feat(ssr): ssrPrefetch option + context.rendered hook (#9017)

Author: Akryum

Diff for: flow/options.js

@@ -44,6 +44,7 @@ declare type ComponentOptions = {
   beforeDestroy?: Function;
   destroyed?: Function;
   errorCaptured?: () => boolean | void;
+  ssrPrefetch?: Function;
 
   // assets
   directives?: { [key: string]: Object };

Diff for: src/server/create-renderer.js

@@ -79,6 +79,9 @@ export function createRenderer ({
       }, cb)
       try {
         render(component, write, context, err => {
+          if (context && context.rendered) {
+            context.rendered(context)
+          }
           if (template) {
             result = templateRenderer.renderSync(result, context)
           }
@@ -106,13 +109,25 @@ export function createRenderer ({
         render(component, write, context, done)
       })
       if (!template) {
+        if (context && context.rendered) {
+          const rendered = context.rendered
+          renderStream.once('beforeEnd', () => {
+            rendered(context)
+          })
+        }
         return renderStream
       } else {
         const templateStream = templateRenderer.createStream(context)
         renderStream.on('error', err => {
           templateStream.emit('error', err)
         })
         renderStream.pipe(templateStream)
+        if (context && context.rendered) {
+          const rendered = context.rendered
+          renderStream.once('beforeEnd', () => {
+            rendered(context)
+          })
+        }
         return templateStream
       }
     }

Diff for: src/server/render-stream.js

@@ -42,6 +42,7 @@ export default class RenderStream extends stream.Readable {
     })
 
     this.end = () => {
+      this.emit('beforeEnd')
       // the rendering is finished; we should push out the last of the buffer.
       this.done = true
       this.push(this.buffer)

Diff for: src/server/render.js

@@ -19,6 +19,7 @@ let warned = Object.create(null)
 const warnOnce = msg => {
   if (!warned[msg]) {
     warned[msg] = true
+    // eslint-disable-next-line no-console
     console.warn(`\n\u001b[31m${msg}\u001b[39m\n`)
   }
 }
@@ -49,6 +50,27 @@ const normalizeRender = vm => {
   }
 }
 
+function waitForSsrPrefetch (vm, resolve, reject) {
+  let handlers = vm.$options.ssrPrefetch
+  if (isDef(handlers)) {
+    if (!Array.isArray(handlers)) handlers = [handlers]
+    try {
+      const promises = []
+      for (let i = 0, j = handlers.length; i < j; i++) {
+        const result = handlers[i].call(vm, vm)
+        if (result && typeof result.then === 'function') {
+          promises.push(result)
+        }
+      }
+      Promise.all(promises).then(resolve).catch(reject)
+      return
+    } catch (e) {
+      reject(e)
+    }
+  }
+  resolve()
+}
+
 function renderNode (node, isRoot, context) {
   if (node.isString) {
     renderStringNode(node, context)
@@ -166,13 +188,20 @@ function renderComponentInner (node, isRoot, context) {
     context.activeInstance
   )
   normalizeRender(child)
-  const childNode = child._render()
-  childNode.parent = node
-  context.renderStates.push({
-    type: 'Component',
-    prevActive
-  })
-  renderNode(childNode, isRoot, context)
+  
+  const resolve = () => {
+    const childNode = child._render()
+    childNode.parent = node
+    context.renderStates.push({
+      type: 'Component',
+      prevActive
+    })
+    renderNode(childNode, isRoot, context)
+  }
+
+  const reject = context.done
+
+  waitForSsrPrefetch(child, resolve, reject)
 }
 
 function renderAsyncComponent (node, isRoot, context) {
@@ -394,6 +423,10 @@ export function createRenderFunction (
     })
     installSSRHelpers(component)
     normalizeRender(component)
-    renderNode(component._render(), true, context)
+
+    const resolve = () => {
+      renderNode(component._render(), true, context)
+    }
+    waitForSsrPrefetch(component, resolve, done)
   }
 }

Diff for: src/shared/constants.js

@@ -17,5 +17,6 @@ export const LIFECYCLE_HOOKS = [
   'destroyed',
   'activated',
   'deactivated',
-  'errorCaptured'
+  'errorCaptured',
+  'ssrPrefetch'
 ]

Diff for: test/ssr/ssr-stream.spec.js

@@ -102,4 +102,26 @@ describe('SSR: renderToStream', () => {
     stream1.read(1)
     stream2.read(1)
   })
+
+  it('should call context.rendered', done => {
+    let a = 0
+    const stream = renderToStream(new Vue({
+      template: `
+        <div>Hello</div>
+      `
+    }), {
+      rendered: () => {
+        a = 42
+      }
+    })
+    let res = ''
+    stream.on('data', chunk => {
+      res += chunk
+    })
+    stream.on('end', () => {
+      expect(res).toContain('<div data-server-rendered="true">Hello</div>')
+      expect(a).toBe(42)
+      done()
+    })
+  })
 })

