IPython/utils/tokenize2.py

"""Patched version of standard library tokenize, to deal with various bugs.

Based on Python 3.2 code.

Patches:

- Gareth Rees' patch for Python issue #12691 (untokenizing)
  - Except we don't encode the output of untokenize
  - Python 2 compatible syntax, so that it can be byte-compiled at installation
- Newlines in comments and blank lines should be either NL or NEWLINE, depending
  on whether they are in a multi-line statement. Filed as Python issue #17061.
- Export generate_tokens & TokenError
- u and rb literals are allowed under Python 3.3 and above.

------------------------------------------------------------------------------
Tokenization help for Python programs.

tokenize(readline) is a generator that breaks a stream of bytes into
Python tokens.  It decodes the bytes according to PEP-0263 for
determining source file encoding.

It accepts a readline-like method which is called repeatedly to get the
next line of input (or b"" for EOF).  It generates 5-tuples with these
members:

    the token type (see token.py)
    the token (a string)
    the starting (row, column) indices of the token (a 2-tuple of ints)
    the ending (row, column) indices of the token (a 2-tuple of ints)
    the original line (string)

It is designed to match the working of the Python tokenizer exactly, except
that it produces COMMENT tokens for comments and gives type OP for all
operators.  Additionally, all token lists start with an ENCODING token
which tells you which encoding was used to decode the bytes stream.
"""

__author__ = 'Ka-Ping Yee <[e-mail]>'
__credits__ = ('GvR, ESR, Tim Peters, Thomas Wouters, Fred Drake, '
               'Skip Montanaro, Raymond Hettinger, Trent Nelson, '
               'Michael Foord')
import builtins
import re
import sys
from token import *
from codecs import lookup, BOM_UTF8
import collections
from io import TextIOWrapper
cookie_re = re.compile("coding[:=]\s*([-\w.]+)")

import token
__all__ = token.__all__ + ["COMMENT", "tokenize", "detect_encoding",
                           "NL", "untokenize", "ENCODING", "TokenInfo"]
del token

__all__ += ["generate_tokens", "TokenError"]

COMMENT = N_TOKENS
tok_name[COMMENT] = 'COMMENT'
NL = N_TOKENS + 1
tok_name[NL] = 'NL'
ENCODING = N_TOKENS + 2
tok_name[ENCODING] = 'ENCODING'
N_TOKENS += 3

class TokenInfo(collections.namedtuple('TokenInfo', 'type string start end line')):
    def __repr__(self):
        annotated_type = '%d (%s)' % (self.type, tok_name[self.type])
        return ('TokenInfo(type=%s, string=%r, start=%r, end=%r, line=%r)' %
                self._replace(type=annotated_type))

def group(*choices): return '(' + '|'.join(choices) + ')'
def any(*choices): return group(*choices) + '*'
def maybe(*choices): return group(*choices) + '?'

# Note: we use unicode matching for names ("\w") but ascii matching for
# number literals.
Whitespace = r'[ \f\t]*'
Comment = r'#[^\r\n]*'
Ignore = Whitespace + any(r'\\\r?\n' + Whitespace) + maybe(Comment)
Name = r'\w+'

Hexnumber = r'0[xX][0-9a-fA-F]+'
Binnumber = r'0[bB][01]+'
Octnumber = r'0[oO][0-7]+'
Decnumber = r'(?:0+|[1-9][0-9]*)'
Intnumber = group(Hexnumber, Binnumber, Octnumber, Decnumber)
Exponent = r'[eE][-+]?[0-9]+'
Pointfloat = group(r'[0-9]+\.[0-9]*', r'\.[0-9]+') + maybe(Exponent)
Expfloat = r'[0-9]+' + Exponent
Floatnumber = group(Pointfloat, Expfloat)
Imagnumber = group(r'[0-9]+[jJ]', Floatnumber + r'[jJ]')
Number = group(Imagnumber, Floatnumber, Intnumber)

if sys.version_info.minor >= 3:
    StringPrefix = r'(?:[bB][rR]?|[rR][bB]?|[uU])?'
else:
    StringPrefix = r'(?:[bB]?[rR]?)?'

