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Post-merge cleanup

tags/gm/2021-09-23T00Z/github.com--lark-parser-lark/0.5.1
Erez Shinan 7 years ago
parent
2d0f2af0aa
commit
dda0719375
6 changed files with 110 additions and 325 deletions
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  1. +5
    -5
      examples/json_parser.py
  2. +3
    -69
      lark/parser_frontends.py
  3. +3
    -3
      lark/parsers/earley.py
  4. +13
    -182
      lark/parsers/xearley.py
  5. +14
    -1
      tests/__main__.py
  6. +72
    -65
      tests/test_parser.py

+ 5
- 5
examples/json_parser.py View File

@@ -47,12 +47,12 @@ class TreeToJson(Transformer):
true = lambda self, _: True
false = lambda self, _: False

json_parser = Lark(json_grammar, parser='earley', lexer='dynamic')
def parse(x):
return TreeToJson().transform(json_parser.parse(x))
# json_parser = Lark(json_grammar, parser='earley', lexer='standard')
# def parse(x):
# return TreeToJson().transform(json_parser.parse(x))

# json_parser = Lark(json_grammar, parser='lalr', transformer=TreeToJson())
# parse = json_parser.parse
json_parser = Lark(json_grammar, parser='lalr', transformer=TreeToJson())
parse = json_parser.parse

def test():
test_json = '''


+ 3
- 69
lark/parser_frontends.py View File

@@ -4,7 +4,7 @@ import sre_parse
from .lexer import Lexer, ContextualLexer, Token

from .common import is_terminal, GrammarError, ParserConf, Terminal_Regexp, Terminal_Token
from .parsers import lalr_parser, old_earley, nearley, earley
from .parsers import lalr_parser, earley
from .tree import Transformer

from .parsers import xearley
@@ -49,47 +49,6 @@ class LALR_ContextualLexer:
tokens = self.lexer_conf.postlex.process(tokens)
return self.parser.parse(tokens, self.lexer.set_parser_state)



class Nearley(WithLexer):
def __init__(self, lexer_conf, parser_conf):
WithLexer.__init__(self, lexer_conf)

rules = [{'name':n,
'symbols': self._prepare_expansion(x),
'postprocess': getattr(parser_conf.callback, a)}
for n,x,a in parser_conf.rules]

self.parser = nearley.Parser(rules, parser_conf.start)

def _prepare_expansion(self, expansion):
return [(sym, None) if is_terminal(sym) else sym for sym in expansion]

def parse(self, text):
tokens = list(self.lex(text))
res = self.parser.parse(tokens)
assert len(res) ==1 , 'Ambiguious Parse! Not handled yet'
return res[0]


class OldEarley(WithLexer):
def __init__(self, lexer_conf, parser_conf):
WithLexer.__init__(self, lexer_conf)

rules = [(n, self._prepare_expansion(x), a) for n,x,a in parser_conf.rules]

self.parser = old_earley.Parser(ParserConf(rules, parser_conf.callback, parser_conf.start))

def _prepare_expansion(self, expansion):
return [(sym,) if is_terminal(sym) else sym for sym in expansion]

def parse(self, text):
tokens = list(self.lex(text))
res = self.parser.parse(tokens)
assert len(res) ==1 , 'Ambiguious Parse! Not handled yet'
return res[0]


def tokenize_text(text):
new_text = []
line = 1
@@ -101,32 +60,6 @@ def tokenize_text(text):
new_text.append(Token('CHAR', ch, line=line, column=i - col_start_pos))
return new_text


class OldEarley_NoLex:
def __init__(self, lexer_conf, parser_conf):
self.token_by_name = {t.name:t for t in lexer_conf.tokens}

rules = [(n, list(self._prepare_expansion(x)), a) for n,x,a in parser_conf.rules]

self.parser = old_earley.Parser(ParserConf(rules, parser_conf.callback, parser_conf.start))

