Automatically install missing dependencies, part 2

src/Bundler.js

@@ -16,6 +16,7 @@ const config = require('./utils/config');
 const emoji = require('./utils/emoji');
 const loadEnv = require('./utils/env');
 const PromiseQueue = require('./utils/PromiseQueue');
+const installPackage = require('./utils/installPackage');
 const bundleReport = require('./utils/bundleReport');
 const prettifyTime = require('./utils/prettifyTime');
 
@@ -96,7 +97,9 @@ class Bundler extends EventEmitter {
           ? options.sourceMaps
           : !isProduction,
       hmrHostname: options.hmrHostname || '',
-      detailedReport: options.detailedReport || false
+      detailedReport: options.detailedReport || false,
+      autoinstall: (options.autoinstall || false) && !isProduction,
+      packageManager: options.packageManager
     };
   }
 
@@ -332,14 +335,28 @@ class Bundler extends EventEmitter {
       let thrown = err;
 
       if (thrown.message.indexOf(`Cannot find module '${dep.name}'`) === 0) {
+        let isLocalFile = dep.name.startsWith('.');
+        // Attempt to install missing npm dependencies
+        if (!isLocalFile && this.options.autoinstall) {
+          logger.status(emoji.progress, `Installing ${dep.name}...`);
+          await installPackage(
+            Path.dirname(asset.name),
+            [dep.name],
+            false,
+            false,
+            this.options.packageManager
+          );
+          return await this.resolveAsset(dep.name, asset.name);
+        }
+
         if (dep.optional) {
           return;
         }
 
         thrown.message = `Cannot resolve dependency '${dep.name}'`;
 
         // Add absolute path to the error message if the dependency specifies a relative path
-        if (dep.name.startsWith('.')) {
+        if (isLocalFile) {
           const absPath = Path.resolve(Path.dirname(asset.name), dep.name);
           err.message += ` at '${absPath}'`;
         }

src/cli.js

@@ -39,6 +39,12 @@ program
   .option('--no-hmr', 'disable hot module replacement')
   .option('--no-cache', 'disable the filesystem cache')
   .option('--no-source-maps', 'disable sourcemaps')
+  .option('--no-autoinstall', 'disable autoinstall')
+  .option(
+    '-m, --package-manager <packageManager>',
+    'set the package manger for autoinstall (npm or yarn)',
+    /^(npm|yarn)$/
+  )
   .option(
     '-t, --target [target]',
     'set the runtime environment, either "node", "browser" or "electron". defaults to "browser"',
@@ -65,6 +71,12 @@ program
   .option('--no-hmr', 'disable hot module replacement')
   .option('--no-cache', 'disable the filesystem cache')
   .option('--no-source-maps', 'disable sourcemaps')
+  .option('--no-autoinstall', 'disable autoinstall')
+  .option(
+    '-m, --package-manager <packageManager>',
+    'set the package manger for autoinstall (npm or yarn)',
+    /^(npm|yarn)$/
+  )
   .option(
     '-t, --target [target]',
     'set the runtime environment, either "node", "browser" or "electron". defaults to "browser"',

src/utils/installPackage.js

@@ -3,22 +3,67 @@ const config = require('./config');
 const path = require('path');
 const promisify = require('./promisify');
 const resolve = promisify(require('resolve'));
+const commandExists = require('command-exists').sync;
+const logger = require('../Logger');
+const fs = require('./fs');
 
-async function install(dir, modules, installPeers = true) {
-  let location = await config.resolve(dir, ['yarn.lock', 'package.json']);
+async function install(
+  dir,
+  modules,
+  installPeers = true,
+  saveDev = true,
+  packageManager
+) {
+  let projectRootLocation = dir;
 
-  return new Promise((resolve, reject) => {
+  let configFileLocation = await config.resolve(dir, [
+    'yarn.lock',
+    'package.json'
+  ]);
+
+  if (configFileLocation)
+    projectRootLocation = path.dirname(configFileLocation);
+
+  return new Promise(async (resolve, reject) => {
     let install;
     let options = {
-      cwd: location ? path.dirname(location) : dir
+      cwd: projectRootLocation
     };
 
-    if (location && path.basename(location) === 'yarn.lock') {
-      install = spawn('yarn', ['add', ...modules, '--dev'], options);
+    let packageManagerToUse;
+    if (packageManager) {
+      packageManagerToUse = packageManager;
+    } else {
+      // If no package manager specified, try to figure out which one to use:
+      // Default to npm
+      packageManagerToUse = 'npm';
+      // If the yarn command exists and we find a yarn.lock, use yarn
+      if (commandExists('yarn')) {
+        if (await fs.exists(path.join(projectRootLocation, 'yarn.lock'))) {
+          packageManagerToUse = 'yarn';
+        } else {
+          logger.warn(
+            "Using NPM instead of Yarn. No 'yarn.lock' found in project directory, use the --package-manager flag to explicitly specify which package manager to use."
+          );
+        }
+      }
+    }
+
+    let commandToUse;
+    if (packageManagerToUse === 'npm') {
+      commandToUse = 'install';
     } else {
-      install = spawn('npm', ['install', ...modules, '--save-dev'], options);
+      commandToUse = 'add';
     }
 
+    let args = [commandToUse, ...modules];
+
+    if (saveDev) {
+      args.push('-D');
+    }
+
+    install = spawn(packageManagerToUse, args, options);
+
     install.stdout.pipe(process.stdout);
     install.stderr.pipe(process.stderr);