fixes 624 - ability to require node modules using their package.json info

@@ -185,10 +185,33 @@ CasperError.prototype = Object.getPrototypeOf(new Error());
         if (require.patched) {
             return require;
         }
+        function fromPackageJson(module, dir) {
+            var pkgPath, pkgContents, pkg;
+            pkgPath = fs.pathJoin(dir, module, 'package.json');
+            if (!fs.exists(pkgPath)) {
+                return;
+            }
+            pkgContents = fs.read(pkgPath);
+            if (!pkgContents) {
+                return;
+            }
+            try {
+                pkg = JSON.parse(pkgContents);
+            } catch (e) {
+                return;
+            }
+            if (typeof pkg === "object" && pkg.main) {
+                return fs.absolute(fs.pathJoin(dir, module, pkg.main));
+            }
+        }
         function resolveFile(path, dir) {
             var extensions = ['js', 'coffee', 'json'];
             var basenames = [path, path + '/index'];
             var paths = [];
+            var nodejsScript = fromPackageJson(path, dir);
+            if (nodejsScript) {
+                return nodejsScript;
+            }
             basenames.forEach(function(basename) {
                 paths.push(fs.absolute(fs.pathJoin(dir, basename)));
                 extensions.forEach(function(extension) {

@@ -13,7 +13,8 @@ PHANTOMJS_EXEC = os.environ['PHANTOMJS_EXECUTABLE']
 # make it to an absolute path, because some test change the working directory
 # and relative path to phantomjs would be invalid
 if not os.path.isabs(PHANTOMJS_EXEC):
-    os.environ['PHANTOMJS_EXECUTABLE'] = os.path.join(CASPERJS_ROOT, PHANTOMJS_EXEC)
+    os.environ['PHANTOMJS_EXECUTABLE'] = os.path.join(CASPERJS_ROOT,
+                                                      PHANTOMJS_EXEC)
 
 class TimeoutException(Exception):
     pass
@@ -53,7 +54,8 @@ class CasperExecTestBase(unittest.TestCase):
         except subprocess.CalledProcessError as err:
             if failing:
                 return err.output.decode('utf-8')
-            raise IOError('Command %s exited: %s \n %s' % (cmd, err, err.output.decode('utf-8')))
+            raise IOError('Command %s exited: %s \n %s'
+                          % (cmd, err, err.output.decode('utf-8')))
 
     def assertCommandOutputEquals(self, cmd, result, **kwargs):
         self.assertEqual(self.runCommand(cmd), result)
@@ -96,7 +98,14 @@ class RequireScriptFullPathTest(CasperExecTestBase):
 
     @timeout(20)
     def test_node_module_require_index(self):
-        script_path = os.path.join(TEST_ROOT, 'modules', 'test_node_mod_index.js')
+        script_path = os.path.join(
+            TEST_ROOT, 'modules', 'test_node_mod_index.js')
+        self.assertCommandOutputEquals(script_path, '42')
+
+    @timeout(20)
+    def test_node_module_require_json_package(self):
+        script_path = os.path.join(
+            TEST_ROOT, 'modules', 'test_node_mod_json_package.js')
         self.assertCommandOutputEquals(script_path, '42')
 
     @timeout(20)
@@ -105,7 +114,6 @@ class RequireScriptFullPathTest(CasperExecTestBase):
         self.assertCommandOutputEquals(script_path, '42')
 
 
-
 class RequireWithOnlyScriptNameTest(CasperExecTestBase):
 
     def setUp(self):
@@ -123,7 +131,8 @@ class RequireWithOnlyScriptNameTest(CasperExecTestBase):
 
     @timeout(20)
     def test_simple_patched_require(self):
-        self.assertCommandOutputEquals('test_patched_require.js', 'hello, world')
+        self.assertCommandOutputEquals(
+            'test_patched_require.js', 'hello, world')
 
     @timeout(20)
     def test_require_coffee(self):
@@ -138,11 +147,15 @@ class RequireWithOnlyScriptNameTest(CasperExecTestBase):
         self.assertCommandOutputEquals('test_node_mod_index.js', '42')
 
     @timeout(20)
+    def test_node_module_require_json_package(self):
+        self.assertCommandOutputEquals('test_node_mod_json_package.js', '42')
+
+    @timeout(20)
     def test_node_module_require_json(self):
         self.assertCommandOutputEquals('test_node_json.js', '42')
 
-class RequireWithRelativeScriptPathTest(CasperExecTestBase):
 
+class RequireWithRelativeScriptPathTest(CasperExecTestBase):
     def setUp(self):
         self.currentPath = os.getcwd()
         os.chdir(os.path.join(TEST_ROOT, 'modules'))
@@ -158,7 +171,8 @@ class RequireWithRelativeScriptPathTest(CasperExecTestBase):
 
     @timeout(20)
     def test_simple_patched_require(self):
-        self.assertCommandOutputEquals('test_patched_require.js', 'hello, world')
+        self.assertCommandOutputEquals(
+            'test_patched_require.js', 'hello, world')
 
     @timeout(20)
     def test_require_coffee(self):
@@ -173,9 +187,14 @@ class RequireWithRelativeScriptPathTest(CasperExecTestBase):
         self.assertCommandOutputEquals('./test_node_mod_index.js', '42')
 
     @timeout(20)
+    def test_node_module_require_json_package(self):
+        self.assertCommandOutputEquals('./test_node_mod_json_package.js', '42')
+
+    @timeout(20)
     def test_node_module_require_json(self):
         self.assertCommandOutputEquals('./test_node_json.js', '42')
 
+
 class ScriptOutputTest(CasperExecTestBase):
     @timeout(20)
     def test_simple_script(self):