feat(ssr): renderToStream (#1197)

packages/server-renderer/src/renderToStream.ts

@@ -0,0 +1,59 @@
+import {
+  App,
+  VNode,
+  createVNode,
+  ssrUtils,
+  createApp,
+  ssrContextKey
+} from 'vue'
+import { isString, isPromise } from '@vue/shared'
+import { renderComponentVNode, SSRBuffer, SSRContext } from './render'
+import { Readable } from 'stream'
+
+const { isVNode } = ssrUtils
+
+async function unrollBuffer(
+  buffer: SSRBuffer,
+  stream: Readable
+): Promise<void> {
+  for (let i = 0; i < buffer.length; i++) {
+    let item = buffer[i]
+    if (isPromise(item)) {
+      item = await item
+    }
+    if (isString(item)) {
+      stream.push(item)
+    } else {
+      await unrollBuffer(item, stream)
+    }
+  }
+}
+
+export function renderToStream(
+  input: App | VNode,
+  context: SSRContext = {}
+): Readable {
+  if (isVNode(input)) {
+    // raw vnode, wrap with app (for context)
+    return renderToStream(createApp({ render: () => input }), context)
+  }
+
+  // rendering an app
+  const vnode = createVNode(input._component, input._props)
+  vnode.appContext = input._context
+  // provide the ssr context to the tree
+  input.provide(ssrContextKey, context)
+
+  const stream = new Readable()
+
+  Promise.resolve(renderComponentVNode(vnode))
+    .then(buffer => unrollBuffer(buffer, stream))
+    .then(() => {
+      stream.push(null)
+    })
+    .catch(error => {
+      stream.destroy(error)
+    })
+
+  return stream
+}