Default type to object if undefined

[domharrington]

Prerequisites

• I have read the documentation;
• In the case of a bug report, I understand that providing a SSCCE example is tremendously useful to the maintainers.
• Ideally, I'm providing a sample JSFiddle or a shared playground link demonstrating the issue.

Description

Can we default the type to object if it's undefined? We accept user submitted JSON Schemas and this is a common thing that people miss. I'm not 100% sure if it's valid JSON Schema or not, but https://www.jsonschemavalidator.net/ appears to say the following is valid:

{
  "properties": {
    "a": {
      "type": "string"
    }
  }
}

But when passing that into this module, we get the following error:

Playground link: https://mozilla-services.github.io/react-jsonschema-form/#eyJmb3JtRGF0YSI6e30sInNjaGVtYSI6eyJwcm9wZXJ0aWVzIjp7ImEiOnsidHlwZSI6InN0cmluZyJ9fX0sInVpU2NoZW1hIjp7fX0=

Steps to Reproduce

1. Pass in a JSON Schema without a type
2. Observe that the UnsupportedField is instantiated

Expected behavior

Default type to object if it is undefined
If type is set to something that is unknown, still create the UnsupportedField e.g. type: 'someothertype'

Affected blocks of code:
Could check for undefined in here and return object: https://github.com/mozilla-services/react-jsonschema-form/blob/2d63594e075bba3b134ef09709c773a9ea037923/src/utils.js#L68-L84

This is where it will bubble up to, but I don't think this code would have to change at all: https://github.com/mozilla-services/react-jsonschema-form/blob/2d63594e075bba3b134ef09709c773a9ea037923/src/components/fields/SchemaField.js#L49-L59

Happy to send over a PR for this if it'll get accepted!

Version

v1.5.0

[epicfaace]

Yes, I believe that makes sense.

Why would you make the default type object when undefined? Wouldn't it be enough just to make the type default to object only if a properties keyword is defined as well?

[domharrington]

Yeah that would also work, though you'd then also have to check for additionalProperties as well. Any other edge cases you can think of?

[epicfaace]

I think that's it!