fix(markdown): preserve entity for surrogate pair (#4832)

src/language-markdown/parser-markdown.js

@@ -6,6 +6,9 @@ const pragma = require("./pragma");
 const parseFrontMatter = require("../utils/front-matter");
 const util = require("../common/util");
 
+// 0x0 ~ 0x10ffff
+const isSingleCharRegex = /^([\u0000-\uffff]|[\ud800-\udbff][\udc00-\udfff])$/;
+
 /**
  * based on [MDAST](https://github.com/syntax-tree/mdast) with following modifications:
  *
@@ -66,8 +69,9 @@ function restoreUnescapedCharacter(originalText) {
             value:
               node.value !== "*" &&
               node.value !== "_" && // handle these two cases in printer
-              node.value.length === 1 &&
-              node.position.end.offset - node.position.start.offset > 1
+              isSingleCharRegex.test(node.value) &&
+              node.position.end.offset - node.position.start.offset !==
+                node.value.length
                 ? originalText.slice(
                     node.position.start.offset,
                     node.position.end.offset

tests/markdown_word/__snapshots__/jsfmt.spec.js.snap

@@ -18,6 +18,18 @@ asd & asd „ 123
 123 * 123 * 123
 
 ## 类的 prototype 属性和\\_\\_proto\\_\\_属性
+
+123�123
+
+123#123
+
+123Ϡ123
+
+123😉123
+
+123"123
+
+123�123
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 hello \\* world \\_ ~~ ya
 
@@ -37,4 +49,16 @@ asd & asd „ 123
 
 ## 类的 prototype 属性和\\_\\_proto\\_\\_属性
 
+123�123
+
+123#123
+
+123Ϡ123
+
+123😉123
+
+123"123
+
+123�123
+
 `;

tests/markdown_word/escape.md

@@ -15,3 +15,15 @@ asd & asd „ 123
 123 * 123 * 123
 
 ## 类的 prototype 属性和\_\_proto\_\_属性
+
+123�123
+
+123#123
+
+123Ϡ123
+
+123😉123
+
+123"123
+
+123�123