False positive for E0202 (method-hidden)

[pylint-bot]

Originally reported by: Anonymous

---

With this code:

#!python

import json


class MyEncoder(json.JSONEncoder):
    def default(self, o):
        json.JSONEncoder.default(self, o)

I have the following pylint output:

#!bash

C:\Documents\Projects\Test>pylint --disable=C0111,R0903 --msg-template="{msg_id}:{line:3d},{column}: {obj}: {msg} ({symbol})" --report=n example.py
No config file found, using default configuration
************* Module example
E0202:  5,4: MyEncoder.default: An attribute defined in json.encoder line 152 hides this method (method-hidden)

Version:

#!bash

C:\Documents\Projects\Test>pylint --version
No config file found, using default configuration
pylint 1.4.0,
astroid 1.3.2, common 0.63.2
Python 3.4.2 (v3.4.2:ab2c023a9432, Oct  6 2014, 22:16:31) [MSC v.1600 64 bit (AMD64)]

---

• Bitbucket: https://bitbucket.org/logilab/pylint/issue/414

[yuyang00]

I'm also having the problem. Looks like pylint does not like overloading a method with 'default' as the method name. Our build system is using pylint to check code, and the result is I cannot extend the JSONEncoder class.

[Lothiraldan]

I have the same problem

[cemsbr]

Same problem.

[cemsbr]

Workaround: def default(self, o): # pylint: disable=E0202

[PCManticore]

This is indeed a false positive, but it has nothing to do with the fact that the method is called 'default' and partially, it is an oddity with the json.JSONEncoder class as well. The problem is that it can accept a default argument, which gets set into a property here https://hg.python.org/cpython/file/tip/Lib/json/encoder.py#l157, although later it also defines a default method for being overridden by subclasses. I need to think of a potential fix though.

[sylann]

I get this error too when overriding the run method of flask_script's Command class

[pylint] E0202:An attribute defined in flask_script.commands line 153 hides this method

[brycepg]

Possible solutions:

• Only raise message at site of assignment instead of at FunctionDef. This would leave the maintainers of the module with the warning, but not the users.
• Automatically ignore this message if the any of the overridden functions are "abstract" (i.e. always raises NotImplementedError)
• Ignore method-hidden if the FunctionDef is below the assignment location in the mro

Any thoughts?

[PCManticore]

@brycepg the first one sounds like the best option in my opinion.

[nickdallege]

What's the status of this bug? Is there any fix likely to be implemented soon?

[Meng-Gen]

pylint: disable=E0202

pylint: disable=method-hidden will be better.

[brianjmurrell]

Use of disable workaround also ends up leaving one with long lines.

def default(self, o): # pylint: disable=E0202

works but

def default(self,
            o): # pylint: disable=E0202

and neither does:

# pylint: disable=E0202
def default(self, o):
# pylint: enable=E0202

[jaanisfehling]

Use of disable workaround also ends up leaving one with long lines.

def default(self, o): # pylint: disable=E0202

works but

def default(self,
            o): # pylint: disable=E0202

and neither does:

# pylint: disable=E0202
def default(self, o):
# pylint: enable=E0202

What works is this ugly variant:

def default(self, # pylint: disable=E0202 o):

[Pierre-Sassoulas]

If you use black to format automatically you'll get this:

def default(
    self,  # pylint: disable=E0202
    o,
):

The disable algorithm is based on the lineno of the affected node given by the ast module and is very unlikely to change.