Format date errors according to the style guide

The GOVUK design system describes specific error styling for date fields
that the current helpers don't support.

Due to the way we build the errors and Rails conventions, there is no
support for highlighting errors with specific parts of a date input.

Adding support for this requires a few changes in the form builder.

I considered adding these changes upstream in the form builder gem but
opted instead to monkey-patch them initially so that we can explore them
in a real environment first.

Once we have seen these changes work, I will propose the changes to the
form library and remove the monkey-patch if they are accepted.

Mostly, the changes are around how we determine if an error message is
present for one of the date part input fields.

app/models/search.rb

@@ -1,3 +1,102 @@
+module GOVUKDesignSystemFormBuilder
+  module Elements
+    class Date
+      using PrefixableArray
+
+      def field_id(segment:, link_errors: false)
+        if link_errors && has_errors?(segment)
+          build_id('field-error', attribute_name: segment, include_value: false)
+        else
+          build_id('field')
+        end
+      end
+
+      private
+
+      def classes(width, segment = nil)
+        build_classes(
+          %(input),
+          %(date-input__input),
+          %(input--width-#{width}),
+          %(input--error) => has_errors?(segment),
+        ).prefix(brand)
+      end
+
+      def has_errors?(segment = nil)
+        @builder.object.respond_to?(:errors) && @builder.object.errors.any? && 
+          (@builder.object.errors.messages[@attribute_name].present? || 
+          @builder.object.errors.messages[segment].present?)
+      end
+
+      def id(segment, link_errors)
+        if has_errors?(segment) && link_errors
+          field_id(link_errors:, segment:)
+        else
+          [@object_name, @attribute_name, SEGMENTS.fetch(segment)].join("_")
+        end
+      end
+
+      def input(segment, link_errors, width, value)
+        tag.input(
+          id: id(segment, link_errors),
+          class: classes(width, segment),
+          name: name(segment),
+          type: 'text',
+          inputmode: 'numeric',
+          value:,
+          autocomplete: date_of_birth_autocomplete_value(segment),
+          maxlength: (width if maxlength_enabled?),
+        )
+      end
+
+      def day
+        date_part(:day, width: 2, link_errors: true)
+      end
+
+      def month
+        date_part(:month, width: 2, link_errors: true)
+      end
+
+      def year
+        date_part(:year, width: 4, link_errors: true)
+      end
+    end
+
+    class ErrorMessage < Base
+      def has_errors?
+        @builder.object.respond_to?(:errors) && @builder.object.errors.any? && 
+          (@builder.object.errors[@attribute_name].present? || 
+            (@attribute_name == :date_of_birth && 
+              (@builder.object.errors.messages.keys & %i[date_of_birth day month year]).any?
+            )
+          )
+      end
+
+      private
+
+      def message
+        error = @builder.object.errors.messages[@attribute_name]&.first
+        error ||= @builder.object.errors.messages[:day]&.first if has_errors?
+        set_message_safety(error)
+      end
+    end
+  end
+
+  module Containers
+    class FormGroup < Base
+      def has_errors?
+        @builder.object.respond_to?(:errors) && 
+          @builder.object.errors.any? && 
+          (@builder.object.errors[@attribute_name].present? || 
+            (@attribute_name == :date_of_birth && 
+              (@builder.object.errors.messages.keys & %i[date_of_birth day month year]).any?
+            )
+          )
+      end
+    end
+  end
+end
+
 class Search
   DateOfBirth =
     Struct.new(:year, :month, :day) do
@@ -12,7 +111,8 @@ def to_s
   attr_reader :date_of_birth
 
   validates :last_name, presence: true
-  validate :date_of_birth_is_valid
+  validates :date_of_birth, presence: true
+  validate :date_of_birth_is_valid, if: -> { date_of_birth.present? }
 
   def date_of_birth=(date_fields)
     return if date_fields.nil?
@@ -28,28 +128,20 @@ def date_of_birth=(date_fields)
   private
 
   def date_of_birth_is_valid
-    if @date_of_birth.nil?
-      errors.add(:date_of_birth, t(:blank))
-      return
-    end
-
-    year = @date_of_birth.year.to_i
-    month = @date_of_birth.month.to_i
-    day = @date_of_birth.day.to_i
-
-    if day.zero? && month.zero? && year.zero?
-      errors.add(:date_of_birth, t(:blank))
-      return
-    end
+    year = date_of_birth.year.to_i
+    month = date_of_birth.month.to_i
+    day = date_of_birth.day.to_i
 
