# Copyright 2006 Google, Inc. All Rights Reserved.

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# Licensed to PSF under a Contributor Agreement.

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"""Pattern compiler.

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The grammar is taken from PatternGrammar.txt.

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The compiler compiles a pattern to a pytree.*Pattern instance.

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"""

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__author__ = "Guido van Rossum <guido@python.org>"

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# Python imports

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import io

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# Fairly local imports

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from .pgen2 import driver, literals, token, tokenize, parse, grammar

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# Really local imports

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from . import pytree

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from . import pygram

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class PatternSyntaxError(Exception):

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pass

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def tokenize_wrapper(input):

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"""Tokenizes a string suppressing significant whitespace."""

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skip = {token.NEWLINE, token.INDENT, token.DEDENT}

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tokens = tokenize.generate_tokens(io.StringIO(input).readline)

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for quintuple in tokens:

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type, value, start, end, line_text = quintuple

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if type not in skip:

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yield quintuple

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class PatternCompiler(object):

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def __init__(self, grammar_file=None):

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"""Initializer.

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Takes an optional alternative filename for the pattern grammar.

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"""

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if grammar_file is None:

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self.grammar = pygram.pattern_grammar

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self.syms = pygram.pattern_symbols

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else:

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self.grammar = driver.load_grammar(grammar_file)

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self.syms = pygram.Symbols(self.grammar)

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self.pygrammar = pygram.python_grammar

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self.pysyms = pygram.python_symbols

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self.driver = driver.Driver(self.grammar, convert=pattern_convert)

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def compile_pattern(self, input, debug=False, with_tree=False):

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"""Compiles a pattern string to a nested pytree.*Pattern object."""

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tokens = tokenize_wrapper(input)

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try:

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root = self.driver.parse_tokens(tokens, debug=debug)

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except parse.ParseError as e:

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raise PatternSyntaxError(str(e)) from None

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if with_tree:

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return self.compile_node(root), root

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else:

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return self.compile_node(root)

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def compile_node(self, node):

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"""Compiles a node, recursively.

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This is one big switch on the node type.

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"""

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# XXX Optimize certain Wildcard-containing-Wildcard patterns

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# that can be merged

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if node.type == self.syms.Matcher:

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node = node.children[0] # Avoid unneeded recursion

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if node.type == self.syms.Alternatives:

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# Skip the odd children since they are just '|' tokens

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alts = [self.compile_node(ch) for ch in node.children[::2]]

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if len(alts) == 1:

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return alts[0]

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p = pytree.WildcardPattern([[a] for a in alts], min=1, max=1)

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return p.optimize()

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if node.type == self.syms.Alternative:

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units = [self.compile_node(ch) for ch in node.children]

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if len(units) == 1:

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return units[0]

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p = pytree.WildcardPattern([units], min=1, max=1)

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return p.optimize()

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if node.type == self.syms.NegatedUnit:

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pattern = self.compile_basic(node.children[1:])

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p = pytree.NegatedPattern(pattern)

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return p.optimize()

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assert node.type == self.syms.Unit

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name = None

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nodes = node.children

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if len(nodes) >= 3 and nodes[1].type == token.EQUAL:

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name = nodes[0].value

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nodes = nodes[2:]

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repeat = None

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if len(nodes) >= 2 and nodes[-1].type == self.syms.Repeater:

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repeat = nodes[-1]

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nodes = nodes[:-1]

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# Now we've reduced it to: STRING | NAME [Details] | (...) | [...]

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pattern = self.compile_basic(nodes, repeat)

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if repeat is not None:

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assert repeat.type == self.syms.Repeater

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children = repeat.children

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child = children[0]

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if child.type == token.STAR:

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min = 0

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max = pytree.HUGE

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elif child.type == token.PLUS:

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min = 1

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max = pytree.HUGE

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elif child.type == token.LBRACE:

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assert children[-1].type == token.RBRACE

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assert len(children) in (3, 5)

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min = max = self.get_int(children[1])

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if len(children) == 5:

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max = self.get_int(children[3])

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else:

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assert False

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if min != 1 or max != 1:

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pattern = pattern.optimize()

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pattern = pytree.WildcardPattern([[pattern]], min=min, max=max)

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if name is not None:

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pattern.name = name

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return pattern.optimize()

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def compile_basic(self, nodes, repeat=None):

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# Compile STRING | NAME [Details] | (...) | [...]

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assert len(nodes) >= 1

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node = nodes[0]

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if node.type == token.STRING:

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value = str(literals.evalString(node.value))

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return pytree.LeafPattern(_type_of_literal(value), value)

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elif node.type == token.NAME:

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value = node.value

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if value.isupper():

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if value not in TOKEN_MAP:

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raise PatternSyntaxError("Invalid token: %r" % value)

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if nodes[1:]:

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raise PatternSyntaxError("Can't have details for token")

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return pytree.LeafPattern(TOKEN_MAP[value])

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else:

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if value == "any":

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type = None

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elif not value.startswith("_"):

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type = getattr(self.pysyms, value, None)

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if type is None:

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raise PatternSyntaxError("Invalid symbol: %r" % value)

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if nodes[1:]: # Details present

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content = [self.compile_node(nodes[1].children[1])]

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else:

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content = None

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return pytree.NodePattern(type, content)

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elif node.value == "(":

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return self.compile_node(nodes[1])

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elif node.value == "[":

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assert repeat is None

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subpattern = self.compile_node(nodes[1])

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return pytree.WildcardPattern([[subpattern]], min=0, max=1)

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assert False, node

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def get_int(self, node):

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assert node.type == token.NUMBER

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return int(node.value)

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# Map named tokens to the type value for a LeafPattern

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TOKEN_MAP = {"NAME": token.NAME,

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"STRING": token.STRING,

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"NUMBER": token.NUMBER,

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"TOKEN": None}

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def _type_of_literal(value):

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if value[0].isalpha():

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return token.NAME

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elif value in grammar.opmap:

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return grammar.opmap[value]

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else:

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return None

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def pattern_convert(grammar, raw_node_info):

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"""Converts raw node information to a Node or Leaf instance."""

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type, value, context, children = raw_node_info

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if children or type in grammar.number2symbol:

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return pytree.Node(type, children, context=context)

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else:

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return pytree.Leaf(type, value, context=context)

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def compile_pattern(pattern):

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return PatternCompiler().compile_pattern(pattern)

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