def _prepare_expansion(self, expansion):
for sym in expansion:
if is_terminal(sym):
regexp = self.token_by_name[sym].pattern.to_regexp()
width = sre_parse.parse(regexp).getwidth()
if width != (1,1):
raise GrammarError('Scanless parsing (lexer=None) requires all tokens to have a width of 1 (terminal %s: %s is %s)' % (sym, regexp, width))
yield (re.compile(regexp).match, regexp)
else:
yield sym

def parse(self, text):
new_text = tokenize_text(text)
res = self.parser.parse(new_text)
assert len(res) ==1 , 'Ambiguious Parse! Not handled yet'
return res[0]

class Earley_NoLex:
def __init__(self, lexer_conf, parser_conf, options=None):
self.token_by_name = {t.name:t for t in lexer_conf.tokens}
@@ -178,7 +111,7 @@ class XEarley:
def __init__(self, lexer_conf, parser_conf, options=None):
self.token_by_name = {t.name:t for t in lexer_conf.tokens}

rules = [(n, list(self._prepare_expansion(x)), a) for n,x,a in parser_conf.rules]
rules = [(n, list(self._prepare_expansion(x)), a, o) for n,x,a,o in parser_conf.rules]

resolve_ambiguity = (options.ambiguity=='resolve') if options else True
ignore = [Terminal_Regexp(self.token_by_name[x].pattern.to_regexp()) for x in lexer_conf.ignore]
@@ -195,6 +128,7 @@ class XEarley:
if is_terminal(sym):
regexp = self.token_by_name[sym].pattern.to_regexp()
width = sre_parse.parse(regexp).getwidth()
assert width
yield Terminal_Regexp(regexp)
else:
yield sym


+ 3
- 3
lark/parsers/earley.py View File

@@ -238,13 +238,13 @@ def _compare_rules(rule1, rule2):

def _compare_drv(tree1, tree2):
if not (isinstance(tree1, Tree) and isinstance(tree2, Tree)):
return compare(tree1, tree2)
return -compare(tree1, tree2)

try:
rule1, rule2 = tree1.rule, tree2.rule
except AttributeError:
# Probably trees that don't take part in this parse (better way to distinguish?)
return compare(tree1, tree2)
return -compare(tree1, tree2)

# XXX These artifacts can appear due to imperfections in the ordering of Visitor_NoRecurse,
# when confronted with duplicate (same-id) nodes. Fixing this ordering is possible, but would be
@@ -264,7 +264,7 @@ def _compare_drv(tree1, tree2):
if c:
return c

return compare(len(tree1.children), len(tree2.children))
return -compare(len(tree1.children), len(tree2.children))


def _resolve_ambig(tree):


+ 13
- 182
lark/parsers/xearley.py View File

@@ -1,4 +1,4 @@
"This module implements an Earley Parser"
"This module implements an experimental Earley Parser with a dynamic lexer"

# The parser uses a parse-forest to keep track of derivations and ambiguations.
# When the parse ends successfully, a disambiguation stage resolves all ambiguity
@@ -10,121 +10,21 @@
# The algorithm keeps track of each state set, using a corresponding Column instance.
# Column keeps track of new items using NewsList instances.
#
# Instead of running a lexer beforehand, or using a costy char-by-char method, this parser
# uses regular expressions by necessity, achieving high-performance while maintaining all of
# Earley's power in parsing any CFG.
#
#
# Author: Erez Shinan (2017)
# Email : erezshin@gmail.com

from functools import cmp_to_key
from collections import defaultdict

from ..utils import compare
from ..common import ParseError, UnexpectedToken, Terminal
from ..tree import Tree, Visitor_NoRecurse, Transformer_NoRecurse
from ..tree import Tree
from .grammar_analysis import GrammarAnalyzer


class EndToken:
type = '$end'

class Derivation(Tree):
def __init__(self, rule, items=None):
Tree.__init__(self, 'drv', items or [])
self.rule = rule

END_TOKEN = EndToken()

class Item(object):
"An Earley Item, the atom of the algorithm."

