thoughtbot / thoughtbot/factory_bot

Question/Feature - Access `traits` and `overrides` arguments in public API

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feature
Dominant language
Ruby
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Description

Problem this feature will solve

I'd like to safely bypass the creation of a factory when no overrides or traits were specified. Ultimately, the idea is to reduce the number of records created after a test setup by defaulting to a fixture when no special attributes are required.

Note: This problem may already have been solved, and I need to learn about the solution. See the "Additional Context" section for questions.

Something along these lines:

factory :user do
  to_create do |record, evaluator|
    if evaluator.traits.empty? && evaluator.overrides.empty?
      User.find(1) # users(:one) 
    else
      record.save!
    end
  end

  sequence(:name) { |n| 'Name #{n}' }
end

The formats could fit exactly the ones used in FactoryBot::FactoryRunner initialization

FactoryBot.create(:user)
=> overrides: {}, traits: []

FactoryBot.create(:user, name: 'Alex')
=> overrides: {name: 'Alex'}, traits: []

FactoryBot.create(:user, :with_password, name: 'Alex')
=> overrides: {name: 'Alex'}, traits: [:with_password]
Desired solution

It seems that exposing these methods to the evaluator could be a solution?

Note: Naming can change as the evaluator already has @overrides variable, but unless mistaken is for all the record attributes.

Alternatives considered

Custom FactoryBot::FactoryRunner with hook?

I can access these exact values by monkey patching FactoryBot::FactoryRunner which doesn't feel right.

module FactoryBot
  class FactoryRunner
    alias old_run run
    def run(runner_strategy = @strategy, &block)
      if Strategy::Create === @strategy && @traits.empty? && @overrides.empty?
        record = case @name
                 when :user then User.find(1) # users(:one) 
                 end

        return record if record
      end

      old_run(runner_strategy, &block)
    end
  end
end

The FactoryRunner could be registered/injected like strategies with some hooks?

Additional context

I guess it relates to some extent to #1681

Questions

  • Is there a way to access these values safely and not monkey patch or tinker with private APIs?
  • Is there an existing approach to prevent the creation of a record when no arguments are passed other than the name of the factory?

Any input would be appreciated about that issue, except maybe feedback about how bad the idea is; I already know that 😂
The number of records created in specs with factories is known to have issues.
Any change helping developers with this issue would be significant, especially when dealing with legacy codebases.

EDIT: Maybe using a custom strategy and redefining the #association would be good enough as often the number of records created are from linked associations.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading the FactoryBot::FactoryRunner initialization and the evaluator APIs mentioned in the issue, then compare the questions with issue #1681. Review the custom strategy and #association alternatives described here. Done means establishing whether a supported public API already exists or defining the requested behavior and its API boundaries.

Written by the indexing model from the issue text.

Assessment

Tech stack
ruby
Domain
testing
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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