Reduce transformers error message chain

src/utils/transform.js

@@ -31,9 +31,12 @@ export default function transform ( source, id, plugins ) {
 				return result.code;
 			});
 		}).catch( err => {
-			err.id = id;
-			err.plugin = plugin.name;
-			err.message = `Error transforming ${id}${plugin.name ? ` with '${plugin.name}' plugin` : ''}: ${err.message}`;
+			if ( !err.rollupTransform ) {
+				err.rollupTransform = true;
+				err.id = id;
+				err.plugin = plugin.name;
+				err.message = `Error transforming ${id}${plugin.name ? ` with '${plugin.name}' plugin` : ''}: ${err.message}`;
+			}
 			throw err;
 		});
 	}, Promise.resolve( source.code ) )

test/function/throws-only-first-transform-bundle/_config.js

@@ -0,0 +1,25 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'throws error only with first plugin transformBundle',
+	options: {
+		plugins: [
+			{
+				name: 'plugin1',
+				transformBundle: function () {
+					throw Error('Something happend 1');
+				}
+			},
+			{
+				name: 'plugin2',
+				transformBundle: function () {
+					throw Error('Something happend 2');
+				}
+			}
+		]
+	},
+	generateError: function ( err ) {
+		assert.equal( err.plugin, 'plugin1' );
+		assert.equal( err.message, 'Error transforming bundle with \'plugin1\' plugin: Something happend 1' );
+	}
+};

test/function/throws-only-first-transform-bundle/main.js

@@ -0,0 +1 @@
+console.log(1);

test/function/throws-only-first-transform/_config.js

@@ -0,0 +1,29 @@
+var assert = require( 'assert' );
+var path = require( 'path' );
+
+module.exports = {
+	description: 'throws error only with first plugin transform',
+	options: {
+		plugins: [
+			{
+				name: 'plugin1',
+				transform: function () {
+					throw Error('Something happend 1');
+				}
+			},
+			{
+				name: 'plugin2',
+				transform: function () {
+					throw Error('Something happend 2');
+				}
+			}
+		]
+	},
+	error: function ( err ) {
+		var id = path.resolve( __dirname, 'main.js' );
+		assert.equal( err.rollupTransform, true );
+		assert.equal( err.id, id );
+		assert.equal( err.plugin, 'plugin1' );
+		assert.equal( err.message, 'Error transforming ' + id + ' with \'plugin1\' plugin: Something happend 1' );
+	}
+};

test/function/throws-only-first-transform/main.js

@@ -0,0 +1 @@
+console.log(1);