Make error summary callable

src/govuk/components/error-summary/error-summary.yaml

@@ -15,6 +15,10 @@ params:
   type: string
   required: false
   description: HTML to use for the description of the errors. If you set this option, the component will ignore `descriptionText`.
+- name: caller
+  type: nunjucks-block
+  required: false
+  description: Not strictly a parameter but [Nunjucks code convention](https://mozilla.github.io/nunjucks/templating.html#call). Using a `call` block enables you to call a macro with all the text inside the tag. This is helpful if you want to pass a lot of content into a macro. To use it, you will need to wrap the entire error summary component in a `call` block.
 - name: errorList
   type: array
   required: true

src/govuk/components/error-summary/template.njk

@@ -6,9 +6,9 @@
     {{ params.titleHtml | safe if params.titleHtml else params.titleText }}
   </h2>
   <div class="govuk-error-summary__body">
-    {% if params.descriptionHtml or params.descriptionText %}
+    {% if caller or params.descriptionHtml or params.descriptionText %}
     <p>
-      {{ params.descriptionHtml | safe if params.descriptionHtml else params.descriptionText }}
+      {{ caller() if caller else (params.descriptionHtml | safe if params.descriptionHtml else params.descriptionText) }}
     </p>
     {% endif %}
     <ul class="govuk-list govuk-error-summary__list">

src/govuk/components/error-summary/template.test.js

@@ -97,6 +97,12 @@ describe('Error-summary', () => {
       expect(summaryDescription).toEqual('See <span>errors</span> below')
     })
 
+    it('renders nested components in description using `call`', () => {
+      const $ = render('error-summary', {}, '<div class="app-nested-component"></div>')
+
+      expect($('.govuk-error-summary .app-nested-component').length).toBeTruthy()
+    })
+
     it('allows additional classes to be added to the error-summary component', () => {
       const $ = render('error-summary', examples.classes)