Source code for google.appengine.api.search.expression_parser

#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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"""Wrapper for ExpressionParser."""



from google.appengine._internal import antlr3
from google.appengine.api.search import ExpressionLexer
from google.appengine.api.search import ExpressionParser
from google.appengine.api.search import unicode_util


[docs]class ExpressionException(Exception): """An error occurred while parsing the expression input string."""
[docs]class ExpressionLexerWithErrors(ExpressionLexer.ExpressionLexer): """An overridden Lexer that raises exceptions."""
[docs] def emitErrorMessage(self, msg): """Raise an exception if the input fails to parse correctly. Overriding the default, which normally just prints a message to stderr. Arguments: msg: the error message Raises: ExpressionException: always. """ raise ExpressionException(msg)
[docs]class ExpressionParserWithErrors(ExpressionParser.ExpressionParser): """An overridden Parser that raises exceptions."""
[docs] def emitErrorMessage(self, msg): """Raise an exception if the input fails to parse correctly. Overriding the default, which normally just prints a message to stderr. Arguments: msg: the error message Raises: ExpressionException: always. """ raise ExpressionException(msg)
[docs]def CreateParser(expression): """Creates a Expression Parser.""" input_string = antlr3.ANTLRStringStream(unicode_util.LimitUnicode(expression)) lexer = ExpressionLexerWithErrors(input_string) tokens = antlr3.CommonTokenStream(lexer) parser = ExpressionParserWithErrors(tokens) return parser
[docs]def Parse(expression): """Parses an expression and returns the ANTLR tree.""" parser = CreateParser(expression) try: return parser.expression() except Exception, e: raise ExpressionException(e.message)

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