Make InputFieldJSONSchema.properties work with specialized types

[jonathaningram]

InputFieldJSONSchema is a base type that can be specialized. E.g. InputField specializes it.

However, in the base type, properties is defined in terms of a specialized type.

This makes it hard to correctly type properties. For example, specializing InputField with, say, EditableInputField means that properties would be defined in terms of InputField, not EditableInputField.

Instead, we can use TypeScript's polymorphic this type to define properties.

Testing

Let's define some sample input field arrays to demonstrate:

const xs: InputFieldJSONSchema[] = [
  {
    label: 'l',
    type: 'string',
    description: 'd',
    properties: {
      a: {
        label: 'a',
      }
    },
  }
];

const ys: InputField[] = [
  {
    label: 'l',
    type: 'string',
    description: 'd',
    properties: {
      a: {
        label: 'a',
      }
    },
  }
];

Compare how TS sees these two arrays of input fields.

Old code

TS only understands that properties is a map of InputField, which makes sense because it's hard coded.

For xs:

And ys:

New code

TS uses the specialized type for the properties map.

For xs:

For ys:

Add a new specialized type EditableInputField:

interface EditableInputField extends InputField {
  value: FieldValue;
}

And a test array for this:

const zs: EditableInputField[] = [
  {
    label: 'l',
    type: 'string',
    description: 'd',
    value: {
      '@path': '$.l'
    },
    properties: {
      a: {
        label: 'a',
      }
    },
  }
];

And we can see that TS also correctly understands that properties is now this specialized type: