fix: translate parent_as/1 references in correlated subqueries

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+
+- **Correlated Subqueries with `parent_as/1`** - The `parent_as/1` field references that correlate a subquery to its parent query had no `expr/3` clause and fell through to the catch-all, which rendered them as a bare `?` placeholder: the next bound parameter stood in for the field, silently changing the query. They are now translated to the parent query's source, as in the `ecto_sqlite3` adapter.
+
 ## [0.9.1] - 2026-05-07
 
 ### Fixed

lib/ecto/adapters/libsql/connection.ex

@@ -672,6 +672,15 @@ defmodule Ecto.Adapters.LibSql.Connection do
   defp quote_table(nil, name), do: quote_name(name)
   defp quote_table(prefix, name), do: quote_name(prefix) <> "." <> quote_name(name)
 
+  # Index and sources of the query named `as`, looked up through the parents
+  # of a subquery.
+  defp get_parent_sources_ix(query, as) do
+    case query.aliases[@parent_as] do
+      {%{aliases: %{^as => ix}}, sources} -> {ix, sources}
+      {%{} = parent, _sources} -> get_parent_sources_ix(parent, as)
+    end
+  end
+
   defp quote_name(name) when is_atom(name), do: quote_name(Atom.to_string(name))
 
   defp quote_name(name) do
@@ -1193,6 +1202,15 @@ defmodule Ecto.Adapters.LibSql.Connection do
     [name, ?. | quote_name(field)]
   end
 
+  # Field of a parent query named with `as:`, in a correlated subquery:
+  # parent_as(:user).id -> s0.id
+  defp expr({{:., _, [{:parent_as, _, [as]}, field]}, _, []}, _sources, query)
+       when is_atom(field) or is_binary(field) do
+    {ix, sources} = get_parent_sources_ix(query, as)
+    {_, name, _} = elem(sources, ix)
+    [name, ?. | quote_name(field)]
+  end
+
   # Table reference: &0 -> s0
   defp expr({:&, _, [idx]}, sources, _query) do
     {_, name} = get_source(nil, sources, idx)

test/in_expression_comprehensive_test.exs

@@ -507,4 +507,35 @@ defmodule EctoLibSql.InExpressionComprehensiveTest do
       assert "item3" in result
     end
   end
+
+  describe "parent_as/1 - correlated subqueries" do
+    test "IN clause with a subquery referring to the parent query" do
+      Ecto.Adapters.SQL.query!(TestRepo, """
+      INSERT INTO test_items (id, state, name, inserted_at, updated_at)
+      VALUES (1, 'scheduled', 'job1', datetime('now'), datetime('now')),
+             (2, 'completed', 'job2', datetime('now'), datetime('now'))
+      """)
+
+      Ecto.Adapters.SQL.query!(TestRepo, """
+      INSERT INTO archived_items (item_id, state, name, inserted_at, updated_at)
+      VALUES (1, 'archived', 'job1_archived', datetime('now'), datetime('now'))
+      """)
+
+      # BEFORE FIX: parent_as/1 fell through to the catch-all expr clause,
+      # generating "?" in place of t.id: the next parameter was bound to it.
+      archived =
+        from(a in "archived_items",
+          where: a.item_id == parent_as(:item).id and a.state == ^"archived",
+          select: a.item_id
+        )
+
+      query =
+        from(t in "test_items", as: :item, where: t.id in subquery(archived), select: t.name)
+
+      {sql, _params} = Ecto.Adapters.SQL.to_sql(:all, TestRepo, query)
+      assert sql =~ ~r/\."item_id" = s0\."id"/
+
+      assert TestRepo.all(query) == ["job1"]
+    end
+  end
 end