Supabase type error when filtering RPC results

[gwax]

Bug report

• [x] I confirm this is a bug with Supabase, not with my own application.
• [x] I confirm I have searched the Docs, GitHub Discussions, and Discord.

Describe the bug

Supabase supports filtering RPC results via postgrest but the type system shows an error when attempting to do so

Errors show up as Property 'eq' does not exist on type 'PostgrestTransformBuilder<...> but the query still works as expected.

To Reproduce

Minimal reproduction is available in the gwax/rpc-filtering branch here: https://github.com/manapoolinc/supabase-playground/tree/gwax/rpc-filtering

1. Make a table returning rpc: https://github.com/manapoolinc/supabase-playground/blob/gwax/rpc-filtering/supabase/migrations/20250127194033_create_country_fns.sql#L1
2. Query the rpc with a select and a filter: https://github.com/manapoolinc/supabase-playground/blob/gwax/rpc-filtering/src/lib/db/countries.ts#L35
3. See type error in IDE, compiler, linter: https://github.com/manapoolinc/supabase-playground/blob/gwax/rpc-filtering/src/lib/db/countries.ts#L53

Essentially:

const result = await supabase
  .rpc(...)
  .select(...)
  .eq(...); // <-- This causes the error

Expected behavior

No Type Errors in reproduction code

System information

• Version of supabase: 2.6.8
• Version of supabase-js: 2.48.1