Prototype transformer to assemble logical lines

IPython/utils/untokenize.py

@@ -0,0 +1,125 b''
+"""This is a patched copy of the untokenize machinery from the standard library.
+
+untokenize has a number of major bugs that render it almost useless. We're using
+the patch written by Gareth Rees on Python issue 12961:
+
+http://bugs.python.org/issue12691
+
+We've undone one part of the patch - it encoded the output to bytes, to neatly
+round-trip from tokenize. We want to keep working with text, so we don't encode.
+"""
+
+__author__ = 'Ka-Ping Yee <[e-mail]>'
+__credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
+               'Skip Montanaro, Raymond Hettinger, Trent Nelson, '
+               'Michael Foord')
+from token import *
+
+
+from tokenize import COMMENT, NL
+
+try:
+    # Python 3
+    from tokenize import ENCODING
+except:
+    ENCODING = 987654321
+
+class Untokenizer:
+
+    def __init__(self):
+        self.tokens = []
+        self.prev_row = 1
+        self.prev_col = 0
+        self.encoding = 'utf-8'
+
+    def add_whitespace(self, tok_type, start):
+        row, col = start
+        assert row >= self.prev_row
+        col_offset = col - self.prev_col
+        if col_offset > 0:
+            self.tokens.append(" " * col_offset)
+        elif row > self.prev_row and tok_type not in (NEWLINE, NL, ENDMARKER):
+            # Line was backslash-continued.
+            self.tokens.append(" ")
+
+    def untokenize(self, tokens):
+        iterable = iter(tokens)
+        for t in iterable:
+            if len(t) == 2:
+                self.compat(t, iterable)
+                break
+            # IPython modification - valid Python 2 syntax
+            tok_type, token, start, end = t[:4]
+            if tok_type == ENCODING:
+                self.encoding = token
+                continue
+            self.add_whitespace(tok_type, start)
+            self.tokens.append(token)
+            self.prev_row, self.prev_col = end
+            if tok_type in (NEWLINE, NL):
+                self.prev_row += 1
+                self.prev_col = 0
+        # IPython modification - don't encode output
+        return "".join(self.tokens)
+
+    def compat(self, token, iterable):
+        # This import is here to avoid problems when the itertools
+        # module is not built yet and tokenize is imported.
+        from itertools import chain
+        startline = False
+        prevstring = False
+        indents = []
+        toks_append = self.tokens.append
+
+        for tok in chain([token], iterable):
+            toknum, tokval = tok[:2]
+            if toknum == ENCODING:
+                self.encoding = tokval
+                continue
+
+            if toknum in (NAME, NUMBER):
+                tokval += ' '
+
+            # Insert a space between two consecutive strings
+            if toknum == STRING:
+                if prevstring:
+                    tokval = ' ' + tokval
+                prevstring = True
+            else:
+                prevstring = False
+
+            if toknum == INDENT:
+                indents.append(tokval)
+                continue
+            elif toknum == DEDENT:
+                indents.pop()
+                continue
+            elif toknum in (NEWLINE, NL):
+                startline = True
+            elif startline and indents:
+                toks_append(indents[-1])
+                startline = False
+            toks_append(tokval)
+
+
+def untokenize(tokens):
+    """
+    Convert ``tokens`` (an iterable) back into Python source code. Return
+    a bytes object, encoded using the encoding specified by the last
+    ENCODING token in ``tokens``, or UTF-8 if no ENCODING token is found.
+
+    The result is guaranteed to tokenize back to match the input so that
+    the conversion is lossless and round-trips are assured.  The
+    guarantee applies only to the token type and token string as the
+    spacing between tokens (column positions) may change.
+
+    :func:`untokenize` has two modes. If the input tokens are sequences
+    of length 2 (``type``, ``string``) then spaces are added as necessary to
+    preserve the round-trip property.
+
+    If the input tokens are sequences of length 4 or more (``type``,
+    ``string``, ``start``, ``end``), as returned by :func:`tokenize`, then
+    spaces are added so that each token appears in the result at the
+    position indicated by ``start`` and ``end``, if possible.
+    """
+    return Untokenizer().untokenize(tokens)

IPython/core/inputsplitter.py

@@ -1,652 +1,651 b''
 """Analysis of text input into executable blocks.
 
 The main class in this module, :class:`InputSplitter`, is designed to break
 input from either interactive, line-by-line environments or block-based ones,
 into standalone blocks that can be executed by Python as 'single' statements
 (thus triggering sys.displayhook).
 
 A companion, :class:`IPythonInputSplitter`, provides the same functionality but
 with full support for the extended IPython syntax (magics, system calls, etc).
 
 For more details, see the class docstring below.
 