     if day.zero?
-      errors.add(:date_of_birth, t(:missing_day))
-      return
+      errors.add(:day, t(:missing_day))
     end
 
     if month.zero?
-      errors.add(:date_of_birth, t(:missing_month))
-      nil
+      errors.add(:month, t(:missing_month))
+    end
+
+    if year.zero?
+      errors.add(:year, t(:missing_year))
     end
 
     begin
@@ -60,22 +152,20 @@ def date_of_birth_is_valid
       end
 
       if date.after?(16.years.ago)
-        errors.add(:date_of_birth, t(:inclusion))
+        errors.add(:year, t(:inclusion))
         return
       end
 
       if date.year < 1000
-        errors.add(:date_of_birth, t(:missing_year))
+        errors.add(:year, t(:missing_year))
         return
       end
 
       if date.year < 1900
-        errors.add(:date_of_birth, t(:born_after_1900))
-        nil
+        errors.add(:year, t(:born_after_1900))
       end
     rescue Date::Error
-      errors.add(:date_of_birth, t(:blank))
-      nil
+      errors.add(:date_of_birth, t(:invalid)) if (errors.messages.keys & %i[day month year]).empty?
     end
   end
 

config/locales/en.yml

@@ -18,9 +18,10 @@ en:
         search:
           attributes:
             date_of_birth:
-              blank: Enter a valid date of birth
+              blank: Enter a your date of birth
               born_after_1900: Enter a year of birth later than 1900
               inclusion: People must be 16 or over to use this service
+              invalid: Date of birth must be a real date
               missing_day: Enter a day for the date of birth, formatted as a number
               missing_month: Enter a month for the date of birth, formatted as a number
               missing_year: Enter a year with 4 digits

spec/models/search_spec.rb

@@ -22,7 +22,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include(
+        expect(search.errors[:day]).to include(
           "Enter a day for the date of birth, formatted as a number"
         )
       end
@@ -33,7 +33,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include(
+        expect(search.errors[:month]).to include(
           "Enter a month for the date of birth, formatted as a number"
         )
       end
@@ -62,7 +62,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include("Enter a valid date of birth")
+        expect(search.errors[:date_of_birth]).to include("Date of birth must be a real date")
       end
     end
 
@@ -80,7 +80,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include(
+        expect(search.errors[:year]).to include(
           "People must be 16 or over to use this service"
         )
       end
@@ -91,7 +91,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include("Enter a year of birth later than 1900")
+        expect(search.errors[:year]).to include("Enter a year of birth later than 1900")
       end
     end
 
@@ -100,7 +100,7 @@
 
       it "is invalid" do
         expect(search).to be_invalid
-        expect(search.errors[:date_of_birth]).to include("Enter a year with 4 digits")
+        expect(search.errors[:year]).to include("Enter a year with 4 digits")
       end
     end
   end

spec/system/check_records/user_searches_with_an_invalid_date_of_birth_spec.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe "Teacher search", host: :check_records, type: :system do
+  include ActivateFeaturesSteps
+  include CheckRecords::AuthenticationSteps
+
+  scenario "User searches with an invalid date of birth",
+           test: %i[with_stubbed_auth with_fake_quals_api] do
+    given_the_service_is_open
+    when_i_sign_in_via_dsi
+    and_search_with_a_missing_dob
+    then_i_see_an_error_message
+  end
+
+  private
+
+  def and_search_with_a_missing_dob
+    fill_in "Last name", with: "Walsh"
+    fill_in "Day", with: "5"
+    fill_in "Month", with: "April"
+    click_button "Find record"
+  end
+
+  def then_i_see_an_error_message
+    expect(page).to have_text("Enter a year with 4 digits")
+    page.click_link("Enter a year with 4 digits")
+    expect(page).to have_css("#search-year-field-error")
+  end
+end

spec/system/check_records/user_searches_with_invalid_values_spec.rb

@@ -47,7 +47,7 @@ def then_i_see_the_error_summary
   def then_i_see_the_missing_dob_error
     within "#search-date-of-birth-error" do
       expect(page).to have_content "Error:"
-      expect(page).to have_content "Enter a valid date of birth"
+      expect(page).to have_content "Enter a day for the date of birth, formatted as a number"
     end
   end