Add support for json_agg_strict (PostgreSQL only)

[leibale]

Add support for json_agg_strict (PostgreSQL only) - this function is just like json_agg, but skips null (see https://www.postgresql.org/docs/current/functions-aggregate.html)

A few notes:

1. I've duplicated all json_agg tests and changed them to use json_agg_strict, but I'm not sure if:
   1. Should we test all cases for both json_agg and json_agg_strict?
   2. If we want to fully test both, do you prefer duplicating the code, using a loop, or using a function?
2. json_agg might return null (for example, when using left join and there is nothing to join with), but the types ignore that.. I guess fixing it is a breaking change, so I did not include it in this PR

Thanks for this awesome package! :)

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Name	Status	Preview	Comments	Updated (UTC)
kysely	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Apr 21, 2024 10:28am

[leibale]

When using it with left join every field becomes nullable (I think that left join changes DB[table] to a "nullable version"), which is not true for json_agg (which will reply with [null] for "empty join", or json_agg_strict (which will reply with [] for "empty join").
I'm not too sure if this will be easy to solve.. any help will be appreciated :)

[igalklebanov]

Hey 👋

Thanks! 🙏

I'm on the fence on this one for now:

• This only collected 2 reactions in almost a year.
• It is supported just in PostgreSQL.
• It can be achieved in other ways:

const results = await db
  .selectFrom("person")
  .leftJoin("pet", "pet.owner_id", "person.id")
  .groupBy("person.first_name")
  .select((eb) => [
    "first_name",
    eb.fn
      .coalesce( // <-- ensures defaults to empty array instead of null
        eb.fn
          .jsonAgg("pet")
          .filterWhere("pet.owner_id", "is not", null), // <-- removes null rows
        sql.lit("[]"),
      )
      .as("pets"),
  ])
  .$narrowType<{ pets: Selectable<PetTable>[] }>() // <-- this makes all pet fields not nullable in a type-safe way.
  .execute();

https://kyse.link/ZIU7y