 Syntax Transformations
 ----------------------
 
 One of the main jobs of the code in this file is to apply all syntax
 transformations that make up 'the IPython language', i.e. magics, shell
 escapes, etc.  All transformations should be implemented as *fully stateless*
 entities, that simply take one line as their input and return a line.
 Internally for implementation purposes they may be a normal function or a
 callable object, but the only input they receive will be a single line and they
 should only return a line, without holding any data-dependent state between
 calls.
 
 As an example, the EscapedTransformer is a class so we can more clearly group
 together the functionality of dispatching to individual functions based on the
 starting escape character, but the only method for public use is its call
 method.
 
 
 ToDo
 ----
 
 - Should we make push() actually raise an exception once push_accepts_more()
   returns False?
 
 - Naming cleanups.  The tr_* names aren't the most elegant, though now they are
   at least just attributes of a class so not really very exposed.
 
 - Think about the best way to support dynamic things: automagic, autocall,
   macros, etc.
 
 - Think of a better heuristic for the application of the transforms in
   IPythonInputSplitter.push() than looking at the buffer ending in ':'.  Idea:
   track indentation change events (indent, dedent, nothing) and apply them only
   if the indentation went up, but not otherwise.
 
 - Think of the cleanest way for supporting user-specified transformations (the
   user prefilters we had before).
 
 Authors
 -------
 
 * Fernando Perez
 * Brian Granger
 """
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2010  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
 #-----------------------------------------------------------------------------
 # stdlib
 import ast
 import codeop
 import re
 import sys
 
 # IPython modules
 from IPython.core.splitinput import split_user_input, LineInfo
 from IPython.utils.py3compat import cast_unicode
 from IPython.core.inputtransformer import (leading_indent,
                                            classic_prompt,
                                            ipy_prompt,
                                            cellmagic,
+                                           assemble_logical_lines,
                                            help_end,
                                            escaped_transformer,
                                            assign_from_magic,
                                            assign_from_system,
                                            )
 
 # Temporary!
 from IPython.core.inputtransformer import (ESC_SHELL, ESC_SH_CAP, ESC_HELP,
                                         ESC_HELP2, ESC_MAGIC, ESC_MAGIC2,
                                         ESC_QUOTE, ESC_QUOTE2, ESC_PAREN, ESC_SEQUENCES)
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 # FIXME: These are general-purpose utilities that later can be moved to the
 # general ward.  Kept here for now because we're being very strict about test
 # coverage with this code, and this lets us ensure that we keep 100% coverage
 # while developing.
 
 # compiled regexps for autoindent management
 dedent_re = re.compile('|'.join([
     r'^\s+raise(\s.*)?$', # raise statement (+ space + other stuff, maybe)
     r'^\s+raise\([^\)]*\).*$', # wacky raise with immediate open paren
     r'^\s+return(\s.*)?$', # normal return (+ space + other stuff, maybe)
     r'^\s+return\([^\)]*\).*$', # wacky return with immediate open paren
     r'^\s+pass\s*$', # pass (optionally followed by trailing spaces)
     r'^\s+break\s*$', # break (optionally followed by trailing spaces)
     r'^\s+continue\s*$', # continue (optionally followed by trailing spaces)
 ]))
 ini_spaces_re = re.compile(r'^([ \t\r\f\v]+)')
 
 # regexp to match pure comment lines so we don't accidentally insert 'if 1:'
 # before pure comments
 comment_line_re = re.compile('^\s*\#')
 
 
 def num_ini_spaces(s):
     """Return the number of initial spaces in a string.
 
     Note that tabs are counted as a single space.  For now, we do *not* support
     mixing of tabs and spaces in the user's input.
 
     Parameters
     ----------
     s : string
 
     Returns
     -------
     n : int
     """
 
     ini_spaces = ini_spaces_re.match(s)
     if ini_spaces:
         return ini_spaces.end()
     else:
         return 0
 
 def last_blank(src):
     """Determine if the input source ends in a blank.
 
     A blank is either a newline or a line consisting of whitespace.
 
     Parameters
     ----------
     src : string
       A single or multiline string.
     """
     if not src: return False
     ll  = src.splitlines()[-1]
     return (ll == '') or ll.isspace()
 
 
 last_two_blanks_re = re.compile(r'\n\s*\n\s*$', re.MULTILINE)
 last_two_blanks_re2 = re.compile(r'.+\n\s*\n\s+$', re.MULTILINE)
 
 def last_two_blanks(src):
     """Determine if the input source ends in two blanks.
 
     A blank is either a newline or a line consisting of whitespace.
 
     Parameters
     ----------
     src : string
       A single or multiline string.
     """
     if not src: return False
     # The logic here is tricky: I couldn't get a regexp to work and pass all
     # the tests, so I took a different approach: split the source by lines,
     # grab the last two and prepend '###\n' as a stand-in for whatever was in
     # the body before the last two lines.  Then, with that structure, it's
     # possible to analyze with two regexps.  Not the most elegant solution, but
     # it works.  If anyone tries to change this logic, make sure to validate
     # the whole test suite first!
     new_src = '\n'.join(['###\n'] + src.splitlines()[-2:])
     return (bool(last_two_blanks_re.match(new_src)) or
             bool(last_two_blanks_re2.match(new_src)) )
 
 
 def remove_comments(src):
     """Remove all comments from input source.
 
