From 677da0ca87ffefb36676200fee5cf5cf0136b22e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Claud=C3=A9ric=20Demers?= <clauderic.d@gmail.com>
Date: Sun, 26 Sep 2021 11:07:14 -0400
Subject: [PATCH] Fix `toSlatePoint` when text node ends in `\n` in Firefox
 (#4547)

In Firefox, `range.cloneContents()` returns an extra trailing '\n', when the document ends with a new-line character. This results in the offset length being off by one, so we need to subtract one to account for this.
---
 .changeset/firefox-newline-bug.md             |  5 +++++
 .../slate-react/src/plugin/react-editor.ts    | 19 ++++++++++++-------
 2 files changed, 17 insertions(+), 7 deletions(-)
 create mode 100644 .changeset/firefox-newline-bug.md

diff --git a/.changeset/firefox-newline-bug.md b/.changeset/firefox-newline-bug.md
new file mode 100644
index 000000000..9f1457436
--- /dev/null
+++ b/.changeset/firefox-newline-bug.md
@@ -0,0 +1,5 @@
+---
+'slate-react': patch
+---
+
+Fixed a bug that caused the editor to be unable to resolve a Slate point from a DOM point when selecting an entire document that ended in a new line in Firefox.
diff --git a/packages/slate-react/src/plugin/react-editor.ts b/packages/slate-react/src/plugin/react-editor.ts
index 4e7e178c6..a41ce4bed 100644
--- a/packages/slate-react/src/plugin/react-editor.ts
+++ b/packages/slate-react/src/plugin/react-editor.ts
@@ -24,7 +24,7 @@ import {
   normalizeDOMPoint,
   hasShadowRoot,
 } from '../utils/dom'
-import { IS_CHROME } from '../utils/environment'
+import { IS_CHROME, IS_FIREFOX } from '../utils/environment'
 
 /**
  * A React and DOM-specific version of the `Editor` interface.
@@ -463,6 +463,7 @@ export const ReactEditor = {
         const range = window.document.createRange()
         range.setStart(textNode, 0)
         range.setEnd(nearestNode, nearestOffset)
+
         const contents = range.cloneContents()
         const removals = [
           ...Array.prototype.slice.call(
@@ -502,15 +503,19 @@ export const ReactEditor = {
         }
       }
 
-      // COMPAT: If the parent node is a Slate zero-width space, editor is
-      // because the text node should have no characters. However, during IME
-      // composition the ASCII characters will be prepended to the zero-width
-      // space, so subtract 1 from the offset to account for the zero-width
-      // space character.
       if (
         domNode &&
         offset === domNode.textContent!.length &&
-        parentNode.hasAttribute('data-slate-zero-width')
+        // COMPAT: If the parent node is a Slate zero-width space, editor is
+        // because the text node should have no characters. However, during IME
+        // composition the ASCII characters will be prepended to the zero-width
+        // space, so subtract 1 from the offset to account for the zero-width
+        // space character.
+        (parentNode.hasAttribute('data-slate-zero-width') ||
+          // COMPAT: In Firefox, `range.cloneContents()` returns an extra trailing '\n'
+          // when the document ends with a new-line character. This results in the offset
+          // length being off by one, so we need to subtract one to account for this.
+          (IS_FIREFOX && domNode.textContent?.endsWith('\n')))
       ) {
         offset--
       }