fix(html): do not format non-normal whitespaces as normal whitespaces (#5797)

CHANGELOG.unreleased.md

@@ -47,5 +47,23 @@ Examples:
   In Prettier 1.16.0 and 1.16.1, `--list-different` and `--check` logged every file in some CI environments, instead of just unformatted files.
   This unwanted behavior is now fixed.
 
-[#5804]: https://github.com/prettier/prettier/pull/5804
-[@kachkaev]: https://github.com/kachkaev
+- HTML: Do not format non-normal whitespace as normal whitespace ([#5797] by [@ikatyang])
+
+  Previously, only non-breaking whitespaces (U+00A0) are marked as non-normal whitespace,
+  which means other non-normal whitespaces such as non-breaking narrow whitespaces (U+202F)
+  could be formatted as normal whitespaces, which breaks the output. We now follow the spec to
+  exclude all non-[ASCII whitespace](https://infra.spec.whatwg.org/#ascii-whitespace) from whitespace normalization.
+
+  (`·` represents a non-breaking narrow whitespace)
+
+  <!-- prettier-ignore -->
+  ```html
+  <!-- Input -->
+  Prix·:·32·€
+
+  <!-- Output (Prettier stable) -->
+  Prix : 32 €
+
+  <!-- Output (Prettier master) -->
+  Prix·:·32·€
+  ```

src/language-html/printer-html.js

@@ -900,8 +900,8 @@ function getTextValueParts(node, value = node.value) {
           dedentString(value.replace(/^\s*?\n|\n\s*?$/g, "")),
           hardline
         )
-    : // non-breaking whitespace: 0xA0
-      join(line, value.split(/[^\S\xA0]+/)).parts;
+    : // https://infra.spec.whatwg.org/#ascii-whitespace
+      join(line, value.split(/[\t\n\f\r ]+/)).parts;
 }
 
 function printEmbeddedAttributeValue(node, originalTextToDoc, options) {

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

@@ -203,6 +203,8 @@ printWidth: 80
 <span>Nihil aut odit omnis. Quam maxime est molestiae. Maxime dolorem dolores voluptas quaerat ut qui sunt vitae error.</span>
 <!-- non-breaking whitespaces -->
 <span>Nihil aut odit omnis. Quam maxime est molestiae. Maxime dolorem dolores voluptas quaerat ut qui sunt vitae error.</span>
+<!-- non-breaking narrow whitespaces -->
+<span>Prix : 32 €</span>
 
 =====================================output=====================================
 <!-- normal whitespaces -->
@@ -214,6 +216,8 @@ printWidth: 80
 <span
   >Nihil aut odit omnis. Quam maxime est molestiae. Maxime dolorem dolores voluptas quaerat ut qui sunt vitae error.</span
 >
+<!-- non-breaking narrow whitespaces -->
+<span>Prix : 32 €</span>
 
 ================================================================================
 `;

tests/html_whitespace/non-breaking-whitespace.html

@@ -2,3 +2,5 @@
 <span>Nihil aut odit omnis. Quam maxime est molestiae. Maxime dolorem dolores voluptas quaerat ut qui sunt vitae error.</span>
 <!-- non-breaking whitespaces -->
 <span>Nihil aut odit omnis. Quam maxime est molestiae. Maxime dolorem dolores voluptas quaerat ut qui sunt vitae error.</span>
+<!-- non-breaking narrow whitespaces -->
+<span>Prix : 32 €</span>