FEATURE: Add anchor links to headings (#12379)

app/assets/javascripts/discourse/tests/unit/lib/pretty-text-test.js

@@ -664,13 +664,13 @@ eviltrout</p>
 
     assert.cooked(
       "># #category-hashtag\n",
-      '<blockquote>\n<h1><span class="hashtag">#category-hashtag</span></h1>\n</blockquote>',
+      '<blockquote>\n<h1><a name="category-hashtag" class="anchor" href="#category-hashtag"></a><span class="hashtag">#category-hashtag</span></h1>\n</blockquote>',
       "it handles category hashtags in simple quotes"
     );
 
     assert.cooked(
       "# #category-hashtag",
-      '<h1><span class="hashtag">#category-hashtag</span></h1>',
+      '<h1><a name="category-hashtag" class="anchor" href="#category-hashtag"></a><span class="hashtag">#category-hashtag</span></h1>',
       "it works within ATX-style headers"
     );
 
@@ -696,7 +696,7 @@ eviltrout</p>
   test("Heading", function (assert) {
     assert.cooked(
       "**Bold**\n----------",
-      "<h2><strong>Bold</strong></h2>",
+      '<h2><a name="bold" class="anchor" href="#bold"></a><strong>Bold</strong></h2>',
       "It will bold the heading"
     );
   });
@@ -939,7 +939,7 @@ eviltrout</p>
 
     assert.cooked(
       "## a\nb\n```\nc\n```",
-      '<h2>a</h2>\n<p>b</p>\n<pre><code class="lang-auto">c\n</code></pre>',
+      '<h2><a name="a" class="anchor" href="#a"></a>a</h2>\n<p>b</p>\n<pre><code class="lang-auto">c\n</code></pre>',
       "it handles headings with code blocks after them."
     );
   });

app/assets/javascripts/pretty-text/addon/allow-lister.js

@@ -130,6 +130,7 @@ export default class AllowLister {
 // Only add to `default` when you always want your allowlist to occur. In other words,
 // don't change this for a plugin or a feature that can be disabled
 export const DEFAULT_LIST = [
+  "a.anchor",
   "a.attachment",
   "a.hashtag",
   "a.mention",

app/assets/javascripts/pretty-text/engines/discourse-markdown/anchor.js

@@ -0,0 +1,29 @@
+export function setup(helper) {
+  helper.registerPlugin((md) => {
+    md.core.ruler.push("anchor", (state) => {
+      for (let idx = 0; idx < state.tokens.length; idx++) {
+        if (state.tokens[idx].type !== "heading_open") {
+          continue;
+        }
+
+        const linkOpen = new state.Token("link_open", "a", 1);
+        const linkClose = new state.Token("link_close", "a", -1);
+
+        const slug = state.tokens[idx + 1].content
+          .toLowerCase()
+          .replace(/\s+/g, "-")
+          .replace(/[^\w\-]+/g, "")
+          .replace(/\-\-+/g, "-")
+          .replace(/^-+/, "")
+          .replace(/-+$/, "");
+
+        linkOpen.attrSet("name", slug);
+        linkOpen.attrSet("class", "anchor");
+        linkOpen.attrSet("href", "#" + slug);
+
+        state.tokens[idx + 1].children.unshift(linkClose);
+        state.tokens[idx + 1].children.unshift(linkOpen);
+      }
+    });
+  });
+}

