Chokidar TS

A thin wrapper on top of chokidar file watcher that relies on the tsconfig.json file to distinguish between the TypeScript source files and other files.

Why does this package exists?

When running a Node.js backend development server with a file watcher, we need to know whether a newly added or changed file is part of our TypeScript project.

The best way to establish if a file is part of a TypeScript project is to rely on the tsconfig.json file.

This is precisely what this package does. It will create a file watcher using chokidar and then uses the includes and excludes patterns from the tsconfig.json file to know if a changed file is part of a TypeScript project.

Setup

Install the package from the npm packages registry. In addition, the package has a peer dependency on the typescript package, so make sure to install that as well.

npm i @poppinss/chokidar-ts@next

And use it as follows.

import typescript from 'typescript'
import { ConfigParser, Watcher } from '@poppinss/chokidar-ts'

const projectRoot = new URL('./', import.meta.url)
const configFileName = 'tsconfig.json'

const { config } = new ConfigParser(
  projectRoot,
  configFileName,
  typescript,
).parse()

if (config) {
  const watcher = new Watcher(projectRoot, config)
  watcher.watch(['.'])
}

Listening for events

The Watcher class emits the following events. Events prefixed with source refers to files included by the tsconfig.json file, and other events refer to non-typescript or files excluded by the tsconfig.json file.

• add: A new file has been added. The file is either not a TypeScript file or is excluded by the tsconfig.json file.
• source:add: A new TypeScript source file has been added.
• change: An existing file has been updated. The file is either not a TypeScript file or is excluded by the tsconfig.json file.
• source:change: An existing TypeScript source file has been changed.
• unlink: An existing file has been deleted. The file is not a TypeScript source file.
• source:unlink: An existing TypeScript source file has been deleted.

const watcher = new Watcher(projectRoot, config)

watcher.on('add', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.on('source:add', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.on('change', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.on('source:change', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.on('unlink', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.on('source:unlink', (file) => {
  console.log(file.absPath)
  console.log(file.relativePath)
})

watcher.watch(['.'])

Handling config parser errors

Parsing the tsconfig.json file can produce errors, and you can display them using the TypeScript compiler as follows.

import typescript from 'typescript'
const { error, config } = new ConfigParser(
  projectRoot,
  configFileName,
  typescript,
).parse()

if (error) {
  const compilerHost = typescript.createCompilerHost({})
  console.log(
    typescript.formatDiagnosticsWithColorAndContext([error], compilerHost)
  )

  return
}

if (!config) {
  return
}

if (config.errors) {
  const compilerHost = typescript.createCompilerHost({})
  console.log(
    typescript.formatDiagnosticsWithColorAndContext(config.errors, compilerHost)
  )

  return
}