Avoid infinite recursion in Bundle.sort()

src/Bundle.js

@@ -422,15 +422,17 @@ export default class Bundle {
 						// b imports a, a is placed before b. We need to find the module
 						// in question, so we can provide a useful error message
 						let parent = '[[unknown]]';
+						const visited = {};
 
 						const findParent = module => {
 							if ( dependsOn[ module.id ][ a.id ] && dependsOn[ module.id ][ b.id ] ) {
 								parent = module.id;
-							} else {
+								return true;
+							}
+							visited[ module.id ] = true;
 							for ( let i = 0; i < module.dependencies.length; i += 1 ) {
 								const dependency = module.dependencies[i];
-									if ( findParent( dependency ) ) return;
+								if ( !visited[ dependency.id ] && findParent( dependency ) ) return true;
-								}
 							}
 						};
 

test/function/cycles-pathological-2/_config.js

@@ -0,0 +1,11 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'resolves even more pathological cyclical dependencies gracefully',
+	buble: true,
+	options: {
+		onwarn: function ( message ) {
+			assert.ok( /unable to evaluate without/.test( message ) );
+		}
+	}
+};

test/function/cycles-pathological-2/b.js

@@ -0,0 +1,11 @@
+import { a, av } from './main';
+import { d, dv } from './d';
+import { c, cv } from './c';
+
+export function b() {
+    a(av);
+    d(dv);
+    c(cv);
+};
+
+export const bv = av + dv + cv;

test/function/cycles-pathological-2/c.js

@@ -0,0 +1,9 @@
+import { b, bv } from './b';
+import { a, av } from './main';
+
+export function c() {
+    a(av);
+    b(bv);
+};
+
+export const cv = av + bv;

test/function/cycles-pathological-2/d.js

@@ -0,0 +1,7 @@
+import { c, cv } from './c';
+
+export function d() {
+    c(cv);
+};
+
+export const dv = cv;

test/function/cycles-pathological-2/main.js

@@ -0,0 +1,11 @@
+import { b, bv } from './b';
+import { d, dv } from './d';
+import { c, cv } from './c';
+
+export function a() {
+    b(bv);
+    d(dv);
+    c(cv);
+};
+
+export const av = bv + dv + cv;