From 5e612f4e0c0040ea38ddfd35446d032e0048d190 Mon Sep 17 00:00:00 2001
From: Zihua Li <635902+luin@users.noreply.github.com>
Date: Wed, 17 Jul 2024 23:24:07 +0800
Subject: [PATCH] Fix white spaces not being preserved when pasted into editor

---
 packages/quill/src/modules/clipboard.ts | 47 +++++++++++++++++++++----
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/packages/quill/src/modules/clipboard.ts b/packages/quill/src/modules/clipboard.ts
index e4c3f755b5..6884686310 100644
--- a/packages/quill/src/modules/clipboard.ts
+++ b/packages/quill/src/modules/clipboard.ts
@@ -365,14 +365,47 @@ function isBetweenInlineElements(node: HTMLElement, scroll: ScrollBlot) {
 }
 
 const preNodes = new WeakMap();
-function isPre(node: Node | null) {
+
+enum WhiteSpaceStyle {
+  Collapsed,
+  Preserved,
+  Inherited,
+}
+const getWhiteSpaceStyle = (node: Node) => {
+  if (node instanceof HTMLElement) {
+    const { whiteSpace } = node.style;
+    if (
+      whiteSpace === 'pre' ||
+      whiteSpace === 'pre-wrap' ||
+      whiteSpace === 'break-spaces'
+    ) {
+      return WhiteSpaceStyle.Preserved;
+    }
+    if (whiteSpace && whiteSpace !== 'inherit') {
+      return WhiteSpaceStyle.Collapsed;
+    }
+    if (node.tagName === 'PRE') {
+      return WhiteSpaceStyle.Preserved;
+    }
+  }
+  return WhiteSpaceStyle.Inherited;
+};
+
+function shouldPreserveWhiteSpaces(node: Node | null) {
   if (node == null) return false;
+
   if (!preNodes.has(node)) {
-    // @ts-expect-error
-    if (node.tagName === 'PRE') {
-      preNodes.set(node, true);
-    } else {
-      preNodes.set(node, isPre(node.parentNode));
+    const type = getWhiteSpaceStyle(node);
+    switch (type) {
+      case WhiteSpaceStyle.Preserved:
+        preNodes.set(node, true);
+        break;
+      case WhiteSpaceStyle.Collapsed:
+        preNodes.set(node, false);
+        break;
+      case WhiteSpaceStyle.Inherited:
+        preNodes.set(node, shouldPreserveWhiteSpaces(node.parentNode));
+        break;
     }
   }
   return preNodes.get(node);
@@ -631,7 +664,7 @@ function matchText(node: HTMLElement, delta: Delta, scroll: ScrollBlot) {
   if (node.parentElement?.tagName === 'O:P') {
     return delta.insert(text.trim());
   }
-  if (!isPre(node)) {
+  if (!shouldPreserveWhiteSpaces(node)) {
     if (
       text.trim().length === 0 &&
       text.includes('\n') &&