def __init__(self, rule, ptr, start, tree):
self.rule = rule
self.ptr = ptr
self.start = start
self.tree = tree if tree is not None else Derivation(self.rule)

@property
def expect(self):
return self.rule.expansion[self.ptr]

@property
def is_complete(self):
return self.ptr == len(self.rule.expansion)

def advance(self, tree):
assert self.tree.data == 'drv'
new_tree = Derivation(self.rule, self.tree.children + [tree])
return Item(self.rule, self.ptr+1, self.start, new_tree)

def __eq__(self, other):
return self.start is other.start and self.ptr == other.ptr and self.rule == other.rule
def __hash__(self):
return hash((self.rule, self.ptr, id(self.start)))

def __repr__(self):
before = list(map(str, self.rule.expansion[:self.ptr]))
after = list(map(str, self.rule.expansion[self.ptr:]))
return '<(%d) %s : %s * %s>' % (id(self.start), self.rule.origin, ' '.join(before), ' '.join(after))


class NewsList(list):
"Keeps track of newly added items (append-only)"

def __init__(self, initial=None):
list.__init__(self, initial or [])
self.last_iter = 0

def get_news(self):
i = self.last_iter
self.last_iter = len(self)
return self[i:]



class Column:
"An entry in the table, aka Earley Chart. Contains lists of items."
def __init__(self, i):
self.i = i
self.to_reduce = NewsList()
self.to_predict = NewsList()
self.to_scan = NewsList()
self.item_count = 0

self.added = set()
self.completed = {}

def add(self, items):
"""Sort items into scan/predict/reduce newslists

Makes sure only unique items are added.
"""

for item in items:

if item.is_complete:
# XXX Potential bug: What happens if there's ambiguity in an empty rule?
if item.rule.expansion and item in self.completed:
old_tree = self.completed[item].tree
if old_tree.data != '_ambig':
new_tree = old_tree.copy()
new_tree.rule = old_tree.rule
old_tree.set('_ambig', [new_tree])
if item.tree.children[0] is old_tree: # XXX a little hacky!
raise ParseError("Infinite recursion in grammar!")
old_tree.children.append(item.tree)
else:
self.completed[item] = item
self.to_reduce.append(item)
else:
if item not in self.added:
self.added.add(item)
if isinstance(item.expect, Terminal):
self.to_scan.append(item)
else:
self.to_predict.append(item)

self.item_count += 1 # Only count if actually added

def __nonzero__(self):
return bool(self.item_count)
from earley import ResolveAmbig, ApplyCallbacks, Item, NewsList, Derivation, END_TOKEN, Column

class Parser:
def __init__(self, rules, start_symbol, callback, resolve_ambiguity=True, ignore=()):
@@ -144,7 +44,7 @@ class Parser:
def parse(self, stream, start_symbol=None):
# Define parser functions
start_symbol = start_symbol or self.start_symbol
matched_terminals = defaultdict(list)
delayed_matches = defaultdict(list)

def predict(nonterm, column):
assert not isinstance(nonterm, Terminal), nonterm
@@ -178,16 +78,17 @@ class Parser:
for item in to_scan:
m = item.expect.match(stream, i)
if m:
matched_terminals[m.end()].append(item.advance(m.group(0)))
delayed_matches[m.end()].append(item.advance(m.group(0)))

s = m.group(0)
for j in range(1, len(s)):
m = item.expect.match(s[:-j])
if m:
matched_terminals[m.end()].append(item.advance(m.group(0)))
delayed_matches[m.end()].append(item.advance(m.group(0)))

next_set = Column(i+1)
next_set.add(matched_terminals[i+1])
next_set.add(delayed_matches[i+1])
del delayed_matches[i+1] # No longer needed, so unburden memory

return next_set

@@ -220,73 +121,3 @@ class Parser:
return ApplyCallbacks(self.postprocess).transform(tree)



class ApplyCallbacks(Transformer_NoRecurse):
def __init__(self, postprocess):
self.postprocess = postprocess

