BaseModel.construct(): Incorrect field order with default values

[jonas-t-k]

Checks

• I added a descriptive title to this issue
• I have searched (google, github) for similar issues and couldn't find anything
• I have read and followed the docs and still think this is a bug

Bug

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.7.3
            pydantic compiled: True
                 install path: C:\Users\JonasTK\miniconda3\envs\testenv\Lib\site-packages\pydantic
               python version: 3.8.5 (default, Sep  3 2020, 21:29:08) [MSC v.1916 64 bit (AMD64)]
                     platform: Windows-10-10.0.19041-SP0
     optional deps. installed: ['typing-extensions']

I know this is (sort of) showcased in the docs, but I still think it is a problem that .construct() does not give correct field order when there are fields with default values. Most of the time this is not a problem: comparing instances and .dict() outputs do not depend on the field order. But for JSON export, it does matter.

Shouldn't the JSON export from an instance generated via .construct() with pre-validated input be identical to the JSON export of a properly validated instance?

from pydantic import BaseModel


class Foo(BaseModel):
    a: int
    b: int = 42
    c: float


instance = Foo(a=1, c=3.14)  # Correct field order
instance_construct = Foo.construct(**instance.dict())  # Incorrect field order

print(instance)            # Output: a=1 b=42 c=3.14
print(instance_construct)  # Output: b=42 a=1 c=3.14

print(instance.json())            # Output: {"a": 1, "b": 42, "c": 3.14}
print(instance_construct.json())  # Output: {"b": 42, "a": 1, "c": 3.14}

assert instance == instance_construct  # No Error
assert instance.dict() == instance_construct.dict()  # No Error
assert instance.json() == instance_construct.json()  # AssertionError