Amending into a Mapping inside a class

[fhalde]

I have the following class

class User {
  name: String
  properties: Mapping<String, String>?
}

and the following JSON which is a partial representation of User

{ "name": "foo" }

I read this json in my pkl and use the deepToTyped to convert it into a User instance

me: User = deepToTyped.apply(User, read(<json>))

How can someone amend the properties Mapping?

me: User = (deepToTyped.apply(User, read(<json>))) {
 properties = new Mapping {
   ["x"] = "ok"
 }
}

works, however, it wipes out the properties if they were there in JSON

{ "name": "foo", "properties": { "y": "notok" } }

[fhalde]

My requirements is to ensure, both the remote properties & locally defined properties get merged into the final properties Mapping

[fhalde]

At first I thought I could just set a default in the class

properties: Mapping<String, String>? = new Mapping {}

but this failed with an error

Expected value of type `Mapping`, but got type `Dynamic`.
Value: new Dynamic { ["x"] = ? }

me: User = (deepToTyped.apply(User, read(<json>))) {
 properties {
   ["x"] = "ok"
 }
}

[fhalde]

This worked after I did the following change

properties: Mapping<String, String>? = new Mapping { }

to

properties: Mapping<String, String> = new Mapping { }

removing the optionality ?
not sure why though

[bioball]

I haven't dug into this, but, it's probably because of these lines: https://github.com/apple/pkl-pantry/blob/b7d8b68eb980d3cb6f6babb16537580425419fd6/packages/pkl.experimental.deepToTyped/deepToTyped.pkl#L129-L132

properties: Mapping<String, String>? is sugar for: properties: Mapping<String, String>? = Null(new Mapping<String, String> {})

Null(new Mapping<String, String> {}) is a different null than the null literal; they behave differently when amended.

This is probably a bug in deepToTyped, feel free to create a GitHub issue for it (or submit a PR to fix it)

[fhalde]

you're right !!