IPython/core/inputtransformer.py

import abc
import functools
import re
from StringIO import StringIO

from IPython.core.splitinput import LineInfo
from IPython.utils import tokenize2
from IPython.utils.tokenize2 import generate_tokens, untokenize, TokenError

#-----------------------------------------------------------------------------
# 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
    
    @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(**kwargs):
            return cls(func, **kwargs)
        
        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={0!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, **kwargs):
        # Prime it
        self.coro = coro(**kwargs)
        next(self.coro)
    
    def __repr__(self):
        return "CoroutineInputTransformer(coro={0!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.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 TokenError
        self.line_used = True
        return self.current_line
    
    def push(self, line):
        self.current_line += line + "\n"
        if self.current_line.isspace():
            return self.reset()
        
        self.line_used = False
        tokens = []
        stop_at_NL = False
        try:
            for intok in self.tokenizer:
                tokens.append(intok)
                t = intok[0]
                if t == tokenize2.NEWLINE or (stop_at_NL and t == tokenize2.NL):
                    # Stop before we try to pull a line we don't have yet
                    break
                elif t == tokenize2.ERRORTOKEN:
                    stop_at_NL = True
        except TokenError:
            # Multi-line statement - stop and try again with the next line
            self.reset_tokenizer()
            return None
        
        return self.output(tokens)
    
    def output(self, tokens):
        self.current_line = ""
        self.reset_tokenizer()
        return untokenize(self.func(tokens)).rstrip('\n')
    
    def reset(self):
        l = self.current_line
        self.current_line = ""
        self.reset_tokenizer()
        if l:
            return l.rstrip('\n')

class assemble_python_lines(TokenInputTransformer):
    def __init__(self):
        super(assemble_python_lines, self).__init__(None)
    
    def output(self, tokens):
        return self.reset()

@CoroutineInputTransformer.wrap
def assemble_logical_lines():
    """Join lines following explicit line continuations (\)"""
    line = ''
    while True:
        line = (yield line)
        if not line or line.isspace():
            continue
        
        parts = []
        while line is not None:
            if line.endswith('\\') and (not has_comment(line)):
                parts.append(line[:-1])
                line = (yield None) # Get another line
            else:
                parts.append(line)
                break
        
        # Output
        line = ''.join(parts)

# 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)
    
# 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 }

@StatelessInputTransformer.wrap
def escaped_commands(line):
    """Transform escaped commands - %magic, !system, ?help + various autocalls.
    """
    if not line or line.isspace():
        return line
    lineinf = LineInfo(line)
    if lineinf.esc not in tr:
        return line
    
    return 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
    -------
    comment : bool
        True if source has a comment.
    """
    readline = StringIO(src).readline
    toktypes = set()
    try:
        for t in generate_tokens(readline):
            toktypes.add(t[0])
    except TokenError:
        pass
    return(tokenize2.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(end_on_blank_line=False):
    """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() != '') or not end_on_blank_line):
            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(prompt_re):
    """Remove matching input prompts from a block of input."""
    line = ''
    while True:
        line = (yield line)
        
        # First line of cell
        if line is None:
            continue
        out, n1 = prompt_re.subn('', line, count=1)
        line = (yield out)
        
        # Second line of cell, because people often copy from just after the
        # first prompt, so we might not see it in the first line.
        if line is None:
            continue
        out, n2 = prompt_re.subn('', line, count=1)
        line = (yield out)
        
        if n1 or n2:
            # Found the input prompt in the first two lines - check for it in
            # the rest of the cell as well.
            while line is not None:
                line = (yield prompt_re.sub('', line, count=1))
        
        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."""
    prompt_re = re.compile(r'^(>>> ?|^\.\.\. ?)')
    return _strip_prompts(prompt_re)

@CoroutineInputTransformer.wrap
def ipy_prompt():
    """Strip IPython's In [1]:/...: prompts."""
    prompt_re = re.compile(r'^(In \[\d+\]: |^\ \ \ \.\.\.+: )')
    return _strip_prompts(prompt_re)


@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)


assign_system_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                              r'\s*=\s*!\s*(?P<cmd>.*)')
assign_system_template = '%s = get_ipython().getoutput(%r)'
@StatelessInputTransformer.wrap
def assign_from_system(line):
    """Transform assignment from system commands (e.g. files = !ls)"""
    m = assign_system_re.match(line)
    if m is None:
        return line
    
    return assign_system_template % m.group('lhs', 'cmd')

assign_magic_re = re.compile(r'(?P<lhs>(\s*)([\w\.]+)((\s*,\s*[\w\.]+)*))'
                             r'\s*=\s*%\s*(?P<cmd>.*)')
assign_magic_template = '%s = get_ipython().magic(%r)'
@StatelessInputTransformer.wrap
def assign_from_magic(line):
    """Transform assignment from magic commands (e.g. a = %who_ls)"""
    m = assign_magic_re.match(line)
    if m is None:
        return line
    
    return assign_magic_template % m.group('lhs', 'cmd')