Use [disabled] attribute only on tags that support it

Add Capybara selector for disabled links.

app/assets/stylesheets/application.css

@@ -57,6 +57,11 @@
 }
 /* NOTE: move to higher priority layer instead of using !important?; add CSS
  * @layer requirements in README */
+/* Disable elements with:
+ *  `[aria-disabled=true]` - non-form elements (e.g. links),
+ *  `[disabled]` - form controls, that may be enabled conditionally,
+ *  `[readonly]` - form controls, that stay disabled for form lifetime. */
+[aria-disabled=true],
 [disabled] {
   border-color: var(--color-border-gray) !important;
   color: var(--color-border-gray) !important;

app/javascript/application.js

@@ -50,21 +50,30 @@ function formValidate(event) {
 window.formValidate = formValidate
 
 
-/* Turbo stream actions */
+// Turbo stream actions.
+const FORM_CONTROLS = ["BUTTON", "FIELDSET", "INPUT", "OPTGROUP", "OPTION", "SELECT",
+                       "TEXTAREA"]
 Turbo.StreamElement.prototype.disableElement = function(element) {
+  if (FORM_CONTROLS.includes(element.tagName)) {
     element.setAttribute("disabled", "disabled")
+  } else {
     element.setAttribute("aria-disabled", "true")
+    // NOTE: tabindex should not be disabled?
     element.setAttribute("tabindex", "-1")
+  }
 }
 Turbo.StreamActions.disable = function() {
   this.targetElements.forEach((e) => { this.disableElement(e) })
 }
 
 Turbo.StreamElement.prototype.enableElement = function(element) {
+  if (FORM_CONTROLS.includes(element.tagName)) {
     element.removeAttribute("disabled")
+  } else {
     element.removeAttribute("aria-disabled")
-    // Assume 'tabindex' is not used explicitly, so removing it is safe
+    // Assume 'tabindex' is not used explicitly, so removing it is safe.
     element.removeAttribute("tabindex")
+  }
 }
 Turbo.StreamActions.enable = function() {
   this.targetElements.forEach((e) => { this.enableElement(e) })

test/application_system_test_case.rb

@@ -67,21 +67,11 @@ class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
     ActiveRecord::Base.establish_connection(TEST_CONFIGS[name.to_sym])
   end
 
-  #def assert_stale(element)
-  #  assert_raises(Selenium::WebDriver::Error::StaleElementReferenceError) { element.tag_name }
-  #end
+  Capybara.modify_selector(:link) do
+    expression_filter(:disabled) do |xpath, value|
+      builder(xpath).add_attribute_conditions('aria-disabled': value)
+    end
+  end
 
-  # HTML does not allow [disabled] attribute on <a> tag, so it's not possible to
-  # easily find them using e.g. :link selector
-  #Capybara.add_selector(:disabled_link) do
-  #  label "<a> tag with [disabled] attribute"
-  #end
 
-  #test "click disabled link" do
-    # Link should be unclickable
-    # assert_raises(Selenium::WebDriver::Error::ElementClickInterceptedError) do
-    #   # Use custom selector for disabled links
-    #   find('a[disabled]').click
-    # end
-  #end
 end

test/system/units_test.rb

@@ -41,9 +41,10 @@ class UnitsTest < ApplicationSystemTestCase
     sign_in
     link_labels.slice!(:new_unit, :new_subunit)
     type, label = link_labels.to_a.sample
-    new_link = all(:link, exact_text: label).sample
-    new_link.click
-    assert_equal 'disabled', new_link[:disabled]
+    all(:link, exact_text: label).sample.then do |link|
+      link.click
+      link.assert_matches_selector :link, disabled: true
+    end
 
     values = nil
     within 'tbody > tr:has(input[type=text], textarea)' do
@@ -74,7 +75,7 @@ class UnitsTest < ApplicationSystemTestCase
       assert_no_selector :fillable_field
       assert_selector 'tr', count: @user.units.count
     end
-    assert_no_selector :element, :a, 'disabled': 'disabled',
+    assert_no_selector :link, disabled: true,
       exact_text: Regexp.union(link_labels.values)
     assert_equal values, Unit.last.attributes.slice(*values.keys)
   end
@@ -126,7 +127,7 @@ class UnitsTest < ApplicationSystemTestCase
     if type == :edit
       assert_no_selector :link, exact_text: link[:text]
     else
-      assert_equal 'disabled', link[:disabled]
+      link.assert_matches_selector :link, disabled: true
     end
 
     within 'tbody > tr:has(input[type=text])' do
@@ -159,7 +160,7 @@ class UnitsTest < ApplicationSystemTestCase
       refute subunit_link&.visible?
       links[:new_subunit].delete(subunit_link)
     else
-      assert link[:disabled]
+      link.assert_matches_selector :link, disabled: true
     end
 
     type, link = random_link[]

test/system/users_test.rb

@@ -8,7 +8,7 @@ class UsersTest < ApplicationSystemTestCase
 
   test 'sign in' do
     visit root_url
-    assert find_link(href: new_user_session_path)[:disabled]
+    assert_selector :link, text: t(:sign_in), disabled: true
 
     sign_in
     assert_no_current_path new_user_session_path
@@ -27,7 +27,7 @@ class UsersTest < ApplicationSystemTestCase
 
     assert_current_path new_user_session_path
     assert_text t('devise.failure.invalid', authentication_keys: label.downcase_first)
-    assert find_link(href: new_user_session_path)[:disabled]
+    assert_selector :link, text: t(:sign_in), disabled: true
     assert has_field?(label, with: email)
   end
 
@@ -89,7 +89,7 @@ class UsersTest < ApplicationSystemTestCase
   test 'register' do
     visit root_url
     click_on t(:register)
-    assert find_link(href: new_user_registration_path)[:disabled]
+    assert_selector :link, text: t(:register), disabled: true
 
     fill_in User.human_attribute_name(:email), with: random_email
     password = random_password