Merge pull request #38 from github/accessibility/issues/1293/migrate-a11y-erblint-rules

Migrate accessibility rule `a11y_link_has_href` from dotcom to erblint-github

Author: Adrián Bolonio

README.md

@@ -31,6 +31,8 @@ linters:
     enabled: true
   GitHub::Accessibility::ImageHasAlt:
     enabled: true
+  GitHub::Accessibility::LinkHasHrefCounter:
+    enabled: true
   GitHub::Accessibility::NoAriaLabelMisuseCounter:
     enabled: true
   GitHub::Accessibility::NoPositiveTabIndex:
@@ -47,6 +49,7 @@ linters:
 - [GitHub::Accessibility::AvoidGenericLinkTextCounter](./docs/rules/accessibility/avoid-generic-link-text-counter.md)
 - [GitHub::Accessibility::IframeHasTitle](./docs/rules/accessibility/iframe-has-title.md)
 - [GitHub::Accessibility::ImageHasAlt](./docs/rules/accessibility/image-has-alt.md)
+- [GitHub::Accessibility::LinkHasHrefCounter](./docs/rules/accessibility/link_has_href-counter.md)
 - [GitHub::Accessibility::NoAriaLabelMisuseCounter](./docs/rules/accessibility/no-aria-label-misuse-counter.md)
 - [GitHub::Accessibility::NoPositiveTabIndex](./docs/rules/accessibility/no-positive-tab-index.md)
 - [GitHub::Accessibility::NoRedundantImageAlt](./docs/rules/accessibility/no-redundant-image-alt.md)

docs/rules/accessibility/link-has-href-counter.md

@@ -0,0 +1,27 @@
+# Link Has Href counter
+
+## Rule Details
+
+An `<a>` element that has an href attribute represents a hyperlink (a hypertext anchor) labeled by its contents. Links, `<a>` elements, should go somewhere, you probably want to use a `<button>` instead.
+
+
+## Resources
+
+- [`<a>`: The Anchor element](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a)
+- [Primer: Links](https://primer.style/design/accessibility/links)
+- [HTML Spec: The a element](https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-a-element)
+
+## Examples
+### **Incorrect** code for this rule 👎
+
+```erb
+<!-- incorrect -->
+<a>Go to GitHub</a>
+```
+
+### **Correct** code for this rule  👍
+
+```erb
+<!-- correct -->
+<a href='https://github.com/'>Go to GitHub</a>
+```

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

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+require_relative "../../custom_helpers"
+
+module ERBLint
+  module Linters
+    module GitHub
+      module Accessibility
+        class LinkHasHrefCounter < Linter
+          include ERBLint::Linters::CustomHelpers
+          include LinterRegistry
+
+          MESSAGE = "Links should go somewhere, you probably want to use a `<button>` instead."
+
+          def run(processed_source)
+            tags(processed_source).each do |tag|
+              next if tag.name != "a"
+              next if tag.closing?
+
+              href = possible_attribute_values(tag, "href")
+              name = tag.attributes["name"]
+              generate_offense(self.class, processed_source, tag) if (!name && href.empty?) || href.include?("#")
+            end
+
+            counter_correct?(processed_source)
+          end
+
+          def autocorrect(processed_source, offense)
+            return unless offense.context
+
+            lambda do |corrector|
+              if processed_source.file_content.include?("erblint:counter #{simple_class_name}")
+                # update the counter if exists
+                corrector.replace(offense.source_range, offense.context)
+              else
+                # add comment with counter if none
+                corrector.insert_before(processed_source.source_buffer.source_range, "#{offense.context}\n")
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

test/linters/accessibility/link_has_href_counter_test.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class LinkHasHrefCounter < LinterTestCase
+  def linter_class
+    ERBLint::Linters::GitHub::Accessibility::LinkHasHrefCounter
+  end
+
+  def test_warns_if_link_has_no_href_attribute
+    @file = "<a>Go to GitHub</a>"
+    @linter.run(processed_source)
+
+    assert_equal(2, @linter.offenses.count)
+    error_messages = @linter.offenses.map(&:message).sort
+    assert_match(/If you must, add <%# erblint:counter GitHub::Accessibility::LinkHasHrefCounter 1 %> to bypass this check./, error_messages.first)
+    assert_match(/Links should go somewhere, you probably want to use a `<button>` instead./, error_messages.last)
+  end
+
+  def test_does_not_warn_if_link_has_href_attribute
+    @file = "<a href='https://github.com/'>Go to GitHub</a>"
+    @linter.run(processed_source)
+
+    assert_empty @linter.offenses
+  end
+
+  def test_does_not_warn_if_link_has_href_attribute_and_has_correct_counter_comment
+    @file = <<~ERB
+      <%# erblint:counter GitHub::Accessibility::LinkHasHrefCounter 1 %>
+      <a>Go to GitHub</a>
+    ERB
+    @linter.run(processed_source)
+
+    assert_equal 0, @linter.offenses.count
+  end
+
+  def test_does_not_autocorrect_when_ignores_are_correct
+    @file = <<~ERB
+      <%# erblint:counter GitHub::Accessibility::LinkHasHrefCounter 1 %>
+      <a>Go to GitHub</a>
+    ERB
+
+    assert_equal @file, corrected_content
+  end
+
+  def test_does_autocorrect_when_ignores_are_not_correct
+    @file = <<~ERB
+      <%# erblint:counter GitHub::Accessibility::LinkHasHrefCounter 3 %>
+      <a>Go to GitHub</a>
+    ERB
+    refute_equal @file, corrected_content
+
+    expected_content = <<~ERB
+      <%# erblint:counter GitHub::Accessibility::LinkHasHrefCounter 1 %>
+      <a>Go to GitHub</a>
+    ERB
+    assert_equal expected_content, corrected_content
+  end
+end