Fix namespaced models foreign key (#460)

First of all, thank you very much for all the effort you put into this
gem. It is amazing. 🚀

## What this does

Version 1.8.2 breaks namespaced models with custom foreign keys.
Consider the following example:
```rb
ActiveRecord::Migration.create_table :support_conversations, force: true do |t|
  t.string :model_id
  t.timestamps
end

ActiveRecord::Migration.create_table :support_messages, force: true do |t|
  t.references :conversation, foreign_key: { to_table: :support_conversations }
  t.string :role
  t.text :content
  t.string :model_id
  t.integer :input_tokens
  t.integer :output_tokens
  t.references :tool_call, foreign_key: { to_table: :support_tool_calls }
  t.timestamps
end

ActiveRecord::Migration.create_table :support_tool_calls, force: true do |t|
  t.references :message, foreign_key: { to_table: :support_messages }
  t.string :tool_call_id
  t.string :name
  t.json :arguments
  t.timestamps
end
```
```rb
module Support
  def self.table_name_prefix
    'support_'
  end

  class Conversation < ActiveRecord::Base
    acts_as_chat message_class: 'Support::Message'
  end

  class Message < ActiveRecord::Base
    acts_as_message chat: :conversation, chat_class: 'Support::Conversation', tool_call_class: 'Support::ToolCall'
  end

  class ToolCall < ActiveRecord::Base
    acts_as_tool_call message_class: 'Support::Message'
  end
end
```
```rb
Support::Conversation.last.messages
=> #<ActiveRecord::StatementInvalid:"PG::UndefinedColumn: ERROR:  column support_messages.support_conversation_id does not exist
```

It does not work, since the correct foreign key should have been
`support_messages.conversation_id`.

I have added a test showcasing this and implemented a fix.

Since we cannot infer foreign keys automatically when it doesn't match
the model-name, we expose options to pass in a foreign key, similarly to
[associations in
Rails](https://guides.rubyonrails.org/association_basics.html#foreign-key):
```rb
class Support::Message < ActiveRecord::Base
  acts_as_message chat_class: 'Conversation',
                  chat_foreign_key: 'conversation_id'
end
```

Generators have also been updated to add foreign keys if needed.

## Type of change

- [X] Bug fix
- [ ] New feature
- [ ] Breaking change
- [ ] Documentation
- [ ] Performance improvement

## Scope check

- [X] I read the [Contributing
Guide](https://github.com/crmne/ruby_llm/blob/main/CONTRIBUTING.md)
- [X] This aligns with RubyLLM's focus on **LLM communication**
- [X] This isn't application-specific logic that belongs in user code
- [X] This benefits most users, not just my specific use case

## Quality check

- [X] I ran `overcommit --install` and all hooks pass
- [X] I tested my changes thoroughly
- [ ] For provider changes: Re-recorded VCR cassettes with `bundle exec
rake vcr:record[provider_name]`
  - [X] All tests pass: `bundle exec rspec`
- [ ] I updated documentation if needed
- [X] I didn't modify auto-generated files manually (`models.json`,
`aliases.json`)

## API changes

- [ ] Breaking change
- [ ] New public methods/classes
- [X] Changed method signatures
- [ ] No API changes

## Related issues

Fixes bug introduced in #425

---------

Co-authored-by: Carmine Paolino <[email protected]>

Author: andreaslillebo

lib/generators/ruby_llm/generator_helpers.rb

@@ -52,34 +52,41 @@ def parse_model_mappings
       def acts_as_chat_declaration
         params = []
 
-        add_association_params(params, :messages, message_table_name, message_model_name, plural: true)
-        add_association_params(params, :model, model_table_name, model_model_name)
+        add_association_params(params, :messages, message_table_name, message_model_name,
+                               owner_table: chat_table_name, plural: true)
+        add_association_params(params, :model, model_table_name, model_model_name,
+                               owner_table: chat_table_name)
 
         "acts_as_chat#{" #{params.join(', ')}" if params.any?}"
       end
 
       def acts_as_message_declaration
         params = []
 
-        add_association_params(params, :chat, chat_table_name, chat_model_name)
-        add_association_params(params, :tool_calls, tool_call_table_name, tool_call_model_name, plural: true)
-        add_association_params(params, :model, model_table_name, model_model_name)
+        add_association_params(params, :chat, chat_table_name, chat_model_name,
+                               owner_table: message_table_name)
+        add_association_params(params, :tool_calls, tool_call_table_name, tool_call_model_name,
+                               owner_table: message_table_name, plural: true)
+        add_association_params(params, :model, model_table_name, model_model_name,
+                               owner_table: message_table_name)
 
         "acts_as_message#{" #{params.join(', ')}" if params.any?}"
       end
 
       def acts_as_model_declaration
         params = []
 
-        add_association_params(params, :chats, chat_table_name, chat_model_name, plural: true)
+        add_association_params(params, :chats, chat_table_name, chat_model_name,
+                               owner_table: model_table_name, plural: true)
 
