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# error.py - error handling for DHParser
#
# Copyright 2016  by Eckhart Arnold (arnold@badw.de)
#                 Bavarian Academy of Sciences an Humanities (badw.de)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.  See the License for the specific language governing
# permissions and limitations under the License.
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"""
Module ``error`` defines class Error and a few helpful functions that are
needed for error reporting of DHParser. Usually, what is of interest are
the string representations of the error objects. For example::

    from DHParser import compile_source, has_errors

    result, errors, ast = compile_source(source, preprocessor, grammar,
                                         transformer, compiler)
    if errors:
        for error in errors:
            print(error)

        if has_errors(errors):
            print("There have been fatal errors!")
            sys.exit(1)
        else:
            print("There have been warnings, but no errors.")
"""

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import bisect

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from DHParser.preprocess import SourceMapFunc
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from DHParser.stringview import StringView
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from DHParser.toolkit import typing
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from typing import Iterable, Iterator, Union, Tuple, List, Optional
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__all__ = ('Error',
           'is_error',
           'is_warning',
           'has_errors',
           'only_errors',
           'linebreaks',
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           'line_col',
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           'adjust_error_locations')
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class Error:
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    __slots__ = ['message', 'level', 'code', '_pos', 'orig_pos', 'line', 'column', '_node']
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    # error levels

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    NO_ERROR  = 0
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    WARNING   = 1
    ERROR     = 1000
    HIGHEST   = ERROR

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    # warning codes

    REDEFINED_DIRECTIVE_WARNING = 101
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    REDECLARED_TOKEN_WARNING = 102
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    UNDEFINED_SYMBOL_IN_TRANSFORMATION_TABLE = 601

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    # error codes

    MANDATORY_CONTINUATION = 1001

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    def __init__(self, message: str, code: int = ERROR, pos: int = -1,
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                 orig_pos: int = -1, line: int = -1, column: int = -1,
                 node: Optional['Node'] = None) -> None:
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        self.message = message
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        assert code >= 0
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        self.code = code
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        self._pos = pos
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        self.orig_pos = orig_pos
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        self.line = line
        self.column = column
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        if node is not None and node._pos >= 0:
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            assert self._pos < 0 or self._pos == node._pos
            self._pos = node._pos
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            self._node = None      # if node is not needed, if pos has been set
        else:
            self._node = node
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    def __str__(self):
        prefix = ''
        if self.line > 0:
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            prefix = "%i:%i: " % (max(self.line, 0), max(self.column, 0))
        return prefix + "%s: %s" % (self.severity, self.message)
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    def __repr__(self):
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        return 'Error("%s", %s, %i, %i, %i, %i)' \
               % (self.message, repr(self.code), self.pos, self.orig_pos, self.line, self.column)
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    @property
    def pos(self):
        if self._pos < 0:
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            assert self._node and self._node.pos >= 0, "pos value not ready yet"
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            self._pos = self._node.pos   # lazy evaluation of position
        self._node = None  # forget node to allow GC to free memory
        return self._pos

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    @property
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    def severity(self):
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        """Returns a string representation of the error level, e.g. "warning"."""
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        return "Warning" if is_warning(self.code) else "Error"
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    def visualize(self, document: str) -> str:
        """Shows the line of the document and the position where the error
        occurred."""
        start = document.rfind('\n', 0, self.pos) + 1
        stop = document.find('\n', self.pos)
        return document[start:stop] + '\n' + ' ' * (self.pos - start) + '^\n'

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def is_warning(code: int) -> bool:
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    """Returns True, if error is merely a warning."""
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    return code < Error.ERROR
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def is_error(code: int) -> bool:
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    """Returns True, if error is an error, not just a warning."""
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    return code >= Error.ERROR
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def has_errors(messages: Iterable[Error], level: int = Error.ERROR) -> bool:
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    """
    Returns True, if at least one entry in `messages` has at
    least the given error `level`.
    """
    for err_obj in messages:
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        if err_obj.code >= level:
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            return True
    return False


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def only_errors(messages: Iterable[Error], level: int = Error.ERROR) -> Iterator[Error]:
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    """
    Returns an Iterator that yields only those messages that have
    at least the given error level.
    """
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    return (err for err in messages if err.code >= level)
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#######################################################################
#
# Setting of line, column and position properties of error messages.
#
#######################################################################


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def linebreaks(text: Union[StringView, str]) -> List[int]:
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    """
    Returns a list of indices all line breaks in the text.
    """
    lbr = [-1]
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    i = text.find('\n', 0)
    while i >= 0:
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        lbr.append(i)
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        i = text.find('\n', i + 1)
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    lbr.append(len(text))
    return lbr
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def line_col(lbreaks: List[int], pos: int) -> Tuple[int, int]:
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    """
    Returns the position within a text as (line, column)-tuple based
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    on a list of all line breaks, including -1 and EOF.
    """
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    if not lbreaks and pos >= 0:
        return 0, pos
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    if pos < 0 or pos > lbreaks[-1]:  # one character behind EOF is still an allowed position!
        raise ValueError('Position %i outside text of length %s !' % (pos, lbreaks[-1]))
    line = bisect.bisect_left(lbreaks, pos)
    column = pos - lbreaks[line - 1]
    return line, column

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# def line_col(text: Union[StringView, str], pos: int) -> Tuple[int, int]:
#     """
#     Returns the position within a text as (line, column)-tuple.
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#     """
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#     if pos < 0 or add_pos > len(text):  # one character behind EOF is still an allowed position!
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#         raise ValueError('Position %i outside text of length %s !' % (pos, len(text)))
#     line = text.count("\n", 0, pos) + 1
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#     column = pos - text.rfind("\n", 0, add_pos)
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#     return line, column


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def adjust_error_locations(errors: List[Error],
                           original_text: Union[StringView, str],
                           source_mapping: SourceMapFunc=lambda i: i) -> List[Error]:
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    """Adds (or adjusts) line and column numbers of error messages in place.

    Args:
        errors:  The list of errors as returned by the method
            ``collect_errors()`` of a Node object
        original_text:  The source text on which the errors occurred.
            (Needed in order to determine the line and column numbers.)
        source_mapping:  A function that maps error positions to their
            positions in the original source file.
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    Returns:
        The list of errors. (Returning the list of errors is just syntactical
        sugar. Be aware that the line, col and orig_pos attributes have been
        changed in place.)
    """
    line_breaks = linebreaks(original_text)
    for err in errors:
        assert err.pos >= 0
        err.orig_pos = source_mapping(err.pos)
        err.line, err.column = line_col(line_breaks, err.orig_pos)
    return errors