AdditionalProperties true by default

[injeniero]

Hi @LucasRoesler!

While I was working on the issue #136 I found that starting from OpenAPI 3.0.2 they clarified that additionalProperties is true by default.

The current implementation does not follow this. So wanted to start a discussion on this, should this be fixed?

[injeniero]

I personally don't like the idea of having to set additionalProperties: false on every schema. Feels like an odd direction to follow, but it is the standard. Not sure how many generators respect this.

I would be fine not following it and explain that in the documentation. I think the current implementation is as follow:

Object with no properties

Here it assumes additionalProperties: true

type: object

map[string]interface{}

Object with additionalProperties set to true|{}

This is just like not setting it

type: object
additionalProperties: true|{}

map[string]interface{}

Object with additionalProperties set to false

This is a weird case, but it should be supported.

type: object
additionalProperties: false

struct{}

Object with properties

It assumes additionalProperties: false

type: object
properties:
  field1:
    type: string

struct {
  Field1 string
}

Object with properties and additionalProperties set to true|{}

type: object
properties:
  field1:
    type: string
additionalProperties: true|{}

struct {
  Field1 string
  AdditionalProperties map[string]interface{}
}

[LucasRoesler]

I very much agree with you, this is a weird default and would be very annoying to model and use in Go. I would rather document this as an exception.

[LucasRoesler]

I guess we could also consider a flag --strict to toggle this behavior.

But it is definitely not something I would use. When I am designing an API I never assume additional properties, I design the fields I want and only rarely allow additional properties when the application needs it.

[injeniero]

Great, I was also thinking on the "--strict" flag, but that could be something for the future.