fix(markdown): preserve non-breakable whitespaces (#3327)

src/util.js

@@ -683,8 +683,7 @@ function splitText(text) {
 
   text
     .replace(new RegExp(`(${cjkPattern})\n(${cjkPattern})`, "g"), "$1$2")
-    // `\s` but exclude full-width whitspace (`\u3000`)
-    .split(/([^\S\u3000]+)/)
+    .split(/([ \t\n]+)/)
     .forEach((token, index, tokens) => {
       // whitespace
       if (index % 2 === 1) {

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

@@ -185,3 +185,42 @@ abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc abc
 * [valid-expect](/packages/eslint-plugin-jest/docs/rules/valid-expect.md) - ensure expect is called correctly.
 
 `;
+
+exports[`whitespace.md 1`] = `
+<!-- 0xA0 non-breaking whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+<!-- 0x20 standard whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<!-- 0xA0 non-breaking whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+<!-- 0x20 standard whitespace -->
+
+keep these words together keep these words together keep these words together
+keep these words together
+
+`;
+
+exports[`whitespace.md 2`] = `
+<!-- 0xA0 non-breaking whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+<!-- 0x20 standard whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<!-- 0xA0 non-breaking whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+<!-- 0x20 standard whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+`;

tests/markdown_paragraph/whitespace.md

@@ -0,0 +1,7 @@
+<!-- 0xA0 non-breaking whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together
+
+<!-- 0x20 standard whitespace -->
+
+keep these words together keep these words together keep these words together keep these words together

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

@@ -3635,7 +3635,7 @@ a*"foo"*
 exports[`example-328.md 1`] = `
 * a *
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-_ a _
+_ a _
 
 `;