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Erez Shinan Fixed examples for error reporting e721226 Jun 27, 2018
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#
# This demonstrates example-driven error reporting with the LALR parser
#
from lark import Lark, UnexpectedInput
from .json_parser import json_grammar # Using the grammar from the json_parser example
json_parser = Lark(json_grammar, parser='lalr')
class JsonSyntaxError(SyntaxError):
def __str__(self):
context, line, column = self.args
return '%s at line %s, column %s.\n\n%s' % (self.label, line, column, context)
class JsonMissingValue(JsonSyntaxError):
label = 'Missing Value'
class JsonMissingOpening(JsonSyntaxError):
label = 'Missing Opening'
class JsonMissingClosing(JsonSyntaxError):
label = 'Missing Closing'
class JsonMissingComma(JsonSyntaxError):
label = 'Missing Comma'
class JsonTrailingComma(JsonSyntaxError):
label = 'Trailing Comma'
def parse(json_text):
try:
j = json_parser.parse(json_text)
except UnexpectedInput as u:
exc_class = u.match_examples(json_parser.parse, {
JsonMissingOpening: ['{"foo": ]}',
'{"foor": }}',
'{"foo": }'],
JsonMissingClosing: ['{"foo": [}',
'{',
'{"a": 1',
'[1'],
JsonMissingComma: ['[1 2]',
'[false 1]',
'["b" 1]',
'{"a":true 1:4}',
'{"a":1 1:4}',
'{"a":"b" 1:4}'],
JsonTrailingComma: ['[,]',
'[1,]',
'[1,2,]',
'{"foo":1,}',
'{"foo":false,"bar":true,}']
})
if not exc_class:
raise
raise exc_class(u.get_context(json_text), u.line, u.column)
def test():
try:
parse('{"example1": "value"')
except JsonMissingClosing as e:
print(e)
try:
parse('{"example2": ] ')
except JsonMissingOpening as e:
print(e)
if __name__ == '__main__':
test()
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