Project-compatible path validations

There are path validation differences for namespaces vs projects:
* project can end with `.`
* namespace path length must be at least 2 chars

When a project namespace is created for each project, we have
to use same restrictions as for project, instead of for namespace.

app/models/namespace.rb

@@ -63,17 +63,27 @@ class Namespace < ApplicationRecord
     length: { maximum: 255 }
 
   validates :description, length: { maximum: 255 }
+
   validates :path,
     presence: true,
-    length: { maximum: URL_MAX_LENGTH },
-    namespace_path: true
+    length: { maximum: URL_MAX_LENGTH }
+
+  validates :path, namespace_path: true, if: ->(n) { !n.project_namespace? }
+  # Project path validator is used for project namespaces for now to assure
+  # compatibility with project paths
+  # Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/341764
+  validates :path, project_path: true, if: ->(n) { n.project_namespace? }
 
   # Introduce minimal path length of 2 characters.
   # Allow change of other attributes without forcing users to
   # rename their user or group. At the same time prevent changing
   # the path without complying with new 2 chars requirement.
   # Issue https://gitlab.com/gitlab-org/gitlab/-/issues/225214
-  validates :path, length: { minimum: 2 }, if: :path_changed?
+  #
+  # For ProjectNamespace we don't check minimal path length to keep
+  # compatibility with existing project restrictions.
+  # Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/341764
+  validates :path, length: { minimum: 2 }, if: :enforce_minimum_path_length?
 
   validates :max_artifacts_size, numericality: { only_integer: true, greater_than: 0, allow_nil: true }
 
@@ -575,6 +585,10 @@ class Namespace < ApplicationRecord
       project.track_project_repository
     end
   end
+
+  def enforce_minimum_path_length?
+    path_changed? && !project_namespace?
+  end
 end
 
 Namespace.prepend_mod_with('Namespace')

spec/models/namespace_spec.rb

@@ -133,39 +133,77 @@ RSpec.describe Namespace do
       end
 
       context 'top-level group' do
-        let(:group) { build(:group, path: 'tree') }
+        let(:group) { build(:namespace, path: 'tree') }
 
         it { expect(group).to be_valid }
       end
     end
 
-    describe '1 char path length' do
-      it 'does not allow to create one' do
-        namespace = build(:namespace, path: 'j')
+    describe 'path validator' do
+      using RSpec::Parameterized::TableSyntax
 
-        expect(namespace).not_to be_valid
-        expect(namespace.errors[:path].first).to eq('is too short (minimum is 2 characters)')
+      let_it_be(:parent) { create(:namespace) }
+
+      # rubocop:disable Lint/BinaryOperatorWithIdenticalOperands
+      where(:namespace_type, :path, :valid) do
+        ref(:project_sti_name)   | 'j'     | true
+        ref(:project_sti_name)   | 'path.' | true
+        ref(:project_sti_name)   | 'blob'  | false
+        ref(:group_sti_name)     | 'j'     | false
+        ref(:group_sti_name)     | 'path.' | false
+        ref(:group_sti_name)     | 'blob'  | true
+        ref(:user_sti_name)      | 'j'     | false
+        ref(:user_sti_name)      | 'path.' | false
+        ref(:user_sti_name)      | 'blob'  | true
       end
+      # rubocop:enable Lint/BinaryOperatorWithIdenticalOperands
 
-      it 'does not allow to update one' do
-        namespace = create(:namespace)
-        namespace.update(path: 'j')
+      with_them do
+        it 'validates namespace path' do
+          parent_namespace = parent if namespace_type == Namespaces::ProjectNamespace.sti_name
+          namespace = build(:namespace, type: namespace_type, parent: parent_namespace, path: path)
 
-        expect(namespace).not_to be_valid
-        expect(namespace.errors[:path].first).to eq('is too short (minimum is 2 characters)')
+          expect(namespace.valid?).to be(valid)
+        end
       end
+    end
 
-      it 'allows updating other attributes for existing record' do
-        namespace = build(:namespace, path: 'j', owner: create(:user))
-        namespace.save(validate: false)
-        namespace.reload
+    describe '1 char path length' do
+      context 'with user namespace' do
+        let(:namespace) { build(:namespace) }
 
-        expect(namespace.path).to eq('j')
+        it 'does not allow to update path to single char' do
+          namespace.save!
 
-        namespace.update(name: 'something new')
+          namespace.path = 'j'
 
-        expect(namespace).to be_valid
-        expect(namespace.name).to eq('something new')
+          expect(namespace).not_to be_valid
+          expect(namespace.errors[:path].first).to eq('is too short (minimum is 2 characters)')
+        end
+
+        it 'allows updating other attributes for existing record' do
+          namespace.save!
+          namespace.update_attribute(:path, 'j')
+          namespace.reload
+
+          expect(namespace.path).to eq('j')
+
+          namespace.update(name: 'something new')
+
+          expect(namespace).to be_valid
+          expect(namespace.name).to eq('something new')
+        end
+      end
+
+      context 'with project namespace' do
+        let(:namespace) { build(:project_namespace) }
+
+        it 'allows to update path to single char' do
+          namespace = create(:project_namespace)
+          namespace.update(path: 'j')
+
+          expect(namespace).to be_valid
+        end
       end
     end
   end