don't allow undeclared object properties

[jaymccon]

Thanks for the great work on this project, been really useful thus far.

We used "additionalProperties": false for objects in our (hand-written) json-schema's, which was helpful to prevent invalid inputs. In this project I see no way of achieving the same.

from dataclasses import dataclass
from dataclasses_jsonschema import JsonSchemaMixin

@dataclass
class Point(JsonSchemaMixin):
    "A 2D point"
    x: float
    y: float

# adding an additional key to the dict results in the key being dropped
print(Point.from_dict({"x": 1.1, "y": 2.2, "z": 3.3}))
Point(x=1.1, y=2.2)

This is especially problematic with items that have defaults, if a field name is typod validation will still pass, but the resulting object will have unexpected values.

desired validation can be achieved by updating dataclass_jsonschema/__init__.py on line 690:

schema = {
                'type': 'object',
                'required': required,
                'properties': properties,
                'additionalProperties': False
            }

Point.from_dict({"x": 1.1, "y": 2.2, "z": 3.3})
Traceback (most recent call last):
  File "/Users/jmmccon/.pyenv/versions/taskcat-v9-3.6.9/lib/python3.6/site-packages/dataclasses_jsonschema/__init__.py", line 421, in _validate
    validate_func(data, cls.json_schema())
  File "/Users/jmmccon/.pyenv/versions/taskcat-v9-3.6.9/lib/python3.6/site-packages/jsonschema/validators.py", line 899, in validate
    raise error
jsonschema.exceptions.ValidationError: Additional properties are not allowed ('z' was unexpected)

I'm happy to pr a change, but not sure if I've missed some way to do this that is already catered for, or even if others want this behavior (One thought to make it optional is to provide an additional mixin StrictJsonSchemaMixin that adds this)

[s-knibbs]

I could probably add a class argument to control whether additional properties are allowed or not:

class Person(JsonSchemaMixin, allow_additional_props=False):
    name: str
    age: int

This will need to be False by default to preserve backwards compatibility.

[jaymccon]

thanks for this @s-knibbs. When can we expect a release to pip ?

[s-knibbs]

This has now been released in v2.10.0