IPython/core/inputtransformer.py

import abc
import re
from StringIO import StringIO
import tokenize

from IPython.core.splitinput import split_user_input, LineInfo

#-----------------------------------------------------------------------------
# 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

def stateless_input_transformer(func):
    class StatelessInputTransformer(InputTransformer):
        """Decorator for a stateless input transformer implemented as a function."""
        def __init__(self):
            self.func = 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
    
    return StatelessInputTransformer

def coroutine_input_transformer(coro):
    class CoroutineInputTransformer(InputTransformer):
        """Wrapper for input transformers based on coroutines."""
        def __init__(self):
            # Prime it
            self.coro = coro()
            next(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)
    
    return CoroutineInputTransformer


# 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)

@coroutine_input_transformer
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)


@stateless_input_transformer
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)


@coroutine_input_transformer
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)

@coroutine_input_transformer
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

@coroutine_input_transformer
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


@coroutine_input_transformer
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'))

@coroutine_input_transformer
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)

@coroutine_input_transformer
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)