Make circular require()'s and exception.

apache · Aug 24, 2012 · 775c526 · 775c526
1 parent 2e6cb6e
commit 775c526
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Showing 2 changed files with 51 additions and 2 deletions.
diff --git a/lib/scripts/require.js b/lib/scripts/require.js
@@ -3,6 +3,10 @@ var require,
 
 (function () {
     var modules = {};
+    // Stack of moduleIds currently being built.
+    var requireStack = [];
+    // Map of module ID -> index into requireStack of modules currently being built.
+    var inProgressModules = {};
 
     function build(module) {
         var factory = module.factory;
@@ -15,8 +19,21 @@ var require,
     require = function (id) {
         if (!modules[id]) {
             throw "module " + id + " not found";
+        } else if (id in inProgressModules) {
+            var cycle = requireStack.slice(inProgressModules[id]).join('->') + '->' + id;
+            throw "Cycle in require graph: " + cycle;
         }
-        return modules[id].factory ? build(modules[id]) : modules[id].exports;
+        if (modules[id].factory) {
+            try {
+                inProgressModules[id] = requireStack.length;
+                requireStack.push(id);
+                return build(modules[id]);
+            } finally {
+                delete inProgressModules[id];
+                requireStack.pop();
+            }
+        }
+        return modules[id].exports;
     };
 
     define = function (id, factory) {
@@ -40,4 +57,4 @@ var require,
 if (typeof module === "object" && typeof require === "function") {
     module.exports.require = require;
     module.exports.define = define;
-}
+}
diff --git a/test/test.require.js b/test/test.require.js
@@ -35,6 +35,38 @@ describe("require + define", function () {
             }).toThrow("module your mom not found");
         });
 
+        it("throws an exception when modules depend on each other", function () {
+            define("ModuleA", function(require, exports, module) {
+                require("ModuleB");
+            });
+            define("ModuleB", function(require, exports, module) {
+                require("ModuleA");
+            });
+            expect(function () {
+                require("ModuleA");
+            }).toThrow("Cycle in require graph: ModuleA->ModuleB->ModuleA");
+            define.remove("ModuleA");
+            define.remove("ModuleB");
+        });
+
+        it("throws an exception when a cycle of requires occurs", function () {
+            define("ModuleA", function(require, exports, module) {
+                require("ModuleB");
+            });
+            define("ModuleB", function(require, exports, module) {
+                require("ModuleC");
+            });
+            define("ModuleC", function(require, exports, module) {
+                require("ModuleA");
+            });
+            expect(function () {
+                require("ModuleA");
+            }).toThrow("Cycle in require graph: ModuleA->ModuleB->ModuleC->ModuleA");
+            define.remove("ModuleA");
+            define.remove("ModuleB");
+            define.remove("ModuleC");
+        });
+
         it("calls the factory method when requiring", function () {
             var factory = jasmine.createSpy();
             define("dino", factory);