gitmirror/lark/exceptions.py

import logging

from .utils import STRING_TYPE

###{standalone
class LarkError(Exception):
    pass

class GrammarError(LarkError):
    pass

class ParseError(LarkError):
    pass

class LexError(LarkError):
    pass

class UnexpectedEOF(ParseError):
    def __init__(self, expected):
        self.expected = expected

        message = ("Unexpected end-of-input. Expected one of: \n\t* %s\n" % '\n\t* '.join(x.name for x in self.expected))
        super(UnexpectedEOF, self).__init__(message)


class UnexpectedInput(LarkError):
    pos_in_stream = None

    def get_context(self, text, span=40):
        pos = self.pos_in_stream
        start = max(pos - span, 0)
        end = pos + span
        if not isinstance(text, bytes):
            before = text[start:pos].rsplit('\n', 1)[-1]
            after = text[pos:end].split('\n', 1)[0]
            return before + after + '\n' + ' ' * len(before) + '^\n'
        else:
            before = text[start:pos].rsplit(b'\n', 1)[-1]
            after = text[pos:end].split(b'\n', 1)[0]
            return (before + after + b'\n' + b' ' * len(before) + b'^\n').decode("ascii", "backslashreplace")

    def match_examples(self, parse_fn, examples, token_type_match_fallback=False, use_accepts=False):
        """ Given a parser instance and a dictionary mapping some label with
            some malformed syntax examples, it'll return the label for the
            example that bests matches the current error.
        """
        assert self.state is not None, "Not supported for this exception"

        if isinstance(examples, dict):
            examples = examples.items()

        candidate = (None, False)
        for i, (label, example) in enumerate(examples):
            assert not isinstance(example, STRING_TYPE)

            for j, malformed in enumerate(example):
                try:
                    parse_fn(malformed)
                except UnexpectedInput as ut:
                    if ut.state == self.state:
                        if use_accepts and ut.accepts != self.accepts:
                            logging.debug("Different accepts with same state[%d]: %s != %s at example [%s][%s]" %
                                        (self.state, self.accepts, ut.accepts, i, j))
                            continue
                        try:
                            if ut.token == self.token:  # Try exact match first
                                logging.debug("Exact Match at example [%s][%s]" % (i, j))
                                return label

                            if token_type_match_fallback:
                                # Fallback to token types match
                                if (ut.token.type == self.token.type) and not candidate[-1]:
                                    logging.debug("Token Type Fallback at example [%s][%s]" % (i, j))
                                    candidate = label, True

                        except AttributeError:
                            pass
                        if not candidate[0]:
                            logging.debug("Same State match at example [%s][%s]" % (i, j))
                            candidate = label, False

        return candidate[0]


class UnexpectedCharacters(LexError, UnexpectedInput):
    def __init__(self, seq, lex_pos, line, column, allowed=None, considered_tokens=None, state=None, token_history=None):
        self.line = line
        self.column = column
        self.pos_in_stream = lex_pos
        self.state = state

        self.allowed = allowed
        self.considered_tokens = considered_tokens

        if isinstance(seq, bytes):
            message = "No terminal defined for '%s' at line %d col %d" % (seq[lex_pos:lex_pos+1].decode("ascii", "backslashreplace"), line, column)
        else:
            message = "No terminal defined for '%s' at line %d col %d" % (seq[lex_pos], line, column)

        message += '\n\n' + self.get_context(seq)
        if allowed:
            message += '\nExpecting: %s\n' % allowed
        if token_history:
            message += '\nPrevious tokens: %s\n' % ', '.join(repr(t) for t in token_history)

        super(UnexpectedCharacters, self).__init__(message)



class UnexpectedToken(ParseError, UnexpectedInput):
    def __init__(self, token, expected, considered_rules=None, state=None, puppet=None):
        self.line = getattr(token, 'line', '?')
        self.column = getattr(token, 'column', '?')
        self.pos_in_stream = getattr(token, 'pos_in_stream', None)
        self.state = state

        self.token = token
        self.expected = expected     # XXX deprecate? `accepts` is better
        self.considered_rules = considered_rules
        self.puppet = puppet

        # TODO Only calculate `accepts()` when we need to display it to the user
        # This will improve performance when doing automatic error handling
        self.accepts = puppet and puppet.accepts()

        message = ("Unexpected token %r at line %s, column %s.\n"
                   "Expected one of: \n\t* %s\n"
                   % (token, self.line, self.column, '\n\t* '.join(self.accepts or self.expected)))

        super(UnexpectedToken, self).__init__(message)

class VisitError(LarkError):
    """VisitError is raised when visitors are interrupted by an exception

    It provides the following attributes for inspection:
    - obj: the tree node or token it was processing when the exception was raised
    - orig_exc: the exception that cause it to fail
    """
    def __init__(self, rule, obj, orig_exc):
        self.obj = obj
        self.orig_exc = orig_exc

        message = 'Error trying to process rule "%s":\n\n%s' % (rule, orig_exc)
        super(VisitError, self).__init__(message)
###}