feat(slugs): allow filters in template strings

Process template filters first, then strip `'` and `.` characters from
slug strings.

Fixes #4783

packages/netlify-cms-core/src/lib/__tests__/formatters.spec.js

@@ -274,7 +274,7 @@ describe('formatters', () => {
  };
 
  describe('slugFormatter', () => {
- const date = new Date('2020-01-01');
+ const date = new Date('2020-01-01T13:28:27.679Z');
  jest.spyOn(global, 'Date').mockImplementation(() => date);
 
  const { selectIdentifier } = require('../../reducers/collections');
@@ -312,6 +312,18 @@ describe('formatters', () => {
  ).toBe('entry-slug');
  });
 
+ it('should allow filters in slug templates', () => {
+ selectIdentifier.mockReturnValueOnce('published');
+
+ expect(
+ slugFormatter(
+ Map({ slug: "{{published | date('MM-DD')}}" }),
+ Map({ title: 'Post Title', published: date }),
+ slugConfig,
+ ),
+ ).toBe('01-01');
+ });
+
  it('should return slug', () => {
  selectIdentifier.mockReturnValueOnce('title');
 

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

@@ -190,13 +190,13 @@ export function compileStringTemplate(
  replacement = data.getIn(keyToPathArray(key), '') as string;
  }
 
+ const filterFunction = getFilterFunction(filter);
+ if (filterFunction) {
+ replacement = filterFunction(replacement);
+ }
+
  if (processor) {
- return processor(replacement);
- } else {
- const filterFunction = getFilterFunction(filter);
- if (filterFunction) {
- replacement = filterFunction(replacement);
- }
+ replacement = processor(replacement);
  }
 
  return replacement;