feat(markdown): don't create excerpt if there is no <!--more-->

docs/content/3.guide/1.writing/2.markdown.md

@@ -87,6 +87,8 @@ Full amount of content beyond the more divider.
 
 Description property will contain the excerpt content unless defined within the Front Matter props.
 
+If there is no `<!--more-->` divider in the text then excerpt is undefined.
+
 Example variables will be injected into the document:
 
 ```json

src/runtime/markdown-parser/index.ts

@@ -105,5 +105,5 @@ function useExcerpt (content: string, delimiter = /<!--\s*?more\s*?-->/i) {
   if (idx !== -1) {
     return content.slice(0, idx)
   }
-  return content
+  return
 }

test/features/parser-markdown-excerpt.ts

@@ -57,5 +57,22 @@ export const testMarkdownParserExcerpt = () => {
         }
       `)
     })
+
+    test('When no <!--more--> then excerpt is undefined', async () => {
+      const parsed = await $fetch('/api/parse', {
+        method: 'POST',
+        body: {
+          id: 'content:index.md',
+          content: [
+            '# Index',
+            'First paragraph',
+            '',
+            'Second paragraph'
+          ].join('\n')
+        }
+      })
+
+      expect(parsed.excerpt).not.toBeDefined()
+    })
   })
 }