Diff for: test/ssr/ssr-string.spec.js

@@ -1311,6 +1311,194 @@ describe('SSR: renderToString', () => {
       done()
     })
   })
+
+  it('should support ssrPrefetch option', done => {
+    renderVmWithOptions({
+      template: `
+        <div>{{ count }}</div>
+      `,
+      data: {
+        count: 0
+      },
+      ssrPrefetch () {
+        return new Promise((resolve) => {
+          setTimeout(() => {
+            this.count = 42
+            resolve()
+          }, 1)
+        })
+      }
+    }, result => {
+      expect(result).toContain('<div data-server-rendered="true">42</div>')
+      done()
+    })
+  })
+
+  it('should support ssrPrefetch option (nested)', done => {
+    renderVmWithOptions({
+      template: `
+        <div>
+          <span>{{ count }}</span>
+          <nested-prefetch></nested-prefetch>
+        </div>
+      `,
+      data: {
+        count: 0
+      },
+      ssrPrefetch () {
+        return new Promise((resolve) => {
+          setTimeout(() => {
+            this.count = 42
+            resolve()
+          }, 1)
+        })
+      },
+      components: {
+        nestedPrefetch: {
+          template: `
+            <div>{{ message }}</div>
+          `,
+          data () {
+            return {
+              message: ''
+            }
+          },
+          ssrPrefetch () {
+            return new Promise((resolve) => {
+              setTimeout(() => {
+                this.message = 'vue.js'
+                resolve()
+              }, 1)
+            })
+          }
+        }
+      }
+    }, result => {
+      expect(result).toContain('<div data-server-rendered="true"><span>42</span> <div>vue.js</div></div>')
+      done()
+    })
+  })
+
+  it('should support ssrPrefetch option (nested async)', done => {
+    renderVmWithOptions({
+      template: `
+        <div>
+          <span>{{ count }}</span>
+          <nested-prefetch></nested-prefetch>
+        </div>
+      `,
+      data: {
+        count: 0
+      },
+      ssrPrefetch () {
+        return new Promise((resolve) => {
+          setTimeout(() => {
+            this.count = 42
+            resolve()
+          }, 1)
+        })
+      },
+      components: {
+        nestedPrefetch (resolve) {
+          resolve({
+            template: `
+              <div>{{ message }}</div>
+            `,
+            data () {
+              return {
+                message: ''
+              }
+            },
+            ssrPrefetch () {
+              return new Promise((resolve) => {
+                setTimeout(() => {
+                  this.message = 'vue.js'
+                  resolve()
+                }, 1)
+              })
+            }
+          })
+        }
+      }
+    }, result => {
+      expect(result).toContain('<div data-server-rendered="true"><span>42</span> <div>vue.js</div></div>')
+      done()
+    })
+  })
+
+  it('should merge ssrPrefetch option', done => {
+    const mixin = {
+      data: {
+        message: ''
+      },
+      ssrPrefetch () {
+        return new Promise((resolve) => {
+          setTimeout(() => {
+            this.message = 'vue.js'
+            resolve()
+          }, 1)
+        })
+      }
+    }
+    renderVmWithOptions({
+      mixins: [mixin],
+      template: `
+        <div>
+          <span>{{ count }}</span>
+          <div>{{ message }}</div>
+        </div>
+      `,
+      data: {
+        count: 0
+      },
+      ssrPrefetch () {
+        return new Promise((resolve) => {
+          setTimeout(() => {
+            this.count = 42
+            resolve()
+          }, 1)
+        })
+      }
+    }, result => {
+      expect(result).toContain('<div data-server-rendered="true"><span>42</span> <div>vue.js</div></div>')
+      done()
+    })
+  })
+
+  it(`should skip ssrPrefetch option that doesn't return a promise`, done => {
+    renderVmWithOptions({
+      template: `
+        <div>{{ count }}</div>
+      `,
+      data: {
+        count: 0
+      },
+      ssrPrefetch () {
+        setTimeout(() => {
+          this.count = 42
+        }, 1)
+      }
+    }, result => {
+      expect(result).toContain('<div data-server-rendered="true">0</div>')
+      done()
+    })
+  })
+
+  it('should call context.rendered', done => {
+    let a = 0
+    renderToString(new Vue({
+      template: '<div>Hello</div>'
+    }), {
+      rendered: () => {
+        a = 42
+      }
+    }, (err, res) => {
+      expect(err).toBeNull()
+      expect(res).toContain('<div data-server-rendered="true">Hello</div>')
+      expect(a).toBe(42)
+      done()
+    })
+  })
 })
 
 function renderVmWithOptions (options, cb) {