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78 lines
3 KiB
Python
78 lines
3 KiB
Python
"""
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The ``Parser`` tries to convert the available Python code in an easy to read
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format, something like an abstract syntax tree. The classes who represent this
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tree, are sitting in the :mod:`parso.tree` module.
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The Python module ``tokenize`` is a very important part in the ``Parser``,
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because it splits the code into different words (tokens). Sometimes it looks a
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bit messy. Sorry for that! You might ask now: "Why didn't you use the ``ast``
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module for this? Well, ``ast`` does a very good job understanding proper Python
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code, but fails to work as soon as there's a single line of broken code.
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There's one important optimization that needs to be known: Statements are not
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being parsed completely. ``Statement`` is just a representation of the tokens
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within the statement. This lowers memory usage and cpu time and reduces the
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complexity of the ``Parser`` (there's another parser sitting inside
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``Statement``, which produces ``Array`` and ``Call``).
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"""
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from parso import tree
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from parso.pgen2.parse import PgenParser
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class ParserSyntaxError(Exception):
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"""
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Contains error information about the parser tree.
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May be raised as an exception.
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"""
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def __init__(self, message, error_leaf):
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self.message = message
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self.error_leaf = error_leaf
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class BaseParser(object):
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node_map = {}
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default_node = tree.Node
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leaf_map = {
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}
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default_leaf = tree.Leaf
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def __init__(self, pgen_grammar, start_symbol='file_input', error_recovery=False):
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self._pgen_grammar = pgen_grammar
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self._start_symbol = start_symbol
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self._error_recovery = error_recovery
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def parse(self, tokens):
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start_number = self._pgen_grammar.symbol2number[self._start_symbol]
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self.pgen_parser = PgenParser(
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self._pgen_grammar, self.convert_node, self.convert_leaf,
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self.error_recovery, start_number
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)
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node = self.pgen_parser.parse(tokens)
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# The stack is empty now, we don't need it anymore.
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del self.pgen_parser
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return node
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def error_recovery(self, pgen_grammar, stack, arcs, typ, value, start_pos, prefix,
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add_token_callback):
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if self._error_recovery:
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raise NotImplementedError("Error Recovery is not implemented")
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else:
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error_leaf = tree.ErrorLeaf('TODO %s' % typ, value, start_pos, prefix)
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raise ParserSyntaxError('SyntaxError: invalid syntax', error_leaf)
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def convert_node(self, pgen_grammar, type_, children):
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# TODO REMOVE symbol, we don't want type here.
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symbol = pgen_grammar.number2symbol[type_]
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try:
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return self.node_map[symbol](children)
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except KeyError:
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return self.default_node(symbol, children)
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def convert_leaf(self, pgen_grammar, type_, value, prefix, start_pos):
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try:
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return self.leaf_map[type_](value, start_pos, prefix)
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except KeyError:
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return self.default_leaf(value, start_pos, prefix)
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