     Note: comments are NOT recognized inside of strings!
 
     Parameters
     ----------
     src : string
       A single or multiline input string.
 
     Returns
     -------
     String with all Python comments removed.
     """
 
     return re.sub('#.*', '', src)
 
 
 def get_input_encoding():
     """Return the default standard input encoding.
 
     If sys.stdin has no encoding, 'ascii' is returned."""
     # There are strange environments for which sys.stdin.encoding is None. We
     # ensure that a valid encoding is returned.
     encoding = getattr(sys.stdin, 'encoding', None)
     if encoding is None:
         encoding = 'ascii'
     return encoding
 
 #-----------------------------------------------------------------------------
 # Classes and functions for normal Python syntax handling
 #-----------------------------------------------------------------------------
 
 class InputSplitter(object):
     """An object that can accumulate lines of Python source before execution.
 
     This object is designed to be fed python source line-by-line, using
        :meth:`push`. It will return on each push whether the currently pushed
        code could be executed already. In addition, it provides a method called
        :meth:`push_accepts_more` that can be used to query whether more input
        can be pushed into a single interactive block.
 
     This is a simple example of how an interactive terminal-based client can use
     this tool::
 
         isp = InputSplitter()
         while isp.push_accepts_more():
             indent = ' '*isp.indent_spaces
             prompt = '>>> ' + indent
             line = indent + raw_input(prompt)
             isp.push(line)
         print 'Input source was:\n', isp.source_reset(),
     """
     # Number of spaces of indentation computed from input that has been pushed
     # so far.  This is the attributes callers should query to get the current
     # indentation level, in order to provide auto-indent facilities.
     indent_spaces = 0
     # String, indicating the default input encoding.  It is computed by default
     # at initialization time via get_input_encoding(), but it can be reset by a
     # client with specific knowledge of the encoding.
     encoding = ''
     # String where the current full source input is stored, properly encoded.
     # Reading this attribute is the normal way of querying the currently pushed
     # source code, that has been properly encoded.
     source = ''
     # Code object corresponding to the current source.  It is automatically
     # synced to the source, so it can be queried at any time to obtain the code
     # object; it will be None if the source doesn't compile to valid Python.
     code = None
     # Input mode
     input_mode = 'line'
 
     # Private attributes
 
     # List with lines of input accumulated so far
     _buffer = None
     # Command compiler
     _compile = None
     # Mark when input has changed indentation all the way back to flush-left
     _full_dedent = False
     # Boolean indicating whether the current block is complete
     _is_complete = None
 
     def __init__(self, input_mode=None):
         """Create a new InputSplitter instance.
 
         Parameters
         ----------
         input_mode : str
 
           One of ['line', 'cell']; default is 'line'.
 
        The input_mode parameter controls how new inputs are used when fed via
        the :meth:`push` method:
 
        - 'line': meant for line-oriented clients, inputs are appended one at a
          time to the internal buffer and the whole buffer is compiled.
 
        - 'cell': meant for clients that can edit multi-line 'cells' of text at
           a time.  A cell can contain one or more blocks that can be compile in
           'single' mode by Python.  In this mode, each new input new input
           completely replaces all prior inputs.  Cell mode is thus equivalent
           to prepending a full reset() to every push() call.
         """
         self._buffer = []
         self._compile = codeop.CommandCompiler()
         self.encoding = get_input_encoding()
         self.input_mode = InputSplitter.input_mode if input_mode is None \
                           else input_mode
 
     def reset(self):
         """Reset the input buffer and associated state."""
         self.indent_spaces = 0
         self._buffer[:] = []
         self.source = ''
         self.code = None
         self._is_complete = False
         self._full_dedent = False
 
     def source_reset(self):
         """Return the input source and perform a full reset.
         """
         out = self.source
         self.reset()
         return out
 
     def push(self, lines):
         """Push one or more lines of input.
 
         This stores the given lines and returns a status code indicating
         whether the code forms a complete Python block or not.
 
         Any exceptions generated in compilation are swallowed, but if an
         exception was produced, the method returns True.
 
         Parameters
         ----------
         lines : string
           One or more lines of Python input.
 
