Feature request: Templates for conditional queries

[o-dasher]

It would be interesting to have a way to declare a conditional query template that would help reduce a lot of code repetition such as in this case. It could work something along the way of this "pseudo-like code":

    create_query_template!(
       id_kind,
       match kind {
           SettingKind::Guild => "guild",
           SettingKind::Channel => "channel",
           SettingKind::User => "user"
       }
   );

   sqlx_conditional_queries::conditional_query_as!(
       BigID,
       "
       INSERT INTO discord_{#id_kind} (id{#args}) VALUES ({to_id}{#binds})
       ON CONFLICT DO NOTHING RETURNING id
       ",
       #(with(id_kind), args, binds) = match kind {
           SettingKind::Guild => ("", ""),
           SettingKind::Channel => (", guild_id", ", {guild_id_stored}"),
           SettingKind::User => ("", "")
       }
   )
   .fetch_one(pool)
   .await?;

   let booru_setting_insertion = sqlx_conditional_queries::conditional_query_as!(
       ID,
       "
       INSERT INTO booru_setting ({#id_kind}_id) VALUES ({to_id})
       ON CONFLICT DO NOTHING RETURNING id
       ",
       #with(id_kind)
   )
   .fetch_one(pool)
   .await?;

[o-dasher]

Just giving an update I did somewhat of an implementation of this using another macro: https://github.com/o-dasher/sqlx-conditional-queries-layering if you find it interesting as a proof-of-concept or whatever

[kyrias]

@o-dasher Hey, sorry for not responding to this yet. Overall I think the idea is interesting, but I feel like how you actually use it and what the new macros actually do feels a bit non-obvious.

In particular, looking at the example in your repo I feel like if someone were to start reading the code of a project using it without already being familiar with what these macros do, I don't think they would be likely to understand what's actually going on.

For instance, it's very unclear to me looking at the code that feed_keehee_query was generated by create_conditional_query_as. I feel like the UI would be much clearer if there was a single macro you used where you passed in the old and new macro names, even if it ended up expanding to the same thing internally. Similarly it doesn't feel obvious that keehee_query and lewdy are names for new macros being emitted.

(This also feels like something that would be helped a lot by postfix macros, hmm.)

[o-dasher]

https://github.com/o-dasher/sqlx-conditional-queries-layering/blob/main/example%2Fsrc%2Fmain.rs still didn't document it, but now I believe it should be way better than before, better meaning understanding what actually goes on