# Tail end of ' string.
Single = r"[^'\\]*(?:\\.[^'\\]*)*'"
# Tail end of " string.
Double = r'[^"\\]*(?:\\.[^"\\]*)*"'
# Tail end of ''' string.
Single3 = r"[^'\\]*(?:(?:\\.|'(?!''))[^'\\]*)*'''"
# Tail end of """ string.
Double3 = r'[^"\\]*(?:(?:\\.|"(?!""))[^"\\]*)*"""'
Triple = group(StringPrefix + "'''", StringPrefix + '"""')
# Single-line ' or " string.
String = group(StringPrefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*'",
               StringPrefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*"')

# Because of leftmost-then-longest match semantics, be sure to put the
# longest operators first (e.g., if = came before ==, == would get
# recognized as two instances of =).
Operator = group(r"\*\*=?", r">>=?", r"<<=?", r"!=",
                 r"//=?", r"->",
                 r"[+\-*/%&|^=<>]=?",
                 r"~")

Bracket = '[][(){}]'
Special = group(r'\r?\n', r'\.\.\.', r'[:;.,@]')
Funny = group(Operator, Bracket, Special)

PlainToken = group(Number, Funny, String, Name)
Token = Ignore + PlainToken

# First (or only) line of ' or " string.
ContStr = group(StringPrefix + r"'[^\n'\\]*(?:\\.[^\n'\\]*)*" +
                group("'", r'\\\r?\n'),
                StringPrefix + r'"[^\n"\\]*(?:\\.[^\n"\\]*)*' +
                group('"', r'\\\r?\n'))
PseudoExtras = group(r'\\\r?\n', Comment, Triple)
PseudoToken = Whitespace + group(PseudoExtras, Number, Funny, ContStr, Name)

def _compile(expr):
    return re.compile(expr, re.UNICODE)

tokenprog, pseudoprog, single3prog, double3prog = map(
    _compile, (Token, PseudoToken, Single3, Double3))
endprogs = {"'": _compile(Single), '"': _compile(Double),
            "'''": single3prog, '"""': double3prog,
            "r'''": single3prog, 'r"""': double3prog,
            "b'''": single3prog, 'b"""': double3prog,
            "R'''": single3prog, 'R"""': double3prog,
            "B'''": single3prog, 'B"""': double3prog,
            "br'''": single3prog, 'br"""': double3prog,
            "bR'''": single3prog, 'bR"""': double3prog,
            "Br'''": single3prog, 'Br"""': double3prog,
            "BR'''": single3prog, 'BR"""': double3prog,
            'r': None, 'R': None, 'b': None, 'B': None}

triple_quoted = {}
for t in ("'''", '"""',
          "r'''", 'r"""', "R'''", 'R"""',
          "b'''", 'b"""', "B'''", 'B"""',
          "br'''", 'br"""', "Br'''", 'Br"""',
          "bR'''", 'bR"""', "BR'''", 'BR"""'):
    triple_quoted[t] = t
single_quoted = {}
for t in ("'", '"',
          "r'", 'r"', "R'", 'R"',
          "b'", 'b"', "B'", 'B"',
          "br'", 'br"', "Br'", 'Br"',
          "bR'", 'bR"', "BR'", 'BR"' ):
    single_quoted[t] = t

if sys.version_info.minor >= 3:
    # Python 3.3
    for _prefix in ['rb', 'rB', 'Rb', 'RB', 'u', 'U']:
        _t2 = _prefix+'"""'
        endprogs[_t2] = double3prog
        triple_quoted[_t2] = _t2
        _t1 = _prefix + "'''"
        endprogs[_t1] = single3prog
        triple_quoted[_t1] = _t1
        single_quoted[_prefix+'"'] = _prefix+'"'
        single_quoted[_prefix+"'"] = _prefix+"'"
    del _prefix, _t2, _t1
    endprogs['u'] = None
    endprogs['U'] = None

del _compile

tabsize = 8

class TokenError(Exception): pass

class StopTokenizing(Exception): pass


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
            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
        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)


def _get_normal_name(orig_enc):
    """Imitates get_normal_name in tokenizer.c."""
    # Only care about the first 12 characters.
    enc = orig_enc[:12].lower().replace("_", "-")
    if enc == "utf-8" or enc.startswith("utf-8-"):
        return "utf-8"
    if enc in ("latin-1", "iso-8859-1", "iso-latin-1") or \
       enc.startswith(("latin-1-", "iso-8859-1-", "iso-latin-1-")):
        return "iso-8859-1"
    return orig_enc

def detect_encoding(readline):
    """
    The detect_encoding() function is used to detect the encoding that should
    be used to decode a Python source file.  It requires one argment, readline,
    in the same way as the tokenize() generator.

    It will call readline a maximum of twice, and return the encoding used
    (as a string) and a list of any lines (left as bytes) it has read in.

    It detects the encoding from the presence of a utf-8 bom or an encoding
    cookie as specified in pep-0263.  If both a bom and a cookie are present,
    but disagree, a SyntaxError will be raised.  If the encoding cookie is an
    invalid charset, raise a SyntaxError.  Note that if a utf-8 bom is found,
    'utf-8-sig' is returned.

