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September 25, 2017 03:06
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pylint plugin example
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| """Checker for unneccessary use of str() in format() arguments.""" | |
| import six | |
| import astroid | |
| from pylint.checkers import BaseChecker, utils | |
| from pylint.interfaces import IAstroidChecker | |
| #from .common import BASE_ID | |
| BASE_ID=99 | |
| def register(linter): | |
| """Register checkers.""" | |
| linter.register_checker(format_str_checker(linter)) | |
| class format_str_checker(BaseChecker): | |
| """ | |
| Checks that the arguments to format() are not str(something) | |
| Bad: | |
| "Bad {}".format(str(a)) | |
| "Bad {nope}".format(nope=str(a)) | |
| OK: | |
| "Good".format(a) | |
| "Good {yeah}".format(yeah=a) | |
| """ | |
| __implements__ = (IAstroidChecker,) | |
| name = 'no-need-to-call-str-on-format-args-checker' | |
| POSITIONAL_MESSAGE_ID = 'str-used-on-positional-format-argument' | |
| KEYWORD_MESSAGE_ID = 'str-used-on-keyword-format-argument' | |
| msgs = { | |
| 'C%d10' % BASE_ID: ( | |
| "format argument #%d should be called without str()", | |
| POSITIONAL_MESSAGE_ID, | |
| "format() already converts its arguments to strings", | |
| ), | |
| 'C%d11' % BASE_ID: ( | |
| "format argument '%s' should be called without str()", | |
| KEYWORD_MESSAGE_ID, | |
| "format() already converts its arguments to strings", | |
| ), | |
| } | |
| @utils.check_messages(POSITIONAL_MESSAGE_ID, KEYWORD_MESSAGE_ID) | |
| def visit_callfunc(self, node): | |
| """Called for every function call in the source code.""" | |
| if not isinstance(node.func, astroid.Attribute): | |
| return | |
| if node.func.attrname != "format": | |
| # Be gone | |
| return | |
| if not self.linter.is_message_enabled(self.POSITIONAL_MESSAGE_ID, line=node.fromlineno): | |
| return | |
| # Check the positional args | |
| index = 0 | |
| for child in node.args: | |
| index += 1 | |
| if isinstance(child, astroid.Call): | |
| if child.func.name == "str": | |
| self.add_message(self.POSITIONAL_MESSAGE_ID, args=index, node=node) | |
| if not self.linter.is_message_enabled(self.KEYWORD_MESSAGE_ID, line=node.fromlineno): | |
| return | |
| # Check the keyword args | |
| if not node.keywords: | |
| return | |
| for child in node.keywords: | |
| if isinstance(child.value, astroid.Call): | |
| if child.value.func.name == "str": | |
| self.add_message(self.KEYWORD_MESSAGE_ID, args=child.arg, node=node) | |
| return |
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