         Returns
         -------
         is_complete : boolean
           True if the current input source (the result of the current input
           plus prior inputs) forms a complete Python execution block.  Note that
           this value is also stored as a private attribute (``_is_complete``), so it
           can be queried at any time.
         """
         if self.input_mode == 'cell':
             self.reset()
 
         self._store(lines)
         source = self.source
 
         # Before calling _compile(), reset the code object to None so that if an
         # exception is raised in compilation, we don't mislead by having
         # inconsistent code/source attributes.
         self.code, self._is_complete = None, None
 
         # Honor termination lines properly
         if source.endswith('\\\n'):
             return False
 
         self._update_indent(lines)
         try:
             self.code = self._compile(source, symbol="exec")
         # Invalid syntax can produce any of a number of different errors from
         # inside the compiler, so we have to catch them all.  Syntax errors
         # immediately produce a 'ready' block, so the invalid Python can be
         # sent to the kernel for evaluation with possible ipython
         # special-syntax conversion.
         except (SyntaxError, OverflowError, ValueError, TypeError,
                 MemoryError):
             self._is_complete = True
         else:
             # Compilation didn't produce any exceptions (though it may not have
             # given a complete code object)
             self._is_complete = self.code is not None
 
         return self._is_complete
 
     def push_accepts_more(self):
         """Return whether a block of interactive input can accept more input.
 
         This method is meant to be used by line-oriented frontends, who need to
         guess whether a block is complete or not based solely on prior and
         current input lines.  The InputSplitter considers it has a complete
         interactive block and will not accept more input only when either a
         SyntaxError is raised, or *all* of the following are true:
 
         1. The input compiles to a complete statement.
 
         2. The indentation level is flush-left (because if we are indented,
            like inside a function definition or for loop, we need to keep
            reading new input).
 
         3. There is one extra line consisting only of whitespace.
 
         Because of condition #3, this method should be used only by
         *line-oriented* frontends, since it means that intermediate blank lines
         are not allowed in function definitions (or any other indented block).
 
         If the current input produces a syntax error, this method immediately
         returns False but does *not* raise the syntax error exception, as
         typically clients will want to send invalid syntax to an execution
         backend which might convert the invalid syntax into valid Python via
         one of the dynamic IPython mechanisms.
         """
 
         # With incomplete input, unconditionally accept more
         if not self._is_complete:
             return True
 
         # If we already have complete input and we're flush left, the answer
         # depends.  In line mode, if there hasn't been any indentation,
         # that's it. If we've come back from some indentation, we need
         # the blank final line to finish.
         # In cell mode, we need to check how many blocks the input so far
         # compiles into, because if there's already more than one full
         # independent block of input, then the client has entered full
         # 'cell' mode and is feeding lines that each is complete.  In this
         # case we should then keep accepting. The Qt terminal-like console
         # does precisely this, to provide the convenience of terminal-like
         # input of single expressions, but allowing the user (with a
         # separate keystroke) to switch to 'cell' mode and type multiple
         # expressions in one shot.
         if self.indent_spaces==0:
             if self.input_mode=='line':
                 if not self._full_dedent:
                     return False
             else:
                 try:
                     code_ast = ast.parse(u''.join(self._buffer))
                 except Exception:
                     return False
                 else:
                     if len(code_ast.body) == 1:
                         return False
 
         # When input is complete, then termination is marked by an extra blank
         # line at the end.
         last_line = self.source.splitlines()[-1]
         return bool(last_line and not last_line.isspace())
 
     #------------------------------------------------------------------------
     # Private interface
     #------------------------------------------------------------------------
 
     def _find_indent(self, line):
         """Compute the new indentation level for a single line.
 
         Parameters
         ----------
         line : str
           A single new line of non-whitespace, non-comment Python input.
 
         Returns
         -------
         indent_spaces : int
           New value for the indent level (it may be equal to self.indent_spaces
         if indentation doesn't change.
 
         full_dedent : boolean
           Whether the new line causes a full flush-left dedent.
         """
         indent_spaces = self.indent_spaces
         full_dedent = self._full_dedent
 
         inisp = num_ini_spaces(line)
         if inisp < indent_spaces:
             indent_spaces = inisp
             if indent_spaces <= 0:
                 #print 'Full dedent in text',self.source # dbg
                 full_dedent = True
 
         if line.rstrip()[-1] == ':':
             indent_spaces += 4
         elif dedent_re.match(line):
             indent_spaces -= 4
             if indent_spaces <= 0:
                 full_dedent = True
 
         # Safety
         if indent_spaces < 0:
             indent_spaces = 0
             #print 'safety' # dbg
 
         return indent_spaces, full_dedent
 
     def _update_indent(self, lines):
         for line in remove_comments(lines).splitlines():
             if line and not line.isspace():
                 self.indent_spaces, self._full_dedent = self._find_indent(line)
 
     def _store(self, lines, buffer=None, store='source'):
         """Store one or more lines of input.
 
         If input lines are not newline-terminated, a newline is automatically
         appended."""
 
         if buffer is None:
             buffer = self._buffer
 
         if lines.endswith('\n'):
             buffer.append(lines)
         else:
             buffer.append(lines+'\n')
         setattr(self, store, self._set_source(buffer))
 
     def _set_source(self, buffer):
         return u''.join(buffer)
 
 
 class IPythonInputSplitter(InputSplitter):
     """An input splitter that recognizes all of IPython's special syntax."""
 
