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Commit 83a0b5dd authored by eckhart's avatar eckhart
Browse files

further cleanups

parent f1e8895d
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.noseids 0 → 100644
View file @ 83a0b5dd
File added
DHParser/parser.py
View file @ 83a0b5dd
......@@ -93,8 +93,6 @@ __all__ = ('PreprocessorFunc',
'AllOf',
'SomeOf',
'Unordered',
'FlowOperator',
# 'Required',
'Lookahead',
'NegativeLookahead',
'Lookbehind',
......@@ -454,7 +452,7 @@ def mixin_comment(whitespace: str, comment: str) -> str:
class Grammar:
"""
r"""
Class Grammar directs the parsing process and stores global state
information of the parsers, i.e. state information that is shared
accross parsers.
......@@ -748,6 +746,11 @@ class Grammar:
@property
def reversed__(self) -> StringView:
"""
Returns a reversed version of the currently parsed document. As
about the only case where this is needed is the Lookbehind-parser,
this is done lazily.
"""
if not self._reversed__:
self._reversed__ = StringView(self.document__.text[::-1])
return self._reversed__
......@@ -801,7 +804,7 @@ class Grammar:
stitches = [] # type: List[Node]
rest = self.document__
if not rest:
result, ignore = parser(rest)
result, _ = parser(rest)
if result is None:
result = Node(None, '')
result.add_error('Parser "%s" did not match empty document.' % str(parser))
......@@ -1664,14 +1667,13 @@ def Unordered(parser: NaryOperator, name: str = '') -> NaryOperator:
#
########################################################################
class FlowOperator(UnaryOperator):
"""
Base class of all flow operators, like lookahead, lookbehing,
negative lookahead...
Base class for all flow operator parsers like Lookahead and Lookbehind.
"""
def __init__(self, parser: Parser, name: str = '') -> None:
super(FlowOperator, self).__init__(parser, name)
def sign(self, bool_value) -> bool:
"""Returns the value. Can be overriden to return the inverted bool."""
return bool_value
# class Required(FlowOperator):
......@@ -1695,9 +1697,10 @@ class FlowOperator(UnaryOperator):
class Lookahead(FlowOperator):
# def __init__(self, parser: Parser, name: str = '') -> None:
# super(Lookahead, self).__init__(parser, name)
"""
Matches, if the contained parser would match for the following text,
but does not consume any text.
"""
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
node, _ = self.parser(text)
if self.sign(node is not None):
......@@ -1708,11 +1711,12 @@ class Lookahead(FlowOperator):
def __repr__(self):
return '&' + self.parser.repr
def sign(self, bool_value) -> bool:
return bool_value
class NegativeLookahead(Lookahead):
"""
Matches, if the contained parser would *not* match for the following
text.
"""
def __repr__(self):
return '!' + self.parser.repr
......@@ -1721,17 +1725,21 @@ class NegativeLookahead(Lookahead):
class Lookbehind(FlowOperator):
"""EXPERIMENTAL!!!"""
"""
Matches, if the contained parser would match backwards. Requires
the contained parser to be a RegExp-parser.
"""
def __init__(self, parser: Parser, name: str = '') -> None:
p = parser
while isinstance(p, Synonym):
p = p.parser
assert isinstance(p, RegExp), str(type(p))
self.regexp = cast(RE, p).main.regexp if isinstance(p, RE) else p.regexp
super(Lookbehind, self).__init__(parser, name)
super().__init__(parser, name)
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
backwards_text = self.grammar.reversed__[len(text):] # self.grammar.document__[-len(text) - 1::-1]
# backwards_text = self.grammar.document__[-len(text) - 1::-1]
backwards_text = self.grammar.reversed__[len(text):]
if self.sign(backwards_text.match(self.regexp)):
return Node(self, ''), text
else:
......@@ -1740,12 +1748,12 @@ class Lookbehind(FlowOperator):
def __repr__(self):
return '-&' + self.parser.repr
def sign(self, bool_value) -> bool:
return bool(bool_value)
class NegativeLookbehind(Lookbehind):
"""EXPERIMENTAL AND NEVER TESTED!!!"""
"""
Matches, if the contained parser would *not* match backwards. Requires
the contained parser to be a RegExp-parser.
