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');
 
 /**
  * The Bundler is the main entry point. It resolves and loads assets,
@@ -328,26 +329,42 @@ class Bundler extends EventEmitter {
       let thrown = err;
 
       if (thrown.message.indexOf(`Cannot find module '${dep.name}'`) === 0) {
-        if (dep.optional) {
-          return;
-        }
-
-        thrown.message = `Cannot resolve dependency '${dep.name}'`;
-
-        // Add absolute path to the error message if the dependency specifies a relative path
-        if (dep.name.startsWith('.')) {
-          const absPath = Path.resolve(Path.dirname(asset.name), dep.name);
-          err.message += ` at '${absPath}'`;
-        }
-
-        // Generate a code frame where the dependency was used
-        if (dep.loc) {
-          await asset.loadIfNeeded();
-          thrown.loc = dep.loc;
-          thrown = asset.generateErrorMessage(thrown);
+        let isLocalFile = dep.name.startsWith('.');
+
+        if (!isLocalFile) {
+          try {
+            try {
+              logger.status(emoji.progress, `Installing ${dep.name}...`);
+              let dir = Path.dirname(asset.name);
+              await installPackage(dir, [dep.name], true, false);
+            } catch (npmError) {
+              logger.error(npmError.message);
+            }
+
+            return await this.resolveAsset(dep.name, asset.name);
+          } catch (e) {
+            if (dep.optional) {
+              return;
+            }
+
+            thrown.message = `Cannot resolve dependency '${dep.name}'`;
+
+            // Add absolute path to the error message if the dependency specifies a relative path
+            if (isLocalFile) {
+              const absPath = Path.resolve(Path.dirname(asset.name), dep.name);
+              err.message += ` at '${absPath}'`;
+            }
+
+            // Generate a code frame where the dependency was used
+            if (dep.loc) {
+              await asset.loadIfNeeded();
+              thrown.loc = dep.loc;
+              thrown = asset.generateErrorMessage(thrown);
+            }
+
+            thrown.fileName = asset.name;
+          }
         }
-
-        thrown.fileName = asset.name;
       }
       throw thrown;
     }

src/utils/installPackage.js

@@ -3,8 +3,9 @@ const config = require('./config');
 const path = require('path');
 const promisify = require('./promisify');
 const resolve = promisify(require('resolve'));
+const commandExists = require('command-exists').sync;
 
-async function install(dir, modules, installPeers = true) {
+async function install(dir, modules, installPeers = true, saveDev = true) {
   let location = await config.resolve(dir, ['yarn.lock', 'package.json']);
 
   return new Promise((resolve, reject) => {
@@ -13,12 +14,18 @@ async function install(dir, modules, installPeers = true) {
       cwd: location ? path.dirname(location) : dir
     };
 
-    if (location && path.basename(location) === 'yarn.lock') {
-      install = spawn('yarn', ['add', ...modules, '--dev'], options);
-    } else {
-      install = spawn('npm', ['install', ...modules, '--save-dev'], options);
+    let args = ['add', ...modules];
+    if (saveDev) {
+      args.push('-D');
     }
 
+    let command = 'npm';
+    if (commandExists('yarn')) {
+      command = 'yarn';
+    }
+
+    install = spawn(command, args, options);
+
     install.stdout.pipe(process.stdout);
     install.stderr.pipe(process.stderr);