From 509502b17016edc27af5808624986557197e57e7 Mon Sep 17 00:00:00 2001
From: Rich-Harris <richard.a.harris@gmail.com>
Date: Fri, 1 Jan 2016 16:12:09 -0500
Subject: [PATCH] fix failing preflight check in absence of class transformer
 (closes #23)

---
 packages/rollup-plugin-babel/package.json     |  1 +
 packages/rollup-plugin-babel/src/index.js     | 33 ++++++++++++++-----
 .../samples/no-class-transformer/.babelrc     |  1 +
 .../test/samples/no-class-transformer/main.js |  1 +
 packages/rollup-plugin-babel/test/test.js     |  7 ++++
 5 files changed, 35 insertions(+), 8 deletions(-)
 create mode 100644 packages/rollup-plugin-babel/test/samples/no-class-transformer/.babelrc
 create mode 100644 packages/rollup-plugin-babel/test/samples/no-class-transformer/main.js

diff --git a/packages/rollup-plugin-babel/package.json b/packages/rollup-plugin-babel/package.json
index d60bedba7..05fb68a3a 100644
--- a/packages/rollup-plugin-babel/package.json
+++ b/packages/rollup-plugin-babel/package.json
@@ -29,6 +29,7 @@
   },
   "dependencies": {
     "babel-core": "6",
+    "babel-plugin-transform-es2015-classes": "^6.3.15",
     "object-assign": "^4.0.1",
     "rollup-pluginutils": "^1.1.0"
   },
diff --git a/packages/rollup-plugin-babel/src/index.js b/packages/rollup-plugin-babel/src/index.js
index ab61ca2e9..8a71ef0ac 100644
--- a/packages/rollup-plugin-babel/src/index.js
+++ b/packages/rollup-plugin-babel/src/index.js
@@ -1,3 +1,4 @@
+import { dirname, join } from 'path';
 import { buildExternalHelpers, transform } from 'babel-core';
 import { createFilter } from 'rollup-pluginutils';
 
@@ -5,16 +6,32 @@ const INLINE = {};
 const RUNTIME = {};
 const BUNDLED = {};
 
-function preflightCheck ( localOpts ) {
-	var check = transform( 'export default class Foo {}', localOpts ).code;
+let preflightCheckResults = {};
 
-	if ( !~check.indexOf( 'export default' ) && !~check.indexOf( 'export { Foo as default }' ) ) throw new Error( 'It looks like your Babel configuration specifies a module transformer. Please disable it. If you\'re using the "es2015" preset, consider using "es2015-rollup" instead. See https://github.com/rollup/rollup-plugin-babel#TK for more information' );
+function preflightCheck ( options, dir ) {
+	let helpers;
 
-	if ( ~check.indexOf( 'import _classCallCheck from "babel-runtime' ) ) return RUNTIME;
-	if ( ~check.indexOf( 'function _classCallCheck' ) ) return INLINE;
-	if ( ~check.indexOf( 'babelHelpers' ) ) return BUNDLED;
+	if ( !preflightCheckResults[ dir ] ) {
+		options = assign( {}, options );
+		options.filename = join( dir, 'x.js' );
 
-	throw new Error( 'An unexpected situation arose. Please raise an issue at https://github.com/rollup/rollup-plugin-babel/issues. Thanks!' );
+		if ( !options.plugins ) options.plugins = [];
+		options.plugins.push( 'transform-es2015-classes' );
+
+		const check = transform( 'export default class Foo {}', options ).code;
+
+		if ( !~check.indexOf( 'export default' ) && !~check.indexOf( 'export { Foo as default }' ) ) throw new Error( 'It looks like your Babel configuration specifies a module transformer. Please disable it. If you\'re using the "es2015" preset, consider using "es2015-rollup" instead. See https://github.com/rollup/rollup-plugin-babel#configuring-babel for more information' );
+
+		if ( ~check.indexOf( 'import _classCallCheck from "babel-runtime' ) ) helpers = RUNTIME;
+		else if ( ~check.indexOf( 'function _classCallCheck' ) ) helpers = INLINE;
+		else if ( ~check.indexOf( 'babelHelpers' ) ) helpers = BUNDLED;
+
+		else {
+			throw new Error( 'An unexpected situation arose. Please raise an issue at https://github.com/rollup/rollup-plugin-babel/issues. Thanks!' );
+		}
+	}
+
+	return preflightCheckResults[ dir ] = helpers;
 }
 
 function assign ( target, source ) {
@@ -51,8 +68,8 @@ export default function babel ( options ) {
 		transform ( code, id ) {
 			if ( !filter( id ) ) return null;
 
+			const helpers = preflightCheck( options, dirname( id ) );
 			var localOpts = assign({ filename: id }, options );
-			const helpers = preflightCheck( localOpts );
 
 			var transformed = transform( code, localOpts );
 			const { usedHelpers } = transformed.metadata;
diff --git a/packages/rollup-plugin-babel/test/samples/no-class-transformer/.babelrc b/packages/rollup-plugin-babel/test/samples/no-class-transformer/.babelrc
new file mode 100644
index 000000000..0967ef424
--- /dev/null
+++ b/packages/rollup-plugin-babel/test/samples/no-class-transformer/.babelrc
@@ -0,0 +1 @@
+{}
diff --git a/packages/rollup-plugin-babel/test/samples/no-class-transformer/main.js b/packages/rollup-plugin-babel/test/samples/no-class-transformer/main.js
new file mode 100644
index 000000000..17eee8f1f
--- /dev/null
+++ b/packages/rollup-plugin-babel/test/samples/no-class-transformer/main.js
@@ -0,0 +1 @@
+assert.equal( 1 + 1, 2 );
diff --git a/packages/rollup-plugin-babel/test/test.js b/packages/rollup-plugin-babel/test/test.js
index 8d4ff1a6e..c2e518a23 100644
--- a/packages/rollup-plugin-babel/test/test.js
+++ b/packages/rollup-plugin-babel/test/test.js
@@ -149,4 +149,11 @@ describe( 'rollup-plugin-babel', function () {
 			assert.ok( !~cjs.indexOf( 'babelHelpers_get get' ), 'helper was incorrectly renamed' );
 		});
 	});
+
+	it( 'runs preflight check correctly in absence of class transformer (#23)', () => {
+		return rollup.rollup({
+			entry: 'samples/no-class-transformer/main.js',
+			plugins: [ babelPlugin() ]
+		});
+	});
 });