python-bibtexparser/bibtexparser/bibtexexpression.py at master · echomehran/python-bibtexparser · GitHub

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import pyparsing as pp

from .bibdatabase import BibDataStringExpression

# General helpers

def _strip_after_new_lines(s):

"""Removes leading and trailing whitespaces in all but first line."""

lines = s.splitlines()

if len(lines) > 1:

lines = [lines[0]] + [l.lstrip() for l in lines[1:]]

return '\n'.join(lines)

def strip_after_new_lines(s):

"""Removes leading and trailing whitespaces in all but first line.

:param s: string or BibDataStringExpression

"""

if isinstance(s, BibDataStringExpression):

s.apply_on_strings(_strip_after_new_lines)

return s

else:

return _strip_after_new_lines(s)

def add_logger_parse_action(expr, log_func):

"""Register a callback on expression parsing with the adequate message."""

def action(s, l, t):

log_func("Found {}: {}".format(expr.resultsName, t))

expr.addParseAction(action)

# Parse action helpers

# Helpers for returning values from the parsed tokens. Shaped as pyparsing's

# parse actions. See pyparsing documentation for the arguments.

def first_token(string_, location, token):

# TODO Handle this case correctly!

assert(len(token) == 1)

return token[0]

def remove_trailing_newlines(string_, location, token):

if token[0]:

return token[0].rstrip('\n')

def remove_braces(string_, location, token):

if len(token[0]) < 1:

return ''

else:

start = 1 if token[0][0] == '{' else 0

end = -1 if token[0][-1] == '}' else None

return token[0][start:end]

def field_to_pair(string_, location, token):

"""

Looks for parsed element named 'Field'.

:returns: (name, value).

"""

field = token.get('Field')

value = field.get('Value')

if isinstance(value, pp.ParseResults):

# For pyparsing >= 2.3.1 (see #225 and API change note in pyparsing's

# Changelog).

value = value[0]

return (field.get('FieldName'),

strip_after_new_lines(value))

# Expressions helpers

def in_braces_or_pars(exp):

"""

exp -> (exp)|{exp}

"""

return ((pp.Suppress('{') + exp + pp.Suppress('}')) |

(pp.Suppress('(') + exp + pp.Suppress(')')))

class BibtexExpression(object):

"""Gives access to pyparsing expressions.

Attributes are pyparsing expressions for the following elements:

* main_expression: the bibtex file

* string_def: a string definition

* preamble_decl: a preamble declaration

* explicit_comment: an explicit comment

* entry: an entry definition

* implicit_comment: an implicit comment

"""

ParseException = pp.ParseException

def __init__(self):

# Init parse action functions

self.set_string_name_parse_action(lambda s, l, t: None)

# Bibtex keywords

string_def_start = pp.CaselessKeyword("@string")

preamble_start = pp.CaselessKeyword("@preamble")

comment_line_start = pp.CaselessKeyword('@comment')

# String names

string_name = pp.Word(pp.alphanums + '_-:')('StringName')

self.set_string_name_parse_action(lambda s, l, t: None)

string_name.addParseAction(self._string_name_parse_action)

# Values inside bibtex fields

# Values can be integer or string expressions. The latter may use

# quoted or braced values.

# Integer values

integer = pp.Word(pp.nums)('Integer')

# Braced values: braced values can contain nested (but balanced) braces

braced_value_content = pp.CharsNotIn('{}')

braced_value = pp.Forward() # Recursive definition for nested braces

braced_value <<= pp.originalTextFor(

'{' + pp.ZeroOrMore(braced_value | braced_value_content) + '}'

)('BracedValue')

braced_value.setParseAction(remove_braces)

# TODO add ignore for "\}" and "\{" ?

# TODO @ are not parsed by bibtex in braces

# Quoted values: may contain braced content with balanced braces

brace_in_quoted = pp.nestedExpr('{', '}', ignoreExpr=None)

text_in_quoted = pp.CharsNotIn('"{}')

# (quotes should be escaped by braces in quoted value)

quoted_value = pp.originalTextFor(

'"' + pp.ZeroOrMore(text_in_quoted | brace_in_quoted) + '"'

)('QuotedValue')

quoted_value.addParseAction(pp.removeQuotes)

# String expressions

string_expr = pp.delimitedList(

(quoted_value | braced_value | string_name), delim='#'

)('StringExpression')

string_expr.addParseAction(self._string_expr_parse_action)

value = (integer | string_expr)('Value')

# Entries

# @EntryType { ...

entry_type = (pp.Suppress('@') + pp.Word(pp.alphas))('EntryType')

entry_type.setParseAction(first_token)

# Entry key: any character up to a ',' without leading and trailing

# spaces. Also exclude spaces and prevent it from being empty.

key = pp.SkipTo(',')('Key') # TODO Maybe also exclude @',\#}{~%

def citekeyParseAction(string_, location, token):

"""Parse action for validating citekeys.

