merge en-US metadata with translated metadata

kumascript/index.js

@@ -15,6 +15,7 @@ const {
   LiveSampleError,
 } = require("./src/live-sample.js");
 const { HTMLTool } = require("./src/api/util.js");
+const { DEFAULT_LOCALE } = require("../libs/constants");
 
 const DEPENDENCY_LOOP_INTRO =
   'The following documents form a circular dependency when rendering (via the "page" and/or "IncludeSubnav" macros):';
@@ -51,7 +52,23 @@ const renderFromURL = async (
         `Tried to find a folder called ${Document.urlToFolderPath(url)}`
     );
   }
-  const { rawBody, metadata, fileInfo, isMarkdown } = document;
+  let { metadata } = document;
+  // If we're rendering a translation, merge in the parent document's
+  // metadata into this metadata.
+  if (metadata.locale !== DEFAULT_LOCALE) {
+    const parentURL = url
+      .toLowerCase()
+      .replace(`/${metadata.locale.toLowerCase()}/`, `/${DEFAULT_LOCALE}/`);
+
+    const parentDocument = invalidateCache
+      ? Document.findByURL(parentURL, Document.MEMOIZE_INVALIDATE)
+      : Document.findByURL(parentURL);
+    if (parentDocument) {
+      metadata = { ...parentDocument.metadata, ...metadata };
+    }
+  }
+
+  const { rawBody, fileInfo, isMarkdown } = document;
   const rawHTML = isMarkdown ? await m2h(rawBody) : rawBody;
   const [renderedHtml, errors] = await renderMacros(
     rawHTML,

testing/tests/index.test.js

@@ -254,6 +254,29 @@ test("content built French foo page", () => {
   );
 });
 
+test("French translation using English front-matter bits", () => {
+  const builtFolder = path.join(
+    buildRoot,
+    "fr",
+    "docs",
+    "web",
+    "spec_section_extraction"
+  );
+  const jsonFile = path.join(builtFolder, "index.json");
+  const { doc } = JSON.parse(fs.readFileSync(jsonFile));
+  expect(doc.title).toBe("Extraction de sections de spécifications");
+  const specifications = doc.body.find(
+    (section) => section.type === "specifications"
+  );
+  expect(specifications.value.query).toBe(
+    "javascript.builtins.Array.toLocaleString"
+  );
+  const bcd = doc.body.find(
+    (section) => section.type === "browser_compatibility"
+  );
+  expect(bcd.value.query).toBe("javascript.builtins.Array.toLocaleString");
+});
+
 test("content built zh-TW page with en-US fallback image", () => {
   const builtFolder = path.join(buildRoot, "zh-tw", "docs", "web", "foo");
   const jsonFile = path.join(builtFolder, "index.json");

testing/translated-content/files/fr/web/spec_section_extraction/index.html

@@ -0,0 +1,18 @@
+---
+title: Extraction de sections de spécifications
+slug: Web/Spec_Section_Extraction
+---
+
+<p>
+  The purpose of this fixture is to test that this translated document can
+  benefit from the <code>browser-compat</code> front-matter in it's en-US
+  parent.
+</p>
+
+<h2 id="Specifications">Spécifications</h2>
+
+<p>{{Specifications}}</p>
+
+<h2 id="Browser_compatibility">Compatibilité des navigateur</h2>
+
+<p>{{Compat}}</p>