[aethr]

Using `as` in TypeScript is a dangerous practice, since it sidesteps the entire type safety system. If it has to be used, it should be used minimally, in controlled circumstances. Using a system like this allows your types to be specified in a very small surface for re-use. If they have to be changed, they can be changed in one place (the schema) which will cause type warnings to flow out if there are any problems.

Futhermore, a lot of the value of these systems is to provide type safety within the query. You choose a typed column in your select clause, and then in your join or where clause the column type is inferred, and warns you if you attempt a comparison that doesn't work with that type.

If the purpose of TypeScript is to add type safety to your logic, why wouldn't you want type safety in the logic that happens to be database queries? I haven't used this library but have used kysely which seems very similar, and all the benefits I enjoy from TypeScript, I now enjoy in my SQL.

> It seems like a step back to have to write SQL in Javascript syntax with a non-standard API.

Like TypeScript, this is an attempt to add type safety and hinting to an untyped language: SQL. With that in mind, some compromises seem inevitable.

[jmull]

> …why wouldn't you want type safety in the logic that happens to be database queries?

The problem is you’re writing queries in Litdb’s Javascript/typescript-based query language instead of SQL, but the types it provides still aren’t real — you need to ensure they match the data some other way, just like with “as”.

What the types here really accomplish is code-completion. That’s nice but there are ways to do that without giving up real SQL. Not to mention databases have their own type systems, which differ from each other and typescript. Maybe they nail all the mapping, but I suspect their are misses (probably by not allowing valid things, since typescript is generally more strict that dbms’s).

[aethr]

Systems like litdb typically include (or work alongside) a schema migration tool, which either reads the current structure of the database and writes that back to a TypeScript file, or reads a TypeScript/schema file and generates a migration to update the database to match the schema. I haven't seen one that works perfectly, and it's up to you to keep it up to date, but as I said it shrinks the surface of where "mistypes" can occur.

It's quite similar to working with a web API. You can invent all the types you want, maybe generated from an OpenAPI schema, but if the server sends something different, TypeScript can't help you. That's not what TypeScript is for.

At the end of the day, most non-scalar TypeScript types "aren't real". Objects can be mutated at runtime, libraries can ship incorrect types, TS can be mixed with JS, etc. We try to introduce types as early as possible to catch a wide swath of possible errors, but where it's really important you still need to verify at runtime.