mirror of https://github.com/lark-parser/lark.git
82 lines
2.2 KiB
Python
82 lines
2.2 KiB
Python
#
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# This demonstrates example-driven error reporting with the LALR parser
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#
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from lark import Lark, UnexpectedToken
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from .json_parser import json_grammar # Using the grammar from the json_parser example
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json_parser = Lark(json_grammar, parser='lalr')
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class JsonSyntaxError(SyntaxError):
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def __str__(self):
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context, line, column = self.args
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return '%s at line %s, column %s.\n\n%s' % (self.label, line, column, context)
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class JsonMissingValue(JsonSyntaxError):
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label = 'Missing Value'
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class JsonMissingOpening(JsonSyntaxError):
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label = 'Missing Opening'
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class JsonMissingClosing(JsonSyntaxError):
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label = 'Missing Closing'
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class JsonMissingComma(JsonSyntaxError):
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label = 'Missing Comma'
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class JsonTrailingComma(JsonSyntaxError):
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label = 'Trailing Comma'
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def parse(json_text):
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try:
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j = json_parser.parse(json_text)
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except UnexpectedToken as ut:
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exc_class = ut.match_examples(json_parser.parse, {
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JsonMissingValue: ['{"foo": }'],
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JsonMissingOpening: ['{"foo": ]}',
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'{"foor": }}'],
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JsonMissingClosing: ['{"foo": [}',
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'{',
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'{"a": 1',
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'[1'],
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JsonMissingComma: ['[1 2]',
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'[false 1]',
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'["b" 1]',
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'{"a":true 1:4}',
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'{"a":1 1:4}',
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'{"a":"b" 1:4}'],
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JsonTrailingComma: ['[,]',
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'[1,]',
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'[1,2,]',
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'{"foo":1,}',
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'{"foo":false,"bar":true,}']
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})
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if not exc_class:
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raise
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raise exc_class(ut.get_context(json_text), ut.line, ut.column)
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def test():
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try:
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parse('{"key":')
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except JsonMissingValue:
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pass
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try:
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parse('{"key": "value"')
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except JsonMissingClosing:
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pass
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try:
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parse('{"key": ] ')
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except JsonMissingOpening:
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pass
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if __name__ == '__main__':
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test()
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