Fix Newline handling in Web's Composer (#6658)

src/view/com/composer/text-input/TextInput.web.tsx

@@ -11,6 +11,7 @@ import {Paragraph} from '@tiptap/extension-paragraph'
 import {Placeholder} from '@tiptap/extension-placeholder'
 import {Text as TiptapText} from '@tiptap/extension-text'
 import {generateJSON} from '@tiptap/html'
+import {Fragment, Node, Slice} from '@tiptap/pm/model'
 import {EditorContent, JSONContent, useEditor} from '@tiptap/react'
 
 import {useColorSchemeStyle} from '#/lib/hooks/useColorSchemeStyle'
@@ -166,6 +167,11 @@ export const TextInput = React.forwardRef(function TextInputImpl(
   const editor = useEditor(
     {
       extensions,
+      coreExtensionOptions: {
+        clipboardTextSerializer: {
+          blockSeparator: '\n',
+        },
+      },
       onFocus() {
         onFocus?.()
       },
@@ -173,6 +179,20 @@ export const TextInput = React.forwardRef(function TextInputImpl(
         attributes: {
           class: modeClass,
         },
+        clipboardTextParser: (text, context) => {
+          const blocks = text.split(/(?:\r\n?|\n)/)
+          const nodes: Node[] = blocks.map(line => {
+            return Node.fromJSON(
+              context.doc.type.schema,
+              line.length > 0
+                ? {type: 'paragraph', content: [{type: 'text', text: line}]}
+                : {type: 'paragraph', content: []},
+            )
+          })
+
+          const fragment = Fragment.fromArray(nodes)
+          return Slice.maxOpen(fragment)
+        },
         handlePaste: (view, event) => {
           const clipboardData = event.clipboardData
           let preventDefault = false