Refactor checking personal project limits

This refactors the code used for checking if a user has exceeded the
personal projects limit. As part of this refactor the method has been
renamed from Project#check_limit to "check_personal_projects_limit", as
this name makes it much more clear what the purpose of the method is.
Standalone unit tests have also been added, as before we only had a
single generic validation test that did not cover all cases.

The old implementation of the refactored method also included a `rescue`
statement. This code would only run when a project creator was not set.
The error that would be added wasn't super useful, especially since
there would already be errors for the creator not being present. As none
of the other code in the "check_personal_projects_limit" raises, it has
been removed.

app/models/project.rb

@@ -331,7 +331,7 @@ class Project < ActiveRecord::Base
                                        ports: ->(project) { project.persisted? ? VALID_MIRROR_PORTS : VALID_IMPORT_PORTS },
                                        enforce_user: true }, if: [:external_import?, :import_url_changed?]
   validates :star_count, numericality: { greater_than_or_equal_to: 0 }
-  validate :check_limit, on: :create
+  validate :check_personal_projects_limit, on: :create
   validate :check_repository_path_availability, on: :update, if: ->(project) { project.renamed? }
   validate :visibility_level_allowed_by_group, if: -> { changes.has_key?(:visibility_level) }
   validate :visibility_level_allowed_as_fork, if: -> { changes.has_key?(:visibility_level) }
@@ -809,18 +809,22 @@ class Project < ActiveRecord::Base
       ::Gitlab::CurrentSettings.mirror_available
   end
 
-  def check_limit
-    unless creator.can_create_project? || namespace.kind == 'group'
-      projects_limit = creator.projects_limit
+  def check_personal_projects_limit
+    # Since this method is called as validation hook, `creator` might not be
+    # present. Since the validation for that will fail, we can just return
+    # early.
+    return if !creator || creator.can_create_project? ||
+        namespace.kind == 'group'
 
-      if projects_limit == 0
-        self.errors.add(:limit_reached, "Personal project creation is not allowed. Please contact your administrator with questions")
+    limit = creator.projects_limit
+    error =
+      if limit.zero?
+        _('Personal project creation is not allowed. Please contact your administrator with questions')
       else
-        self.errors.add(:limit_reached, "Your project limit is #{projects_limit} projects! Please contact your administrator to increase it")
+        _('Your project limit is %{limit} projects! Please contact your administrator to increase it')
       end
-    end
-  rescue
-    self.errors.add(:base, "Can't check your ability to create project")
+
+    self.errors.add(:limit_reached, error % { limit: limit })
   end
 
   def visibility_level_allowed_by_group

locale/gitlab.pot

@@ -4907,6 +4907,9 @@ msgstr ""
 msgid "Personal Access Token"
 msgstr ""
 
+msgid "Personal project creation is not allowed. Please contact your administrator with questions"
+msgstr ""
+
 msgid "Pick a name"
 msgstr ""
 
@@ -8070,6 +8073,9 @@ msgstr ""
 msgid "Your name"
 msgstr ""
 
+msgid "Your project limit is %{limit} projects! Please contact your administrator to increase it"
+msgstr ""
+
 msgid "Your projects"
 msgstr ""
 

spec/models/project_spec.rb

@@ -209,9 +209,14 @@ describe Project do
 
     it 'does not allow new projects beyond user limits' do
       project2 = build(:project)
-      allow(project2).to receive(:creator).and_return(double(can_create_project?: false, projects_limit: 0).as_null_object)
+
+      allow(project2)
+        .to receive(:creator)
+        .and_return(
+          double(can_create_project?: false, projects_limit: 0).as_null_object
+        )
+
       expect(project2).not_to be_valid
-      expect(project2.errors[:limit_reached].first).to match(/Personal project creation is not allowed/)
     end
 
     describe 'wiki path conflict' do
@@ -4431,6 +4436,75 @@ describe Project do
     end
   end
 
+  describe '#check_personal_projects_limit' do
+    context 'when creating a project for a group' do
+      it 'does nothing' do
+        creator = build(:user)
+        project = build(:project, namespace: build(:group), creator: creator)
+
+        allow(creator)
+          .to receive(:can_create_project?)
+          .and_return(false)
+
+        project.check_personal_projects_limit
+
+        expect(project.errors).to be_empty
+      end
+    end
+
+    context 'when the user is not allowed to create a personal project' do
+      let(:user) { build(:user) }
+      let(:project) { build(:project, creator: user) }
+
+      before do
+        allow(user)
+          .to receive(:can_create_project?)
+          .and_return(false)
+      end
+
+      context 'when the project limit is zero' do
+        it 'adds a validation error' do
+          allow(user)
+            .to receive(:projects_limit)
+            .and_return(0)
+
+          project.check_personal_projects_limit
+
+          expect(project.errors[:limit_reached].first)
+            .to match(/Personal project creation is not allowed/)
+        end
+      end
+
+      context 'when the project limit is greater than zero' do
+        it 'adds a validation error' do
+          allow(user)
+            .to receive(:projects_limit)
+            .and_return(5)
+
+          project.check_personal_projects_limit
+
+          expect(project.errors[:limit_reached].first)
+            .to match(/Your project limit is 5 projects/)
+        end
+      end
+    end
+
+    context 'when the user is allowed to create personal projects' do
+      it 'does nothing' do
+        user = build(:user)
+        project = build(:project, creator: user)
+
+        allow(user)
+          .to receive(:can_create_project?)
+          .and_return(true)
+
+        project.check_personal_projects_limit
+
+        expect(project.errors).to be_empty
+      end
+    end
+  end
+
   def rugged_config
     rugged_repo(project.repository).config
   end