         "acts_as_model#{" #{params.join(', ')}" if params.any?}"
       end
 
       def acts_as_tool_call_declaration
         params = []
 
-        add_association_params(params, :message, message_table_name, message_model_name)
+        add_association_params(params, :message, message_table_name, message_model_name,
+                               owner_table: tool_call_table_name)
 
         "acts_as_tool_call#{" #{params.join(', ')}" if params.any?}"
       end
@@ -134,13 +141,21 @@ def table_exists?(table_name)
 
       private
 
-      def add_association_params(params, default_assoc, table_name, model_name, plural: false)
+      def add_association_params(params, default_assoc, table_name, model_name, owner_table:, plural: false) # rubocop:disable Metrics/ParameterLists
         assoc = plural ? table_name.to_sym : table_name.singularize.to_sym
 
-        return if assoc == default_assoc
+        default_foreign_key = "#{default_assoc}_id"
+        # has_many/has_one: foreign key is on the associated table pointing back to owner
+        # belongs_to:       foreign key is on the owner table pointing to associated table
+        foreign_key = if plural || default_assoc.to_s.pluralize == default_assoc.to_s # has_many or has_one
+                        "#{owner_table.singularize}_id"
+                      else # belongs_to
+                        "#{table_name.singularize}_id"
+                      end
 
-        params << "#{default_assoc}: :#{assoc}"
+        params << "#{default_assoc}: :#{assoc}" if assoc != default_assoc
         params << "#{default_assoc.to_s.singularize}_class: '#{model_name}'" if model_name != assoc.to_s.classify
+        params << "#{default_assoc}_foreign_key: :#{foreign_key}" if foreign_key != default_foreign_key
       end
 
       # Convert namespaced model names to proper table names

lib/ruby_llm/active_record/acts_as.rb

@@ -31,8 +31,8 @@ def load_from_database!
       end
 
       class_methods do # rubocop:disable Metrics/BlockLength
-        def acts_as_chat(messages: :messages, message_class: nil,
-                         model: :model, model_class: nil)
+        def acts_as_chat(messages: :messages, message_class: nil, messages_foreign_key: nil, # rubocop:disable Metrics/ParameterLists
+                         model: :model, model_class: nil, model_foreign_key: nil)
           include RubyLLM::ActiveRecord::ChatMethods
 
           class_attribute :messages_association_name, :model_association_name, :message_class, :model_class
@@ -45,12 +45,12 @@ def acts_as_chat(messages: :messages, message_class: nil,
           has_many messages,
                    -> { order(created_at: :asc) },
                    class_name: self.message_class,
-                   foreign_key: ActiveSupport::Inflector.foreign_key(table_name.singularize),
+                   foreign_key: messages_foreign_key,
                    dependent: :destroy
 
           belongs_to model,
                      class_name: self.model_class,
-                     foreign_key: ActiveSupport::Inflector.foreign_key(model.to_s.singularize),
+                     foreign_key: model_foreign_key,
                      optional: true
 
           delegate :add_message, to: :to_llm
@@ -68,7 +68,7 @@ def acts_as_chat(messages: :messages, message_class: nil,
           end
         end
 
-        def acts_as_model(chats: :chats, chat_class: nil)
+        def acts_as_model(chats: :chats, chat_class: nil, chats_foreign_key: nil)
           include RubyLLM::ActiveRecord::ModelMethods
 
           class_attribute :chats_association_name, :chat_class
@@ -80,18 +80,16 @@ def acts_as_model(chats: :chats, chat_class: nil)
           validates :provider, presence: true
           validates :name, presence: true
 
-          has_many chats,
-                   class_name: self.chat_class,
-                   foreign_key: ActiveSupport::Inflector.foreign_key(table_name.singularize)
+          has_many chats, class_name: self.chat_class, foreign_key: chats_foreign_key
 
           define_method :chats_association do
             send(chats_association_name)
           end
         end
 
-        def acts_as_message(chat: :chat, chat_class: nil, touch_chat: false, # rubocop:disable Metrics/ParameterLists
-                            tool_calls: :tool_calls, tool_call_class: nil,
-                            model: :model, model_class: nil)
+        def acts_as_message(chat: :chat, chat_class: nil, chat_foreign_key: nil, touch_chat: false, # rubocop:disable Metrics/ParameterLists
+                            tool_calls: :tool_calls, tool_call_class: nil, tool_calls_foreign_key: nil,
+                            model: :model, model_class: nil, model_foreign_key: nil)
           include RubyLLM::ActiveRecord::MessageMethods
 
           class_attribute :chat_association_name, :tool_calls_association_name, :model_association_name,
@@ -106,12 +104,12 @@ def acts_as_message(chat: :chat, chat_class: nil, touch_chat: false, # rubocop:d
 
           belongs_to chat,
                      class_name: self.chat_class,
-                     foreign_key: ActiveSupport::Inflector.foreign_key(chat.to_s.singularize),
+                     foreign_key: chat_foreign_key,
                      touch: touch_chat
 
