feat: add string template filters "default" and "ternary" (#3677) (#5878)

packages/netlify-cms-lib-widgets/src/__tests__/stringTemplate.spec.js

@@ -130,6 +130,28 @@ describe('stringTemplate', () => {
         ),
       ).toBe('BACKENDSLUG-title-01-02-2020');
     });
+
+    it('return apply filter for default value', () => {
+      expect(
+        compileStringTemplate(
+          "{{slug | upper}}-{{title | default('none')}}-{{subtitle | default('none')}}",
+          date,
+          'backendSlug',
+          fromJS({ slug: 'entrySlug', title: 'title', subtitle: null, published: date, date }),
+        ),
+      ).toBe('BACKENDSLUG-title-none');
+    });
+
+    it('return apply filter for ternary', () => {
+      expect(
+        compileStringTemplate(
+          "{{slug | upper}}-{{starred | ternary('star️','nostar')}}-{{done | ternary('done', 'open️')}}",
+          date,
+          'backendSlug',
+          fromJS({ slug: 'entrySlug', starred: true, done: false }),
+        ),
+      ).toBe('BACKENDSLUG-star️-open️');
+    });
   });
 
   describe('expandPath', () => {

packages/netlify-cms-lib-widgets/src/stringTemplate.ts

@@ -13,6 +13,14 @@ const filters = [
     pattern: /^date\('(.+)'\)$/,
     transform: (str: string, match: RegExpMatchArray) => moment(str).format(match[1]),
   },
+  {
+    pattern: /^default\('(.+)'\)$/,
+    transform: (str: string, match: RegExpMatchArray) => (str ? str : match[1]),
+  },
+  {
+    pattern: /^ternary\('(.*)',\s*'(.*)'\)$/,
+    transform: (str: string, match: RegExpMatchArray) => (str ? match[1] : match[2]),
+  },
 ];
 
 const FIELD_PREFIX = 'fields.';