fix: nested embeds (JS in HTML in JS) (#6038)

CHANGELOG.unreleased.md

@@ -363,6 +363,26 @@ new (x())!.y();
 new e[f().x].y();
 ```
 
+### JavaScript: Fix nested embeds (JS in HTML in JS) ([#6038] by [@thorn0])
+
+Previously, if JS code embedded in HTML (via `<script>`) embedded in JS (via a template literal) contained template literals, the inner JS was not formatted.
+
+<!-- prettier-ignore -->
+```js
+// Input
+const html = /* HTML */ `<script>var a=\`\`</script>`;
+
+// Output (Prettier stable)
+// SyntaxError: Expecting Unicode escape sequence \uXXXX (1:8)
+
+// Output (Prettier master)
+const html = /* HTML */ `
+  <script>
+    var a = \`\`;
+  </script>
+`;
+```
+
 ### TypeScript: Keep line breaks within mapped types.([#6146] by [@sosukesuzuki])
 
 Previously, Prettier has removed line breaks within mapped types.This change keeps it, similar to how it treats other object types.
@@ -429,6 +449,7 @@ f[a::b];
 [#6133]: https://github.com/prettier/prettier/pull/6133
 [#6136]: https://github.com/prettier/prettier/pull/6136
 [#6140]: https://github.com/prettier/prettier/pull/6140
+[#6038]: https://github.com/prettier/prettier/pull/6038
 [#6148]: https://github.com/prettier/prettier/pull/6148
 [#6146]: https://github.com/prettier/prettier/pull/6146
 [#6152]: https://github.com/prettier/prettier/pull/6152

src/common/util.js

@@ -500,10 +500,7 @@ function printString(raw, options, isDirectiveLiteral) {
       options.parser === "css" ||
       options.parser === "less" ||
       options.parser === "scss" ||
-      options.parentParser === "html" ||
-      options.parentParser === "vue" ||
-      options.parentParser === "angular" ||
-      options.parentParser === "lwc"
+      options.embeddedInHtml
     )
   );
 }

src/language-html/printer-html.js

@@ -113,7 +113,7 @@ function embed(path, print, textToDoc, options) {
 
       // lit-html: html`<my-element obj=${obj}></my-element>`
       if (
-        /^PRETTIER_HTML_PLACEHOLDER_\d+_IN_JS$/.test(
+        /^PRETTIER_HTML_PLACEHOLDER_\d+_\d+_IN_JS$/.test(
           options.originalText.slice(
             node.valueSpan.start.offset,
             node.valueSpan.end.offset

src/language-js/embed.js

@@ -16,7 +16,7 @@ const {
   utils: { mapDoc, stripTrailingHardline }
 } = require("../doc");
 
-function embed(path, print, textToDoc /*, options */) {
+function embed(path, print, textToDoc, options) {
   const node = path.getValue();
   const parent = path.getParentNode();
   const parentParent = path.getParentNode(1);
@@ -135,12 +135,20 @@ function embed(path, print, textToDoc /*, options */) {
         ]);
       }
 
-      if (isHtml(path)) {
-        return printHtmlTemplateLiteral(path, print, textToDoc, "html");
-      }
+      const htmlParser = isHtml(path)
+        ? "html"
+        : isAngularComponentTemplate(path)
+        ? "angular"
+        : undefined;
 
-      if (isAngularComponentTemplate(path)) {
-        return printHtmlTemplateLiteral(path, print, textToDoc, "angular");
+      if (htmlParser) {
+        return printHtmlTemplateLiteral(
+          path,
+          print,
+          textToDoc,
+          htmlParser,
+          options.embeddedInHtml
+        );
       }
 
       break;
@@ -195,6 +203,10 @@ function getIndentation(str) {
   return firstMatchedIndent === null ? "" : firstMatchedIndent[1];
 }
 
+function uncook(cookedValue) {
+  return cookedValue.replace(/([\\`]|\$\{)/g, "\\$1");
+}
+
 function escapeTemplateCharacters(doc, raw) {
   return mapDoc(doc, currentDoc => {
     if (!currentDoc.parts) {
@@ -205,11 +217,7 @@ function escapeTemplateCharacters(doc, raw) {
 
     currentDoc.parts.forEach(part => {
       if (typeof part === "string") {
-        parts.push(
-          raw
-            ? part.replace(/(\\*)`/g, "$1$1\\`")
-            : part.replace(/([\\`]|\$\{)/g, "\\$1")
-        );
+        parts.push(raw ? part.replace(/(\\*)`/g, "$1$1\\`") : uncook(part));
       } else {
         parts.push(part);
       }
@@ -576,19 +584,29 @@ function isHtml(path) {
   );
 }
 
-function printHtmlTemplateLiteral(path, print, textToDoc, parser) {
+// The counter is needed to distinguish nested embeds.