app/assets/stylesheets/common/base/topic-post.scss

@@ -94,6 +94,20 @@ $quote-share-maxwidth: 150px;
   h6 {
     margin: 30px 0 10px;
     line-height: $line-height-medium;
+
+    &:hover {
+      a.anchor {
+        &:before {
+          content: svg-uri(
+            '<svg xmlns="http://www.w3.org/2000/svg" width="16px" height="16px" viewBox="0 0 512 512"><path d="M326.612 185.391c59.747 59.809 58.927 155.698.36 214.59-.11.12-.24.25-.36.37l-67.2 67.2c-59.27 59.27-155.699 59.262-214.96 0-59.27-59.26-59.27-155.7 0-214.96l37.106-37.106c9.84-9.84 26.786-3.3 27.294 10.606.648 17.722 3.826 35.527 9.69 52.721 1.986 5.822.567 12.262-3.783 16.612l-13.087 13.087c-28.026 28.026-28.905 73.66-1.155 101.96 28.024 28.579 74.086 28.749 102.325.51l67.2-67.19c28.191-28.191 28.073-73.757 0-101.83-3.701-3.694-7.429-6.564-10.341-8.569a16.037 16.037 0 0 1-6.947-12.606c-.396-10.567 3.348-21.456 11.698-29.806l21.054-21.055c5.521-5.521 14.182-6.199 20.584-1.731a152.482 152.482 0 0 1 20.522 17.197zM467.547 44.449c-59.261-59.262-155.69-59.27-214.96 0l-67.2 67.2c-.12.12-.25.25-.36.37-58.566 58.892-59.387 154.781.36 214.59a152.454 152.454 0 0 0 20.521 17.196c6.402 4.468 15.064 3.789 20.584-1.731l21.054-21.055c8.35-8.35 12.094-19.239 11.698-29.806a16.037 16.037 0 0 0-6.947-12.606c-2.912-2.005-6.64-4.875-10.341-8.569-28.073-28.073-28.191-73.639 0-101.83l67.2-67.19c28.239-28.239 74.3-28.069 102.325.51 27.75 28.3 26.872 73.934-1.155 101.96l-13.087 13.087c-4.35 4.35-5.769 10.79-3.783 16.612 5.864 17.194 9.042 34.999 9.69 52.721.509 13.906 17.454 20.446 27.294 10.606l37.106-37.106c59.271-59.259 59.271-155.699.001-214.959z"></path></svg>'
+          );
+          float: left;
+          margin-left: -20px;
+          padding-right: 4px;
+          position: absolute;
+        }
+      }
+    }
   }
 
   h1 {

plugins/poll/spec/lib/pretty_text_spec.rb

@@ -189,8 +189,8 @@ describe PrettyText do
       </div>
     HTML
 
-    expect(cooked).to include("<h1>Pre-heading</h1>")
+    expect(cooked).to include("<h1>\n<a name=\"pre-heading\" class=\"anchor\" href=\"#pre-heading\"></a>Pre-heading</h1>")
-    expect(cooked).to include("<h1>Post-heading</h1>")
+    expect(cooked).to include("<h1>\n<a name=\"post-heading\" class=\"anchor\" href=\"#post-heading\"></a>Post-heading</h1>")
   end
 
   it "does not break when there are headings before/after a poll without a title" do
@@ -211,7 +211,7 @@ describe PrettyText do
       <div class="poll" data-poll-status="open" data-poll-name="poll">
     HTML
 
-    expect(cooked).to include("<h1>Pre-heading</h1>")
+    expect(cooked).to include("<h1>\n<a name=\"pre-heading\" class=\"anchor\" href=\"#pre-heading\"></a>Pre-heading</h1>")
-    expect(cooked).to include("<h1>Post-heading</h1>")
+    expect(cooked).to include("<h1>\n<a name=\"post-heading\" class=\"anchor\" href=\"#post-heading\"></a>Post-heading</h1>")
   end
 end

spec/components/pretty_text_spec.rb

@@ -1903,4 +1903,17 @@ HTML
       expect(cooked).to eq(html.strip)
     end
   end
+
+  it "adds anchor links to headings" do
+    cooked = PrettyText.cook('# Hello world')
+
+    html = <<~HTML
+      <h1>
+      <a name="hello-world" class="anchor" href="#hello-world"></a>
+      Hello world
+      </h1>
+    HTML
+
+    expect(cooked).to match_html(html)
+  end
 end

spec/integrity/common_mark_spec.rb

@@ -33,6 +33,7 @@ describe "CommonMark" do
         cooked.strip!
         cooked.gsub!(" class=\"lang-auto\"", '')
         cooked.gsub!(/<span class="hashtag">(.*)<\/span>/, "\\1")
+        cooked.gsub!(/<a name="(.*)" class="anchor" href="#\1*"><\/a>/, "")
         # we don't care about this
         cooked.gsub!("<blockquote>\n</blockquote>", "<blockquote></blockquote>")
         html.gsub!("<blockquote>\n</blockquote>", "<blockquote></blockquote>")