add WebhookPayload definition

[donny-dont]

Add WebhookPayload which contains a discriminator to map the different payload types based on the value of event_type.

[ahurtado-figma]

LGTM!

[ahurtado-figma]

Took another look and leaving a request for further explanation. At face value, this change makes sense to me -- but how do you see the WebhookPayload being used in this repo? It make sense to me that each webhook endpoint returns a different webhook payload type

[donny-dont]

Took another look and leaving a request for further explanation. At face value, this change makes sense to me -- but how do you see the WebhookPayload being used in this repo? It make sense to me that each webhook endpoint returns a different webhook payload type

👋 thanks for looking at this @ahurtado-figma !

So the point of adding WebhookPayload is to more accurately reflect a class hierarchy within the spec. OpenAPI uses this concept of a discriminator where it specifies a type to map to based on the value of a property. In this case each type defined in the oneOf section of WebhookPayload has a corresponding value of the event_type property that maps to that different type.

So in the case of generated code from the OpenAPI definition for a typed language there can be a WebhookPayload class that has a factory constructor which looks at event_type then creates the correct WebhookPayload class from the JSON data.

Within this repository this functionality is used in a few places. Here's Effect as an example.

rest-api-spec/openapi/openapi.yaml

Lines 5075 to 5090 in 04e02c3

	Effect:
	oneOf:
	- $ref: "#/components/schemas/DropShadowEffect"
	- $ref: "#/components/schemas/InnerShadowEffect"
	- $ref: "#/components/schemas/BlurEffect"
	- $ref: "#/components/schemas/TextureEffect"
	- $ref: "#/components/schemas/NoiseEffect"
	discriminator:
	propertyName: type
	mapping:
	DROP_SHADOW: "#/components/schemas/DropShadowEffect"
	INNER_SHADOW: "#/components/schemas/InnerShadowEffect"
	LAYER_BLUR: "#/components/schemas/BlurEffect"
	BACKGROUND_BLUR: "#/components/schemas/BlurEffect"
	TEXTURE: "#/components/schemas/TextureEffect"
	NOISE: "#/components/schemas/NoiseEffect"

[donny-dont]

For some additional context I'm working on a client library in Dart and am converting the JSON values from the Figma API into Dart types. So by the definition having a discriminator I can generate a base class WebhookPayload that has a factory constructor which converts the JSON payload into a type.

abstract class WebhookPayload extends Equatable {
  const WebhookPayload({
    required this.passcode,
    required this.timestamp,
    required this.webhookId,
  });

  factory WebhookPayload.fromJson(Map<String, Object?> json) {
    final discriminator = json['event_type'];
    final construct = switch (discriminator) {
      'PING' => PingPayload.fromJson,
      'FILE_UPDATE' => FileUpdatePayload.fromJson,
      'FILE_DELETE' => FileDeletePayload.fromJson,
      'FILE_VERSION_UPDATE' => FileVersionUpdatePayload.fromJson,
      'LIBRARY_PUBLISH' => LibraryPublishPayload.fromJson,
      'FILE_COMMENT' => FileCommentPayload.fromJson,
      'DEV_MODE_STATUS_UPDATE' => DevModeStatusUpdatePayload.fromJson,
      _ => throw ArgumentError.value(
        discriminator,
        'event_type',
        'unknown event_type',
      ),
    };

    return construct(json);
  }

  /// Discriminator for [WebhookPayload] types.
  WebhookEvent get eventType;
}

You can see from ☝️ that it looks at the value of event_type and then calls the appropriate constructor based on that.

A good chunk of the patches I have locally are adding discriminators so I'd like to know if this change is acceptable before preparing those patches.