cpython/Lib/idlelib/HyperParser.py

"""
HyperParser
===========
This module defines the HyperParser class, which provides advanced parsing
abilities for the ParenMatch and other extensions.
The HyperParser uses PyParser. PyParser is intended mostly to give information
on the proper indentation of code. HyperParser gives some information on the
structure of code, used by extensions to help the user.
"""

import string
import keyword
from idlelib import PyParse

class HyperParser:

    def __init__(self, editwin, index):
        """Initialize the HyperParser to analyze the surroundings of the given
        index.
        """

        self.editwin = editwin
        self.text = text = editwin.text

        parser = PyParse.Parser(editwin.indentwidth, editwin.tabwidth)

        def index2line(index):
            return int(float(index))
        lno = index2line(text.index(index))

        if not editwin.context_use_ps1:
            for context in editwin.num_context_lines:
                startat = max(lno - context, 1)
                startatindex = `startat` + ".0"
                stopatindex = "%d.end" % lno
                # We add the newline because PyParse requires a newline at end.
                # We add a space so that index won't be at end of line, so that
                # its status will be the same as the char before it, if should.
                parser.set_str(text.get(startatindex, stopatindex)+' \n')
                bod = parser.find_good_parse_start(
                          editwin._build_char_in_string_func(startatindex))
                if bod is not None or startat == 1:
                    break
            parser.set_lo(bod or 0)
        else:
            r = text.tag_prevrange("console", index)
            if r:
                startatindex = r[1]
            else:
                startatindex = "1.0"
            stopatindex = "%d.end" % lno
            # We add the newline because PyParse requires a newline at end.
            # We add a space so that index won't be at end of line, so that
            # its status will be the same as the char before it, if should.
            parser.set_str(text.get(startatindex, stopatindex)+' \n')
            parser.set_lo(0)

        # We want what the parser has, except for the last newline and space.
        self.rawtext = parser.str[:-2]
        # As far as I can see, parser.str preserves the statement we are in,
        # so that stopatindex can be used to synchronize the string with the
        # text box indices.
        self.stopatindex = stopatindex
        self.bracketing = parser.get_last_stmt_bracketing()
        # find which pairs of bracketing are openers. These always correspond
        # to a character of rawtext.
        self.isopener = [i>0 and self.bracketing[i][1] > self.bracketing[i-1][1]
                         for i in range(len(self.bracketing))]

        self.set_index(index)

    def set_index(self, index):
        """Set the index to which the functions relate. Note that it must be
        in the same statement.
        """
        indexinrawtext = \
            len(self.rawtext) - len(self.text.get(index, self.stopatindex))
        if indexinrawtext < 0:
            raise ValueError("The index given is before the analyzed statement")
        self.indexinrawtext = indexinrawtext
        # find the rightmost bracket to which index belongs
        self.indexbracket = 0
        while self.indexbracket < len(self.bracketing)-1 and \
              self.bracketing[self.indexbracket+1][0] < self.indexinrawtext:
            self.indexbracket += 1
        if self.indexbracket < len(self.bracketing)-1 and \
           self.bracketing[self.indexbracket+1][0] == self.indexinrawtext and \
           not self.isopener[self.indexbracket+1]:
            self.indexbracket += 1

    def is_in_string(self):
        """Is the index given to the HyperParser is in a string?"""
        # The bracket to which we belong should be an opener.
        # If it's an opener, it has to have a character.
        return self.isopener[self.indexbracket] and \
               self.rawtext[self.bracketing[self.indexbracket][0]] in ('"', "'")

    def is_in_code(self):
        """Is the index given to the HyperParser is in a normal code?"""
        return not self.isopener[self.indexbracket] or \
               self.rawtext[self.bracketing[self.indexbracket][0]] not in \
                                                                ('#', '"', "'")

    def get_surrounding_brackets(self, openers='([{', mustclose=False):
        """If the index given to the HyperParser is surrounded by a bracket
        defined in openers (or at least has one before it), return the
        indices of the opening bracket and the closing bracket (or the
        end of line, whichever comes first).
        If it is not surrounded by brackets, or the end of line comes before
        the closing bracket and mustclose is True, returns None.
        """
        bracketinglevel = self.bracketing[self.indexbracket][1]
        before = self.indexbracket
        while not self.isopener[before] or \
              self.rawtext[self.bracketing[before][0]] not in openers or \
              self.bracketing[before][1] > bracketinglevel:
            before -= 1
            if before < 0:
                return None
            bracketinglevel = min(bracketinglevel, self.bracketing[before][1])
        after = self.indexbracket + 1
        while after < len(self.bracketing) and \
              self.bracketing[after][1] >= bracketinglevel:
            after += 1

