model_dump should serialise bools as bools for json

[Booplicate]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

Currently when dumping model to json, objects of type bool are being serialised as integers in json. I think this is a bug because json natively supports booleans (true/false).

Example Code

class SomeModel(BaseModel):
    value: StrictFloat | StrictInt | StrictBool

m = SomeModel(value=True)

# Passes
assert type(m.model_dump(mode="python")["value"]) is bool
# This will fail
assert type(m.model_dump(mode="json")["value"]) is bool, "didn't serialise as bool"

Python, Pydantic & OS Version

Python 3.11.4
Pydantic 2.1.1
Pydantic Core 2.4.0
Windows 10

Selected Assignee: @davidhewitt

[fatelei]

recommend to use model_dump_json

[Booplicate]

model_dump_json dumps to a str, I need to serialise to json data types (object/array/int//float/bool/string).

[sydney-runkle]

Hi @Booplicate,

Thanks very much for reporting this. I can confirm that this is a bug. This issue is a duplicate of the #6830 bug. We're working on fixing this issue in pydantic-core.

The issue is actually with the wrong type being selected when serializing a Union.

See the example below:

from pydantic import BaseModel, StrictBool, StrictFloat, StrictInt


class SomeModel(BaseModel):
    value: StrictFloat | StrictInt | StrictBool


class BoolModel(BaseModel):
    value: StrictBool


m1 = SomeModel(value=True)
m2 = BoolModel(value=True)

# Passes
assert type(m1.model_dump(mode="python")["value"]) is bool
# This will fail
assert type(m1.model_dump(mode="json")["value"]) is bool, "didn't serialise as bool"


# Passes
assert type(m2.model_dump(mode="python")["value"]) is bool
# Passes
assert type(m2.model_dump(mode="json")["value"]) is bool

I'm going to close this issue given that it's a duplicate of #6830, but we will include a test case like this one in our test suite once we fix this bug.

[Booplicate]

Good to know, thank you.

[gustelle]

Hello, is that fixed ? I'm having the issue with pydantic==2.8.2

See below:

class MyModel(BaseModel):
    value: str | float | int | bool

m1 = MyModel(value=True)

# fails
assert type(m1.model_dump(mode="json")["value"]) is bool 

NB : the ordering of types seems to be a fix for the issue

see below

class MyModel(BaseModel):
    value: str | bool | float | int

m1 = MyModel(value=True)

# passes
assert type(m1.model_dump(mode="json")["value"]) is bool 

[sydney-runkle]

You're right, this is still an issue

[dexterionut]

You're right, this is still an issue

@sydney-runkle Was this fixed with pydantic/pydantic-core#1398 ? I can't figure it out from the test case in that PR as it doesn't test to_json and it only uses ints.

[sydney-runkle]

Ah @dexterionut, yep! This is fixed by that PR, great call!