path: root/pygments/lexer.py

# -*- coding: utf-8 -*-
"""
    pygments.lexer
    ~~~~~~~~~~~~~~

    Base lexer classes.

    :copyright: Copyright 2006-2009 by the Pygments team, see AUTHORS.
    :license: BSD, see LICENSE for details.
"""
import re

try:
    set
except NameError:
    from sets import Set as set

from pygments.filter import apply_filters, Filter
from pygments.filters import get_filter_by_name
from pygments.token import Error, Text, Other, _TokenType
from pygments.util import get_bool_opt, get_int_opt, get_list_opt, \
     make_analysator


__all__ = ['Lexer', 'RegexLexer', 'ExtendedRegexLexer', 'DelegatingLexer',
           'LexerContext', 'include', 'flags', 'bygroups', 'using', 'this']


_default_analyse = staticmethod(lambda x: 0.0)


class LexerMeta(type):
    """
    This metaclass automagically converts ``analyse_text`` methods into
    static methods which always return float values.
    """

    def __new__(cls, name, bases, d):
        if 'analyse_text' in d:
            d['analyse_text'] = make_analysator(d['analyse_text'])
        return type.__new__(cls, name, bases, d)


class Lexer(object):
    """
    Lexer for a specific language.

    Basic options recognized:
    ``stripnl``
        Strip leading and trailing newlines from the input (default: True).
    ``stripall``
        Strip all leading and trailing whitespace from the input
        (default: False).
    ``tabsize``
        If given and greater than 0, expand tabs in the input (default: 0).
    ``encoding``
        If given, must be an encoding name. This encoding will be used to
        convert the input string to Unicode, if it is not already a Unicode
        string (default: ``'latin1'``).
        Can also be ``'guess'`` to use a simple UTF-8 / Latin1 detection, or
        ``'chardet'`` to use the chardet library, if it is installed.
    """

    #: Name of the lexer
    name = None

    #: Shortcuts for the lexer
    aliases = []

    #: fn match rules
    filenames = []

    #: fn alias filenames
    alias_filenames = []

    #: mime types
    mimetypes = []

    __metaclass__ = LexerMeta

    def __init__(self, **options):
        self.options = options
        self.stripnl = get_bool_opt(options, 'stripnl', True)
        self.stripall = get_bool_opt(options, 'stripall', False)
        self.tabsize = get_int_opt(options, 'tabsize', 0)
        self.encoding = options.get('encoding', 'latin1')
        # self.encoding = options.get('inencoding', None) or self.encoding
        self.filters = []
        for filter_ in get_list_opt(options, 'filters', ()):
            self.add_filter(filter_)

    def __repr__(self):
        if self.options:
            return '<pygments.lexers.%s with %r>' % (self.__class__.__name__,
                                                     self.options)
        else:
            return '<pygments.lexers.%s>' % self.__class__.__name__

    def add_filter(self, filter_, **options):
        """
        Add a new stream filter to this lexer.
        """
        if not isinstance(filter_, Filter):
            filter_ = get_filter_by_name(filter_, **options)
        self.filters.append(filter_)

    def analyse_text(text):
        """
        Has to return a float between ``0`` and ``1`` that indicates
        if a lexer wants to highlight this text. Used by ``guess_lexer``.
        If this method returns ``0`` it won't highlight it in any case, if
        it returns ``1`` highlighting with this lexer is guaranteed.

        The `LexerMeta` metaclass automatically wraps this function so
        that it works like a static method (no ``self`` or ``cls``
        parameter) and the return value is automatically converted to
        `float`. If the return value is an object that is boolean `False`
        it's the same as if the return values was ``0.0``.
        """

    def get_tokens(self, text, unfiltered=False):
        """
        Return an iterable of (tokentype, value) pairs generated from
        `text`. If `unfiltered` is set to `True`, the filtering mechanism
        is bypassed even if filters are defined.

        Also preprocess the text, i.e. expand tabs and strip it if
        wanted and applies registered filters.
        """
        if not isinstance(text, unicode):
            if self.encoding == 'guess':
                try:
                    text = text.decode('utf-8')
                    if text.startswith(u'\ufeff'):
                        text = text[len(u'\ufeff'):]
                except UnicodeDecodeError:
                    text = text.decode('latin1')
            elif self.encoding == 'chardet':
                try:
                    import chardet
                except ImportError:
                    raise ImportError('To enable chardet encoding guessing, '
                                      'please install the chardet library '
                                      'from http://chardet.feedparser.org/')
                enc = chardet.detect(text)
                text = text.decode(enc['encoding'])
            else:
                text = text.decode(self.encoding)
        # text now *is* a unicode string
        text = text.replace('\r\n', '\n')
        text = text.replace('\r', '\n')
        if self.stripall:
            text = text.strip()
        elif self.stripnl:
            text = text.strip('\n')
        if self.tabsize > 0:
            text = text.expandtabs(self.tabsize)
        if not text.endswith('\n'):
            text += '\n'