        beforeindex = self.text.index("%s-%dc" %
            (self.stopatindex, len(self.rawtext)-self.bracketing[before][0]))
        if after >= len(self.bracketing) or \
           self.bracketing[after][0] > len(self.rawtext):
            if mustclose:
                return None
            afterindex = self.stopatindex
        else:
            # We are after a real char, so it is a ')' and we give the index
            # before it.
            afterindex = self.text.index("%s-%dc" %
                (self.stopatindex,
                 len(self.rawtext)-(self.bracketing[after][0]-1)))

        return beforeindex, afterindex

    # This string includes all chars that may be in a white space
    _whitespace_chars = " \t\n\\"
    # This string includes all chars that may be in an identifier
    _id_chars = string.ascii_letters + string.digits + "_"
    # This string includes all chars that may be the first char of an identifier
    _id_first_chars = string.ascii_letters + "_"

    # Given a string and pos, return the number of chars in the identifier
    # which ends at pos, or 0 if there is no such one. Saved words are not
    # identifiers.
    def _eat_identifier(self, str, limit, pos):
        i = pos
        while i > limit and str[i-1] in self._id_chars:
            i -= 1
        if i < pos and (str[i] not in self._id_first_chars or \
                        keyword.iskeyword(str[i:pos])):
            i = pos
        return pos - i

    def get_expression(self):
        """Return a string with the Python expression which ends at the given
        index, which is empty if there is no real one.
        """
        if not self.is_in_code():
            raise ValueError("get_expression should only be called if index "\
                             "is inside a code.")

        rawtext = self.rawtext
        bracketing = self.bracketing

        brck_index = self.indexbracket
        brck_limit = bracketing[brck_index][0]
        pos = self.indexinrawtext

        last_identifier_pos = pos
        postdot_phase = True

        while 1:
            # Eat whitespaces, comments, and if postdot_phase is False - one dot
            while 1:
                if pos>brck_limit and rawtext[pos-1] in self._whitespace_chars:
                    # Eat a whitespace
                    pos -= 1
                elif not postdot_phase and \
                     pos > brck_limit and rawtext[pos-1] == '.':
                    # Eat a dot
                    pos -= 1
                    postdot_phase = True
                # The next line will fail if we are *inside* a comment, but we
                # shouldn't be.
                elif pos == brck_limit and brck_index > 0 and \
                     rawtext[bracketing[brck_index-1][0]] == '#':
                    # Eat a comment
                    brck_index -= 2
                    brck_limit = bracketing[brck_index][0]
                    pos = bracketing[brck_index+1][0]
                else:
                    # If we didn't eat anything, quit.
                    break

            if not postdot_phase:
                # We didn't find a dot, so the expression end at the last
                # identifier pos.
                break

            ret = self._eat_identifier(rawtext, brck_limit, pos)
            if ret:
                # There is an identifier to eat
                pos = pos - ret
                last_identifier_pos = pos
                # Now, in order to continue the search, we must find a dot.
                postdot_phase = False
                # (the loop continues now)

            elif pos == brck_limit:
                # We are at a bracketing limit. If it is a closing bracket,
                # eat the bracket, otherwise, stop the search.
                level = bracketing[brck_index][1]
                while brck_index > 0 and bracketing[brck_index-1][1] > level:
                    brck_index -= 1
                if bracketing[brck_index][0] == brck_limit:
                    # We were not at the end of a closing bracket
                    break
                pos = bracketing[brck_index][0]
                brck_index -= 1
                brck_limit = bracketing[brck_index][0]
                last_identifier_pos = pos
                if rawtext[pos] in "([":
                    # [] and () may be used after an identifier, so we
                    # continue. postdot_phase is True, so we don't allow a dot.
                    pass
                else:
                    # We can't continue after other types of brackets
                    break

            else:
                # We've found an operator or something.
                break

        return rawtext[last_identifier_pos:self.indexinrawtext]