wip: first draft of a unit test to reproduce this type of issue:

lib/sql_implementation.ex

@@ -154,21 +154,21 @@ defmodule AshPostgres.SqlImplementation do
   end
 
   def expr(
-    query,
-    %Ash.Query.Ref{
-      attribute: %Ash.Resource.Attribute{
-        type: attr_type,
-        constraints: constraints,
-      },
-      bare?: true
-    } = ref,
-    bindings,
-    embedded?,
-    acc,
-    type
-  ) do
+        query,
+        %Ash.Query.Ref{
+          attribute: %Ash.Resource.Attribute{
+            type: attr_type,
+            constraints: constraints
+          },
+          bare?: true
+        } = ref,
+        bindings,
+        embedded?,
+        acc,
+        type
+      ) do
     if function_exported?(attr_type, :postgres_reference_expr, 3) do
-      non_bare_ref = %Ash.Query.Ref{ ref | bare?: nil }
+      non_bare_ref = %Ash.Query.Ref{ref | bare?: nil}
       {expr, acc} = AshSql.Expr.dynamic_expr(query, non_bare_ref, bindings, embedded?, type, acc)
 
       case attr_type.postgres_reference_expr(attr_type, constraints, expr) do

priv/resource_snapshots/test_repo/co_authored_posts/20241208221219.json

@@ -0,0 +1,97 @@
+{
+  "attributes": [
+    {
+      "allow_nil?": false,
+      "default": "nil",
+      "generated?": false,
+      "primary_key?": false,
+      "references": null,
+      "size": null,
+      "source": "role",
+      "type": "text"
+    },
+    {
+      "allow_nil?": true,
+      "default": "nil",
+      "generated?": false,
+      "primary_key?": false,
+      "references": null,
+      "size": null,
+      "source": "was_cancelled_at",
+      "type": "utc_datetime"
+    },
+    {
+      "allow_nil?": false,
+      "default": "nil",
+      "generated?": false,
+      "primary_key?": true,
+      "references": {
+        "deferrable": false,
+        "destination_attribute": "id",
+        "destination_attribute_default": null,
+        "destination_attribute_generated": null,
+        "index?": false,
+        "match_type": null,
+        "match_with": null,
+        "multitenancy": {
+          "attribute": null,
+          "global": null,
+          "strategy": null
+        },
+        "name": "co_authored_posts_author_id_fkey",
+        "on_delete": null,
+        "on_update": null,
+        "primary_key?": true,
+        "schema": "public",
+        "table": "authors"
+      },
+      "size": null,
+      "source": "author_id",
+      "type": "uuid"
+    },
+    {
+      "allow_nil?": false,
+      "default": "nil",
+      "generated?": false,
+      "primary_key?": true,
+      "references": {
+        "deferrable": false,
+        "destination_attribute": "id",
+        "destination_attribute_default": null,
+        "destination_attribute_generated": null,
+        "index?": false,
+        "match_type": null,
+        "match_with": null,
+        "multitenancy": {
+          "attribute": null,
+          "global": null,
+          "strategy": null
+        },
+        "name": "co_authored_posts_post_id_fkey",
+        "on_delete": null,
+        "on_update": null,
+        "primary_key?": true,
+        "schema": "public",
+        "table": "posts"
+      },
+      "size": null,
+      "source": "post_id",
+      "type": "uuid"
+    }
+  ],
+  "base_filter": null,
+  "check_constraints": [],
+  "custom_indexes": [],
+  "custom_statements": [],
+  "has_create_action": true,
+  "hash": "E1F2AC3AED1987928E3A2446584C268EC54D0BCA616D81A495F4AB26E3999444",
+  "identities": [],
+  "multitenancy": {
+    "attribute": null,
+    "global": null,
+    "strategy": null
+  },
+  "repo": "Elixir.AshPostgres.TestRepo",
+  "schema": null,
+  "table": "co_authored_posts"
+}

priv/test_repo/migrations/20241208221219_migrate_resources44.exs

@@ -0,0 +1,48 @@
+defmodule AshPostgres.TestRepo.Migrations.MigrateResources44 do
+  @moduledoc """
+  Updates resources based on their most recent snapshots.
+
+  This file was autogenerated with `mix ash_postgres.generate_migrations`
+  """
+
+  use Ecto.Migration
+
+  def up do
+    create table(:co_authored_posts, primary_key: false) do
+      add(:role, :text, null: false)
+      add(:was_cancelled_at, :utc_datetime)
+
+      add(
+        :author_id,
+        references(:authors,
+          column: :id,
+          name: "co_authored_posts_author_id_fkey",
+          type: :uuid,
+          prefix: "public"
+        ),
+        primary_key: true,
+        null: false
+      )
+
+      add(
+        :post_id,
+        references(:posts,
+          column: :id,
+          name: "co_authored_posts_post_id_fkey",
+          type: :uuid,
+          prefix: "public"
+        ),
+        primary_key: true,
+        null: false
+      )
+    end
+  end
+
+  def down do
+    drop(constraint(:co_authored_posts, "co_authored_posts_author_id_fkey"))
+
+    drop(constraint(:co_authored_posts, "co_authored_posts_post_id_fkey"))
+
+    drop(table(:co_authored_posts))
+  end
+end