Fix enum array error

CHANGELOG.md

@@ -1,5 +1,10 @@
 # CHANGELOG
 
+## Unreleased
+
+- Fixed a bug where queries with enum arrays would cause an error.
+  ([Leah Ulmschneider](https://github.com/leah-u))
+
 ## v2.0.4 - 2024-12-04
 
 - Replace deprecated `gleam/regex` module with `gleam/regexp`.

birdie_snapshots/enum_array_decoding.accepted

@@ -0,0 +1,60 @@
+---
+version: 1.2.3
+title: enum array decoding
+file: ./test/squirrel_test.gleam
+test_name: enum_array_decoding_test
+---
+import decode/zero
+import pog
+
+/// A row you get from running the `query` query
+/// defined in `query.sql`.
+///
+/// > 🐿️ This type definition was generated automatically using v-test of the
+/// > [squirrel package](https://github.com/giacomocavalieri/squirrel).
+///
+pub type QueryRow {
+  QueryRow(res: List(SquirrelColour))
+}
+
+/// Runs the `query` query
+/// defined in `query.sql`.
+///
+/// > 🐿️ This function was generated automatically using v-test of
+/// > the [squirrel package](https://github.com/giacomocavalieri/squirrel).
+///
+pub fn query(db) {
+  let decoder = {
+    use res <- zero.field(0, zero.list(squirrel_colour_decoder()))
+    zero.success(QueryRow(res:))
+  }
+
+  let query = "select array['red'::squirrel_colour] as res"
+
+  pog.query(query)
+  |> pog.returning(zero.run(_, decoder))
+  |> pog.execute(db)
+}
+
+// --- Enums -------------------------------------------------------------------
+
+/// Corresponds to the Postgres `squirrel_colour` enum.
+///
+/// > 🐿️ This type definition was generated automatically using v-test of the
+/// > [squirrel package](https://github.com/giacomocavalieri/squirrel).
+///
+pub type SquirrelColour {
+  LightBrown
+  Grey
+  Red
+}
+
+fn squirrel_colour_decoder() {
+  use variant <- zero.then(zero.string)
+  case variant {
+    "light brown" -> zero.success(LightBrown)
+    "grey" -> zero.success(Grey)
+    "red" -> zero.success(Red)
+    _ -> zero.failure(LightBrown, "SquirrelColour")
+  }
+}

src/squirrel/internal/database/postgres.gleam

@@ -60,6 +60,12 @@ select
     else elem.typname
  	end as type,
 
+  -- The oid of the type or the array item type.
+  case
+    when elem.typname is null then type.oid
+    else elem.oid
+ 	end as oid,
+
   -- Tells us how to interpret the first column: if this is true then the first
   -- column is the type of the elements of the array type.
   -- Otherwise it means we've found a base type.
@@ -664,13 +670,14 @@ fn find_gleam_type(query: UntypedQuery, oid: Int) -> Db(gleam.Type) {
   let params = [pg.Parameter(<<oid:32>>)]
   use res <- eval.try(run_query(find_postgres_type_query(), params, [23]))
 
-  // We know the output must only contain two values: the name and a boolean to
-  // check wether it is an array or not.
+  // We know the output must only contain four values: the name, the oid, a boolean to
+  // check wether it is an array or not and the type of the type / array item.
   // It's safe to assert because this query is hard coded in our code and the
   // output shape cannot change without us changing that query.
-  let assert [[name, is_array, kind]] = res
+  let assert [[name, oid, is_array, kind]] = res
   let assert Ok(name) = bit_array.to_string(name)
   let assert Ok(kind) = bit_array.to_string(kind)
+  let assert <<oid:size(32)>> = oid
 
   use type_ <- eval.try(case kind {
     "e" -> resolve_enum_type(name, oid)

test/squirrel_test.gleam

@@ -426,6 +426,12 @@ pub fn enum_encoding_test() {
   |> birdie.snap(title: "enum encoding")
 }
 
+pub fn enum_array_decoding_test() {
+  "select array['red'::squirrel_colour] as res"
+  |> should_codegen
+  |> birdie.snap(title: "enum array decoding")
+}
+
 // --- CODEGEN STRUCTURE TESTS -------------------------------------------------
 // This is a group of tests to ensure the generated code has some specific
 // structure (e.g. the names and comments are what we expect...)