Change to return undefined, not null

Author: wooorm

lib/index.js

@@ -37,14 +37,13 @@ const markerExpression = new RegExp(
   '(\\s*<!--' + commentExpression.source + '-->\\s*)'
 )
 
-// To do: next major: replace `null` with `undefined` in API output.
 /**
  * Parse a comment marker.
  *
  * @param {unknown} value
  *   Thing to parse, typically `Node`.
- * @returns {Marker | null}
- *   Info when applicable or `null`.
+ * @returns {Marker | undefined}
+ *   Info when applicable or `undefined`.
  */
 export function commentMarker(value) {
   if (
@@ -53,17 +52,9 @@ export function commentMarker(value) {
       value.type === 'mdxFlowExpression' ||
       value.type === 'mdxTextExpression')
   ) {
-    /** @type {RegExpMatchArray | null | undefined} */
-    let match
-
-    if (value.type === 'html') {
-      match = value.value.match(markerExpression)
-    } else if (
-      value.type === 'mdxFlowExpression' ||
-      value.type === 'mdxTextExpression'
-    ) {
-      match = value.value.match(esCommentExpression)
-    }
+    const match = value.value.match(
+      value.type === 'html' ? markerExpression : esCommentExpression
+    )
 
     if (match && match[0].length === value.value.length) {
       const parameters = parseParameters(match[3] || '')
@@ -78,8 +69,6 @@ export function commentMarker(value) {
       }
     }
   }
-
-  return null
 }
 
 /**

readme.md

@@ -103,7 +103,7 @@ Yields:
     value: `<!--foo bar baz=12.4 qux="test test" quux='false'-->`
   }
 }
-null
+undefined
 {
   name: 'lint',
   attributes: 'disable heading-style',
@@ -131,7 +131,7 @@ Parse a comment marker.
 
 ###### Returns
 
-Info ([`Marker`][api-marker]) when applicable or `null`.
+Info ([`Marker`][api-marker]) when applicable or `undefined`.
 
 ### `Marker`
 

test.js

@@ -13,32 +13,32 @@ test('commentMaker', async function (t) {
     assert.equal(
       // @ts-expect-error: check that the runtime handles a missing node.
       commentMarker(),
-      null
+      undefined
     )
   })
 
   await t.test('should work without html node', async function () {
     const paragraph = {type: 'paragraph', children: []}
 
-    assert.equal(commentMarker(paragraph), null)
+    assert.equal(commentMarker(paragraph), undefined)
   })
 
   await t.test('should work without comment', async function () {
     const html = {type: 'html', value: '<div></div>'}
 
-    assert.equal(commentMarker(html), null)
+    assert.equal(commentMarker(html), undefined)
   })
 
   await t.test('should work for empty comments', async function () {
     const html = {type: 'html', value: '<!-- -->'}
 
-    assert.equal(commentMarker(html), null)
+    assert.equal(commentMarker(html), undefined)
   })
 
   await t.test('should work for partial comments', async function () {
     const html = {type: 'html', value: '<!--foo-->this is something else.'}
 
-    assert.equal(commentMarker(html), null)
+    assert.equal(commentMarker(html), undefined)
   })
 
   await t.test('should support a marker without attributes', async function () {
@@ -160,7 +160,7 @@ test('commentMaker', async function (t) {
     async function () {
       const html = {type: 'html', value: '<!--foo bar=-->'}
 
-      assert.equal(commentMarker(html), null)
+      assert.equal(commentMarker(html), undefined)
     }
   )
 
@@ -169,7 +169,7 @@ test('commentMaker', async function (t) {
     async function () {
       const html = {type: 'html', value: '<!--foo bar= qux-->'}
 
-      assert.equal(commentMarker(html), null)
+      assert.equal(commentMarker(html), undefined)
     }
   )
 
@@ -178,7 +178,7 @@ test('commentMaker', async function (t) {
     async function () {
       const html = {type: 'html', value: '<!--foo |-->'}
 
-      assert.equal(commentMarker(html), null)
+      assert.equal(commentMarker(html), undefined)
     }
   )