feat(compiler-ssr): compile portal (#775)

packages/server-renderer/__tests__/ssrRenderPortal.spec.ts

@@ -0,0 +1,29 @@
+import { createApp } from 'vue'
+import { renderToString, SSRContext } from '../src/renderToString'
+import { ssrRenderPortal } from '../src/helpers/ssrRenderPortal'
+
+describe('ssrRenderPortal', () => {
+  test('portal rendering', async () => {
+    const ctx = {
+      portals: {}
+    } as SSRContext
+    await renderToString(
+      createApp({
+        data() {
+          return { msg: 'hello' }
+        },
+        ssrRender(_ctx, _push, _parent) {
+          ssrRenderPortal(
+            _push => {
+              _push(`<div>content</div>`)
+            },
+            '#target',
+            _parent
+          )
+        }
+      }),
+      ctx
+    )
+    expect(ctx.portals!['#target']).toBe(`<div>content</div>`)
+  })
+})