        def streamer():
            for i, t, v in self.get_tokens_unprocessed(text):
                yield t, v
        stream = streamer()
        if not unfiltered:
            stream = apply_filters(stream, self.filters, self)
        return stream

    def get_tokens_unprocessed(self, text):
        """
        Return an iterable of (tokentype, value) pairs.
        In subclasses, implement this method as a generator to
        maximize effectiveness.
        """
        raise NotImplementedError


class DelegatingLexer(Lexer):
    """
    This lexer takes two lexer as arguments. A root lexer and
    a language lexer. First everything is scanned using the language
    lexer, afterwards all ``Other`` tokens are lexed using the root
    lexer.

    The lexers from the ``template`` lexer package use this base lexer.
    """

    def __init__(self, _root_lexer, _language_lexer, _needle=Other, **options):
        self.root_lexer = _root_lexer(**options)
        self.language_lexer = _language_lexer(**options)
        self.needle = _needle
        Lexer.__init__(self, **options)

    def get_tokens_unprocessed(self, text):
        buffered = ''
        insertions = []
        lng_buffer = []
        for i, t, v in self.language_lexer.get_tokens_unprocessed(text):
            if t is self.needle:
                if lng_buffer:
                    insertions.append((len(buffered), lng_buffer))
                    lng_buffer = []
                buffered += v
            else:
                lng_buffer.append((i, t, v))
        if lng_buffer:
            insertions.append((len(buffered), lng_buffer))
        return do_insertions(insertions,
                             self.root_lexer.get_tokens_unprocessed(buffered))


#-------------------------------------------------------------------------------
# RegexLexer and ExtendedRegexLexer
#


class include(str):
    """
    Indicates that a state should include rules from another state.
    """
    pass


class combined(tuple):
    """
    Indicates a state combined from multiple states.
    """

    def __new__(cls, *args):
        return tuple.__new__(cls, args)

    def __init__(self, *args):
        # tuple.__init__ doesn't do anything
        pass


class _PseudoMatch(object):
    """
    A pseudo match object constructed from a string.
    """

    def __init__(self, start, text):
        self._text = text
        self._start = start

    def start(self, arg=None):
        return self._start

    def end(self, arg=None):
        return self._start + len(self._text)

    def group(self, arg=None):
        if arg:
            raise IndexError('No such group')
        return self._text

    def groups(self):
        return (self._text,)

    def groupdict(self):
        return {}


def bygroups(*args):
    """
    Callback that yields multiple actions for each group in the match.
    """
    def callback(lexer, match, ctx=None):
        for i, action in enumerate(args):
            if action is None:
                continue
            elif type(action) is _TokenType:
                data = match.group(i + 1)
                if data:
                    yield match.start(i + 1), action, data
            else:
                if ctx:
                    ctx.pos = match.start(i + 1)
                for item in action(lexer, _PseudoMatch(match.start(i + 1),
                                   match.group(i + 1)), ctx):
                    if item:
                        yield item
        if ctx:
            ctx.pos = match.end()
    return callback


class _This(object):
    """
    Special singleton used for indicating the caller class.
    Used by ``using``.
    """
this = _This()


def using(_other, **kwargs):
    """
    Callback that processes the match with a different lexer.

    The keyword arguments are forwarded to the lexer, except `state` which
    is handled separately.

    `state` specifies the state that the new lexer will start in, and can
    be an enumerable such as ('root', 'inline', 'string') or a simple
    string which is assumed to be on top of the root state.

    Note: For that to work, `_other` must not be an `ExtendedRegexLexer`.
    """
    gt_kwargs = {}
    if 'state' in kwargs:
        s = kwargs.pop('state')
        if isinstance(s, (list, tuple)):
            gt_kwargs['stack'] = s
        else:
            gt_kwargs['stack'] = ('root', s)

    if _other is this:
        def callback(lexer, match, ctx=None):
            # if keyword arguments are given the callback
            # function has to create a new lexer instance
            if kwargs:
                # XXX: cache that somehow
                kwargs.update(lexer.options)
                lx = lexer.__class__(**kwargs)
            else:
                lx = lexer
            s = match.start()
            for i, t, v in lx.get_tokens_unprocessed(match.group(), **gt_kwargs):
                yield i + s, t, v
            if ctx:
                ctx.pos = match.end()
    else:
        def callback(lexer, match, ctx=None):
            # XXX: cache that somehow
            kwargs.update(lexer.options)
            lx = _other(**kwargs)

            s = match.start()
            for i, t, v in lx.get_tokens_unprocessed(match.group(), **gt_kwargs):
                yield i + s, t, v
            if ctx:
                ctx.pos = match.end()
    return callback


