1 files changed, 31 insertions, 0 deletions
diff --git a/doc/.markdownlint/rules/tabs_title_markup.js b/doc/.markdownlint/rules/tabs_title_markup.js
new file mode 100644
index 00000000000..9c1de1e630d
--- /dev/null
+++ b/doc/.markdownlint/rules/tabs_title_markup.js
@@ -0,0 +1,31 @@
+const { globalPath } = require('../require_helper');
+const { forEachLine, getLineMetadata } = require(`${globalPath}/markdownlint-rule-helpers`);
+
+module.exports = {
+  names: ['tabs-title-markup'],
+  description: 'Incorrect number of colon characters for tag',
+  information: new URL('https://docs.gitlab.com/ee/development/documentation/styleguide/#tabs'),
+  tags: ['gitlab-docs', 'tabs'],
+  function: (params, onError) => {
+    // Note the correct number of colons in each tab tag type.
+    const wrapperColons = 2;
+    const titleColons = 3;
+
+    forEachLine(getLineMetadata(params), (line, lineIndex) => {
+      // Get the number of colons in this line.
+      const colonCount = [...line].filter((x) => x === ':').length;
+
+      // Throw an error in the case of a mismatch.
+      if (
+        ((line.includes(':Tabs') || line.includes(':EndTabs')) && colonCount !== wrapperColons) ||
+        (line.includes(':TabTitle') && colonCount !== titleColons)
+      ) {
+        const correctColonCount = line.includes(':TabTitle') ? wrapperColons : titleColons;
+        onError({
+          lineNumber: lineIndex + 1,
+          detail: `Actual: ${colonCount}; Expected: ${correctColonCount}`,
+        });
+      }
+    });
+  },
+};