More elegant approach to previous buglet.

IPython/frontend/linefrontendbase.py

@@ -1,307 +1,307
 """
 Base front end class for all line-oriented frontends, rather than
 block-oriented.
 
 Currently this focuses on synchronous frontends.
 """
 __docformat__ = "restructuredtext en"
 
 #-------------------------------------------------------------------------------
 #  Copyright (C) 2008  The IPython Development Team
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #-------------------------------------------------------------------------------
 
 #-------------------------------------------------------------------------------
 # Imports
 #-------------------------------------------------------------------------------
 import re
 
 import IPython
 import sys
 
 from frontendbase import FrontEndBase
 from IPython.kernel.core.interpreter import Interpreter
 
 def common_prefix(strings):
     """ Given a list of strings, return the common prefix between all
         these strings.
     """
     ref = strings[0]
     prefix = ''
     for size in range(len(ref)):
         test_prefix = ref[:size+1]
         for string in strings[1:]:
             if not string.startswith(test_prefix):
                 return prefix
         prefix = test_prefix
 
     return prefix
 
 #-------------------------------------------------------------------------------
 # Base class for the line-oriented front ends
 #-------------------------------------------------------------------------------
 class LineFrontEndBase(FrontEndBase):
     """ Concrete implementation of the FrontEndBase class. This is meant
     to be the base class behind all the frontend that are line-oriented,
     rather than block-oriented.
     """
     
     # We need to keep the prompt number, to be able to increment
     # it when there is an exception.
     prompt_number = 1
 
     # We keep a reference to the last result: it helps testing and
     # programatic control of the frontend. 
     last_result = dict(number=0)
 
     # The input buffer being edited
     input_buffer = ''
 
     # Set to true for debug output
     debug = False
 
     # A banner to print at startup
     banner = None
 
     #--------------------------------------------------------------------------
     # FrontEndBase interface
     #--------------------------------------------------------------------------
 
     def __init__(self, shell=None, history=None, banner=None, *args, **kwargs):
         if shell is None:
             shell = Interpreter()
         FrontEndBase.__init__(self, shell=shell, history=history)
 
         if banner is not None:
             self.banner = banner
 
     def start(self):
         """ Put the frontend in a state where it is ready for user
             interaction.
         """
         if self.banner is not None:
             self.write(self.banner, refresh=False)
 
         self.new_prompt(self.input_prompt_template.substitute(number=1))
 
 
     def complete(self, line):
         """Complete line in engine's user_ns
         
         Parameters
         ----------
         line : string
         
         Result
         ------
         The replacement for the line and the list of possible completions.
         """
         completions = self.shell.complete(line)
         complete_sep =  re.compile('[\s\{\}\[\]\(\)\=]')
         if completions:
             prefix = common_prefix(completions) 
             residual = complete_sep.split(line)[:-1]
             line = line[:-len(residual)] + prefix
         return line, completions 
  
 
     def render_result(self, result):
         """ Frontend-specific rendering of the result of a calculation
         that has been sent to an engine.
         """
         if 'stdout' in result and result['stdout']:
             self.write('\n' + result['stdout'])
         if 'display' in result and result['display']:
             self.write("%s%s\n" % ( 
                             self.output_prompt_template.substitute(
                                     number=result['number']),
                             result['display']['pprint']
                             ) )
        
 
     def render_error(self, failure):
         """ Frontend-specific rendering of error. 
         """
         self.write('\n\n'+str(failure)+'\n\n')
         return failure
 
 
     def is_complete(self, string):
         """ Check if a string forms a complete, executable set of
         commands.
 
         For the line-oriented frontend, multi-line code is not executed
         as soon as it is complete: the users has to enter two line
         returns.
         """
         if string in ('', '\n'):
             # Prefiltering, eg through ipython0, may return an empty
             # string although some operations have been accomplished. We
             # thus want to consider an empty string as a complete
             # statement.
             return True
         elif ( len(self.input_buffer.split('\n'))>2 
                         and not re.findall(r"\n[\t ]*\n[\t ]*$", string)):
             return False
         else:
             # Add line returns here, to make sure that the statement is
             # complete.
             return FrontEndBase.is_complete(self, string.rstrip() + '\n\n')
 
 
     def write(self, string, refresh=True):
         """ Write some characters to the display.
 
             Subclass should overide this method.
 