+let htmlTemplateLiteralCounter = 0;
+
+function printHtmlTemplateLiteral(
+  path,
+  print,
+  textToDoc,
+  parser,
+  escapeClosingScriptTag
+) {
   const node = path.getValue();
 
-  const placeholderPattern = "PRETTIER_HTML_PLACEHOLDER_(\\d+)_IN_JS";
-  const placeholders = node.expressions.map(
-    (_, i) => `PRETTIER_HTML_PLACEHOLDER_${i}_IN_JS`
-  );
+  const counter = htmlTemplateLiteralCounter;
+  htmlTemplateLiteralCounter = (htmlTemplateLiteralCounter + 1) >>> 0;
+
+  const composePlaceholder = index =>
+    `PRETTIER_HTML_PLACEHOLDER_${index}_${counter}_IN_JS`;
 
   const text = node.quasis
     .map((quasi, index, quasis) =>
       index === quasis.length - 1
-        ? quasi.value.raw
-        : quasi.value.raw + placeholders[index]
+        ? quasi.value.cooked
+        : quasi.value.cooked + composePlaceholder(index)
     )
     .join("");
 
@@ -598,14 +616,12 @@ function printHtmlTemplateLiteral(path, print, textToDoc, parser) {
     return "``";
   }
 
+  const placeholderRegex = RegExp(composePlaceholder("(\\d+)"), "g");
+
   const contentDoc = mapDoc(
     stripTrailingHardline(textToDoc(text, { parser })),
     doc => {
-      const placeholderRegex = new RegExp(placeholderPattern, "g");
-      const hasPlaceholder =
-        typeof doc === "string" && placeholderRegex.test(doc);
-
-      if (!hasPlaceholder) {
+      if (typeof doc !== "string") {
         return doc;
       }
 
@@ -613,10 +629,14 @@ function printHtmlTemplateLiteral(path, print, textToDoc, parser) {
 
       const components = doc.split(placeholderRegex);
       for (let i = 0; i < components.length; i++) {
-        const component = components[i];
+        let component = components[i];
 
         if (i % 2 === 0) {
           if (component) {
+            component = uncook(component);
+            if (escapeClosingScriptTag) {
+              component = component.replace(/<\/(script)\b/gi, "<\\/$1");
+            }
             parts.push(component);
           }
           continue;

src/language-js/needs-parens.js

@@ -129,6 +129,18 @@ function needsParens(path, options) {
 
   // Identifiers never need parentheses.
