Add support for afterTransform hook

Reviewed-by: Titus Wormer <tituswormer@gmail.com> Closes GH-14. Closes GH-15.
syntax-tree · Jan 26, 2022 · 57fd68b · 57fd68b
1 parent 5663ec8
commit 57fd68b
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Showing 3 changed files with 52 additions and 3 deletions.
diff --git a/lib/index.js b/lib/index.js
@@ -8,16 +8,30 @@
  * @typedef {HastParent['children'][number]} HastChild
  * @typedef {HastChild|HastRoot} HastNode
  *
+ * @callback AfterTransform
+ *   Function called when a hast node is transformed into a DOM node
+ * @param {HastNode} hastNode
+ *   The hast node that was handled
+ * @param {Node} domNode
+ *   The corresponding DOM node
+ * @returns {void}
+ *
  * @typedef Options
- * @property {boolean} [fragment=false] Whether a DOM fragment should be returned
- * @property {Document} [document] Document interface to use (default: `globalThis.document`)
- * @property {string} [namespace] `namespace` to use to create elements
+ * @property {boolean} [fragment=false]
+ *   Whether a DOM fragment should be returned
+ * @property {Document} [document]
+ *   Document interface to use (default: `globalThis.document`)
+ * @property {string} [namespace]
+ *   `namespace` to use to create elements
+ * @property {AfterTransform} [afterTransform]
+ *   Callback invoked after each node transformation
  *
  * @typedef Context
  * @property {Document} doc
  * @property {boolean} [fragment=false]
  * @property {string} [namespace]
  * @property {string} [impliedNamespace]
+ * @property {AfterTransform} [afterTransform]
  */
 
 import {webNamespaces} from 'web-namespaces'
@@ -30,6 +44,16 @@ import {find, html, svg} from 'property-information'
  * @param {Context} ctx
  */
 function transform(node, ctx) {
+  const transformed = one(node, ctx)
+  if (ctx.afterTransform) ctx.afterTransform(node, transformed)
+  return transformed
+}
+
+/**
+ * @param {HastNode} node
+ * @param {Context} ctx
+ */
+function one(node, ctx) {
   switch (node.type) {
     case 'root':
       return root(node, ctx)

diff --git a/readme.md b/readme.md
@@ -88,6 +88,12 @@ Document interface to use (default: `globalThis.document`).
 
 `namespace` to use to create [*elements*][element].
 
+###### `options.afterTransform`
+
+Function called when a hast node is transformed into a DOM node (`Function?`).
+Given the hast node that was handled as the first parameter and the
+corresponding DOM node as the second parameter.
+
 ## Security
 
 Use of `hast-util-to-dom` can open you up to a

diff --git a/test/index.js b/test/index.js
@@ -359,6 +359,25 @@ test('hast-util-to-dom', (t) => {
     'encodes data properties when string'
   )
 
+  t.deepEqual(
+    (() => {
+      /** @type {Array<[HastNode, string]>} */
+      const calls = []
+      toDom(h('html', [h('title', 'Hi')]), {
+        afterTransform: (node, transformed) => {
+          calls.push([node, serializeNodeToHtmlString(transformed)])
+        }
+      })
+      return calls
+    })(),
+    [
+      [{type: 'text', value: 'Hi'}, 'Hi'],
+      [h('title', 'Hi'), '<title>Hi</title>'],
+      [h('html', [h('title', 'Hi')]), '<html><title>Hi</title></html>']
+    ],
+    'should invoke afterTransform'
+  )
+
   t.end()
 })