Add preferShortcut option

Closes: GH-12.

Author: wooorm

index.d.ts

@@ -17,6 +17,11 @@ export interface ToMarkdownOptions {
    * (default: `true`).
    */
   collapseEmptyAttributes?: boolean | null | undefined
+  /**
+   * Prefer `#` and `.` shortcuts for `id` and `class`
+   * (default: `true`).
+   */
+  preferShortcut?: boolean | null | undefined
   /**
    * Leave attributes unquoted if that results in less bytes
    * (default: `false`).

lib/index.js

@@ -214,10 +214,15 @@ export function directiveToMarkdown(options) {
       ) {
         const value = String(attributes[key])
 
+        // To do: next major:
+        // Do not reorder `id` and `class` attributes when they do not turn into
+        // shortcuts.
+        // Additionally, join shortcuts: `#a .b.c d="e"` -> `#a.b.c d="e"`
         if (key === 'id') {
-          id = shortcut.test(value)
-            ? '#' + value
-            : quoted('id', value, node, state)
+          id =
+            settings.preferShortcut !== false && shortcut.test(value)
+              ? '#' + value
+              : quoted('id', value, node, state)
         } else if (key === 'class') {
           const list = value.split(/[\t\n\r ]+/g)
           /** @type {Array<string>} */
@@ -227,9 +232,10 @@ export function directiveToMarkdown(options) {
           let index = -1
 
           while (++index < list.length) {
-            ;(shortcut.test(list[index]) ? classesList : classesFullList).push(
-              list[index]
-            )
+            ;(settings.preferShortcut !== false && shortcut.test(list[index])
+              ? classesList
+              : classesFullList
+            ).push(list[index])
           }
 
           classesFull =

readme.md

@@ -267,6 +267,9 @@ Configuration.
 * `collapseEmptyAttributes`
   (`boolean`, default: `true`)
   — collapse empty attributes: get `title` instead of `title=""`
+* `preferShortcut`
+  (`boolean`, default: `true`)
+  — prefer `#` and `.` shortcuts for `id` and `class`
 * `preferUnquoted`
   (`boolean`, default: `false`)
   — leave attributes unquoted if that results in less bytes

test.js

@@ -1206,6 +1206,62 @@ test('directiveToMarkdown()', async function (t) {
     )
   })
 
+  await t.test('preferShortcut', async function (t) {
+    await t.test(
+      'should use `#` for `id`, `.` for `class` by default',
+      async function () {
+        assert.deepEqual(
+          toMarkdown(
+            {
+              type: 'textDirective',
+              name: 'i',
+              attributes: {class: 'a b', id: 'c'},
+              children: []
+            },
+            {extensions: [directiveToMarkdown()]}
+          ),
+          ':i{#c .a.b}\n'
+        )
+      }
+    )
+
+    await t.test(
+      'should use `#` for `id`, `.` for `class` w/ `preferShortcut: true`',
+      async function () {
+        assert.deepEqual(
+          toMarkdown(
+            {
+              type: 'textDirective',
+              name: 'i',
+              attributes: {class: 'a b', id: 'c'},
+              children: []
+            },
+            {extensions: [directiveToMarkdown({preferShortcut: true})]}
+          ),
+          ':i{#c .a.b}\n'
+        )
+      }
+    )
+
+    await t.test(
+      'should not use use `#` for `id`, `.` for `class` w/ `preferShortcut: false`',
+      async function () {
+        assert.deepEqual(
+          toMarkdown(
+            {
+              type: 'textDirective',
+              name: 'i',
+              attributes: {class: 'a b', id: 'c'},
+              children: []
+            },
+            {extensions: [directiveToMarkdown({preferShortcut: false})]}
+          ),
+          ':i{id="c" class="a b"}\n'
+        )
+      }
+    )
+  })
+
   await t.test('preferUnquoted', async function (t) {
     await t.test('should omit quotes in `preferUnquoted`', async function () {
       assert.deepEqual(