def drv(self, tree):
children = tree.children
callback = self.postprocess[tree.rule]
if callback:
return callback(children)
else:
return Tree(rule.origin, children)

def _compare_rules(rule1, rule2):
assert rule1.origin == rule2.origin
c = compare( len(rule1.expansion), len(rule2.expansion))
if rule1.origin.startswith('__'): # XXX hack! We need to set priority in parser, not here
c = -c
return c

def _compare_drv(tree1, tree2):
if not (isinstance(tree1, Tree) and isinstance(tree2, Tree)):
return -compare(tree1, tree2)

c = _compare_rules(tree1.rule, tree2.rule)
if c:
return c

# rules are "equal", so compare trees
for t1, t2 in zip(tree1.children, tree2.children):
c = _compare_drv(t1, t2)
if c:
return c

return -compare(len(tree1.children), len(tree2.children))


class ResolveAmbig(Visitor_NoRecurse):
"""Resolves ambiguity in resulting parse tree.

Minimizes rule length, maximizes match length.
"""

def _ambig(self, tree):
best = min(tree.children, key=cmp_to_key(_compare_drv))
assert best.data == 'drv'
tree.set('drv', best.children)
tree.rule = best.rule # needed for applying callbacks


# RULES = [
# ('a', ['d']),
# ('d', ['b']),
# ('b', ['C']),
# ('b', ['b', 'C']),
# ('b', ['C', 'b']),
# ]
# p = Parser(RULES, 'a')
# for x in p.parse('CC'):
# print x.pretty()

#---------------
# RULES = [
# ('s', ['a', 'a']),
# ('a', ['b', 'b']),
# ('b', ['C'], lambda (x,): x),
# ('b', ['b', 'C']),
# ]
# p = Parser(RULES, 's', {})
# print p.parse('CCCCC').pretty()

+ 14
- 1
tests/__main__.py View File

@@ -4,10 +4,23 @@ import unittest
import logging

from .test_trees import TestTrees

# from .test_selectors import TestSelectors
from .test_parser import TestLalrStandard, TestEarleyStandard, TestLalrContextual, TestParsers, TestEarleyScanless, TestEarley, TestEarleyDynamic
# from .test_grammars import TestPythonG, TestConfigG

from .test_parser import (
TestLalrStandard,
TestEarleyStandard,
TestLalrContextual,
TestEarleyScanless,
TestEarleyDynamic,

TestFullEarleyScanless,
TestFullEarleyDynamic,

TestParsers,
)

logging.basicConfig(level=logging.INFO)

if __name__ == '__main__':


+ 72
- 65
tests/test_parser.py View File

@@ -51,90 +51,95 @@ class TestParsers(unittest.TestCase):
self.assertRaises(ParseError, l.parse, 'a')


class TestEarley(unittest.TestCase):
def test_anon_in_scanless(self):
# Fails an Earley implementation without special handling for empty rules,
# or re-processing of already completed rules.
g = Lark(r"""start: B
B: ("ab"|/[^b]/)*
""", lexer='dynamic')
def _make_full_earley_test(LEXER):
class _TestFullEarley(unittest.TestCase):
def test_anon_in_scanless(self):
# Fails an Earley implementation without special handling for empty rules,
# or re-processing of already completed rules.
g = Lark(r"""start: B
B: ("ab"|/[^b]/)*
""", lexer=LEXER)

self.assertEqual( g.parse('abc').children[0], 'abc')
self.assertEqual( g.parse('abc').children[0], 'abc')

def test_earley_scanless(self):
g = Lark("""start: A "b" c
A: "a"+
c: "abc"
""", parser="earley", lexer='dynamic')
x = g.parse('aaaababc')
def test_earley_scanless(self):
g = Lark("""start: A "b" c
A: "a"+
c: "abc"
""", parser="earley", lexer=LEXER)
x = g.parse('aaaababc')

def test_earley_scanless2(self):
grammar = """
start: statement+
def test_earley_scanless2(self):
grammar = """
start: statement+

statement: "r"
| "c" /[a-z]/+
statement: "r"
| "c" /[a-z]/+

%ignore " "
"""
%ignore " "
"""

