldTransform: request => !blacklisted.has(request)
})

License

MIT