Refactor how a few ActiveRecord enums are definedrefactor-enums-for-ee

In a few models we define ActiveRecord enums that are redefined in EE
using the following pattern:

    enum :some_enum, {
      ...
    }.merge(EE_ENUM_VALUES)

This particular approach is problematic to deal with, because it
requires that we `prepend` and EE module _before_ defining the enum.
This typically translates to the `prepend` being the first line in the
model in EE, but this can easily lead to merge conflicts when developers
add more `include` and/or `prepend` lines.

As part of https://gitlab.com/gitlab-org/gitlab-ee/issues/8244 and
https://gitlab.com/gitlab-org/gitlab-ee/issues/8241 we are moving
`prepend` to the last line in a file, reducing the chances of running
into merge conflicts. This poses a bit of a problem with the pattern
above, because this pattern does not allow us to move the `prepend`
further down a file.

To resolve this problem, we simply move the Hash value of the enum to a
separate class method. This method is defined in a separate module where
necessary, allowing us to use it like so:

    enum :failure_reasons, ::SomeModelEnums.failure_reasons

The method in turn is defined in a very straightforward manner:

    module SomeModelEnums
      def self.failure_reasons
        {
          ...
        }
      end
    end

This makes it easy for EE to add values without requiring the `prepend`
to be placed before the `enum` is defined.

For more information, see the following issues and merge requests:

* https://gitlab.com/gitlab-org/gitlab-ee/issues/8244
* https://gitlab.com/gitlab-org/gitlab-ee/issues/8241
* https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8424

1 files changed, 3 insertions, 12 deletions

diff --git a/app/models/commit_status.rb b/app/models/commit_status.rb
index 755f8bd4d06..0f50bd39131 100644
--- a/app/models/commit_status.rb
+++ b/app/models/commit_status.rb
@@ -42,18 +42,9 @@ class CommitStatus < ActiveRecord::Base
   scope :retried_ordered, -> { retried.ordered.includes(project: :namespace) }
   scope :after_stage, -> (index) { where('stage_idx > ?', index) }
 
-  enum_with_nil failure_reason: {
-    unknown_failure: nil,
-    script_failure: 1,
-    api_failure: 2,
-    stuck_or_timeout_failure: 3,
-    runner_system_failure: 4,
-    missing_dependency_failure: 5,
-    runner_unsupported: 6,
-    stale_schedule: 7,
-    job_execution_timeout: 8,
-    archived_failure: 9
-  }
+  # We use `CommitStatusEnums.failure_reasons` here so that EE can more easily
+  # extend this `Hash` with new values.
+  enum_with_nil failure_reason: ::CommitStatusEnums.failure_reasons
 
   ##
   # We still create some CommitStatuses outside of CreatePipelineService.