Adding domT method for component interpolation

app/client/lib/localization.ts

@@ -1,4 +1,6 @@
 import {getGristConfig} from 'app/common/urlUtils';
+import {DomContents} from 'grainjs';
+import {G} from 'grainjs/dist/cjs/lib/browserGlobals';
 import i18next from 'i18next';
 
 export async function setupLocale() {
@@ -68,14 +70,48 @@ export async function setupLocale() {
 }
 
 /**
- * Resolves the translation of the given key, using the given options.
+ * Resolves the translation of the given key using the given options.
  */
-export function t(key: string, args?: any): string {
-  if (!i18next.exists(key, args)) {
+export function t(key: string, args?: any, instance = i18next): string {
+  if (!instance.exists(key, args)) {
     const error = new Error(`Missing translation for key: ${key} and language: ${i18next.language}`);
     reportError(error);
   }
-  return i18next.t(key, args);
+  return instance.t(key, args);
+}
+
+
+/**
+ * Resolves the translation of the given key and substitutes. Supports dom elements interpolation.
+ */
+ export function domT(key: string, args?: any, instance = i18next): DomContents {
+  if (!instance.exists(key)) {
+    const error = new Error(`Missing translation for key: ${key} and language: ${i18next.language}`);
+    reportError(error);
+  }
+  // If there are any DomElements in args, handle it with missingInterpolationHandler.
+  const domElements = Object.entries(args).filter(([_, value]) => isLikeDomContents(value));
+  if (!args || !domElements.length) {
+    return t(key, args);
+  } else {
+    // Make a copy of the arguments, and remove any dom elements from it. It will instruct
+    // i18next library to use `missingInterpolationHandler` handler.
+    const copy = {...args};
+    domElements.forEach(([prop]) => delete copy[prop]);
+
+    // Passing `missingInterpolationHandler` will allow as to resolve all missing keys
+    // and replace them with a marker.
+    const result: string = instance.t(key, {...copy, missingInterpolationHandler});
+
+    // Now replace all markers with dom elements passed as arguments.
+    const parts = result.split(new RegExp(`(${DOM_MARKER}\\w+)`));
+    for (let i = 1; i < parts.length; i += 2) { // Every second element is our dom element.
+      const propName = parts[i].replace(DOM_MARKER, "");
+      const domElement = args[propName] ?? `{{${propName}}}`; // If the prop is not there, simulate default behavior.
+      parts[i] = domElement;
+    }
+    return parts;
+  }
 }
 
 /**
@@ -84,3 +120,19 @@ export function t(key: string, args?: any): string {
 export function hasTranslation(key: string) {
   return i18next.exists(key);
 }
+
+const DOM_MARKER = '__domKey_';
+function missingInterpolationHandler(key: string, value: any) {
+  return `${DOM_MARKER}${value[1]}`;
+}
+
+/**
+ * Very naive detection if an element has DomContents type.
+ */
+function isLikeDomContents(value: any): boolean {
+  // As null and undefined are valid DomContents values, we don't treat them as such.
+  if (value === null || value === undefined) { return false; }
+  return value instanceof G.Node || // Node
+    (Array.isArray(value) && isLikeDomContents(value[0])) || // DomComputed
+    typeof value === 'function'; // DomMethod
+}

app/client/ui/HomeIntro.ts

@@ -1,4 +1,4 @@
-import {t} from 'app/client/lib/localization';
+import {domT, t} from 'app/client/lib/localization';
 import {getLoginOrSignupUrl, urlState} from 'app/client/models/gristUrlState';
 import {HomeModel} from 'app/client/models/HomeModel';
 import {productPill} from 'app/client/ui/AppHeader';
@@ -103,7 +103,7 @@ function makePersonalIntro(homeModel: HomeModel, user: FullUser) {
     css.docListHeader(`Welcome to Grist, ${user.name}!`, testId('welcome-title')),
     cssIntroLine('Get started by creating your first Grist document.'),
     (shouldHideUiElement('helpCenter') ? null :
-      cssIntroLine('Visit our ', helpCenterLink(), ' to learn more.',
+      cssIntroLine(domT('HomeIntro.VisitHelpCenter', { link: helpCenterLink() }),
         testId('welcome-text'))
     ),
     makeCreateButtons(homeModel),
@@ -115,8 +115,8 @@ function makeAnonIntro(homeModel: HomeModel) {
   return [
     css.docListHeader(translate('Welcome'), testId('welcome-title')),
     cssIntroLine('Get started by exploring templates, or creating your first Grist document.'),
-    cssIntroLine(signUp, ' to save your work.',
-      (shouldHideUiElement('helpCenter') ? null : [' Visit our ', helpCenterLink(), ' to learn more.']),
+    cssIntroLine(signUp, ' to save your work. ',
+      (shouldHideUiElement('helpCenter') ? null : domT('HomeIntro.VisitHelpCenter', { link: helpCenterLink() })),
       testId('welcome-text')),
     makeCreateButtons(homeModel),
   ];