blob: 662db760af640524a2a0bddea09f09a6718a600b [file] [log] [blame]
#!/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
#
# 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
# limitations under the License.
#
"""Wrapper for ExpressionParser."""
from google.appengine._internal import antlr3
from google.appengine.api.search import ExpressionLexer
from google.appengine.api.search import ExpressionParser
class ExpressionException(Exception):
"""An error occurred while parsing the expression input string."""
class ExpressionLexerWithErrors(ExpressionLexer.ExpressionLexer):
"""An overridden Lexer that raises exceptions."""
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)
class ExpressionParserWithErrors(ExpressionParser.ExpressionParser):
"""An overridden Parser that raises exceptions."""
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)
def CreateParser(expression):
"""Creates a Expression Parser."""
input_string = antlr3.ANTLRStringStream(expression)
lexer = ExpressionLexerWithErrors(input_string)
tokens = antlr3.CommonTokenStream(lexer)
parser = ExpressionParserWithErrors(tokens)
return parser
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)