Kysely•5mo ago

Typing reusable functions for filtering rows

Hi all, we're using Kysely at our company and loving it! We recently encountered some issues when trying to type reusable functions. One example of our current attempt:

function applyFilters<T>({
  query,
  ...args
}: {
  query: SelectQueryBuilder<DB, "conversations", T>;
} & ConversationFilters): SelectQueryBuilder<DB, "conversations", T> {
  if (args.businessId) {
    query = query.where("businessId", "=", args.businessId);
  }
  ...
  return query;
}

function applyFilters<T>({
  query,
  ...args
}: {
  query: SelectQueryBuilder<DB, "conversations", T>;
} & ConversationFilters): SelectQueryBuilder<DB, "conversations", T> {
  if (args.businessId) {
    query = query.where("businessId", "=", args.businessId);
  }
  ...
  return query;
}

This works when our initial query is basic like this:

let query = getDb().selectFrom("conversations");

let query = getDb().selectFrom("conversations");

However, it stops working when we add some joins (which shouldn't break the original filtering function anyway):

let query = getDb()
      .selectFrom("conversations")
      .leftJoin(
        "contactConversations",
        "contactConversations.conversationId",
        "conversations.id",
      )

let query = getDb()
      .selectFrom("conversations")
      .leftJoin(
        "contactConversations",
        "contactConversations.conversationId",
        "conversations.id",
      )

If we update the SelectQueryBuilder middle type to be "conversations" | "contactConversations", it works with neither the simpler, nor the more "complex" query. I'd be thankful for any pointers and general tips on how to type reusable functions!

3 Replies

Unknown User•5mo ago

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lukas.slezevicius•5mo ago

Right, thanks! But how do we type the function to accept SelectQueryBuilder in a flexible manner?

Unknown User•5mo ago

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Typing reusable functions for filtering rows