164 lines
4.4 KiB
Markdown
164 lines
4.4 KiB
Markdown
# Gotchas
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The purpose of this guide is to document potential "gotchas" that contributors
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might encounter or should avoid during development of GitLab CE and EE.
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## Do not assert against the absolute value of a sequence-generated attribute
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Consider the following factory:
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```ruby
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FactoryBot.define do
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factory :label do
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sequence(:title) { |n| "label#{n}" }
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end
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end
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```
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Consider the following API spec:
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```ruby
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require 'spec_helper'
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describe API::Labels do
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it 'creates a first label' do
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create(:label)
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get api("/projects/#{project.id}/labels", user)
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expect(response).to have_http_status(200)
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expect(json_response.first['name']).to eq('label1')
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end
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it 'creates a second label' do
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create(:label)
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get api("/projects/#{project.id}/labels", user)
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expect(response).to have_http_status(200)
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expect(json_response.first['name']).to eq('label1')
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end
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end
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```
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When run, this spec doesn't do what we might expect:
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```sh
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1) API::API reproduce sequence issue creates a second label
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Failure/Error: expect(json_response.first['name']).to eq('label1')
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expected: "label1"
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got: "label2"
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(compared using ==)
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```
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This is because FactoryBot sequences are not reset for each example.
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Please remember that sequence-generated values exist only to avoid having to
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explicitly set attributes that have a uniqueness constraint when using a factory.
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### Solution
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If you assert against a sequence-generated attribute's value, you should set it
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explicitly. Also, the value you set shouldn't match the sequence pattern.
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For instance, using our `:label` factory, writing `create(:label, title: 'foo')`
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is ok, but `create(:label, title: 'label1')` is not.
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Following is the fixed API spec:
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```ruby
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require 'spec_helper'
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describe API::Labels do
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it 'creates a first label' do
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create(:label, title: 'foo')
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get api("/projects/#{project.id}/labels", user)
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expect(response).to have_http_status(200)
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expect(json_response.first['name']).to eq('foo')
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end
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it 'creates a second label' do
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create(:label, title: 'bar')
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get api("/projects/#{project.id}/labels", user)
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expect(response).to have_http_status(200)
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expect(json_response.first['name']).to eq('bar')
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end
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end
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```
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## Avoid using `expect_any_instance_of` or `allow_any_instance_of` in RSpec
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### Why
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- Because it is not isolated therefore it might be broken at times.
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- Because it doesn't work whenever the method we want to stub was defined
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in a prepended module, which is very likely the case in EE. We could see
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error like this:
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```
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1.1) Failure/Error: expect_any_instance_of(ApplicationSetting).to receive_messages(messages)
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Using `any_instance` to stub a method (elasticsearch_indexing) that has been defined on a prepended module (EE::ApplicationSetting) is not supported.
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```
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### Alternative: `expect_next_instance_of`
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Instead of writing:
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```ruby
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# Don't do this:
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expect_any_instance_of(Project).to receive(:add_import_job)
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```
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We could write:
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```ruby
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# Do this:
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expect_next_instance_of(Project) do |project|
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expect(project).to receive(:add_import_job)
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end
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```
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If we also want to expect the instance was initialized with some particular
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arguments, we could also pass it to `expect_next_instance_of` like:
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```ruby
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# Do this:
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expect_next_instance_of(MergeRequests::RefreshService, project, user) do |refresh_service|
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expect(refresh_service).to receive(:execute).with(oldrev, newrev, ref)
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end
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```
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This would expect the following:
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```ruby
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# Above expects:
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refresh_service = MergeRequests::RefreshService.new(project, user)
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refresh_service.execute(oldrev, newrev, ref)
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```
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## Do not `rescue Exception`
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See ["Why is it bad style to `rescue Exception => e` in Ruby?"][Exception].
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_**Note:** This rule is [enforced automatically by
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Rubocop](https://gitlab.com/gitlab-org/gitlab-foss/blob/8-4-stable/.rubocop.yml#L911-914)._
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[Exception]: http://stackoverflow.com/q/10048173/223897
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## Do not use inline JavaScript in views
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Using the inline `:javascript` Haml filters comes with a
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performance overhead. Using inline JavaScript is not a good way to structure your code and should be avoided.
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_**Note:** We've [removed these two filters](https://gitlab.com/gitlab-org/gitlab-foss/blob/master/config/initializers/hamlit.rb)
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in an initializer._
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### Further reading
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- Stack Overflow: [Why you should not write inline JavaScript](http://programmers.stackexchange.com/questions/86589/why-should-i-avoid-inline-scripting)
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