Fix problems when global objects like JSON, etc. have been rewired

Fixes jhnns#40

Author: jhnns

lib/__set__.js

@@ -12,19 +12,30 @@
 function __set__() {
     arguments.varName = arguments[0];
     arguments.varValue = arguments[1];
+    // Saving references to global objects and functions. Thus a test may even change these variables
+    // without interfering with rewire().
+    // @see https://github.com/jhnns/rewire/issues/40
+    arguments.refs = arguments[2] || {
+        isArray: Array.isArray,
+        TypeError: TypeError,
+        stringify: JSON.stringify
+        // We can't save eval() because eval() is a *special* global function
+        // That's why it can't be re-assigned in strict mode
+        //eval: eval
+    };
     arguments.src = "";
     arguments.revertArgs = [];
 
-    if (typeof arguments[0] === "object" && arguments.length === 1) {
+    if (typeof arguments[0] === "object") {
         arguments.env = arguments.varName;
-        if (!arguments.env || Array.isArray(arguments.env)) {
-            throw new TypeError("__set__ expects an object as env");
+        if (!arguments.env || arguments.refs.isArray(arguments.env)) {
+            throw new arguments.refs.TypeError("__set__ expects an object as env");
         }
         arguments.revertArgs[0] = {};
         for (arguments.varName in arguments.env) {
             if (arguments.env.hasOwnProperty(arguments.varName)) {
                 arguments.varValue = arguments.env[arguments.varName];
-                arguments.src += arguments.varName + " = arguments.env[" + JSON.stringify(arguments.varName) + "]; ";
+                arguments.src += arguments.varName + " = arguments.env[" + arguments.refs.stringify(arguments.varName) + "]; ";
                 try {
                     // Allow tests to mock implicit globals
                     // @see https://github.com/jhnns/rewire/issues/35
@@ -34,9 +45,9 @@ function __set__() {
                 }
             }
         }
-    } else if (typeof arguments.varName === "string" && arguments.length === 2) {
+    } else if (typeof arguments.varName === "string") {
         if (!arguments.varName) {
-            throw new TypeError("__set__ expects a non-empty string as a variable name");
+            throw new arguments.refs.TypeError("__set__ expects a non-empty string as a variable name");
         }
         arguments.src = arguments.varName + " = arguments.varValue;";
         try {
@@ -47,9 +58,12 @@ function __set__() {
             arguments.revertArgs = [arguments.varName, undefined];
         }
     } else {
-        throw new TypeError("__set__ expects an environment object or a non-empty string as a variable name");
+        throw new arguments.refs.TypeError("__set__ expects an environment object or a non-empty string as a variable name");
     }
 
+    // Passing our saved references on to the revert function
+    arguments.revertArgs[2] = arguments.refs;
+
     eval(arguments.src);
 
     return function (revertArgs) {

test/__set__.test.js

@@ -121,11 +121,5 @@ describe("__set__", function () {
         expect(function () {
             moduleFake.__set__(function () {});
         }).to.throwException(expectTypeError);
-        expect(function () {
-            moduleFake.__set__({}, true);   // misfitting number of params
-        }).to.throwException(expectTypeError);
-        expect(function () {
-            moduleFake.__set__("someVar");  // misfitting number of params
-        }).to.throwException(expectTypeError);
     });
-});
+});

test/testModules/sharedTestCases.js

@@ -337,4 +337,17 @@ describe("rewire " + (typeof testEnv === "undefined"? "(node)": "(" + testEnv +
         }
     });
 
+    it("should be possible to mock and revert JSON.parse (see #40)", function () {
+        var moduleA = rewire("./moduleA.js"),
+            revert;
+
+        revert = moduleA.__set__({
+            JSON: {
+                parse: function () { return true; }
+            }
+        });
+
+        revert();
+    });
+
 });