     # String with raw, untransformed input.
     source_raw = ''
     
     # Flag to track when a transformer has stored input that it hasn't given
     # back yet.
     transformer_accumulating = False
 
     # Private attributes
 
     # List with lines of raw input accumulated so far.
     _buffer_raw = None
 
     def __init__(self, input_mode=None, transforms=None):
         super(IPythonInputSplitter, self).__init__(input_mode)
         self._buffer_raw = []
         self._validate = True
         if transforms is not None:
             self.transforms = transforms
         else:
             self.transforms = [leading_indent(),
                                classic_prompt(),
                                ipy_prompt(),
                                cellmagic(),
+                               assemble_logical_lines(),
                                help_end(),
                                escaped_transformer(),
                                assign_from_magic(),
                                assign_from_system(),
                               ]
 
     def reset(self):
         """Reset the input buffer and associated state."""
         super(IPythonInputSplitter, self).reset()
         self._buffer_raw[:] = []
         self.source_raw = ''
         self.transformer_accumulating = False
         for t in self.transforms:
             t.reset()
     
     def flush_transformers(self):
         out = None
         for t in self.transforms:
             tmp = t.reset()
             if tmp:
                 out = tmp
         if out:
             self._store(out)
 
     def source_raw_reset(self):
         """Return input and raw source and perform a full reset.
         """
         self.flush_transformers()
         out = self.source
         out_r = self.source_raw
         self.reset()
         return out, out_r
     
     def source_reset(self):
         self.flush_transformers()
         return super(IPythonInputSplitter, self).source_reset()
 
     def push_accepts_more(self):
         if self.transformer_accumulating:
             return True
         else:
             return super(IPythonInputSplitter, self).push_accepts_more()
 
     def transform_cell(self, cell):
         """Process and translate a cell of input.
         """
         self.reset()
         self.push(cell)
         return self.source_reset()
 
     def push(self, lines):
         """Push one or more lines of IPython input.
 
         This stores the given lines and returns a status code indicating
         whether the code forms a complete Python block or not, after processing
         all input lines for special IPython syntax.
 
         Any exceptions generated in compilation are swallowed, but if an
         exception was produced, the method returns True.
 
         Parameters
         ----------
         lines : string
           One or more lines of Python input.
 
         Returns
         -------
         is_complete : boolean
           True if the current input source (the result of the current input
         plus prior inputs) forms a complete Python execution block.  Note that
         this value is also stored as a private attribute (_is_complete), so it
         can be queried at any time.
         """
 
         # We must ensure all input is pure unicode
         lines = cast_unicode(lines, self.encoding)
         
         # ''.splitlines() --> [], but we need to push the empty line to transformers
         lines_list = lines.splitlines()
         if not lines_list:
             lines_list = ['']
 
         # Transform logic
         #
         # We only apply the line transformers to the input if we have either no
         # input yet, or complete input, or if the last line of the buffer ends
         # with ':' (opening an indented block).  This prevents the accidental
         # transformation of escapes inside multiline expressions like
         # triple-quoted strings or parenthesized expressions.
         #
         # The last heuristic, while ugly, ensures that the first line of an
         # indented block is correctly transformed.
         #
         # FIXME: try to find a cleaner approach for this last bit.
 
         # If we were in 'block' mode, since we're going to pump the parent
         # class by hand line by line, we need to temporarily switch out to
         # 'line' mode, do a single manual reset and then feed the lines one
         # by one.  Note that this only matters if the input has more than one
         # line.
         changed_input_mode = False
 
         if self.input_mode == 'cell':
             self.reset()
             changed_input_mode = True
             saved_input_mode = 'cell'
             self.input_mode = 'line'
 
         # Store raw source before applying any transformations to it.  Note
         # that this must be done *after* the reset() call that would otherwise
         # flush the buffer.
         self._store(lines, self._buffer_raw, 'source_raw')
 
         try:
             for line in lines_list:
                 out = self.push_line(line)
         finally:
             if changed_input_mode:
                 self.input_mode = saved_input_mode
         
         return out
     
     def push_line(self, line):
         buf = self._buffer
-        not_in_string =  self._is_complete or not buf or \
-                                (buf and buf[-1].rstrip().endswith((':', ',')))
         for transformer in self.transforms:
-            if not_in_string or transformer.look_in_string:
-                line = transformer.push(line)
-                if line is None:
-                    self.transformer_accumulating = True
-                    return False                
+            line = transformer.push(line)
+            if line is None:
+                self.transformer_accumulating = True
+                return False                
 
         self.transformer_accumulating = False
         return super(IPythonInputSplitter, self).push(line)

