Simplify API.

xonsh/history/base.py

@@ -170,15 +170,6 @@ class History:
 
     def clear(self):
         """Wipes the current session from both the disk and memory."""
-        self.wipe_disk()
-        self.wipe_memory()
-
-    def wipe_disk(self):
-        """Wipes the current session's history from the disk."""
-        pass
-
-    def wipe_memory(self):
-        """Reinitialises History object with blank commands."""
         pass
 
     def remake_file(self):

xonsh/history/json.py

@@ -327,9 +327,9 @@ class JsonCommandField(cabc.Sequence):
                     if isinstance(rtn, xlj.LJNode):
                         rtn = rtn.load()
                 queue.popleft()
+            return rtn
         else:
             return ""
-        return rtn
 
     def i_am_at_the_front(self):
         """Tests if the command field is at the front of the queue."""
@@ -508,14 +508,18 @@ class JsonHistory(History):
             while self.gc.is_alive():  # while waiting for gc.
                 time.sleep(0.1)  # don't monopolize the thread (or Python GIL?)
 
-    def wipe_disk(self):
+    def clear(self):
+        def wipe_disk(hist):
             try:
-            os.remove(self.filename)
+                os.remove(hist.filename)
             except FileNotFoundError:
                 pass
 
-    def wipe_memory(self):  # todo is this enough?
-        self.buffer = []
+        def wipe_memory(hist):  # todo is this enough?
+            hist.buffer = []
+
+        wipe_disk(self)
+        wipe_memory(self)
 
     def remake_file(self):
         meta = dict()