An empty string is a valid JSON attribute name

[SergeyTsaplin]

Checks

• [ x] I added a descriptive title to this issue
• [ x] I have searched (google, github) for similar issues and couldn't find anything
• [ x] 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: 1.9.0
            pydantic compiled: False
                 install path: /Users/s_tsaplin/projects/github.com/sergeytsaplin/pydantic/pydantic
               python version: 3.9.13 (main, May 19 2022, 14:10:54)  [Clang 13.1.6 (clang-1316.0.21.2)]
                     platform: macOS-12.4-x86_64-i386-64bit
     optional deps. installed: ['devtools', 'dotenv', 'email-validator', 'typing-extensions']

from pydantic import BaseModel, Field

class Model(BaseModel):
        empty_string_key: int = Field(alias='')

data = {'': 123}
m = Model(**data)
m.dict(by_alias=True)

Current behavior:

The code causes the exception:

Traceback (most recent call last):
  File "<masked>/.pyenv/versions/3.10.1/lib/python3.10/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "pydantic/main.py", line 341, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for Model
empty_string_key
  field required (type=value_error.missing)

Expected result:

The code should print:

{'': 123}

Links:

• https://stackoverflow.com/questions/58916957/is-an-empty-string-a-valid-json-key
• https://datatracker.ietf.org/doc/html/rfc6901#section-5