IPython/core/inputtransformer.py

@@ -1,441 +1,454 b''
 import abc
 import functools
 import re
 from StringIO import StringIO
 import tokenize
 
+try:
+    generate_tokens = tokenize.generate_tokens
+except AttributeError:
+    # Python 3. Note that we use the undocumented _tokenize because it expects
+    # strings, not bytes. See also Python issue #9969.
+    generate_tokens = tokenize._tokenize
+
 from IPython.core.splitinput import split_user_input, LineInfo
+from IPython.utils.untokenize import untokenize
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 # The escape sequences that define the syntax transformations IPython will
 # apply to user input.  These can NOT be just changed here: many regular
 # expressions and other parts of the code may use their hardcoded values, and
 # for all intents and purposes they constitute the 'IPython syntax', so they
 # should be considered fixed.
 
 ESC_SHELL  = '!'     # Send line to underlying system shell
 ESC_SH_CAP = '!!'    # Send line to system shell and capture output
 ESC_HELP   = '?'     # Find information about object
 ESC_HELP2  = '??'    # Find extra-detailed information about object
 ESC_MAGIC  = '%'     # Call magic function
 ESC_MAGIC2 = '%%'    # Call cell-magic function
 ESC_QUOTE  = ','     # Split args on whitespace, quote each as string and call
 ESC_QUOTE2 = ';'     # Quote all args as a single string, call
 ESC_PAREN  = '/'     # Call first argument with rest of line as arguments
 
 ESC_SEQUENCES = [ESC_SHELL, ESC_SH_CAP, ESC_HELP ,\
                  ESC_HELP2, ESC_MAGIC, ESC_MAGIC2,\
                  ESC_QUOTE, ESC_QUOTE2, ESC_PAREN ]
 
 
 class InputTransformer(object):
     """Abstract base class for line-based input transformers."""
     __metaclass__ = abc.ABCMeta
     
     @abc.abstractmethod
     def push(self, line):
         """Send a line of input to the transformer, returning the transformed
         input or None if the transformer is waiting for more input.
         
         Must be overridden by subclasses.
         """
         pass
     
     @abc.abstractmethod
     def reset(self):
         """Return, transformed any lines that the transformer has accumulated,
         and reset its internal state.
         
         Must be overridden by subclasses.
         """
         pass
     
     # Set this to True to allow the transformer to act on lines inside strings.
     look_in_string = False
     
     @classmethod
     def wrap(cls, func):
         """Can be used by subclasses as a decorator, to return a factory that
         will allow instantiation with the decorated object.
         """
         @functools.wraps(func)
         def transformer_factory():
             transformer = cls(func)
             if getattr(transformer_factory, 'look_in_string', False):
                 transformer.look_in_string = True
             return transformer
         
         return transformer_factory
 
 class StatelessInputTransformer(InputTransformer):
     """Wrapper for a stateless input transformer implemented as a function."""
     def __init__(self, func):
         self.func = func
     
     def __repr__(self):
         return "StatelessInputTransformer(func={!r})".format(self.func)
     
     def push(self, line):
         """Send a line of input to the transformer, returning the
         transformed input."""
         return self.func(line)
     
     def reset(self):
         """No-op - exists for compatibility."""
         pass
 
 class CoroutineInputTransformer(InputTransformer):
     """Wrapper for an input transformer implemented as a coroutine."""
     def __init__(self, coro):
         # Prime it
         self.coro = coro()
         next(self.coro)
     
     def __repr__(self):
         return "CoroutineInputTransformer(coro={!r})".format(self.coro)
     
     def push(self, line):
         """Send a line of input to the transformer, returning the
         transformed input or None if the transformer is waiting for more
         input.
         """
         return self.coro.send(line)
     
     def reset(self):
         """Return, transformed any lines that the transformer has
         accumulated, and reset its internal state.
         """
         return self.coro.send(None)
 
 class TokenInputTransformer(InputTransformer):
     """Wrapper for a token-based input transformer.
     
     func should accept a list of tokens (5-tuples, see tokenize docs), and
     return an iterable which can be passed to tokenize.untokenize().
     """
     def __init__(self, func):
         self.func = func
         self.current_line = ""
-        self.tokenizer = tokenize.generate_tokens(self.get_line)
         self.line_used= False
+        self.reset_tokenizer()
+    
+    def reset_tokenizer(self):
+        self.tokenizer = generate_tokens(self.get_line)
     
     def get_line(self):
         if self.line_used:
             raise tokenize.TokenError
         self.line_used = True
         return self.current_line
     
     def push(self, line):
         self.current_line += line + "\n"
         self.line_used = False
         tokens = []
         try:
             for intok in self.tokenizer:
                 tokens.append(intok)
                 if intok[0] in (tokenize.NEWLINE, tokenize.NL):
                     # Stop before we try to pull a line we don't have yet
                     break
         except tokenize.TokenError:
             # Multi-line statement - stop and try again with the next line
-            self.tokenizer = tokenize.generate_tokens(self.get_line)
+            self.reset_tokenizer()
             return None
         
         self.current_line = ""
-        # Python bug 8478 - untokenize doesn't work quite correctly with a
-        # generator. We call list() to avoid this.
-        return tokenize.untokenize(list(self.func(tokens))).rstrip('\n')
+        self.reset_tokenizer()
+        return untokenize(self.func(tokens)).rstrip('\n')
     
     def reset(self):
         l = self.current_line
         self.current_line = ""
         if l:
             return l.rstrip('\n')
 
