Auto-install peerDependencies (#622)

* Auto-install peerDependencies on local require

* Install all peer dependencies at once

* Minor clean up

src/utils/installPackage.js

@@ -1,8 +1,10 @@
 const spawn = require('cross-spawn');
 const config = require('./config');
 const path = require('path');
+const promisify = require('./promisify');
+const resolve = promisify(require('resolve'));
 
-module.exports = async function(dir, name) {
+async function install(dir, modules, installPeers = true) {
   let location = await config.resolve(dir, ['yarn.lock', 'package.json']);
 
   return new Promise((resolve, reject) => {
@@ -12,19 +14,53 @@ module.exports = async function(dir, name) {
     };
 
     if (location && path.basename(location) === 'yarn.lock') {
-      install = spawn('yarn', ['add', name, '--dev'], options);
+      install = spawn('yarn', ['add', ...modules, '--dev'], options);
     } else {
-      install = spawn('npm', ['install', name, '--save-dev'], options);
+      install = spawn('npm', ['install', ...modules, '--save-dev'], options);
     }
 
     install.stdout.pipe(process.stdout);
     install.stderr.pipe(process.stderr);
 
-    install.on('close', code => {
+    install.on('close', async code => {
       if (code !== 0) {
-        return reject(new Error(`Failed to install ${name}.`));
+        return reject(new Error(`Failed to install ${modules.join(', ')}.`));
       }
-      return resolve();
+
+      if (!installPeers) {
+        return resolve();
+      }
+
+      try {
+        await Promise.all(modules.map(m => installPeerDependencies(dir, m)));
+      } catch (err) {
+        return reject(
+          new Error(
+            `Failed to install peerDependencies for ${modules.join(', ')}.`
+          )
+        );
+      }
+
+      resolve();
     });
   });
-};
+}
+
+async function installPeerDependencies(dir, name) {
+  let basedir = path.dirname(dir);
+
+  const [resolved] = await resolve(name, {basedir});
+  const pkg = await config.load(resolved, ['package.json']);
+  const peers = pkg.peerDependencies || {};
+
+  const modules = [];
+  for (const peer in peers) {
+    modules.push(`${peer}@${peers[peer]}`);
+  }
+
+  if (modules.length) {
+    await install(dir, modules, false);
+  }
+}
+
+module.exports = install;

src/utils/localRequire.js

@@ -13,7 +13,7 @@ async function localRequire(name, path, triedInstall = false) {
       resolved = resolve.sync(name, {basedir});
     } catch (e) {
       if (e.code === 'MODULE_NOT_FOUND' && !triedInstall) {
-        await install(path, name);
+        await install(path, [name]);
         return localRequire(name, path, true);
       }
       throw e;

test/css.js

@@ -200,6 +200,9 @@ describe('css', function() {
     let package = require('./input/package.json');
     assert(package.devDependencies['postcss-cssnext']);
 
+    // peer dependency caniuse-lite was installed
+    assert(package.devDependencies['caniuse-lite']);
+
     // cssnext is applied
     let css = fs.readFileSync(__dirname + '/dist/index.css', 'utf8');
     assert(css.includes('rgba'));
@@ -217,6 +220,9 @@ describe('css', function() {
     let package = require('./input/package.json');
     assert(package.devDependencies['postcss-cssnext']);
 
+    // peer dependency caniuse-lite was installed
+    assert(package.devDependencies['caniuse-lite']);
+
     // appveyor is not currently writing to the yarn.lock file and will require further investigation
     // let lockfile = fs.readFileSync(__dirname + '/input/yarn.lock', 'utf8');
     // assert(lockfile.includes('postcss-cssnext'));