Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.11/site-packages/lark/parsers/lalr_interactive_parser.py: 62%

1# This module provides a LALR interactive parser, which is used for debugging and error handling 

2 

3from typing import Iterator, List 

4from copy import copy 

5import warnings 

6 

7from lark.exceptions import UnexpectedToken 

8from lark.lexer import Token, LexerThread 

9from .lalr_parser_state import ParserState 

10 

11###{standalone 

12 

13class InteractiveParser: 

14 """InteractiveParser gives you advanced control over parsing and error handling when parsing with LALR. 

15 

16 For a simpler interface, see the ``on_error`` argument to ``Lark.parse()``. 

17 """ 

18 def __init__(self, parser, parser_state: ParserState, lexer_thread: LexerThread): 

19 self.parser = parser 

20 self.parser_state = parser_state 

21 self.lexer_thread = lexer_thread 

22 self.result = None 

23 

24 @property 

25 def lexer_state(self) -> LexerThread: 

26 warnings.warn("lexer_state will be removed in subsequent releases. Use lexer_thread instead.", DeprecationWarning) 

27 return self.lexer_thread 

28 

29 def feed_token(self, token: Token): 

30 """Feed the parser with a token, and advance it to the next state, as if it received it from the lexer. 

31 

32 Note that ``token`` has to be an instance of ``Token``. 

33 """ 

34 return self.parser_state.feed_token(token, token.type == '$END') 

35 

36 def iter_parse(self) -> Iterator[Token]: 

37 """Step through the different stages of the parse, by reading tokens from the lexer 

38 and feeding them to the parser, one per iteration. 

39 

40 Returns an iterator of the tokens it encounters. 

41 

42 When the parse is over, the resulting tree can be found in ``InteractiveParser.result``. 

43 """ 

44 for token in self.lexer_thread.lex(self.parser_state): 

45 yield token 

46 self.result = self.feed_token(token) 

47 

48 def exhaust_lexer(self) -> List[Token]: 

49 """Try to feed the rest of the lexer state into the interactive parser. 

50 

51 Note that this modifies the instance in place and does not feed an '$END' Token 

52 """ 

53 return list(self.iter_parse()) 

54 

55 

56 def feed_eof(self, last_token=None): 

57 """Feed a '$END' Token. Borrows from 'last_token' if given.""" 

58 eof = Token.new_borrow_pos('$END', '', last_token) if last_token is not None else self.lexer_thread._Token('$END', '', 0, 1, 1) 

59 return self.feed_token(eof) 

60 

61 

62 def __copy__(self): 

63 """Create a new interactive parser with a separate state. 

64 

65 Calls to feed_token() won't affect the old instance, and vice-versa. 

66 """ 

67 return self.copy() 

68 

69 def copy(self, deepcopy_values=True): 

70 parser_state = self.parser_state.copy(deepcopy_values=deepcopy_values) 

71 return type(self)(self.parser, parser_state, parser_state.lexer) 

72 

73 def __eq__(self, other): 

74 if not isinstance(other, InteractiveParser): 

75 return False 

76 

77 return self.parser_state == other.parser_state and self.lexer_thread == other.lexer_thread 

78 

79 def as_immutable(self): 

80 """Convert to an ``ImmutableInteractiveParser``.""" 

81 p = copy(self) 

82 return ImmutableInteractiveParser(p.parser, p.parser_state, p.lexer_thread) 

83 

84 def pretty(self): 

85 """Print the output of ``choices()`` in a way that's easier to read.""" 

86 out = ["Parser choices:"] 

87 for k, v in self.choices().items(): 

88 out.append('\t- %s -> %r' % (k, v)) 

89 out.append('stack size: %s' % len(self.parser_state.state_stack)) 

90 return '\n'.join(out) 

91 

92 def choices(self): 

93 """Returns a dictionary of token types, matched to their action in the parser. 

94 

95 Only returns token types that are accepted by the current state. 

96 

97 Updated by ``feed_token()``. 

98 """ 

99 return self.parser_state.parse_conf.parse_table.states[self.parser_state.position] 

100 

101 def accepts(self): 

102 """Returns the set of possible tokens that will advance the parser into a new valid state.""" 

103 accepts = set() 

104 conf_no_callbacks = copy(self.parser_state.parse_conf) 

105 # We don't want to call callbacks here since those might have arbitrary side effects 

106 # and are unnecessarily slow. 

107 conf_no_callbacks.callbacks = {} 

108 for t in self.choices(): 

109 if t.isupper(): # is terminal? 

110 new_cursor = self.copy(deepcopy_values=False) 

111 new_cursor.parser_state.parse_conf = conf_no_callbacks 

112 try: 

113 new_cursor.feed_token(self.lexer_thread._Token(t, '')) 

114 except UnexpectedToken: 

115 pass 

116 else: 

117 accepts.add(t) 

118 return accepts 

119 

120 def resume_parse(self): 

121 """Resume automated parsing from the current state. 

122 """ 

123 return self.parser.parse_from_state(self.parser_state, last_token=self.lexer_thread.state.last_token) 

124 

125 

126 

127class ImmutableInteractiveParser(InteractiveParser): 

128 """Same as ``InteractiveParser``, but operations create a new instance instead 

129 of changing it in-place. 

130 """ 

131 

132 result = None 

133 

134 def __hash__(self): 

135 return hash((self.parser_state, self.lexer_thread)) 

136 

137 def feed_token(self, token): 

138 c = copy(self) 

139 c.result = InteractiveParser.feed_token(c, token) 

140 return c 

141 

142 def exhaust_lexer(self): 

143 """Try to feed the rest of the lexer state into the parser. 

144 

145 Note that this returns a new ImmutableInteractiveParser and does not feed an '$END' Token""" 

146 cursor = self.as_mutable() 

147 cursor.exhaust_lexer() 

148 return cursor.as_immutable() 

149 

150 def as_mutable(self): 

151 """Convert to an ``InteractiveParser``.""" 

152 p = copy(self) 

153 return InteractiveParser(p.parser, p.parser_state, p.lexer_thread) 

154 

155###}