Remove support for className prop

Closes GH-781.
Closes GH-799.

Reviewed-by: Christian Murphy <christian.murphy.42@gmail.com>

Co-authored-by: Remco Haszing <remcohaszing@gmail.com>

lib/index.js

@@ -1,5 +1,5 @@
 /**
- * @import {Element, ElementContent, Nodes, Parents, Root} from 'hast'
+ * @import {Element, Nodes, Parents, Root} from 'hast'
  * @import {Root as MdastRoot} from 'mdast'
  * @import {ComponentProps, ElementType, ReactElement} from 'react'
  * @import {Options as RemarkRehypeOptions} from 'remark-rehype'
@@ -127,6 +127,7 @@ const deprecations = [
     id: 'replace-allownode-allowedtypes-and-disallowedtypes',
     to: 'allowedElements'
   },
+  {from: 'className', id: 'deprecate-classname'},
   {
     from: 'disallowedTypes',
     id: 'replace-allownode-allowedtypes-and-disallowedtypes',
@@ -322,19 +323,6 @@ function post(tree, options) {
     )
   }
 
-  // Wrap in `div` if there’s a class name.
-  if (options.className) {
-    tree = {
-      type: 'element',
-      tagName: 'div',
-      properties: {className: options.className},
-      // Assume no doctypes.
-      children: /** @type {Array<ElementContent>} */ (
-        tree.type === 'root' ? tree.children : [tree]
-      )
-    }
-  }
-
   visit(tree, transform)
 
   return toJsxRuntime(tree, {

readme.md

@@ -302,8 +302,6 @@ Configuration (TypeScript type).
   cannot combine w/ `disallowedElements`
 * `children` (`string`, optional)
   — markdown
-* `className` (`string`, optional)
-  — wrap in a `div` with this class name
 * `components` ([`Components`][api-components], optional)
   — map tag names to components
 * `disallowedElements` (`Array<string>`, default: `[]`)

test.jsx

@@ -70,32 +70,6 @@ test('Markdown', async function (t) {
     }, /Unexpected `allowDangerousHtml` prop, remove it/)
   })
 
-  await t.test('should support `className`', function () {
-    assert.equal(
-      renderToStaticMarkup(<Markdown children="a" className="md" />),
-      '<div class="md"><p>a</p></div>'
-    )
-  })
-
-  await t.test('should support `className` (if w/o root)', function () {
-    assert.equal(
-      renderToStaticMarkup(
-        <Markdown children={'a'} className="b" rehypePlugins={[plugin]} />
-      ),
-      '<div class="b"></div>'
-    )
-
-    function plugin() {
-      /**
-       * @returns {Root}
-       */
-      return function () {
-        // @ts-expect-error: check how non-roots are handled.
-        return {type: 'comment', value: 'things!'}
-      }
-    }
-  })
-
   await t.test('should support a block quote', function () {
     assert.equal(
       renderToStaticMarkup(<Markdown children="> a" />),