next.js/client/dev-error-overlay/format-webpack-messages.js

// This file is based on https://github.com/facebook/create-react-app/blob/v1.1.4/packages/react-dev-utils/formatWebpackMessages.js
// It's been edited to remove chalk

'use strict'

// WARNING: this code is untranspiled and is used in browser too.
// Please make sure any changes are in ES5 or contribute a Babel compile step.

// Some custom utilities to prettify Webpack output.
// This is quite hacky and hopefully won't be needed when Webpack fixes this.
// https://github.com/webpack/webpack/issues/2878

var friendlySyntaxErrorLabel = 'Syntax error:'

function isLikelyASyntaxError (message) {
  return message.indexOf(friendlySyntaxErrorLabel) !== -1
}

// Cleans up webpack error messages.
// eslint-disable-next-line no-unused-vars
function formatMessage (message, isError) {
  var lines = message.split('\n')

  if (lines.length > 2 && lines[1] === '') {
    // Remove extra newline.
    lines.splice(1, 1)
  }

  // Remove webpack-specific loader notation from filename.
  // Before:
  // ./~/css-loader!./~/postcss-loader!./src/App.css
  // After:
  // ./src/App.css
  if (lines[0].lastIndexOf('!') !== -1) {
    lines[0] = lines[0].substr(lines[0].lastIndexOf('!') + 1)
  }

  // Remove unnecessary stack added by `thread-loader`
  var threadLoaderIndex = -1
  lines.forEach(function (line, index) {
    if (threadLoaderIndex !== -1) {
      return
    }
    if (/thread.loader/i.test(line)) {
      threadLoaderIndex = index
    }
  })

  if (threadLoaderIndex !== -1) {
    lines = lines.slice(0, threadLoaderIndex)
  }

  lines = lines.filter(function (line) {
    // Webpack adds a list of entry points to warning messages:
    //  @ ./src/index.js
    //  @ multi react-scripts/~/react-dev-utils/webpackHotDevClient.js ...
    // It is misleading (and unrelated to the warnings) so we clean it up.
    // It is only useful for syntax errors but we have beautiful frames for them.
    return line.indexOf(' @ ') !== 0
  })

  // line #0 is filename
  // line #1 is the main error message
  if (!lines[0] || !lines[1]) {
    return lines.join('\n')
  }

  // Cleans up verbose "module not found" messages for files and packages.
  if (lines[1].indexOf('Module not found: ') === 0) {
    lines = [
      lines[0],
      // Clean up message because "Module not found: " is descriptive enough.
      lines[1]
        .replace("Cannot resolve 'file' or 'directory' ", '')
        .replace('Cannot resolve module ', '')
        .replace('Error: ', '')
        .replace('[CaseSensitivePathsPlugin] ', '')
    ]
  }

  // Cleans up syntax error messages.
  if (lines[1].indexOf('Module build failed: ') === 0) {
    lines[1] = lines[1].replace(
      'Module build failed: SyntaxError:',
      friendlySyntaxErrorLabel
    )
  }

  // Clean up export errors.
  // TODO: we should really send a PR to Webpack for this.
  var exportError = /\s*(.+?)\s*(")?export '(.+?)' was not found in '(.+?)'/
  if (lines[1].match(exportError)) {
    lines[1] = lines[1].replace(
      exportError,
      "$1 '$4' does not contain an export named '$3'."
    )
  }

  // Reassemble the message.
  message = lines.join('\n')
  // Internal stacks are generally useless so we strip them... with the
  // exception of stacks containing `webpack:` because they're normally
  // from user code generated by WebPack. For more information see
  // https://github.com/facebook/create-react-app/pull/1050
  message = message.replace(
    /^\s*at\s((?!webpack:).)*:\d+:\d+[\s)]*(\n|$)/gm,
    ''
  ) // at ... ...:x:y

  return message.trim()
}

function formatWebpackMessages (json) {
  var formattedErrors = json.errors.map(function (message) {
    return formatMessage(message, true)
  })
  var formattedWarnings = json.warnings.map(function (message) {
    return formatMessage(message, false)
  })
  var result = {
    errors: formattedErrors,
    warnings: formattedWarnings
  }
  if (result.errors.some(isLikelyASyntaxError)) {
    // If there are any syntax errors, show just them.
    // This prevents a confusing ESLint parsing error
    // preceding a much more useful Babel syntax error.
    result.errors = result.errors.filter(isLikelyASyntaxError)
  }
  return result
}

module.exports = formatWebpackMessages