class RegexLexerMeta(LexerMeta):
    """
    Metaclass for RegexLexer, creates the self._tokens attribute from
    self.tokens on the first instantiation.
    """

    def _process_state(cls, unprocessed, processed, state):
        assert type(state) is str, "wrong state name %r" % state
        assert state[0] != '#', "invalid state name %r" % state
        if state in processed:
            return processed[state]
        tokens = processed[state] = []
        rflags = cls.flags
        for tdef in unprocessed[state]:
            if isinstance(tdef, include):
                # it's a state reference
                assert tdef != state, "circular state reference %r" % state
                tokens.extend(cls._process_state(unprocessed, processed, str(tdef)))
                continue

            assert type(tdef) is tuple, "wrong rule def %r" % tdef

            try:
                rex = re.compile(tdef[0], rflags).match
            except Exception, err:
                raise ValueError("uncompilable regex %r in state %r of %r: %s" %
                                 (tdef[0], state, cls, err))

            assert type(tdef[1]) is _TokenType or callable(tdef[1]), \
                   'token type must be simple type or callable, not %r' % (tdef[1],)

            if len(tdef) == 2:
                new_state = None
            else:
                tdef2 = tdef[2]
                if isinstance(tdef2, str):
                    # an existing state
                    if tdef2 == '#pop':
                        new_state = -1
                    elif tdef2 in unprocessed:
                        new_state = (tdef2,)
                    elif tdef2 == '#push':
                        new_state = tdef2
                    elif tdef2[:5] == '#pop:':
                        new_state = -int(tdef2[5:])
                    else:
                        assert False, 'unknown new state %r' % tdef2
                elif isinstance(tdef2, combined):
                    # combine a new state from existing ones
                    new_state = '_tmp_%d' % cls._tmpname
                    cls._tmpname += 1
                    itokens = []
                    for istate in tdef2:
                        assert istate != state, 'circular state ref %r' % istate
                        itokens.extend(cls._process_state(unprocessed,
                                                          processed, istate))
                    processed[new_state] = itokens
                    new_state = (new_state,)
                elif isinstance(tdef2, tuple):
                    # push more than one state
                    for state in tdef2:
                        assert (state in unprocessed or
                                state in ('#pop', '#push')), \
                               'unknown new state ' + state
                    new_state = tdef2
                else:
                    assert False, 'unknown new state def %r' % tdef2
            tokens.append((rex, tdef[1], new_state))
        return tokens

    def process_tokendef(cls, name, tokendefs=None):
        processed = cls._all_tokens[name] = {}
        tokendefs = tokendefs or cls.tokens[name]
        for state in tokendefs.keys():
            cls._process_state(tokendefs, processed, state)
        return processed

    def __call__(cls, *args, **kwds):
        if not hasattr(cls, '_tokens'):
            cls._all_tokens = {}
            cls._tmpname = 0
            if hasattr(cls, 'token_variants') and cls.token_variants:
                # don't process yet
                pass
            else:
                cls._tokens = cls.process_tokendef('', cls.tokens)

        return type.__call__(cls, *args, **kwds)


class RegexLexer(Lexer):
    """
    Base for simple stateful regular expression-based lexers.
    Simplifies the lexing process so that you need only
    provide a list of states and regular expressions.
    """
    __metaclass__ = RegexLexerMeta

    #: Flags for compiling the regular expressions.
    #: Defaults to MULTILINE.
    flags = re.MULTILINE

    #: Dict of ``{'state': [(regex, tokentype, new_state), ...], ...}``
    #:
    #: The initial state is 'root'.
    #: ``new_state`` can be omitted to signify no state transition.
    #: If it is a string, the state is pushed on the stack and changed.
    #: If it is a tuple of strings, all states are pushed on the stack and
    #: the current state will be the topmost.
    #: It can also be ``combined('state1', 'state2', ...)``
    #: to signify a new, anonymous state combined from the rules of two
    #: or more existing ones.
    #: Furthermore, it can be '#pop' to signify going back one step in
    #: the state stack, or '#push' to push the current state on the stack
    #: again.
    #:
    #: The tuple can also be replaced with ``include('state')``, in which
    #: case the rules from the state named by the string are included in the
    #: current one.
    tokens = {}

    def get_tokens_unprocessed(self, text, stack=('root',)):
        """
        Split ``text`` into (tokentype, text) pairs.

