Improve astroid's inference for simplejson & json

[pylint-bot]

Originally reported by: Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore?)

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The following stackoverflow post http://stackoverflow.com/questions/21545409/pylint-reports-maybe-no-member-error-for-data-loaded-via-simplejson describes a false positive related to simplejson and json. It's more of an inference issue, so this should be fixed in astroid, rather than pylint.

#!python

import astroid.builder
builder = astroid.builder.AstroidBuilder()
ast = builder.string_build("""
import simplejson
import json
x = json.loads('"test"')
y = simplejson.loads('"test"')
""")

json_assignment, simplejson_assignment = list(ast.get_children())[2:]
print("json:", list(json_assignment.get_children())[-1].infered())
print("simplejson:", list(simplejson_assignment.get_children())[-1].infered())

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• Bitbucket: https://bitbucket.org/logilab/astroid/issue/75

[pylint-bot]

Original comment by Florian Bruhin (BitBucket: The-Compiler, GitHub: @The-Compiler?):

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I think astroid got more clever about the json module, which means I get the same false-positive with the astroid tip with the json module.

With this code snippet:

import json

j = json.loads('{"foo": "bar"}')
j.get('foo')

I get this with pylint and astroid from the tip:

E:  4, 0: Instance of 'bool' has no 'get' member (no-member)

but no errors with the last releases.

When looking at what astroid infers:

from astroid.test_utils import extract_node
n = extract_node('''
import json

j = json.loads('{"foo": "bar"}')
j  #@
j.get('foo')
''')
print(n.infered())

I get [YES] with the release and [YES, <Const.NoneType l.42 at ...>, <Const.bool l.44 at ...>, <Const.bool l.46 at ...>] with the tip.

Maybe astroid should just assume something like [None, dict, list, string, int, float] for the json/simplejson load calls?

[pylint-bot]

Original comment by Claudiu Popa (BitBucket: PCManticore, GitHub: @PCManticore?):

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Yes, one solution is to not emit no-member if there are more than one member inferred, because there's no way to reason about that.

[pylint-bot]

Original comment by Sylvain Thénault (BitBucket: sthenault, GitHub: @sthenault?):

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In such case It would make sense to force inference to return Yes/Any