    If no encoding is specified, then the default of 'utf-8' will be returned.
    """
    bom_found = False
    encoding = None
    default = 'utf-8'
    def read_or_stop():
        try:
            return readline()
        except StopIteration:
            return b''

    def find_cookie(line):
        try:
            # Decode as UTF-8. Either the line is an encoding declaration,
            # in which case it should be pure ASCII, or it must be UTF-8
            # per default encoding.
            line_string = line.decode('utf-8')
        except UnicodeDecodeError:
            raise SyntaxError("invalid or missing encoding declaration")

        matches = cookie_re.findall(line_string)
        if not matches:
            return None
        encoding = _get_normal_name(matches[0])
        try:
            codec = lookup(encoding)
        except LookupError:
            # This behaviour mimics the Python interpreter
            raise SyntaxError("unknown encoding: " + encoding)

        if bom_found:
            if encoding != 'utf-8':
                # This behaviour mimics the Python interpreter
                raise SyntaxError('encoding problem: utf-8')
            encoding += '-sig'
        return encoding

    first = read_or_stop()
    if first.startswith(BOM_UTF8):
        bom_found = True
        first = first[3:]
        default = 'utf-8-sig'
    if not first:
        return default, []

    encoding = find_cookie(first)
    if encoding:
        return encoding, [first]

    second = read_or_stop()
    if not second:
        return default, [first]

    encoding = find_cookie(second)
    if encoding:
        return encoding, [first, second]

    return default, [first, second]


def open(filename):
    """Open a file in read only mode using the encoding detected by
    detect_encoding().
    """
    buffer = builtins.open(filename, 'rb')
    encoding, lines = detect_encoding(buffer.readline)
    buffer.seek(0)
    text = TextIOWrapper(buffer, encoding, line_buffering=True)
    text.mode = 'r'
    return text


def tokenize(readline):
    """
    The tokenize() generator requires one argment, readline, which
    must be a callable object which provides the same interface as the
    readline() method of built-in file objects.  Each call to the function
    should return one line of input as bytes.  Alternately, readline
    can be a callable function terminating with StopIteration:
        readline = open(myfile, 'rb').__next__  # Example of alternate readline

    The generator produces 5-tuples with these members: the token type; the
    token string; a 2-tuple (srow, scol) of ints specifying the row and
    column where the token begins in the source; a 2-tuple (erow, ecol) of
    ints specifying the row and column where the token ends in the source;
    and the line on which the token was found.  The line passed is the
    logical line; continuation lines are included.

    The first token sequence will always be an ENCODING token
    which tells you which encoding was used to decode the bytes stream.
    """
    # This import is here to avoid problems when the itertools module is not
    # built yet and tokenize is imported.
    from itertools import chain, repeat
    encoding, consumed = detect_encoding(readline)
    rl_gen = iter(readline, b"")
    empty = repeat(b"")
    return _tokenize(chain(consumed, rl_gen, empty).__next__, encoding)


def _tokenize(readline, encoding):
    lnum = parenlev = continued = 0
    numchars = '0123456789'
    contstr, needcont = '', 0
    contline = None
    indents = [0]

    if encoding is not None:
        if encoding == "utf-8-sig":
            # BOM will already have been stripped.
            encoding = "utf-8"
        yield TokenInfo(ENCODING, encoding, (0, 0), (0, 0), '')
    while True:             # loop over lines in stream
        try:
            line = readline()
        except StopIteration:
            line = b''

        if encoding is not None:
            line = line.decode(encoding)
        lnum += 1
        pos, max = 0, len(line)

        if contstr:                            # continued string
            if not line:
                raise TokenError("EOF in multi-line string", strstart)
            endmatch = endprog.match(line)
            if endmatch:
                pos = end = endmatch.end(0)
                yield TokenInfo(STRING, contstr + line[:end],
                       strstart, (lnum, end), contline + line)
                contstr, needcont = '', 0
                contline = None
            elif needcont and line[-2:] != '\\\n' and line[-3:] != '\\\r\n':
                yield TokenInfo(ERRORTOKEN, contstr + line,
                           strstart, (lnum, len(line)), contline)
                contstr = ''
                contline = None
                continue
            else:
                contstr = contstr + line
                contline = contline + line
                continue

        elif parenlev == 0 and not continued:  # new statement
            if not line: break
            column = 0
            while pos < max:                   # measure leading whitespace
                if line[pos] == ' ':
                    column += 1
                elif line[pos] == '\t':
                    column = (column//tabsize + 1)*tabsize
                elif line[pos] == '\f':
                    column = 0
                else:
                    break
                pos += 1
            if pos == max:
                break

