Add a lock for folks using threading. Mucho helpful.

I can't see any *downside* to including a lock here. Basically, it
just says that two threads running in parallel can't touch the code
between the lock.acquire() <--> lock.release() statements
concurrently. We use it in low-level util functions to prevent
concurrent file reads/writes.

This was a bug that showed up while running our auto-documentation
examples.

Author: theengineear

Diff for: plotly/tools.py

@@ -134,8 +134,7 @@ def get_credentials_file(*args):
 
 def reset_credentials_file():
     ensure_local_plotly_files()  # make sure what's there is OK
-    f = open(CREDENTIALS_FILE, 'w')
-    f.close()
+    utils.save_json_dict(CREDENTIALS_FILE, {})
     ensure_local_plotly_files()  # put the defaults back
 
 

Diff for: plotly/utils.py

@@ -9,21 +9,26 @@
 import json
 import os.path
 import sys
+import threading
 
+### incase people are using threadig, we lock file reads
+lock = threading.Lock()
 
 ### general file setup tools ###
 
 def load_json_dict(filename, *args):
     """Checks if file exists. Returns {} if something fails."""
     data = {}
     if os.path.exists(filename):
+        lock.acquire()
         with open(filename, "r") as f:
             try:
                 data = json.load(f)
                 if not isinstance(data, dict):
                     data = {}
             except:
                 pass # TODO: issue a warning and bubble it up
+        lock.release()
         if args:
             d = dict()
             for key in args:
@@ -39,8 +44,10 @@ def save_json_dict(filename, json_dict):
     """Will error if filename is not appropriate, but it's checked elsewhere.
     """
     if isinstance(json_dict, dict):
+        lock.acquire()
         with open(filename, "w") as f:
             f.write(json.dumps(json_dict, indent=4))
+        lock.release()
     else:
         raise TypeError("json_dict was not a dictionay. couldn't save.")