Spec: Fix projects controllers retry

The problem is with @project variable and it is a general one for all specs under Projects::ApplicationController.

In Projects::ApplicationController we set a global variable @project - which is completely fine for the first try. But this variable is kept for the retries (using rspec-retry) and because we use

def project
  return @project if @project

it doesn't try to re-fetch the project based on the provided params.

Unfortunately, rspec-retry doesn't rerun the example with a clean slate (it only clear let variables), meaning that our json_response method will still return the memoized response from the first run, including the ID of the resource from the first run (i.e. json_response['id'] == 1)...

How to replicate the problem

Locally you can replicate it by changing https://gitlab.com/gitlab-org/gitlab-ce/blob/master/spec/spec_helper.rb#L91 to use retries.

Original description

Note: add rails5 to a branch name to trigger rails5 specific CI jobs.

https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/67494093

 1) Projects::JobsController GET show when requesting JSON exposes needed information
     Failure/Error:
       @builds = @project.pipelines
         .find_by_sha(@build.sha)
         .builds
         .order('id DESC')
         .present(current_user: current_user)

     NoMethodError:
       undefined method `builds' for nil:NilClass
     # ./app/controllers/projects/jobs_controller.rb:50:in `show'
     # ./lib/gitlab/i18n.rb:50:in `with_locale'
     # ./lib/gitlab/i18n.rb:56:in `with_user_locale'
     # ./app/controllers/application_controller.rb:351:in `set_locale'
     # ./spec/controllers/projects/jobs_controller_spec.rb:156:in `get_show'
     # ./spec/controllers/projects/jobs_controller_spec.rb:138:in `block (4 levels) in <top (required)>'
     # ./spec/spec_helper.rb:160:in `block (2 levels) in <top (required)>'

Edited Jan 16, 2024 by Lin Jen-Shin