feat(jasminewd): allow custom matchers to return promises

Allow custom jasmine matchers to return a promise which resolves to a boolean
and match against the resolution of the promise

jasminewd/index.js

@@ -148,6 +148,32 @@ global.expect = function(actual) {
   }
 };
 
+// Wrap internal Jasmine function to allow custom matchers
+// to return promises that resolve to truthy or falsy values
+var originalMatcherFn = jasmine.Matchers.matcherFn_;
+jasmine.Matchers.matcherFn_ = function(matcherName, matcherFunction) {
+  var matcherFnThis = this;
+  var matcherFnArgs = jasmine.util.argsToArray(arguments);
+  return function() {
+    var matcherThis = this;
+    var matcherArgs = jasmine.util.argsToArray(arguments);
+    var result = matcherFunction.apply(this, arguments);
+
+    if (result instanceof webdriver.promise.Promise) {
+      result.then(function(resolution) {
+        matcherFnArgs[1] = function() {
+          return resolution;
+        };
+        originalMatcherFn.apply(matcherFnThis, matcherFnArgs).
+            apply(matcherThis, matcherArgs);
+      });
+    } else {
+      originalMatcherFn.apply(matcherFnThis, matcherFnArgs).
+          apply(matcherThis, matcherArgs);
+    }
+  };
+};
+
 /**
  * A Jasmine reporter which does nothing but execute the input function
  * on a timeout failure.

jasminewd/spec/adapterSpec.js

@@ -47,7 +47,25 @@ var getFakeDriver = function() {
         return flow.execute(function() {
           return webdriver.promise.fulfilled(3.14159);
         });
-      }
+      },
+    getDisplayedElement: function() {
+      return flow.execute(function() {
+        return webdriver.promise.fulfilled({
+          isDisplayed: function() {
+            return webdriver.promise.fulfilled(true);
+          }
+        });
+      });
+    },
+    getHiddenElement: function() {
+      return flow.execute(function() {
+        return webdriver.promise.fulfilled({
+          isDisplayed: function() {
+            return webdriver.promise.fulfilled(false);
+          }
+        });
+      });
+    }
   };
 };
 
@@ -69,6 +87,10 @@ describe('webdriverJS Jasmine adapter', function() {
     this.addMatchers({
       toBeLotsMoreThan: function(expected) {
         return this.actual > expected + 100;
+      },
+      // Example custom matcher returning a promise that resolves to true/false.
+      toBeDisplayed: function() {
+        return this.actual.isDisplayed();
       }
     });
   });
@@ -116,6 +138,11 @@ describe('webdriverJS Jasmine adapter', function() {
     expect(fakeDriver.getBigNumber()).toBeLotsMoreThan(33);
   });
 
+  it('should allow custom matchers to return a promise', function() {
+    expect(fakeDriver.getDisplayedElement()).toBeDisplayed();
+    expect(fakeDriver.getHiddenElement()).not.toBeDisplayed();
+  });
+
   it('should pass multiple arguments to matcher', function() {
       // Passing specific precision
       expect(fakeDriver.getDecimalNumber()).toBeCloseTo(3.1, 1);