   if (node.type === "Identifier") {
+    // ...unless those identifiers are embed placeholders. They might be substituted by complex
+    // expressions, so the parens around them should not be dropped. Example (JS-in-HTML-in-JS):
+    //     let tpl = html`<script> f((${expr}) / 2); </script>`;
+    // If the inner JS formatter removes the parens, the expression might change its meaning:
+    //     f((a + b) / 2)  vs  f(a + b / 2)
+    if (
+      node.extra &&
+      node.extra.parenthesized &&
+      /^PRETTIER_HTML_PLACEHOLDER_\d+_\d+_IN_JS$/.test(node.name)
+    ) {
+      return true;
+    }
     return false;
   }
 

src/main/multiparser.js

@@ -19,6 +19,13 @@ function textToDoc(text, partialNextOptions, parentOptions, printAstToDoc) {
   const nextOptions = normalize(
     Object.assign({}, parentOptions, partialNextOptions, {
       parentParser: parentOptions.parser,
+      embeddedInHtml: !!(
+        parentOptions.embeddedInHtml ||
+        parentOptions.parser === "html" ||
+        parentOptions.parser === "vue" ||
+        parentOptions.parser === "angular" ||
+        parentOptions.parser === "lwc"
+      ),
       originalText: text
     }),
     { passThrough: true }

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

@@ -31,3 +31,47 @@ printWidth: 80
 
 ================================================================================
 `;
+
+exports[`script-tag-escaping.html 1`] = `
+====================================options=====================================
+parsers: ["html"]
+printWidth: 80
+                                                                                | printWidth
+=====================================input======================================
+<script>
+  document.write(/* HTML */ \`
+    <script>
+      document.write(/* HTML */ \\\`
+        <!-- foo1 -->
+        <script>
+          document.write(/* HTML */ \\\\\\\`<!-- bar1 --> bar <!-- bar2 -->\\\\\\\`);
+        <\\\\/script>
+        <!-- foo2 -->
+      \\\`);
+    <\\/script>
+  \`);
+</script>
+
+=====================================output=====================================
+<script>
+  document.write(/* HTML */ \`
+    <script>
+      document.write(/* HTML */ \\\`
+        <!-- foo1 -->
+        <script>
+          document.write(
+            /* HTML */ \\\\\\\`
+              <!-- bar1 -->
+              bar
+              <!-- bar2 -->
+            \\\\\\\`
+          );
+        <\\\\/script>
+        <!-- foo2 -->
+      \\\`);
+    <\\/script>
+  \`);
+</script>
+
+================================================================================
+`;

tests/multiparser_html_js/script-tag-escaping.html

@@ -0,0 +1,13 @@
+<script>
+  document.write(/* HTML */ `
+    <script>
+      document.write(/* HTML */ \`
+        <!-- foo1 -->
+        <script>
+          document.write(/* HTML */ \\\`<!-- bar1 --> bar <!-- bar2 -->\\\`);
+        <\\/script>
+        <!-- foo2 -->
+      \`);
+    <\/script>
+  `);
+</script>

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

@@ -68,6 +68,17 @@ function HelloWorld() {
   \`;
 }
 
+const trickyParens = html\`<script> f((\${expr}) / 2); </script>\`;
+const nestedFun = /* HTML */ \`\${outerExpr( 1 )} <script>const tpl = html\\\`<div>\\\${innerExpr( 1 )} \${outerExpr( 2 )}</div>\\\`</script>\`;
+
+const closingScriptTagShouldBeEscapedProperly = /* HTML */ \`
+  <script>
+    const html = /* HTML */ \\\`<script><\\\\/script>\\\`;
+  </script>
+\`;
+
+const closingScriptTag2 = /* HTML */ \`<script>const  scriptTag='<\\\\/script>'; <\\/script>\`;
+
 =====================================output=====================================
 import { LitElement, html } from "@polymer/lit-element";
 
@@ -130,5 +141,33 @@ function HelloWorld() {
   \`;
 }
 
+const trickyParens = html\`
+  <script>
+    f((\${expr}) / 2);
+  </script>
+\`;
+const nestedFun = /* HTML */ \`
+  \${outerExpr(1)}
+  <script>
+    const tpl = html\\\`
+      <div>\\\${innerExpr(1)} \${outerExpr(2)}</div>
+    \\\`;
+  </script>
+\`;
+
+const closingScriptTagShouldBeEscapedProperly = /* HTML */ \`
+  <script>
+    const html = /* HTML */ \\\`
+      <script><\\\\/script>
+    \\\`;
+  </script>
+\`;
+
+const closingScriptTag2 = /* HTML */ \`
+  <script>
+    const scriptTag = "<\\\\/script>";
+  </script>
+\`;
+
 ================================================================================
 `;

tests/multiparser_js_html/lit-html.js

@@ -59,3 +59,14 @@ function HelloWorld() {
     `)}
   `;
 }
+
+const trickyParens = html`<script> f((${expr}) / 2); </script>`;
+const nestedFun = /* HTML */ `${outerExpr( 1 )} <script>const tpl = html\`<div>\${innerExpr( 1 )} ${outerExpr( 2 )}</div>\`</script>`;
+
+const closingScriptTagShouldBeEscapedProperly = /* HTML */ `
+  <script>
+    const html = /* HTML */ \`<script><\\/script>\`;
+  </script>
+`;
+
+const closingScriptTag2 = /* HTML */ `<script>const  scriptTag='<\\/script>'; <\/script>`;