fix(paste-markdown): Escape backslashes before punctuation (#866)

src/extensions/rich-text/paste-markdown.ts

@@ -5,6 +5,7 @@ import * as linkify from 'linkifyjs'
 
 import { ClipboardDataType } from '../../constants/common'
 import { PASTE_MARKDOWN_EXTENSION_PRIORITY } from '../../constants/extension-priorities'
+import { REGEX_PUNCTUATION } from '../../constants/regular-expressions'
 
 /**
  * A partial type for the the clipboard metadata coming from VS Code.
@@ -110,9 +111,17 @@ const PasteMarkdown = Extension.create({
                             return false
                         }
 
+                        // Escape all backslash characters that precede any punctuation marks, to
+                        // prevent the backslash itself from being interpreted as an escape sequence
+                        // for the subsequent character.
+                        const escapedTextContent = textContent.replace(
+                            new RegExp(`(\\\\${REGEX_PUNCTUATION.source})`, 'g'),
+                            '\\$1',
+                        )
+
                         // Send the clipboard text through the HTML serializer to convert potential
                         // Markdown into HTML, and then insert it into the editor
-                        editor.commands.insertMarkdownContent(textContent)
+                        editor.commands.insertMarkdownContent(escapedTextContent)
 
                         // Suppress the default handling behaviour
                         return true

src/serializers/markdown/markdown.ts

@@ -114,11 +114,10 @@ function createMarkdownSerializer(schema: Schema): MarkdownSerializerReturnType
         turndown.escape = (str) => {
             return (
                 str
-                    // Escape all backslash characters that precedes any punctuation characters,
-                    // otherwise the backslash character itself will be interpreted as escaping the
-                    // character that comes after it (which is not the intent). It's important that
-                    // this escape rule is executed before all other escape rules, otherwise we
-                    // could be double escaping some backslash characters.
+                    // Escape all backslash characters that precede any punctuation marks, to
+                    // prevent the backslash itself from being interpreted as an escape sequence
+                    // for the subsequent character. It's important to apply this rule first to
+                    // avoid double escaping.
                     .replace(new RegExp(`(\\\\${REGEX_PUNCTUATION.source})`, 'g'), '\\$1')
 
                     // Although the CommonMark specification allows for bulleted or ordered lists