With the input validator we can ensure that FarcasterRelationshipRequests that reach the responder will have exactly two entries.

However, there's no way (that I know of) to encode that requirement using flow. Another thing I considered, but scrapped, was something like:

export type FarcasterRelationshipRequest = {
  action: 'farcaster',
  user1ID: string,
  user1FID: string,
  user2ID: string,
  user2FID: string
};

which I felt was clunky and more difficult to work with, but would allow the "two user requirement" to be enforced by type system.

Don't think it really matters but CC @ashoat, @tomek

One option to consider is having a dedicated object describing the relationship:

type UserIDToFID = {
  +userID: string,
  +userFID: string,
};

export type FarcasterRelationshipRequest = {
  +action: 'farcaster',
  +user1: UserIDToFID,
  +user2: UserIDToFID,
};

Yeah! It'll be updated to RelationshipActionSansFarcaster later in the stack,

True, that would definitely be better than the

export type FarcasterRelationshipRequest = {
  action: 'farcaster',
  user1ID: string,
  user1FID: string,
  user2ID: string,
  user2FID: string
};

solution that I proposed.

Will go with what's in the diff for now since I think it's convenient to be able to index in via comm userID for our use case.