From 1835e95c287be0c2b7a5889bc05614ce2c88dd35 Mon Sep 17 00:00:00 2001
From: Jonas Grau <108088+jgrau@users.noreply.github.com>
Date: Mon, 28 Sep 2026 11:47:54 +0200
Subject: [PATCH] Fix relation ids for composite primary keys
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Use the column helper’s composite-aware id path so RBI generation accepts an array primary key and returns typed tuples. Cover composite and nonstandard scalar keys in the Relations compiler specs.

Pax-Session: interactive:terminal/01a0e468-c6cd-7049-8a4c-01fc37048a82
Pax-Origin: interactive:terminal
Co-authored-by: Pax <262454628+hey-pax@users.noreply.github.com>
---
 .../dsl/compilers/active_record_relations.rb  |  3 +-
 .../compilers/active_record_relations_spec.rb | 48 +++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/lib/tapioca/dsl/compilers/active_record_relations.rb b/lib/tapioca/dsl/compilers/active_record_relations.rb
index 1dea3adb7..ccdec2524 100644
--- a/lib/tapioca/dsl/compilers/active_record_relations.rb
+++ b/lib/tapioca/dsl/compilers/active_record_relations.rb
@@ -794,8 +794,7 @@ def create_common_methods
                   constant,
                   column_type_option: Tapioca::Dsl::Helpers::ActiveRecordColumnTypeHelper::ColumnTypeOption::Persisted,
                 )
-                primary_key = constant.primary_key
-                getter_type, _setter_type = column_type_helper.type_for(primary_key)
+                getter_type, _setter_type = column_type_helper.type_for("id")
                 type = getter_type
                 create_common_method("ids", return_type: "T::Array[#{type}]")
               else
diff --git a/spec/tapioca/dsl/compilers/active_record_relations_spec.rb b/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
index e7a0f3dbc..af3ff4e1f 100644
--- a/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
+++ b/spec/tapioca/dsl/compilers/active_record_relations_spec.rb
@@ -778,6 +778,54 @@ def not(opts, *rest); end
               assert_equal(expected, rbi_for(:Post))
             end
 
+            it "generates typed ids for a nonstandard scalar primary key" do
+              add_ruby_file("schema.rb", <<~RUBY)
+                ActiveRecord::Migration.suppress_messages do
+                  ActiveRecord::Schema.define do
+                    create_table :posts, id: :string, primary_key: :code
+                  end
+                end
+              RUBY
+
+              add_ruby_file("post.rb", <<~RUBY)
+                class Post < ActiveRecord::Base
+                end
+              RUBY
+
+              expected = indented(<<~RBI, 4)
+                sig { returns(T::Array[::String]) }
+                def ids; end
+              RBI
+
+              assert_includes(rbi_for(:Post), expected)
+            end
+
+            it "generates typed ids for composite primary keys" do
+              add_ruby_file("schema.rb", <<~RUBY)
+                ActiveRecord::Migration.suppress_messages do
+                  ActiveRecord::Schema.define do
+                    create_table :posts, primary_key: [:listing_id, :checkin_on, :checkout_on] do |t|
+                      t.string :listing_id, null: false
+                      t.date :checkin_on, null: false
+                      t.date :checkout_on, null: false
+                    end
+                  end
+                end
+              RUBY
+
+              add_ruby_file("post.rb", <<~RUBY)
+                class Post < ActiveRecord::Base
+                end
+              RUBY
+
+              expected = indented(<<~RBI, 4)
+                sig { returns(T::Array[[::String, ::Date, ::Date]]) }
+                def ids; end
+              RBI
+
+              assert_includes(rbi_for(:Post), expected)
+            end
+
             it "generates handles composite primary keys" do
               add_ruby_file("post.rb", <<~RUBY)
                 class Post < ActiveRecord::Base