No standard way to define schema for key in "Record-like" objects

[npdev453]

Original issue:
sinclairzx81/typebox#601

I don't like when Record-like objects used in JSON-related things (API, Generators, Validators), basically, I think it because I have "childhood trauma" about JSONSchema that can't strictly declare left side of it.

Args:

• Record-like objects closely woven in JS routine
• no properly way to define its schema of key (like PositiveInt, format:'phone' & etc.)
• no properly way to document it (title, description & etc.)
• jsonschema -> ts (and I think others) generators can't properly generate key type, only indirectly
• can be useful with additionalProperties: true
• will be nice to have option to $ref that key

Input Examples:

const wasWindy = {
    '2018-11-12': true,
    '2018-11-13': false,
    ...
};
// [key: date] : boolean

const sensors = {
    '4c191b6b-fa2c-4aae-bb2a-26fb365c99b3': { active: true },
    'c8f20fd4-138f-4c50-84f9-2eff76300973': { active: false },
    ...
};  
// [key: UUID] : { active: boolean }
// or nominal: (that also can't be reproduced from schema)
// [key: SensorId] : SensorStatus

I don't see a clear way for now, but for the start:
Variant 1:

{ // some extra keys for left & right side
    type: "object",
    keys?: (string | number | sym) scheme, // or
    indexSignature?:  (string | number | sym) scheme, // maybe
    property?: (any) scheme,
    properties?: {}
}

Variant 2:

{ // new type 
    type: "record",
    key: (string | number | sym) scheme,
    value: ...
}

Variant 3:

{ // new key for left side
    type: "object",
    properties: {},
    additionalProperties: (any) scheme
    additionalKeys?: (string | number | sym) scheme,
}

---

Refs:
https://www.typescriptlang.org/docs/handbook/utility-types.html#recordkeys-type
https://www.typescriptlang.org/docs/handbook/2/objects.html#index-signatures

[jdesrosiers]

I'm not entirely following what you're asking for here, but you might be interested in the propertyNames keyword that allows you to define a schema that applies to all properties in an object. Here's a schema that would describe your first example.

{
  "type": "object",
  "description": "Was Windy Record",
  "patternProperties": {
    "": { "type": "boolean" }
  },
  "propertyNames": {
    "description": "The date it was windy",
    "$comment": "'type: string' is implicit because a property name isn't allowed to be anything else in JSON",
    "format": "date"
  }
}

[npdev453]

Yeah, it is! Thanks!

Sorry for the panic, never seen it before (think because Swagger don't support this field)