           has_many tool_calls,
                    class_name: self.tool_call_class,
-                   foreign_key: ActiveSupport::Inflector.foreign_key(table_name.singularize),
+                   foreign_key: tool_calls_foreign_key,
                    dependent: :destroy
 
           belongs_to :parent_tool_call,
@@ -126,7 +124,7 @@ def acts_as_message(chat: :chat, chat_class: nil, touch_chat: false, # rubocop:d
 
           belongs_to model,
                      class_name: self.model_class,
-                     foreign_key: ActiveSupport::Inflector.foreign_key(model.to_s.singularize),
+                     foreign_key: model_foreign_key,
                      optional: true
 
           delegate :tool_call?, :tool_result?, to: :to_llm
@@ -144,8 +142,8 @@ def acts_as_message(chat: :chat, chat_class: nil, touch_chat: false, # rubocop:d
           end
         end
 
-        def acts_as_tool_call(message: :message, message_class: nil,
-                              result: :result, result_class: nil)
+        def acts_as_tool_call(message: :message, message_class: nil, message_foreign_key: nil, # rubocop:disable Metrics/ParameterLists
+                              result: :result, result_class: nil, result_foreign_key: nil)
           class_attribute :message_association_name, :result_association_name, :message_class, :result_class
 
           self.message_association_name = message
@@ -155,11 +153,11 @@ def acts_as_tool_call(message: :message, message_class: nil,
 
           belongs_to message,
                      class_name: self.message_class,
-                     foreign_key: ActiveSupport::Inflector.foreign_key(message.to_s.singularize)
+                     foreign_key: message_foreign_key
 
           has_one result,
                   class_name: self.result_class,
-                  foreign_key: ActiveSupport::Inflector.foreign_key(table_name.singularize),
+                  foreign_key: result_foreign_key,
                   dependent: :nullify
 
           define_method :message_association do

spec/ruby_llm/active_record/acts_as_spec.rb

@@ -393,6 +393,76 @@ class BotToolCall < ActiveRecord::Base # rubocop:disable Lint/ConstantDefinition
       end
     end
 
+    describe 'namespaced chat models with custom foreign keys' do
+      before(:all) do # rubocop:disable RSpec/BeforeAfterAll
+        # Create additional tables for testing edge cases
+        ActiveRecord::Migration.suppress_messages do
+          ActiveRecord::Migration.create_table :support_conversations, force: true do |t|
+            t.string :model_id
+            t.timestamps
+          end
+
+          ActiveRecord::Migration.create_table :support_messages, force: true do |t|
+            t.references :conversation, foreign_key: { to_table: :support_conversations }
+            t.string :role
+            t.text :content
+            t.string :model_id
+            t.integer :input_tokens
+            t.integer :output_tokens
+            t.references :tool_call, foreign_key: { to_table: :support_tool_calls }
+            t.timestamps
+          end
+
+          ActiveRecord::Migration.create_table :support_tool_calls, force: true do |t|
+            t.references :message, foreign_key: { to_table: :support_messages }
+            t.string :tool_call_id
+            t.string :name
+            t.json :arguments
+            t.timestamps
+          end
+        end
+      end
+
+      after(:all) do # rubocop:disable RSpec/BeforeAfterAll
+        ActiveRecord::Migration.suppress_messages do
+          if ActiveRecord::Base.connection.table_exists?(:support_tool_calls)
+            ActiveRecord::Migration.drop_table :support_tool_calls
+          end
+          if ActiveRecord::Base.connection.table_exists?(:support_messages)
+            ActiveRecord::Migration.drop_table :support_messages
+          end
+          if ActiveRecord::Base.connection.table_exists?(:support_conversations)
+            ActiveRecord::Migration.drop_table :support_conversations
+          end
+        end
+      end
+
+      module Support # rubocop:disable Lint/ConstantDefinitionInBlock,RSpec/LeakyConstantDeclaration
+        def self.table_name_prefix
+          'support_'
+        end
+
+        class Conversation < ActiveRecord::Base # rubocop:disable RSpec/LeakyConstantDeclaration
+          acts_as_chat message_class: 'Support::Message'
+        end
+
+        class Message < ActiveRecord::Base # rubocop:disable RSpec/LeakyConstantDeclaration
+          acts_as_message chat: :conversation, chat_class: 'Support::Conversation', tool_call_class: 'Support::ToolCall'
+        end
+
+        class ToolCall < ActiveRecord::Base # rubocop:disable RSpec/LeakyConstantDeclaration
+          acts_as_tool_call message_class: 'Support::Message'
+        end
+      end
+
+      it 'creates messages successfully' do
+        conversation = Support::Conversation.create!(model: model)
+
+        expect { conversation.messages.create!(role: 'user', content: 'Test') }.not_to raise_error
+        expect(conversation.messages.count).to eq(1)
+      end
+    end
+
     describe 'to_llm conversion' do
       it 'correctly converts custom messages to RubyLLM format' do
         bot_chat = Assistants::BotChat.create!(model: model)