[e-mail]
+def assemble_logical_lines(tokens):
+    return tokens
 
 # Utilities
 def _make_help_call(target, esc, lspace, next_input=None):
     """Prepares a pinfo(2)/psearch call from a target name and the escape
     (i.e. ? or ??)"""
     method  = 'pinfo2' if esc == '??' \
                 else 'psearch' if '*' in target \
                 else 'pinfo'
     arg = " ".join([method, target])
     if next_input is None:
         return '%sget_ipython().magic(%r)' % (lspace, arg)
     else:
         return '%sget_ipython().set_next_input(%r);get_ipython().magic(%r)' % \
            (lspace, next_input, arg)
 
 @CoroutineInputTransformer.wrap
 def escaped_transformer():
     """Translate lines beginning with one of IPython's escape characters.
     
     This is stateful to allow magic commands etc. to be continued over several
     lines using explicit line continuations (\ at the end of a line).
     """
     
     # These define the transformations for the different escape characters.
     def _tr_system(line_info):
         "Translate lines escaped with: !"
         cmd = line_info.line.lstrip().lstrip(ESC_SHELL)
         return '%sget_ipython().system(%r)' % (line_info.pre, cmd)
 
     def _tr_system2(line_info):
         "Translate lines escaped with: !!"
         cmd = line_info.line.lstrip()[2:]
         return '%sget_ipython().getoutput(%r)' % (line_info.pre, cmd)
 
     def _tr_help(line_info):
         "Translate lines escaped with: ?/??"
         # A naked help line should just fire the intro help screen
         if not line_info.line[1:]:
             return 'get_ipython().show_usage()'
 
         return _make_help_call(line_info.ifun, line_info.esc, line_info.pre)
 
     def _tr_magic(line_info):
         "Translate lines escaped with: %"
         tpl = '%sget_ipython().magic(%r)'
         cmd = ' '.join([line_info.ifun, line_info.the_rest]).strip()
         return tpl % (line_info.pre, cmd)
 
     def _tr_quote(line_info):
         "Translate lines escaped with: ,"
         return '%s%s("%s")' % (line_info.pre, line_info.ifun,
                              '", "'.join(line_info.the_rest.split()) )
 
     def _tr_quote2(line_info):
         "Translate lines escaped with: ;"
         return '%s%s("%s")' % (line_info.pre, line_info.ifun,
                                line_info.the_rest)
 
     def _tr_paren(line_info):
         "Translate lines escaped with: /"
         return '%s%s(%s)' % (line_info.pre, line_info.ifun,
                              ", ".join(line_info.the_rest.split()))
     
     tr = { ESC_SHELL  : _tr_system,
            ESC_SH_CAP : _tr_system2,
            ESC_HELP   : _tr_help,
            ESC_HELP2  : _tr_help,
            ESC_MAGIC  : _tr_magic,
            ESC_QUOTE  : _tr_quote,
            ESC_QUOTE2 : _tr_quote2,
            ESC_PAREN  : _tr_paren }
     
     line = ''
     while True:
         line = (yield line)
         if not line or line.isspace():
             continue
         lineinf = LineInfo(line)
         if lineinf.esc not in tr:
             continue
         
         parts = []
         while line is not None:
             parts.append(line.rstrip('\\'))
             if not line.endswith('\\'):
                 break
             line = (yield None)
         
         # Output
         lineinf = LineInfo(' '.join(parts))
         line = tr[lineinf.esc](lineinf)
 
 _initial_space_re = re.compile(r'\s*')
 
 _help_end_re = re.compile(r"""(%{0,2}
                               [a-zA-Z_*][\w*]*        # Variable name
                               (\.[a-zA-Z_*][\w*]*)*   # .etc.etc
                               )
                               (\?\??)$                # ? or ??""",
                               re.VERBOSE)
 
 def has_comment(src):
     """Indicate whether an input line has (i.e. ends in, or is) a comment.
 
     This uses tokenize, so it can distinguish comments from # inside strings.
 
     Parameters
     ----------
     src : string
       A single line input string.
 