"""
def __repr__(self):
return '-!' + self.parser.repr
......@@ -1761,19 +1769,20 @@ class NegativeLookbehind(Lookbehind):
class Capture(UnaryOperator):
"""STILL EXPERIMENTAL!"""
def __init__(self, parser: Parser, name: str = '') -> None:
super(Capture, self).__init__(parser, name)
"""
Applies the contained parser and, in case of a match, saves the result
in a variable. A variable is a stack of values associated with the
contained parser's name. This requires the contained parser to be named.
"""
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
node, text_ = self.parser(text)
if node:
assert self.name, """Tried to apply an unnamed capture-parser!"""
stack = self.grammar.variables__.setdefault(self.name, [])
stack.append(str(node))
self.grammar.push_rollback__(len(text), lambda: stack.pop())
# self.grammar.rollback__.append((len(text), lambda : stack.pop()))
# block caching, because it would prevent recapturing of rolled back captures
# caching will be blocked by parser guard (see way above),
# because it would prevent recapturing of rolled back captures
return Node(self, node), text_
else:
return None, text
......@@ -1791,7 +1800,7 @@ def last_value(stack: List[str]) -> str:
def counterpart(stack: List[str]) -> str:
value = stack[-1]
return value.replace("(", ")").replace("[", "]").replace("{", "}").replace(">", "<")
return value.replace("(", ")").replace("[", "]").replace("{", "}").replace("<", ">")
def accumulate(stack: List[str]) -> str:
......@@ -1799,7 +1808,16 @@ def accumulate(stack: List[str]) -> str:
class Retrieve(Parser):
"""STILL EXPERIMENTAL!"""
"""
Matches if the following text starts with the value of a particular
variable. As a variable in this context means a stack of values,
the last value will be compared with the following text. It will not
be removed from the stack! (This is the difference between the
`Retrieve` and the `Pop` parser.)
The constructor parameter `symbol` determines which variable is
used.
"""
def __init__(self, symbol: Parser, rfilter: RetrieveFilter = None, name: str = '') -> None:
super(Retrieve, self).__init__(name)
self.symbol = symbol
......@@ -1809,18 +1827,30 @@ class Retrieve(Parser):
return self.__class__(self.symbol, self.filter, self.name)
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
return self.call(text) # allow call method to be called from subclass circumventing the parser guard
# the following indirection allows the call() method to be called
# from subclass without triggering the parser guard a second time
return self.retrieve_and_match(text)
def __repr__(self):
return ':' + self.symbol.repr
def call(self, text: StringView) -> Tuple[Optional[Node], StringView]:
def retrieve_and_match(self, text: StringView) -> Tuple[Optional[Node], StringView]:
"""
Retrieves variable from stack through the filter function passed to
the class' constructor and tries to match the variable's value with
the following text. Returns a Node containing the value or `None`
accordingly.
This functionality has been move from the __call__ method to an
independent method to allow calling it from a subclasses __call__
method without triggering the parser guard a second time.
"""
try:
stack = self.grammar.variables__[self.symbol.name]
value = self.filter(stack)
except (KeyError, IndexError):
return Node(self, '').add_error(dsl_error_msg(self,
"'%s' undefined or exhausted." % self.symbol.name)), text
return Node(self, '').add_error(
dsl_error_msg(self, "'%s' undefined or exhausted." % self.symbol.name)), text
if text.startswith(value):
return Node(self, value), text[len(value):]
else:
......@@ -1828,16 +1858,24 @@ class Retrieve(Parser):
class Pop(Retrieve):
"""STILL EXPERIMENTAL!!!"""
"""
Matches if the following text starts with the value of a particular
variable. As a variable in this context means a stack of values,
the last value will be compared with the following text. Other
than the `Retrieve`-parser, the `Pop`-parser removes the value
from the stack in case of a match.
The constructor parameter `symbol` determines which variable is
used.