It ensures citekey is not empty and has no space.

:args: see pyparsing documentation.

"""

key = first_token(string_, location, token).strip()

if len(key) < 1:

raise self.ParseException(

string_, loc=location, msg="Empty citekeys are not allowed.")

for i, c in enumerate(key):

if c.isspace():

raise self.ParseException(

string_, loc=(location + i),

msg="Whitespace not allowed in citekeys.")

return key

key.setParseAction(citekeyParseAction)

# Field name: word of letters, digits, dashes and underscores

field_name = pp.Word(pp.alphanums + '_-().+')('FieldName')

field_name.setParseAction(first_token)

# Field: field_name = value

field = pp.Group(field_name + pp.Suppress('=') + value)('Field')

field.setParseAction(field_to_pair)

# List of fields: comma separeted fields

field_list = (pp.delimitedList(field) + pp.Suppress(pp.Optional(','))

)('Fields')

field_list.setParseAction(

lambda s, l, t: {k: v for (k, v) in reversed(t.get('Fields'))})

# Entry: type, key, and fields

self.entry = (entry_type +

in_braces_or_pars(key + pp.Suppress(',') + field_list)

)('Entry')

# Other stuff: comments, string definitions, and preamble declarations

# Explicit comments: @comment + everything up to next valid declaration

# starting on new line.

not_an_implicit_comment = (pp.LineEnd() + pp.Literal('@')

) | pp.StringEnd()

self.explicit_comment = (

pp.Suppress(comment_line_start) +

pp.originalTextFor(pp.SkipTo(not_an_implicit_comment),

asString=True))('ExplicitComment')

self.explicit_comment.addParseAction(remove_trailing_newlines)

self.explicit_comment.addParseAction(remove_braces)

# Previous implementation included comment until next '}'.

# This is however not inline with bibtex behavior that is to only

# ignore until EOL. Brace stipping is arbitrary here but avoids

# duplication on bibtex write.

# Empty implicit_comments lead to infinite loop of zeroOrMore

def mustNotBeEmpty(t):

if not t[0]:

raise pp.ParseException("Match must not be empty.")

# Implicit comments: not anything else

self.implicit_comment = pp.originalTextFor(

pp.SkipTo(not_an_implicit_comment).setParseAction(mustNotBeEmpty),

asString=True)('ImplicitComment')

self.implicit_comment.addParseAction(remove_trailing_newlines)

# String definition

self.string_def = (pp.Suppress(string_def_start) + in_braces_or_pars(

string_name +

pp.Suppress('=') +

string_expr('StringValue')

))('StringDefinition')

# Preamble declaration

self.preamble_decl = (pp.Suppress(preamble_start) +

in_braces_or_pars(value))('PreambleDeclaration')

# Main bibtex expression

self.main_expression = pp.ZeroOrMore(

self.string_def |

self.preamble_decl |

self.explicit_comment |

self.entry |

self.implicit_comment)

def add_log_function(self, log_fun):

"""Add notice to logger on entry, comment, preamble, string definitions.

:param log_fun: logger function

"""

for e in [self.entry,

self.implicit_comment,

self.explicit_comment,

self.preamble_decl,

self.string_def]:

add_logger_parse_action(e, log_fun)

def set_string_name_parse_action(self, fun):

"""Set the parseAction for string name expression.

.. Note::

For some reason pyparsing duplicates the string_name

expression so setting its parseAction a posteriori has no effect

in the context of a string expression. This is why this function

should be used instead.

"""

self._string_name_parse_action_fun = fun

def _string_name_parse_action(self, s, l, t):

return self._string_name_parse_action_fun(s, l, t)

def _string_expr_parse_action(self, s, l, t):

return BibDataStringExpression.expression_if_needed(t)

def parseFile(self, file_obj):

return self.main_expression.parseFile(file_obj, parseAll=True)

python-bibtexparser/bibtexparser/bibtexexpression.py at master · echomehran/python-bibtexparser · GitHub

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