Use JSON for saving method params

* Splitting with a delimiter would break if the delimiter was included
in the params
* Joining the array of params also inadvertently cast params to strings
* Use JSON stringify/parse to avoid these problems
* Catch JSON parse errors and continue, so that the troublesome cookie
gets deleted
* govuk-template provides a JSON shim for older browsers
* Remove old spec helper regarding JSON.parse, all tests pass correctly
with the latest PhantomJS it seems.

app/assets/javascripts/analytics/static-tracker.js

@@ -91,16 +91,20 @@
 
     if (GOVUK.cookie && typeof this[method] === "function") {
       params.unshift(method);
-      GOVUK.cookie('analytics_next_page_call', params.join('|'));
+      GOVUK.cookie('analytics_next_page_call', JSON.stringify(params));
     }
   };
 
   StaticTracker.prototype.callMethodRequestedByPreviousPage = function() {
     if (GOVUK.cookie && GOVUK.cookie('analytics_next_page_call') !== null) {
-      var params = GOVUK.cookie('analytics_next_page_call').split('|'),
-          method = params.shift();
+      var params, method;
 
-      if (typeof this[method] === "function") {
+      try {
+        params = JSON.parse(GOVUK.cookie('analytics_next_page_call'));
+        method = params.shift();
+      } catch(e) {}
+
+      if (method && typeof this[method] === "function") {
         this[method].apply(this, params);
       }
 

spec/javascripts/analytics/static-tracker-spec.js

@@ -54,7 +54,13 @@ describe("GOVUK.StaticTracker", function() {
       it('sets them as a dimension', function() {
         window.ga.calls.reset();
         window._gaq = [];
-        spyOn(GOVUK, 'cookie').and.returnValue("_setCustomVar,21,name,value,3");
+        spyOn(GOVUK, 'cookie').and.callFake(function(name) {
+          if (name === "ga_nextpage_params") {
+            return "_setCustomVar,21,name,value,3";
+          }
+
+          return null;
+        });
         tracker = new GOVUK.StaticTracker({universalId: 'universal-id', classicId: 'classic-id'});
         universalSetupArguments = window.ga.calls.allArgs();
 
@@ -188,17 +194,17 @@ describe("GOVUK.StaticTracker", function() {
     describe('and the method exists', function() {
       it('sets a cookie with the method name', function() {
         tracker.callOnNextPage('trackPageview');
-        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', 'trackPageview');
+        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', '["trackPageview"]');
       });
 
       it('sets a cookie with the parameters to call', function() {
         tracker.callOnNextPage('trackPageview', ['/path', 'Custom Title']);
-        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', 'trackPageview|/path|Custom Title');
+        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', '["trackPageview","/path","Custom Title"]');
       });
 
       it('sets a cookie with the single parameter to call', function() {
         tracker.callOnNextPage('trackPageview', '/path');
-        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', 'trackPageview|/path');
+        expect(GOVUK.cookie).toHaveBeenCalledWith('analytics_next_page_call', '["trackPageview","/path"]');
       });
     });
 
@@ -216,13 +222,26 @@ describe("GOVUK.StaticTracker", function() {
     });
 
     it('calls the method', function() {
-      spyOn(GOVUK, 'cookie').and.returnValue("trackPageview");
+      spyOn(GOVUK, 'cookie').and.callFake(function(name) {
+        if (name === "analytics_next_page_call") {
+          return '["trackPageview"]';
+        }
+
+        return null;
+      });
       tracker.callMethodRequestedByPreviousPage();
       expect(tracker.trackPageview).toHaveBeenCalledWith();
     });
 
     it('calls the method with given parameters', function() {
-      spyOn(GOVUK, 'cookie').and.returnValue("trackPageview|/path|Title");
+      spyOn(GOVUK, 'cookie').and.callFake(function(name) {
+        if (name === "analytics_next_page_call") {
+          return '["trackPageview","/path","Title"]';
+        }
+
+        return null;
+      });
+
       tracker.callMethodRequestedByPreviousPage();
       expect(tracker.trackPageview).toHaveBeenCalledWith('/path', 'Title');
     });

spec/javascripts/helpers/SpecHelper.js

@@ -21,15 +21,3 @@ beforeEach(function () {
     }
   });
 });
-
-// When using phantomJS JSON.parse seems bugged, returning a string instead of a built object.
-// I'm unsure as to why, since when testing this behaviour directly in phantom it behaves
-// as expected. This monkey patches the issue, but It'd be good to find out what's going on here.
-var _JSON_parse = JSON.parse;
-JSON.parse = function(json_string) {
-  var result = _JSON_parse(json_string);
-  if (typeof result == "string") {
-    result = eval(result);
-  }
-  return result;
-}