String passed to field: List[str] gets coerced in a very unexpected way

[pawelswiecki]

Using Python 3.6.5 and pydantic==0.10.

from typing import List                                                        
import pydantic                                                                
                                                                               
                                                                               
class User(pydantic.BaseModel):                                                
    name: str                                                                  
    aliases: List[str]                                                         
                                                                               
                                                                               
u1 = User(name='Bob', aliases=['Panther-Man', 'The Janitor'])  # should validate, and it does
print(u1)                                                                      
# User name='Bob' aliases=['Panther-Man', 'The Janitor']                     
                                                                               
u2 = User(name='Bob', aliases='Small Bob')  # should not validate, but it does 
print(u2)                                                                      
# User name='Bob' aliases=['S', 'm', 'a', 'l', 'l', ' ', 'B', 'o', 'b']

String seems to be treated as an Iterable of (sub)strings (technically it's true in Python), which leads to very unexpected behavior, to say the least; I'd call it a bug, even.

I hope it could be changed in the future, but how can I deal with it in the current version of pydantic?

[samuelcolvin]

I think this is fixed by #200, will be released soon.

[pawelswiecki]

Great, thank you!

[pawelswiecki]

@samuelcolvin I'm on pydantic=0.11.1 and I'm still getting

User name='Bob' aliases=['S', 'm', 'a', 'l', 'l', ' ', 'B', 'o', 'b']

instead of validation error.

[samuelcolvin]

Yes, looks like #200 only works if you use aliases: list not aliases: List[str]. Sorry about that.

[pawelswiecki]

No problem. Thank you for developing this library :)

[samuelcolvin]

Should be fixed by #225, would be very useful if you could check that out and confirm it does everything you need.

[pawelswiecki]

WOW, thanks for so quick fix.

So, I've pip installed from github at this particular commit and List[str] works as expected. My other use-case (which I did not mention), that is List[SomeStringBasedEnum], also validates as expected!

Thank you again :)

[samuelcolvin]

Merged, I'll deploy this in a few days.

[pawelswiecki]

Great, it will simplify my code :)