[issue45054] json module should issue warning about duplicate keys

[Kevin Mills]

New submission from Kevin Mills <kevin.mills226+bugs.python at gmail.com>:

The json module will allow the following without complaint:

import json
d1 = {1: "fromstring", "1": "fromnumber"}
string = json.dumps(d1)
print(string)
d2 = json.loads(string)
print(d2)

And it prints:

{"1": "fromstring", "1": "fromnumber"}
{'1': 'fromnumber'}

This would be extremely confusing to anyone who doesn't already know that JSON keys have to be strings. Not only does `d1 != d2` (which the documentation does mention as a possibility after a round trip through JSON), but `len(d1) != len(d2)` and `d1['1'] != d2['1']`, even though '1' is in both.

I suggest that if json.dump or json.dumps notices that it is producing a JSON document with duplicate keys, it should issue a warning. Similarly, if json.load or json.loads notices that it is reading a JSON document with duplicate keys, it should also issue a warning.

----------
components: Library (Lib)
messages: 400678
nosy: Zeturic
priority: normal
severity: normal
status: open
title: json module should issue warning about duplicate keys
type: enhancement
versions: Python 3.11

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45054>
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