             The refresh keyword argument is used in frontends with an
             event loop, to choose whether the write should trigget an UI
             refresh, and thus be syncrhonous, or not.
         """
         print >>sys.__stderr__, string
 
 
     def execute(self, python_string, raw_string=None):
         """ Stores the raw_string in the history, and sends the
         python string to the interpreter.
         """
         if raw_string is None:
             raw_string = python_string
         # Create a false result, in case there is an exception
         self.last_result = dict(number=self.prompt_number)
         try:
             self.history.input_cache[-1] = raw_string.rstrip()
             result = self.shell.execute(python_string)
             self.last_result = result
             self.render_result(result)
         except:
             self.show_traceback()
         finally:
             self.after_execute()
 
     #--------------------------------------------------------------------------
     # LineFrontEndBase interface
     #--------------------------------------------------------------------------
 
     def prefilter_input(self, string):
         """ Priflter the input to turn it in valid python.
         """
         string = string.replace('\r\n', '\n')
         string = string.replace('\t', 4*' ')
         # Clean the trailing whitespace
         string = '\n'.join(l.rstrip()  for l in string.split('\n'))
         return string
 
 
     def after_execute(self):
         """ All the operations required after an execution to put the
             terminal back in a shape where it is usable.
         """
         self.prompt_number += 1
         self.new_prompt(self.input_prompt_template.substitute(
                             number=(self.last_result['number'] + 1)))
         # Start a new empty history entry
         self._add_history(None, '')
         self.history_cursor = len(self.history.input_cache) - 1
 
 
     def complete_current_input(self):
         """ Do code completion on current line. 
         """
         if self.debug:
             print >>sys.__stdout__, "complete_current_input", 
         line = self.input_buffer
         new_line, completions = self.complete(line)
         if len(completions)>1:
             self.write_completion(completions, new_line=new_line)
-        if not line == new_line:
+        elif not line == new_line:
             self.input_buffer = new_line
         if self.debug:
             print >>sys.__stdout__, 'line', line
             print >>sys.__stdout__, 'new_line', new_line
             print >>sys.__stdout__, completions 
 
 
     def get_line_width(self):
         """ Return the width of the line in characters.
         """
         return 80
 
 
     def write_completion(self, possibilities, new_line=None):
         """ Write the list of possible completions.
 
             new_line is the completed input line that should be displayed
             after the completion are writen. If None, the input_buffer
             before the completion is used.
         """
         if new_line is None:
             new_line = self.input_buffer
         
         self.write('\n')
         max_len = len(max(possibilities, key=len)) + 1
         
         # Now we check how much symbol we can put on a line...
         chars_per_line = self.get_line_width()
         symbols_per_line = max(1, chars_per_line/max_len)
 
         pos = 1
         buf = []
         for symbol in possibilities:
             if pos < symbols_per_line:
                 buf.append(symbol.ljust(max_len))
                 pos += 1
             else:
                 buf.append(symbol.rstrip() + '\n')
                 pos = 1
         self.write(''.join(buf))
         self.new_prompt(self.input_prompt_template.substitute(
                             number=self.last_result['number'] + 1))
         self.input_buffer = new_line
 
 
     def new_prompt(self, prompt):
         """ Prints a prompt and starts a new editing buffer. 
 
             Subclasses should use this method to make sure that the
             terminal is put in a state favorable for a new line
             input.
         """
         self.input_buffer = ''
         self.write(prompt)
 
 
     #--------------------------------------------------------------------------
     # Private API
     #--------------------------------------------------------------------------
  
     def _on_enter(self):
         """ Called when the return key is pressed in a line editing
             buffer.
         """
         current_buffer = self.input_buffer
         cleaned_buffer = self.prefilter_input(current_buffer)
         if self.is_complete(cleaned_buffer):
             self.execute(cleaned_buffer, raw_string=current_buffer)
         else:
             self.input_buffer += self._get_indent_string(
                                                 current_buffer[:-1])
             if current_buffer[:-1].split('\n')[-1].rstrip().endswith(':'):
                 self.input_buffer += '\t'
 
 
     def _get_indent_string(self, string):
         """ Return the string of whitespace that prefixes a line. Used to
         add the right amount of indendation when creating a new line.
         """
         string = string.replace('\t', ' '*4)
         string = string.split('\n')[-1]
         indent_chars = len(string) - len(string.lstrip())
         indent_string = '\t'*(indent_chars // 4) + \
                             ' '*(indent_chars % 4)
 
         return indent_string