netlify-lambda/lib/build.js

var fs = require('fs');
var path = require('path');
var conf = require('./config');
var webpack = require('webpack');
var merge = require('webpack-merge');

const testFilePattern = '\\.(test|spec)\\.?';

// custom babel target for each node version
function getBabelTarget(envConfig) {
  var key = 'AWS_LAMBDA_JS_RUNTIME';
  var runtimes = ['nodejs8.15.0', 'nodejs6.10.3'];
  var current = envConfig[key] || process.env[key] || 'nodejs8.15.0';
  var unknown = runtimes.indexOf(current) === -1;
  return unknown ? '8.15.0' : current.replace(/^nodejs/, '');
}

function haveBabelrc(functionsDir) {
  const cwd = process.cwd();

  return (
    fs.existsSync(path.join(cwd, '.babelrc')) ||
    functionsDir.split('/').some((dir) => {
      const indexOf = functionsDir.indexOf(dir);
      const dirToSearch = functionsDir.substr(0, indexOf);

      return fs.existsSync(path.join(cwd, dirToSearch, '.babelrc'));
    })
  );
}

function webpackConfig(dir, { userWebpackConfig, useBabelrc } = {}) {
  var config = conf.load();
  var envConfig = conf.loadContext(config).environment;
  var babelOpts = { cacheDirectory: true };
  if (!haveBabelrc(dir)) {
    babelOpts.presets = [
      [
        require.resolve('@babel/preset-env'),
        { targets: { node: getBabelTarget(envConfig) } },
      ],
    ];

    babelOpts.plugins = [
      require.resolve('@babel/plugin-proposal-class-properties'),
      require.resolve('@babel/plugin-transform-object-assign'),
      require.resolve('@babel/plugin-proposal-object-rest-spread'),
    ];
  }

  var functionsDir = config.build.functions || config.build.Functions;
  var functionsPath = path.resolve(path.join(process.cwd(), functionsDir));
  var dirPath = path.resolve(path.join(process.cwd(), dir));

  if (dirPath === functionsPath) {
    throw new Error(
      `
      netlify-lambda Error: Function source folder (specified in netlify-lambda serve/build command) and publish folder (specified in netlify.toml)
      should be different. They are both set to ${dirPath}.

      This is a common mistake for people switching from Netlify Dev to netlify-lambda. For an easy fix, change your functions key inside netlify.toml to something else, like "functions-build".
      You will then need to build your functions to that directory before they will work locally and the built functions will also need to be pushed to your repo.
      For more info, check https://github.com/netlify/netlify-lambda#usage
      `,
    );
  }

  // Include environment variables from config if available
  var defineEnv = {};
  Object.keys(envConfig).forEach((key) => {
    defineEnv['process.env.' + key] = JSON.stringify(envConfig[key]);
  });

  // Keep the same NODE_ENV if it was specified
  var nodeEnv = process.env.NODE_ENV || 'production';

  // Set webpack mode based on the nodeEnv
  var webpackMode = ['production', 'development'].includes(nodeEnv)
    ? nodeEnv
    : 'none';

  var webpackConfig = {
    mode: webpackMode,
    resolve: {
      extensions: ['.wasm', '.mjs', '.js', '.json', '.ts'],
      mainFields: ['module', 'main'],
    },
    module: {
      rules: [
        {
          test: /\.(m?js|ts)?$/,
          exclude: new RegExp(
            `(node_modules|bower_components|${testFilePattern})`,
          ),
          use: {
            loader: require.resolve('babel-loader'),
            options: { ...babelOpts, babelrc: useBabelrc },
          },
        },
      ],
    },
    context: dirPath,
    entry: {},
    target: 'node',
    plugins: [
      new webpack.IgnorePlugin(/vertx/),
      new webpack.DefinePlugin(defineEnv),
    ],
    output: {
      path: functionsPath,
      filename: '[name].js',
      libraryTarget: 'commonjs',
    },
    optimization: {
      nodeEnv,
    },
    bail: true,
    devtool: false,
    stats: {
      colors: true,
    },
  };
  fs.readdirSync(dirPath).forEach(function (file) {
    if (file.match(/\.(m?js|ts)$/)) {
      var name = file.replace(/\.(m?js|ts)$/, '');
      if (!name.match(new RegExp(testFilePattern))) {
        webpackConfig.entry[name] = './' + file;
      }
    }
  });
  if (Object.keys(webpackConfig.entry) < 1) {
    console.warn(
      `
      ---Start netlify-lambda notification---
      WARNING: No valid single functions files (ending in .mjs, .js or .ts) were found. 
      This could be because you have nested them in a folder.
      If this is expected (e.g. you have a zipped function built somewhere else), you may ignore this.
      ---End netlify-lambda notification---
      `,
    );
  }
  if (userWebpackConfig) {
    var webpackAdditional = require(path.join(
      process.cwd(),
      userWebpackConfig,
    ));

    return merge.smart(webpackConfig, webpackAdditional);
  }

  return webpackConfig;
}

exports.run = function (dir, additionalConfig) {
  return new Promise(function (resolve, reject) {
    webpack(webpackConfig(dir, additionalConfig), function (err, stats) {
      if (err) {
        return reject(err);
      }
      const errors = stats.compilation.errors || [];
      if (errors.length > 0) {
        return reject(stats.compilation.errors);
      }
      resolve(stats);
    });
  });
};

exports.watch = function (dir, additionalConfig, cb) {
  var compiler = webpack(webpackConfig(dir, additionalConfig));
  compiler.watch(webpackConfig(dir, additionalConfig), cb);
};