Typescript: safer nullability in functions, domain support

[ngasull]

What kind of change does this PR introduce?

Fixes #842

What is the current behavior?

CREATE DOMAIN strict_text AS text NOT NULL;

CREATE FUNCTION some_function(arg strict_text)
RETURNS table (nulltext text, stricttext strict_text)
LANGUAGE SQL AS $$
   SELECT NULL::text, arg
$$;

Generated type with supabase gen types typescript --local

export interface Database {
  public: {
    Functions: {
      some_function: {
        Args: {
          arg: unknown
        }
        Returns: {
          nulltext: string
          stricttext: unknown
        }[]
      }
    }
  }
}

What is the new behavior?

Generated types should be:

export interface Database {
  public: {
    Functions: {
      some_function: {
        Args: {
          arg: string
        }
        Returns: {
          nulltext: string | null
          stricttext: string
        }[]
      }
    }
  }
}

Please review tests for more details on new expected behavior.

• Stop accepting non-nullable types in generated function arguments and return types.
• Add support for domains and take their nullability into account.
• Centralize nullability and array logic in pgTypeToTsType.

Additional context

This is obviously a breaking change for most users using functions. It is however the safe way, exposing sound types.

[jumski]

Hey @ngasull Postgres domains have some troubles with NOT NULL constraint:

CREATE DOMAIN in Postgres cannot safely enforce a NOT NULL constraint because domains are type aliases and do not directly validate constraints at the table level. While the domain itself can define a NOT NULL constraint, the database schema still allows null values in columns of that domain type unless the column explicitly defines NOT NULL. This behavior creates inconsistency: a domain's NOT NULL constraint is ignored unless explicitly reinforced on each column, leading to potential silent failures in enforcing the constraint.

But there is definitely a problem with serializing domain types with "gen-types" - they default to undefined.

[ngasull]

@jumski This PR only aims to improve function generated types, no impact on tables. So the changes are still relevant.

Domains add a layer of safety over types at PostgreSQL runtime. Primitive types are unsafe (nullable) and it makes sense generate them as nullable unless they are a domain defined as NOT NULL.

[Donnerstagnacht]

Hi @soedirgo , just a quick ping to see if you (or another maintainer) might have a chance to take a look at this PR when you have time. It touches on issues discussed in #841 and #842 and it is open since 2 years but still relevant.

[jumski]

@ngasull thanks for clarification,
TIL that domains can enforce NOT NULL when used to type function arguments.

Everything looks fine!