add custom locator strategy (#260)

Author: jlipps

appium/webdriver/common/mobileby.py

@@ -23,3 +23,4 @@ class MobileBy(By):
     ANDROID_VIEWTAG = '-android viewtag'
     ACCESSIBILITY_ID = 'accessibility id'
     IMAGE = '-image'
+    CUSTOM = '-custom'

appium/webdriver/webdriver.py

@@ -110,6 +110,7 @@ def __init__(self, command_executor='http://127.0.0.1:4444/wd/hub',
         By.ANDROID_VIEWTAG = MobileBy.ANDROID_VIEWTAG
         By.ACCESSIBILITY_ID = MobileBy.ACCESSIBILITY_ID
         By.IMAGE = MobileBy.IMAGE
+        By.CUSTOM = MobileBy.CUSTOM
 
     def start_session(self, capabilities, browser_profile=None):
         """
@@ -416,6 +417,34 @@ def find_elements_by_accessibility_id(self, accessibility_id):
         """
         return self.find_elements(by=By.ACCESSIBILITY_ID, value=accessibility_id)
 
+    def find_element_by_custom(self, selector):
+        """Finds an element in conjunction with a custom element finding plugin
+
+        :Args:
+         - selector - a string of the form "module:selector", where "module" is
+           the shortcut name given in the customFindModules capability, and
+           "selector" is the string that will be passed to the custom element
+           finding plugin itself
+
+        :Usage:
+            driver.find_element_by_custom("foo:bar")
+        """
+        return self.find_element(by=By.CUSTOM, value=selector)
+
+    def find_elements_by_custom(self, selector):
+        """Finds elements in conjunction with a custom element finding plugin
+
+        :Args:
+         - selector - a string of the form "module:selector", where "module" is
+           the shortcut name given in the customFindModules capability, and
+           "selector" is the string that will be passed to the custom element
+           finding plugin itself
+
+        :Usage:
+            driver.find_elements_by_custom("foo:bar")
+        """
+        return self.find_elements(by=By.CUSTOM, value=selector)
+
     def create_web_element(self, element_id):
         """
         Creates a web element with the specified element_id.