Migrate iframe title rule

Author: khiga8

README.md

@@ -25,6 +25,8 @@ require "erblint-github/linters"
 linters:
   GitHub::Accessibility::AvoidBothDisabledAndAriaDisabled:
     enabled: true
+  GitHub::Accessibility::IframeHasTitle:
+    enabled: true
   GitHub::Accessibility::ImageHasAlt:
     enabled: true
   GitHub::Accessibility::NoAriaLabelMisuse:
@@ -36,6 +38,7 @@ linters:
 ## Rules
 
 - [GitHub::Accessibility::AvoidBothDisabledAndAriaDisabled](./docs/rules/accessibility/avoid-both-disabled-and-aria-disabled.md)
+- [GitHub::Accessibility::IframeHasTitle](./docs/rules/accessibility/iframe-has-title.md)
 - [GitHub::Accessibility::ImageHasAlt](./docs/rules/accessibility/image-has-alt.md)
 - [GitHub::Accessibility::NoAriaLabelMisuse](./docs/rules/accessibility/no-aria-label-misuse.md)
 - [GitHub::Accessibility::NoRedundantImageAlt](./docs/rules/accessibility/no-redundant-image-alt.md)

docs/rules/accessibility/iframe-has-title.md

@@ -0,0 +1,25 @@
+# Iframe has title
+
+## Rule Details
+
+`<iframe>` should have a unique title attribute that identifies the content. The title will help screen reader users determine whether to explore the frame in detail. If an `<iframe>` contains no meaningful content, hide it by setting `aria-hidden="true"`.
+
+👎 Examples of **incorrect** code for this rule:
+
+```erb
+<iframe src="../welcome-video"></iframe>
+```
+
+👍 Examples of **correct** code for this rule:
+
+```erb
+<!-- good -->
+<iframe  src="../welcome-video" title="Welcome to GitHub Video" ></iframe>
+```
+
+```erb
+<!-- also good -->
+<iframe aria-hidden="true">
+    <!-- Meaningless JavaScript code -->
+</iframe>
+```

lib/erblint-github/linters/github/accessibility/iframe_has_title.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require_relative "../../custom_helpers"
+
+module ERBLint
+  module Linters
+    module GitHub
+      module Accessibility
+        class IframeHasTitle < Linter
+          include ERBLint::Linters::CustomHelpers
+          include LinterRegistry
+
+          MESSAGE = "<iframe> with meaningful content should have a title attribute that identifies the content."\
+          " If <iframe> has no meaningful content, hide it from assistive technology with `aria-hidden='true'`."\
+
+          def run(processed_source)
+            tags(processed_source).each do |tag|
+              next if tag.name != "iframe"
+              next if tag.closing?
+
+              title = possible_attribute_values(tag, "title")
+
+              generate_offense(self.class, processed_source, tag) if title.empty? && !aria_hidden?(tag)
+            end
+
+            rule_disabled?(processed_source)
+          end
+
+          private
+
+          def aria_hidden?(tag)
+            tag.attributes["aria-hidden"]&.value&.present?
+          end
+        end
+      end
+    end
+  end
+end

test/linters/accessibility/iframe_has_title_test.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class IframeHasTitle < LinterTestCase
+  def linter_class
+    ERBLint::Linters::GitHub::Accessibility::IframeHasTitle
+  end
+
+  def test_warns_if_iframe_has_no_title
+    @file = "<iframe alt='image of an octopus'></iframe>"
+    @linter.run(processed_source)
+
+    refute_empty @linter.offenses
+  end
+
+  def test_does_not_warn_if_iframe_has_aria_hidden_to_true
+    @file = "<iframe aria-hidden='true'></iframe>"
+    @linter.run(processed_source)
+
+    assert_empty @linter.offenses
+  end
+
+  def test_does_not_warn_if_iframe_has_title_set_to_string
+    @file = "<iframe title='Video tutorial of GitHub Actions'></iframe>"
+    @linter.run(processed_source)
+
+    assert_empty @linter.offenses
+  end
+end