Handle the case where the path is empty

IPython/nbconvert/preprocessors/execute.py

@@ -1,115 +1,117 b''
 """Module containing a preprocessor that removes the outputs from code cells"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import os
 
 try:
     from queue import Empty  # Py 3
 except ImportError:
     from Queue import Empty  # Py 2
 
 from IPython.utils.traitlets import List, Unicode
 
 from IPython.nbformat.v4 import output_from_msg
 from .base import Preprocessor
 from IPython.utils.traitlets import Integer
 
 
 class ExecutePreprocessor(Preprocessor):
     """
     Executes all the cells in a notebook
     """
     
     timeout = Integer(30, config=True,
         help="The time to wait (in seconds) for output from executions."
     )
     
     extra_arguments = List(Unicode)
 
     def preprocess(self, nb, resources):
-        path = resources.get('metadata', {}).get('path', None)
+        path = resources.get('metadata', {}).get('path', '')
+        if path == '':
+            path = None
 
         from IPython.kernel import run_kernel
         kernel_name = nb.metadata.get('kernelspec', {}).get('name', 'python')
         self.log.info("Executing notebook with kernel: %s" % kernel_name)
         with run_kernel(kernel_name=kernel_name,
                         extra_arguments=self.extra_arguments,
                         stderr=open(os.devnull, 'w'),
                         cwd=path) as kc:
             self.kc = kc
             self.kc.allow_stdin = False
             nb, resources = super(ExecutePreprocessor, self).preprocess(nb, resources)
         return nb, resources
 
     def preprocess_cell(self, cell, resources, cell_index):
         """
         Apply a transformation on each code cell. See base.py for details.
         """
         if cell.cell_type != 'code':
             return cell, resources
         try:
             outputs = self.run_cell(cell)
         except Exception as e:
             self.log.error("failed to run cell: " + repr(e))
             self.log.error(str(cell.source))
             raise
         cell.outputs = outputs
         return cell, resources
 
     def run_cell(self, cell):
         msg_id = self.kc.execute(cell.source)
         self.log.debug("Executing cell:\n%s", cell.source)
         # wait for finish, with timeout
         while True:
             try:
                 msg = self.kc.shell_channel.get_msg(timeout=self.timeout)
             except Empty:
                 self.log.error("Timeout waiting for execute reply")
                 raise
             if msg['parent_header'].get('msg_id') == msg_id:
                 break
             else:
                 # not our reply
                 continue
         
         outs = []
 
         while True:
             try:
                 msg = self.kc.iopub_channel.get_msg(timeout=self.timeout)
             except Empty:
                 self.log.warn("Timeout waiting for IOPub output")
                 break
             if msg['parent_header'].get('msg_id') != msg_id:
                 # not an output from our execution
                 continue
 
             msg_type = msg['msg_type']
             self.log.debug("output: %s", msg_type)
             content = msg['content']
 
             # set the prompt number for the input and the output
             if 'execution_count' in content:
                 cell['execution_count'] = content['execution_count']
 
             if msg_type == 'status':
                 if content['execution_state'] == 'idle':
                     break
                 else:
                     continue
             elif msg_type == 'execute_input':
                 continue
             elif msg_type == 'clear_output':
                 outs = []
                 continue
 
             try:
                 out = output_from_msg(msg)
             except ValueError:
                 self.log.error("unhandled iopub msg: " + msg_type)
             else:
                 outs.append(out)
 
         return outs