Fix alphanumeric identifier validation error cascading

Replace two independent format validators with a single custom
validation that short-circuits on the first error. Previously,
"3INVALID" showed both "must start with a letter" and "may only
contain uppercase letters..." — the second message was misleading
since the input contained only valid characters.

Also pin url identifier tests to numeric mode since the test
environment default is now alphanumeric.

Author: akabiru

app/models/projects/identifier.rb

@@ -70,13 +70,8 @@ module Projects::Identifier
               }
 
     # Validators for the alphanumeric identifier format (e.g. "PROJ1")
-    validates :identifier,
-              format: { with: /\A[A-Z]/, message: :must_start_with_letter },
-              if: ->(p) { p.identifier_changed? && p.identifier.present? && Setting::WorkPackageIdentifier.alphanumeric? }
-    validates :identifier,
-              format: { with: /\A[A-Z][A-Z0-9_]*\z/, message: :no_special_characters },
-              length: { maximum: SEMANTIC_IDENTIFIER_MAX_LENGTH },
-              if: ->(p) { p.identifier_changed? && p.identifier.present? && Setting::WorkPackageIdentifier.alphanumeric? }
+    validate :identifier_alphanumeric_format,
+             if: ->(p) { p.identifier_changed? && p.identifier.present? && Setting::WorkPackageIdentifier.alphanumeric? }
 
     validate :identifier_not_reserved, if: -> { identifier.present? }
 
@@ -132,6 +127,18 @@ def validation_context
 
   private
 
+  def identifier_alphanumeric_format
+    unless identifier.match?(/\A[A-Z]/)
+      errors.add(:identifier, :must_start_with_letter)
+      return
+    end
+
+    errors.add(:identifier, :no_special_characters) unless identifier.match?(/\A[A-Z][A-Z0-9_]*\z/)
+    if identifier.length > SEMANTIC_IDENTIFIER_MAX_LENGTH
+      errors.add(:identifier, :too_long, count: SEMANTIC_IDENTIFIER_MAX_LENGTH)
+    end
+  end
+
   def identifier_not_reserved
     if RESERVED_IDENTIFIERS.include?(identifier&.downcase)
       errors.add(:identifier, :exclusion)

spec/features/projects/create_spec.rb

@@ -592,6 +592,7 @@
 
       fill_in "Name", with: "Flight Planning Algorithm"
       find("body").click
+      expect(page).to have_field "Identifier", with: "FPA"
 
       fill_in "Identifier", with: "3INVALID"
       click_on "Complete"

spec/models/projects/identifier_spec.rb

@@ -81,7 +81,7 @@
     end
   end
 
-  describe "url identifier" do
+  describe "url identifier", with_settings: { work_packages_identifier: "numeric" } do
     let(:reserved) do
       Rails.application.routes.routes
         .map { |route| route.path.spec.to_s }