     Returns
     -------
     Boolean: True if source has a comment.
     """
     readline = StringIO(src).readline
     toktypes = set()
     try:
         for t in tokenize.generate_tokens(readline):
             toktypes.add(t[0])
     except tokenize.TokenError:
         pass
     return(tokenize.COMMENT in toktypes)
 
 
 @StatelessInputTransformer.wrap
 def help_end(line):
     """Translate lines with ?/?? at the end"""
     m = _help_end_re.search(line)
     if m is None or has_comment(line):
         return line
     target = m.group(1)
     esc = m.group(3)
     lspace = _initial_space_re.match(line).group(0)
 
     # If we're mid-command, put it back on the next prompt for the user.
     next_input = line.rstrip('?') if line.strip() != m.group(0) else None
 
     return _make_help_call(target, esc, lspace, next_input)
 
 
 @CoroutineInputTransformer.wrap
 def cellmagic():
     """Captures & transforms cell magics.
     
     After a cell magic is started, this stores up any lines it gets until it is
     reset (sent None).
     """
     tpl = 'get_ipython().run_cell_magic(%r, %r, %r)'
     cellmagic_help_re = re.compile('%%\w+\?')
     line = ''
     while True:
         line = (yield line)
         if (not line) or (not line.startswith(ESC_MAGIC2)):
             continue
         
         if cellmagic_help_re.match(line):
             # This case will be handled by help_end
             continue
         
         first = line
         body = []
         line = (yield None)
         while (line is not None) and (line.strip() != ''):
             body.append(line)
             line = (yield None)
         
         # Output
         magic_name, _, first = first.partition(' ')
         magic_name = magic_name.lstrip(ESC_MAGIC2)
         line = tpl % (magic_name, first, u'\n'.join(body))
 
 
 def _strip_prompts(prompt1_re, prompt2_re):
     """Remove matching input prompts from a block of input."""
     line = ''
     while True:
         line = (yield line)
         
         if line is None:
             continue
         
         m = prompt1_re.match(line)
         if m:
             while m:
                 line = (yield line[len(m.group(0)):])
                 if line is None:
                     break
                 m = prompt2_re.match(line)
         else:
             # Prompts not in input - wait for reset
             while line is not None:
                 line = (yield line)
 
 @CoroutineInputTransformer.wrap
 def classic_prompt():
     """Strip the >>>/... prompts of the Python interactive shell."""
     prompt1_re = re.compile(r'^(>>> )')
     prompt2_re = re.compile(r'^(>>> |^\.\.\. )')
     return _strip_prompts(prompt1_re, prompt2_re)
 
 classic_prompt.look_in_string = True
 
 @CoroutineInputTransformer.wrap
 def ipy_prompt():
     """Strip IPython's In [1]:/...: prompts."""
     prompt1_re = re.compile(r'^In \[\d+\]: ')
     prompt2_re = re.compile(r'^(In \[\d+\]: |^\ \ \ \.\.\.+: )')
     return _strip_prompts(prompt1_re, prompt2_re)
 
 ipy_prompt.look_in_string = True
 
 
 @CoroutineInputTransformer.wrap
 def leading_indent():
     """Remove leading indentation.
     
     If the first line starts with a spaces or tabs, the same whitespace will be
     removed from each following line until it is reset.
     """
     space_re = re.compile(r'^[ \t]+')
     line = ''
     while True:
         line = (yield line)
         
         if line is None:
             continue
         
         m = space_re.match(line)
         if m:
             space = m.group(0)
             while line is not None:
                 if line.startswith(space):
                     line = line[len(space):]
                 line = (yield line)
         else:
             # No leading spaces - wait for reset
             while line is not None:
                 line = (yield line)
 
 leading_indent.look_in_string = True
 
 
 def _special_assignment(assignment_re, template):
     """Transform assignment from system & magic commands.
     
     This is stateful so that it can handle magic commands continued on several
     lines.
     """
     line = ''
     while True:
         line = (yield line)
         if not line or line.isspace():
             continue
         
         m = assignment_re.match(line)
         if not m:
             continue
         
         parts = []
         while line is not None:
             parts.append(line.rstrip('\\'))
             if not line.endswith('\\'):
                 break
             line = (yield None)
         
         # Output
         whole = assignment_re.match(' '.join(parts))
         line = template % (whole.group('lhs'), whole.group('cmd'))
 
 @CoroutineInputTransformer.wrap
 def assign_from_system():
     """Transform assignment from system commands (e.g. files = !ls)"""
     assignment_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                                r'\s*=\s*!\s*(?P<cmd>.*)')
     template = '%s = get_ipython().getoutput(%r)'
     return _special_assignment(assignment_re, template)
 
 @CoroutineInputTransformer.wrap
 def assign_from_magic():
     """Transform assignment from magic commands (e.g. a = %who_ls)"""
     assignment_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                                r'\s*=\s*%\s*(?P<cmd>.*)')
     template = '%s = get_ipython().magic(%r)'
     return _special_assignment(assignment_re, template)