# Copyright 2015 Google Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Verify that the generated code is valid code.
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This takes a line of code and "normalizes" it. I.e., it transforms the snippet
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into something that has the potential to compile.
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VerifyCode(): the main function exported by this module.
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"""
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import ast
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import re
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import sys
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import textwrap
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class InternalError(Exception):
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"""Internal error in verifying formatted code."""
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pass
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def VerifyCode(code):
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"""Verify that the reformatted code is syntactically correct.
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Arguments:
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code: (unicode) The reformatted code snippet.
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Raises:
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SyntaxError if the code was reformatted incorrectly.
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"""
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try:
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compile(textwrap.dedent(code).encode('UTF-8'), '<string>', 'exec')
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except SyntaxError:
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try:
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ast.parse(textwrap.dedent(code.lstrip('\n')).lstrip(), '<string>', 'exec')
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except SyntaxError:
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try:
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normalized_code = _NormalizeCode(code)
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compile(normalized_code.encode('UTF-8'), '<string>', 'exec')
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except SyntaxError:
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raise InternalError(sys.exc_info()[1])
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def _NormalizeCode(code):
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"""Make sure that the code snippet is compilable."""
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code = textwrap.dedent(code.lstrip('\n')).lstrip()
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# Split the code to lines and get rid of all leading full-comment lines as
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# they can mess up the normalization attempt.
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lines = code.split('\n')
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i = 0
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for i, line in enumerate(lines):
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line = line.strip()
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if line and not line.startswith('#'):
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break
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code = '\n'.join(lines[i:]) + '\n'
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if re.match(r'(if|while|for|with|def|class|async|await)\b', code):
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code += '\n pass'
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elif re.match(r'(elif|else)\b', code):
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try:
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try_code = 'if True:\n pass\n' + code + '\n pass'
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ast.parse(
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textwrap.dedent(try_code.lstrip('\n')).lstrip(), '<string>', 'exec')
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code = try_code
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except SyntaxError:
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# The assumption here is that the code is on a single line.
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code = 'if True: pass\n' + code
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elif code.startswith('@'):
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code += '\ndef _():\n pass'
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elif re.match(r'try\b', code):
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code += '\n pass\nexcept:\n pass'
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elif re.match(r'(except|finally)\b', code):
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code = 'try:\n pass\n' + code + '\n pass'
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elif re.match(r'(return|yield)\b', code):
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code = 'def _():\n ' + code
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elif re.match(r'(continue|break)\b', code):
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code = 'while True:\n ' + code
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elif re.match(r'print\b', code):
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code = 'from __future__ import print_function\n' + code
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return code + '\n'
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