Check UI string variables match. (#958)

Would have caught #956
No additional errors.
I've also manually reviewed the ICU plural strings, and while a surprising
number don't seem to be translated there are no structural errors.

Author: microbit-matt-hillsdon

bin/tidy-lang.js

@@ -8,9 +8,41 @@ const path = require("path");
 const en = JSON.parse(fs.readFileSync("lang/ui.en.json"));
 const validKeys = new Set(Object.keys(en));
 
-fs.readdirSync("lang")
+const variableRegExp = /({[a-zA-Z0-9]+})/g;
+
+// This is just a best effort check that variables haven't been changed.
+const areTranslationsValid = (file, enJson, translatedJson) => {
+  let valid = true;
+  const keys = Object.keys(en);
+  for (const k of keys) {
+    const en = enJson[k].defaultMessage;
+    const translated = translatedJson[k].defaultMessage;
+    if (en.match(/, plural/)) {
+      // Skip ICU strings as we don't understand them.
+      continue;
+    }
+    const variablesEn = new Set(en.match(variableRegExp) ?? []);
+    const variablesTranslated = new Set(translated.match(variableRegExp) ?? []);
+    const areSetsEqual = (a, b) =>
+      a.size === b.size && Array.from(a).every((value) => b.has(value));
+    if (!areSetsEqual(variablesEn, variablesTranslated)) {
+      if (valid) {
+        console.error(file);
+        valid = false;
+      }
+      console.error(`  ${en}`);
+      console.error(`  ${translated}`);
+      console.error(`  Differing variables!`);
+      console.error();
+    }
+  }
+  return valid;
+};
+
+const valid = fs
+  .readdirSync("lang")
   .filter((f) => f.endsWith(".json"))
-  .forEach((messages) => {
+  .map((messages) => {
     const file = path.join("lang", messages);
     const data = {
       // Ensure we fallback to English even if we haven't roundtripped via Crowdin yet.
@@ -26,4 +58,7 @@ fs.readdirSync("lang")
     const result = Object.create(null);
     sortedKeys.forEach((k) => (result[k] = data[k]));
     fs.writeFileSync(file, JSON.stringify(result, null, 2));
-  });
+    return areTranslationsValid(file, en, result);
+  })
+  .reduce((prev, curr) => prev && curr, true);
+process.exit(valid ? 0 : 2);