            if line[pos] in '#\r\n':           # skip comments or blank lines
                if line[pos] == '#':
                    comment_token = line[pos:].rstrip('\r\n')
                    nl_pos = pos + len(comment_token)
                    yield TokenInfo(COMMENT, comment_token,
                           (lnum, pos), (lnum, pos + len(comment_token)), line)
                    yield TokenInfo(NEWLINE, line[nl_pos:],
                           (lnum, nl_pos), (lnum, len(line)), line)
                else:
                    yield TokenInfo(NEWLINE, line[pos:],
                           (lnum, pos), (lnum, len(line)), line)
                continue

            if column > indents[-1]:           # count indents or dedents
                indents.append(column)
                yield TokenInfo(INDENT, line[:pos], (lnum, 0), (lnum, pos), line)
            while column < indents[-1]:
                if column not in indents:
                    raise IndentationError(
                        "unindent does not match any outer indentation level",
                        ("<tokenize>", lnum, pos, line))
                indents = indents[:-1]
                yield TokenInfo(DEDENT, '', (lnum, pos), (lnum, pos), line)

        else:                                  # continued statement
            if not line:
                raise TokenError("EOF in multi-line statement", (lnum, 0))
            continued = 0

        while pos < max:
            pseudomatch = pseudoprog.match(line, pos)
            if pseudomatch:                                # scan for tokens
                start, end = pseudomatch.span(1)
                spos, epos, pos = (lnum, start), (lnum, end), end
                token, initial = line[start:end], line[start]

                if (initial in numchars or                  # ordinary number
                    (initial == '.' and token != '.' and token != '...')):
                    yield TokenInfo(NUMBER, token, spos, epos, line)
                elif initial in '\r\n':
                    yield TokenInfo(NL if parenlev > 0 else NEWLINE,
                           token, spos, epos, line)
                elif initial == '#':
                    assert not token.endswith("\n")
                    yield TokenInfo(COMMENT, token, spos, epos, line)
                elif token in triple_quoted:
                    endprog = endprogs[token]
                    endmatch = endprog.match(line, pos)
                    if endmatch:                           # all on one line
                        pos = endmatch.end(0)
                        token = line[start:pos]
                        yield TokenInfo(STRING, token, spos, (lnum, pos), line)
                    else:
                        strstart = (lnum, start)           # multiple lines
                        contstr = line[start:]
                        contline = line
                        break
                elif initial in single_quoted or \
                    token[:2] in single_quoted or \
                    token[:3] in single_quoted:
                    if token[-1] == '\n':                  # continued string
                        strstart = (lnum, start)
                        endprog = (endprogs[initial] or endprogs[token[1]] or
                                   endprogs[token[2]])
                        contstr, needcont = line[start:], 1
                        contline = line
                        break
                    else:                                  # ordinary string
                        yield TokenInfo(STRING, token, spos, epos, line)
                elif initial.isidentifier():               # ordinary name
                    yield TokenInfo(NAME, token, spos, epos, line)
                elif initial == '\\':                      # continued stmt
                    continued = 1
                else:
                    if initial in '([{':
                        parenlev += 1
                    elif initial in ')]}':
                        parenlev -= 1
                    yield TokenInfo(OP, token, spos, epos, line)
            else:
                yield TokenInfo(ERRORTOKEN, line[pos],
                           (lnum, pos), (lnum, pos+1), line)
                pos += 1

    for indent in indents[1:]:                 # pop remaining indent levels
        yield TokenInfo(DEDENT, '', (lnum, 0), (lnum, 0), '')
    yield TokenInfo(ENDMARKER, '', (lnum, 0), (lnum, 0), '')


# An undocumented, backwards compatible, API for all the places in the standard
# library that expect to be able to use tokenize with strings
def generate_tokens(readline):
    return _tokenize(readline, None)

if __name__ == "__main__":
    # Quick sanity check
    s = b'''def parseline(self, line):
            """Parse the line into a command name and a string containing
            the arguments.  Returns a tuple containing (command, args, line).
            'command' and 'args' may be None if the line couldn't be parsed.
            """
            line = line.strip()
            if not line:
                return None, None, line
            elif line[0] == '?':
                line = 'help ' + line[1:]
            elif line[0] == '!':
                if hasattr(self, 'do_shell'):
                    line = 'shell ' + line[1:]
                else:
                    return None, None, line
            i, n = 0, len(line)
            while i < n and line[i] in self.identchars: i = i+1
            cmd, arg = line[:i], line[i:].strip()
            return cmd, arg, line
    '''
    for tok in tokenize(iter(s.splitlines()).__next__):
        print(tok)