        ``stack`` is the inital stack (default: ``['root']``)
        """
        pos = 0
        tokendefs = self._tokens
        statestack = list(stack)
        statetokens = tokendefs[statestack[-1]]
        while 1:
            for rexmatch, action, new_state in statetokens:
                m = rexmatch(text, pos)
                if m:
                    if type(action) is _TokenType:
                        yield pos, action, m.group()
                    else:
                        for item in action(self, m):
                            yield item
                    pos = m.end()
                    if new_state is not None:
                        # state transition
                        if isinstance(new_state, tuple):
                            for state in new_state:
                                if state == '#pop':
                                    statestack.pop()
                                elif state == '#push':
                                    statestack.append(statestack[-1])
                                else:
                                    statestack.append(state)
                        elif isinstance(new_state, int):
                            # pop
                            del statestack[new_state:]
                        elif new_state == '#push':
                            statestack.append(statestack[-1])
                        else:
                            assert False, "wrong state def: %r" % new_state
                        statetokens = tokendefs[statestack[-1]]
                    break
            else:
                try:
                    if text[pos] == '\n':
                        # at EOL, reset state to "root"
                        pos += 1
                        statestack = ['root']
                        statetokens = tokendefs['root']
                        yield pos, Text, u'\n'
                        continue
                    yield pos, Error, text[pos]
                    pos += 1
                except IndexError:
                    break


class LexerContext(object):
    """
    A helper object that holds lexer position data.
    """

    def __init__(self, text, pos, stack=None, end=None):
        self.text = text
        self.pos = pos
        self.end = end or len(text) # end=0 not supported ;-)
        self.stack = stack or ['root']

    def __repr__(self):
        return 'LexerContext(%r, %r, %r)' % (
            self.text, self.pos, self.stack)


class ExtendedRegexLexer(RegexLexer):
    """
    A RegexLexer that uses a context object to store its state.
    """

    def get_tokens_unprocessed(self, text=None, context=None):
        """
        Split ``text`` into (tokentype, text) pairs.
        If ``context`` is given, use this lexer context instead.
        """
        tokendefs = self._tokens
        if not context:
            ctx = LexerContext(text, 0)
            statetokens = tokendefs['root']
        else:
            ctx = context
            statetokens = tokendefs[ctx.stack[-1]]
            text = ctx.text
        while 1:
            for rexmatch, action, new_state in statetokens:
                m = rexmatch(text, ctx.pos, ctx.end)
                if m:
                    if type(action) is _TokenType:
                        yield ctx.pos, action, m.group()
                        ctx.pos = m.end()
                    else:
                        for item in action(self, m, ctx):
                            yield item
                        if not new_state:
                            # altered the state stack?
                            statetokens = tokendefs[ctx.stack[-1]]
                    # CAUTION: callback must set ctx.pos!
                    if new_state is not None:
                        # state transition
                        if isinstance(new_state, tuple):
                            ctx.stack.extend(new_state)
                        elif isinstance(new_state, int):
                            # pop
                            del ctx.stack[new_state:]
                        elif new_state == '#push':
                            ctx.stack.append(ctx.stack[-1])
                        else:
                            assert False, "wrong state def: %r" % new_state
                        statetokens = tokendefs[ctx.stack[-1]]
                    break
            else:
                try:
                    if ctx.pos >= ctx.end:
                        break
                    if text[ctx.pos] == '\n':
                        # at EOL, reset state to "root"
                        ctx.pos += 1
                        ctx.stack = ['root']
                        statetokens = tokendefs['root']
                        yield ctx.pos, Text, u'\n'
                        continue
                    yield ctx.pos, Error, text[ctx.pos]
                    ctx.pos += 1
                except IndexError:
                    break


def do_insertions(insertions, tokens):
    """
    Helper for lexers which must combine the results of several
    sublexers.

    ``insertions`` is a list of ``(index, itokens)`` pairs.
    Each ``itokens`` iterable should be inserted at position
    ``index`` into the token stream given by the ``tokens``
    argument.

    The result is a combined token stream.

    TODO: clean up the code here.
    """
    insertions = iter(insertions)
    try:
        index, itokens = insertions.next()
    except StopIteration:
        # no insertions
        for item in tokens:
            yield item
        return

    realpos = None
    insleft = True

    # iterate over the token stream where we want to insert
    # the tokens from the insertion list.
    for i, t, v in tokens:
        # first iteration. store the postition of first item
        if realpos is None:
            realpos = i
        oldi = 0
        while insleft and i + len(v) >= index:
            tmpval = v[oldi:index - i]
            yield realpos, t, tmpval
            realpos += len(tmpval)
            for it_index, it_token, it_value in itokens:
                yield realpos, it_token, it_value
                realpos += len(it_value)
            oldi = index - i
            try:
                index, itokens = insertions.next()
            except StopIteration:
                insleft = False
                break  # not strictly necessary
        yield realpos, t, v[oldi:]
        realpos += len(v) - oldi

    # leftover tokens
    if insleft:
        # no normal tokens, set realpos to zero
        realpos = realpos or 0
        for p, t, v in itokens:
            yield realpos, t, v
            realpos += len(v)