Add a basic i18n lint implementation that will warn us about missing and unsorted keys

package.json

@@ -7,7 +7,7 @@
     "dist"
   ],
   "scripts": {
-    "lint": "node_modules/.bin/eslint ./ && node_modules/.bin/sass-lint -v ./src/styles/**/*",
+    "lint": "node_modules/.bin/eslint ./ && node_modules/.bin/sass-lint -v ./src/styles/**/* && node ./scripts/i18n-lint.js",
     "server": "node_modules/.bin/http-server",
     "test": "npm run build && npm run lint && npm run size && jest -c jest.json",
     "test:watch": "jest -c jest.json --watch",
@@ -71,6 +71,7 @@
     "babel-eslint": "10.0.1",
     "babel-jest": "^24.1.0",
     "babel-loader": "^8.0.4",
+    "chalk": "^2.4.2",
     "codecov": "^3.1.0",
     "concurrently": "^4.0.1",
     "css-loader": "^2.1.0",
@@ -85,6 +86,7 @@
     "eslint-plugin-jest": "^22.2.2",
     "eslint-plugin-jsx-a11y": "^6.2.0",
     "eslint-plugin-react": "^7.12.4",
+    "glob": "^7.1.3",
     "http-server": "^0.11.1",
     "jest": "^24.1.0",
     "jest-fetch-mock": "^2.1.1",

scripts/i18n-lint.js

+const glob = require('glob'); // eslint-disable-line import/no-extraneous-dependencies
+const fs = require('fs');
+const chalk = require('chalk'); // eslint-disable-line import/no-extraneous-dependencies
+
+const { log } = console;
+const globOpts = { cwd: 'locales' };
+const defaultLocaleFile = 'en/translation.json';
+const files = glob.sync('**/translation.json', globOpts);
+const normalizedFiles = {};
+const errors = {};
+
+/**
+ * Return a new copy of the array lowercased and sorted
+ */
+function lowerCaseSortedArray(arr) {
+  return arr.slice().map(v => v.toLowerCase()).sort();
+}
+
+/**
+ * Return the keys in an array that are not sorted (not considering case in sort)
+ */
+function unsortedKeys(arr) {
+  const sortedArray = lowerCaseSortedArray(arr);
+
+  return arr.filter((v, i) => v.toLowerCase() !== sortedArray[i]);
+}
+
+/**
+ * Return any keys in array 2 that are not in array 1
+ * (values will be sorted and downcased for comparison)
+ */
+function missingKeys(arr1, arr2) {
+  const sortedDonwcasedLeftHandArray = lowerCaseSortedArray(arr1);
+  const sortedDonwcasedRightHandArray = lowerCaseSortedArray(arr2);
+
+  return sortedDonwcasedLeftHandArray.filter((v, i) => v !== sortedDonwcasedRightHandArray[i]);
+}
+
+files.forEach((fileName) => {
+  const fileContent = fs.readFileSync(`locales/${fileName}`);
+  normalizedFiles[fileName] = Object.keys(JSON.parse(fileContent.toString()).translation);
+});
+
+const completeKeys = normalizedFiles[defaultLocaleFile].slice().sort();
+
+
+Object.keys(normalizedFiles).forEach((fileName) => {
+  const unsorted = unsortedKeys(normalizedFiles[fileName]);
+  const missing = missingKeys(completeKeys, normalizedFiles[fileName]);
+
+  if (unsorted.length) {
+    errors[fileName] = errors[fileName] || [];
+    errors[fileName].push('Keys are not sorted properly');
+    errors[fileName].push(
+      `\tSorting starts to be incorrect around: ${unsorted[0]}`,
+    );
+  }
+
+  if (missing.length) {
+    errors[fileName] = errors[fileName] || [];
+    errors[fileName].push('Some keys from the default locale file are missing');
+    errors[fileName].push(
+      `\tMissing keys: ${missing.join(', ')}`,
+    );
+  }
+});
+
+Object.keys(errors).forEach((errorFileName) => {
+  log(chalk.red(`${chalk.inverse.bold(errorFileName)} has ${chalk.underline.bold('internationalization')} errors`));
+  errors[errorFileName].forEach((error) => {
+    log(`\t${chalk.yellow(error)}`);
+  });
+});