Fix the project auto devops API

If `project_auto_devops.enabled` is nil for a project, when setting any
auto devops values via the API, we try to create a new row in the DB,
instead of re-using the existing one. This leads to the project_id
being set to nil, and the database `NOT NULL` constraint leading to a
500 response.

This commit resolves the issue by correctly detecting the presence of a
ProjectAutoDevops row and re-using it. Persistence is also moved away
from explicit `update!` calls and into relying on `autosave: true` on
the model.

3 files changed, 4 insertions, 6 deletions

diff --git a/app/models/concerns/project_api_compatibility.rb b/app/models/concerns/project_api_compatibility.rb
index cb00efb06df..631b2a11e9a 100644
--- a/app/models/concerns/project_api_compatibility.rb
+++ b/app/models/concerns/project_api_compatibility.rb
@@ -9,12 +9,10 @@ module ProjectAPICompatibility
   end
 
   def auto_devops_enabled=(value)
-    self.build_auto_devops if self.auto_devops&.enabled.nil?
-    self.auto_devops.update! enabled: value
+    (auto_devops || build_auto_devops).enabled = value
   end
 
   def auto_devops_deploy_strategy=(value)
-    self.build_auto_devops if self.auto_devops&.enabled.nil?
-    self.auto_devops.update! deploy_strategy: value
+    (auto_devops || build_auto_devops).deploy_strategy = value
   end
 end
diff --git a/app/models/project.rb b/app/models/project.rb
index 2906aca75fc..8dfe2212282 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -277,7 +277,7 @@ class Project < ApplicationRecord
   has_many :project_deploy_tokens
   has_many :deploy_tokens, through: :project_deploy_tokens
 
-  has_one :auto_devops, class_name: 'ProjectAutoDevops'
+  has_one :auto_devops, class_name: 'ProjectAutoDevops', inverse_of: :project, autosave: true
   has_many :custom_attributes, class_name: 'ProjectCustomAttribute'
 
   has_many :project_badges, class_name: 'ProjectBadge'
diff --git a/app/models/project_auto_devops.rb b/app/models/project_auto_devops.rb
index 67c12363a3c..f39f54f0434 100644
--- a/app/models/project_auto_devops.rb
+++ b/app/models/project_auto_devops.rb
@@ -5,7 +5,7 @@ class ProjectAutoDevops < ApplicationRecord
 
   ignore_column :domain
 
-  belongs_to :project
+  belongs_to :project, inverse_of: :auto_devops
 
   enum deploy_strategy: {
     continuous: 0,