Add `JsonSchema` Support for Multiple Types

[solonovamax]

Basically just JSON Schema's anyOf and/or oneOf

This feature is similar, although not identical, to #2980. (in certain cases #2980 is a replacement for this, although it does not fit all cases)

an example syntax would look like this:

val stringOrIntegerListSchema = jsonSchema {
    array {
        anyOf(string(), integer())
    }
}

"""[ "foo", "bar", "baz" ]""" shouldMatchSchema stringOrIntegerListSchema // passes
"""[ 1, 2, 3 ]""" shouldMatchSchema stringOrIntegerListSchema // passes
"""[ true, false ]""" shouldMatchSchema stringOrIntegerListSchema // fails

in order to do this, it would either be necessary to add an additional JsonSchemaElement called something like JsonCompositeElement, which composes multiple elements (imo the less desirable choice) or to change the JsonSchema.JsonObjectBuilder.properties field from a MutableMap<String, JsonSchemaElement> to a MutableMap<String, Matcher<JsonSchemaElement>> (imo the better choice)

[AlexCue987]

can you share some real life use cases where this feature would be needed?

[solonovamax]

can you share some real life use cases where this feature would be needed?

I'm trying to make a schema that matches a fabric.mod.json file. A couple of examples from it:

• the mixins field which is an array of elements that are either Strings or an object with a config key and an optional environment key, the string being equivalent to just specifying the config.
• the license field which is either an array Strings or a String. the string being equivalent to specifying a single element array.
• the icon field which is either a String or an object of String -> String. for the first case, the icon is used at all resolutions, in the second case the resolution of the icon is specified in the key.
• the authors/contributors field which is an array of either Strings or an object with a name key and an optional contact key, the string being equivalent to just specifying the name
• the entrypoints field which is an object of String -> array of String or an object with a value and an optional adapter key, the string being equivalent to just specifying the value.

I don't have any control over this schema, and am just generating some json according to this schema and want to validate it.

[solonovamax]

My serialization code can be found here if that would help: SerialFabricModJson.kt. This should be able to parse all valid fabric.mod.json files and fail on any invalid one.

[solonovamax]

Also, I sent a message in the kotlinlang's kotest slack channel, if you'd like to discuss this further there in a platform more suitable for Q&A