Fix acts_as_message inflection for parent_tool_call causes nil association

[jayelkaake]

What this does

• add parent_tool_call_foreign_key to acts_as_message and use that value if specified, otherwise fall back on original assumtpion.

Bug Description

When you have a custom column name for the parent_tool_call_id foreign key, the current code does:

belongs_to :parent_tool_call,
           class_name: self.tool_call_class,
           foreign_key: ActiveSupport::Inflector.foreign_key(tool_calls.to_s.singularize),
           optional: true

but ActiveSupport::Inflector.foreign_key(tool_calls.to_s.singularize) doesn't assume correctly if tool_calls == :tool_call but the tool_call_class: 'SomethingElse'.

Recreation steps

Setup:

before(:all) do # rubocop:disable RSpec/BeforeAfterAll
  ActiveRecord::Migration.suppress_messages do
    # ...

    ActiveRecord::Migration.create_table :ai_tool_calls, force: true do |t|
      t.references :ai_message
      t.string :ai_tool_call_id
      # ...
    end

    ActiveRecord::Migration.create_table :ai_messages, force: true do |t|
      t.references :ai_chat
      # ...
      t.integer :ai_tool_call_id # <<< Note this
    end

    # ...

  end
end

# ...

class AiMessage
  acts_as_message(
    chat_class: 'AiChat',
    chat_foreign_key: :ai_chat_id,
    tool_call_class: 'AiToolCall', 
    tool_calls_foreign_key: :ai_message_id,
    model_class: 'AiModel', 
    model_foreign_key: 'AiModel')
  # ...
end    

# ...

Test:

AiMessage.where("ai_tool_call_id IS NOT NULL").first.parent_tool_call

• Expected result: instance of AiToolCall
• Current result: nil

Solution

Considered updating the inflection method, but decided it's better to be explicit in this non-standard case. Configuration over convention for once since it's more clear.

Details

Type of change

• Bug fix
• New feature
  • (since it adds a new config option)
• Breaking change
• Documentation
• Performance improvement

Scope check

• I read the Contributing Guide
• This aligns with RubyLLM's focus on LLM communication
• This isn't application-specific logic that belongs in user code
• This benefits most users, not just my specific use case

Quality check

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

AI-generated code

• I used AI tools to help write this code
  • I generated the spec with claude's help. Checked it and tested edge cases. We should split up that file in the future.
• I have reviewed and understand all generated code (required if above is checked)

API changes

• Breaking change
• New public methods/classes
• Changed method signatures
  • added to method signature... does that count?
• No API changes