"""
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
nd, txt = super(Pop, self).call(text) # call() instead of __call__() to avoid parser guard
if nd and not nd.error_flag:
node, txt = super().retrieve_and_match(text)
if node and not node.error_flag:
stack = self.grammar.variables__[self.symbol.name]
value = stack.pop()
self.grammar.push_rollback__(len(text), lambda: stack.append(value))
# self.grammar.rollback__.append((len(text), lambda : stack.append(value)))
return nd, txt
return node, txt
def __repr__(self):
return '::' + self.symbol.repr
......@@ -1851,7 +1889,7 @@ class Pop(Retrieve):
class Synonym(UnaryOperator):
"""
r"""
Simply calls another parser and encapsulates the result in
another node if that parser matches.
......@@ -1862,6 +1900,7 @@ class Synonym(UnaryOperator):
class, in which case it would be unclear whether the parser
RE('\d\d\d\d') carries the name 'JAHRESZAHL' or 'jahr'.
"""
def __call__(self, text: StringView) -> Tuple[Optional[Node], StringView]:
node, text = self.parser(text)
if node:
......@@ -1873,7 +1912,8 @@ class Synonym(UnaryOperator):
class Forward(Parser):
"""Forward allows to declare a parser before it is actually defined.
r"""
Forward allows to declare a parser before it is actually defined.
Forward declarations are needed for parsers that are recursively
nested, e.g.:
class Arithmetic(Grammar):
......@@ -1890,6 +1930,7 @@ class Forward(Parser):
expression.set(term + ZeroOrMore((Token("+") | Token("-")) + term))
root__ = expression
"""
def __init__(self):
Parser.__init__(self)
self.parser = None
......@@ -1976,6 +2017,7 @@ class Compiler:
called at least once and that therefore all compilation
variables must be reset when it is called again.
"""
def __init__(self, grammar_name="", grammar_source=""):
self._reset()
self._dirty_flag = False
......@@ -2009,7 +2051,7 @@ class Compiler:
process. Classes inheriting from `Compiler` can use this
information to name and annotate its output.
"""
assert grammar_name == "" or re.match('\w+\Z', grammar_name)
assert grammar_name == "" or re.match(r'\w+\Z', grammar_name)
if not grammar_name and re.fullmatch(r'[\w/:\\]+', grammar_source):
grammar_name = os.path.splitext(os.path.basename(grammar_source))[0]
self.grammar_name = grammar_name
......@@ -2036,11 +2078,11 @@ class Compiler:
"""
Calls the compilation method for the given node and returns the
result of the compilation.
The method's name is dreived from either the node's parser
The method's name is dreived from either the node's parser
name or, if the parser is anonymous, the node's parser's class
name by adding the prefix 'on_'.
Note that ``compile`` does not call any compilation functions
for the parsers of the sub nodes by itself. Rather, this should
be done within the compilation methods.
......@@ -2084,12 +2126,12 @@ def compile_source(source: str,
file containing the input text.
preprocessor (function): text -> text. A preprocessor function
or None, if no preprocessor is needed.
parser (function): A parsing function or grammar class
parser (function): A parsing function or grammar class
transformer (function): A transformation function that takes
the root-node of the concrete syntax tree as an argument and
transforms it (in place) into an abstract syntax tree.
compiler (function): A compiler function or compiler class
instance
instance
Returns (tuple):
The result of the compilation as a 3-tuple
......@@ -2112,15 +2154,16 @@ def compile_source(source: str,
# only compile if there were no syntax errors, for otherwise it is
# likely that error list gets littered with compile error messages
result = None
ef = syntax_tree.error_flag
efl = syntax_tree.error_flag
messages = syntax_tree.collect_errors(source_text, clear_errors=True)
if not is_error(ef):
if not is_error(efl):
transformer(syntax_tree)
ef = max(ef, syntax_tree.error_flag)
efl = max(efl, syntax_tree.error_flag)
messages.extend(syntax_tree.collect_errors(source_text, clear_errors=True))
if is_logging(): syntax_tree.log(log_file_name + '.ast')
if is_logging():
syntax_tree.log(log_file_name + '.ast')
if not is_error(syntax_tree.error_flag):
result = compiler(syntax_tree)
messages.extend(syntax_tree.collect_errors(source_text))
syntax_tree.error_flag = max(syntax_tree.error_flag, ef)
syntax_tree.error_flag = max(syntax_tree.error_flag, efl)
return result, messages, syntax_tree
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