program = """c b r"""
program = """c b r"""

l = Lark(grammar, parser='earley', lexer='dynamic')
l.parse(program)
l = Lark(grammar, parser='earley', lexer=LEXER)
l.parse(program)

def test_earley_scanless3(self):
"Tests prioritization and disambiguation for pseudo-terminals (there should be only one result)"
def test_earley_scanless3(self):
"Tests prioritization and disambiguation for pseudo-terminals (there should be only one result)"

grammar = """
start: A A
A: "a"+
"""
grammar = """
start: A A
A: "a"+
"""

l = Lark(grammar, parser='earley', lexer='dynamic')
res = l.parse("aaa")
self.assertEqual(res.children, ['aa', 'a'])
l = Lark(grammar, parser='earley', lexer=LEXER)
res = l.parse("aaa")
self.assertEqual(res.children, ['aa', 'a'])

def test_earley_scanless4(self):
grammar = """
start: A A?
A: "a"+
"""
def test_earley_scanless4(self):
grammar = """
start: A A?
A: "a"+
"""

l = Lark(grammar, parser='earley', lexer=LEXER)
res = l.parse("aaa")
self.assertEqual(res.children, ['aaa'])

l = Lark(grammar, parser='earley', lexer='dynamic')
res = l.parse("aaa")
self.assertEqual(res.children, ['aaa'])
def test_earley_repeating_empty(self):
# This was a sneaky bug!

def test_earley_repeating_empty(self):
# This was a sneaky bug!
grammar = """
!start: "a" empty empty "b"
empty: empty2
empty2:
"""

grammar = """
!start: "a" empty empty "b"
empty: empty2
empty2:
"""
parser = Lark(grammar, parser='earley', lexer=LEXER)
res = parser.parse('ab')

parser = Lark(grammar, parser='earley', lexer='dynamic')
res = parser.parse('ab')
empty_tree = Tree('empty', [Tree('empty2', [])])
self.assertSequenceEqual(res.children, ['a', empty_tree, empty_tree, 'b'])

empty_tree = Tree('empty', [Tree('empty2', [])])
self.assertSequenceEqual(res.children, ['a', empty_tree, empty_tree, 'b'])
def test_earley_explicit_ambiguity(self):
# This was a sneaky bug!

def test_earley_explicit_ambiguity(self):
# This was a sneaky bug!
grammar = """
start: a b | ab
a: "a"
b: "b"
ab: "ab"
"""

grammar = """
start: a b | ab
a: "a"
b: "b"
ab: "ab"
"""
parser = Lark(grammar, parser='earley', lexer=LEXER, ambiguity='explicit')
res = parser.parse('ab')

parser = Lark(grammar, parser='earley', lexer='dynamic', ambiguity='explicit')
res = parser.parse('ab')
self.assertEqual( res.data, '_ambig')
self.assertEqual( len(res.children), 2)

self.assertEqual( res.data, '_ambig')
self.assertEqual( len(res.children), 2)
_NAME = "TestFullEarley" + (LEXER or 'Scanless').capitalize()
_TestFullEarley.__name__ = _NAME
globals()[_NAME] = _TestFullEarley


def _make_parser_test(LEXER, PARSER):
@@ -444,7 +449,7 @@ def _make_parser_test(LEXER, PARSER):
""")
x = g.parse('aababc')

@unittest.skipIf(LEXER is None, "Known bug with scanless parsing") # TODO
@unittest.skipIf(LEXER in (None, 'dynamic'), "Known bug with scanless parsing") # TODO
def test_token_not_anon(self):
"""Tests that "a" is matched as A, rather than an anonymous token.

@@ -664,6 +669,8 @@ _TO_TEST = [
for _LEXER, _PARSER in _TO_TEST:
_make_parser_test(_LEXER, _PARSER)

for _LEXER in (None, 'dynamic'):
_make_full_earley_test(_LEXER)

if __name__ == '__main__':
unittest.main()


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