index.js

'use strict'

const path = require('path')
const resolve = require('resolve')
const tsconfigPaths = require('tsconfig-paths')
const debug = require('debug')

const log = debug('eslint-import-resolver-typescript')

/**
 * @param {string} source the module to resolve; i.e './some-module'
 * @param {string} file the importing file's full path; i.e. '/usr/local/bin/file.js'
 */
function resolveFile(source, file, config) {
  log('looking for:', source)

  // don't worry about core node modules
  if (resolve.isCore(source)) {
    log('matched core:', source)

    return {
      found: true,
      path: null,
    }
  }

  // setup tsconfig-paths
  const searchStart = config.directory || process.cwd()
  const configLoaderResult = tsconfigPaths.loadConfig(searchStart)
  if (configLoaderResult.resultType !== 'success') {
    throw new Error(`Unable to find tsconfig in ${searchStart}: ${configLoaderResult.message}`)
  }
  const matchPath = tsconfigPaths.createMatchPath(
    configLoaderResult.absoluteBaseUrl,
    configLoaderResult.paths,
  )

  // look for files based on setup tsconfig "paths"
  const extensions = Object.keys(require.extensions).concat('.ts', '.tsx', '.d.ts')
  const foundTsPath = matchPath(
    source,
    undefined,
    undefined,
    extensions,
  )

  if (foundTsPath) {
    log('matched ts path:', foundTsPath)
  }

  // note that even if we match via tsconfig-paths, we still need to do a final resolve
  let foundNodePath;
  try {
    foundNodePath = resolve.sync(foundTsPath || source, {
      extensions,
      basedir: path.dirname(path.resolve(file)),
    })
  } catch (err) {
    foundNodePath = null;
  }

  if (foundNodePath) {
    log('matched node path:', foundNodePath)

    return {
      found: true,
      path: foundNodePath,
    }
  }

  log('didnt find', source)

  return {
    found: false
  }
}

module.exports = {
  interfaceVersion: 2,
  resolve: resolveFile,
}