From 757a0c708221fe28eca11811a10c81b2b78901f4 Mon Sep 17 00:00:00 2001
From: Shu Ding <g@shud.in>
Date: Fri, 18 Mar 2022 00:21:16 +0100
Subject: [PATCH] Abstract out stream related utils from render and web/utils
 (#35372)

The `readableStreamTee` util is only used by server/render.tsx, but ended up in the middleware runtime bundle. So it's better to add all the utils in one place, and we can remove them once upstream implementation of ReadableStream is ready.

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`
---
 .../next/server/node-web-streams-helper.ts    | 359 ++++++++++++++++++
 packages/next/server/render.tsx               | 344 +----------------
 packages/next/server/web/utils.ts             |  26 --
 3 files changed, 370 insertions(+), 359 deletions(-)
 create mode 100644 packages/next/server/node-web-streams-helper.ts

diff --git a/packages/next/server/node-web-streams-helper.ts b/packages/next/server/node-web-streams-helper.ts
new file mode 100644
index 0000000000000..b8b1cc6ff98da
--- /dev/null
+++ b/packages/next/server/node-web-streams-helper.ts
@@ -0,0 +1,359 @@
+export function readableStreamTee<T = any>(
+  readable: ReadableStream<T>
+): [ReadableStream<T>, ReadableStream<T>] {
+  const transformStream = new TransformStream()
+  const transformStream2 = new TransformStream()
+  const writer = transformStream.writable.getWriter()
+  const writer2 = transformStream2.writable.getWriter()
+
+  const reader = readable.getReader()
+  function read() {
+    reader.read().then(({ done, value }) => {
+      if (done) {
+        writer.close()
+        writer2.close()
+        return
+      }
+      writer.write(value)
+      writer2.write(value)
+      read()
+    })
+  }
+  read()
+
+  return [transformStream.readable, transformStream2.readable]
+}
+
+export function pipeTo<T>(
+  readable: ReadableStream<T>,
+  writable: WritableStream<T>,
+  options?: { preventClose: boolean }
+) {
+  let resolver: () => void
+  const promise = new Promise<void>((resolve) => (resolver = resolve))
+
+  const reader = readable.getReader()
+  const writer = writable.getWriter()
+  function process() {
+    reader.read().then(({ done, value }) => {
+      if (done) {
+        if (options?.preventClose) {
+          writer.releaseLock()
+        } else {
+          writer.close()
+        }
+        resolver()
+      } else {
+        writer.write(value)
+        process()
+      }
+    })
+  }
+  process()
+  return promise
+}
+
+export function pipeThrough<Input, Output>(
+  readable: ReadableStream<Input>,
+  transformStream: TransformStream<Input, Output>
+) {
+  pipeTo(readable, transformStream.writable)
+  return transformStream.readable
+}
+
+export function chainStreams<T>(
+  streams: ReadableStream<T>[]
+): ReadableStream<T> {
+  const { readable, writable } = new TransformStream()
+
+  let promise = Promise.resolve()
+  for (let i = 0; i < streams.length; ++i) {
+    promise = promise.then(() =>
+      pipeTo(streams[i], writable, {
+        preventClose: i + 1 < streams.length,
+      })
+    )
+  }
+
+  return readable
+}
+
+export function streamFromArray(strings: string[]): ReadableStream<Uint8Array> {
+  // Note: we use a TransformStream here instead of instantiating a ReadableStream
+  // because the built-in ReadableStream polyfill runs strings through TextEncoder.
+  const { readable, writable } = new TransformStream()
+
+  const writer = writable.getWriter()
+  strings.forEach((str) => writer.write(encodeText(str)))
+  writer.close()
+
+  return readable
+}
+
+export async function streamToString(
+  stream: ReadableStream<Uint8Array>
+): Promise<string> {
+  const reader = stream.getReader()
+  let bufferedString = ''
+
+  while (true) {
+    const { done, value } = await reader.read()
+
+    if (done) {
+      return bufferedString
+    }
+
+    bufferedString += decodeText(value)
+  }
+}
+
+export function encodeText(input: string) {
+  return new TextEncoder().encode(input)
+}
+
+export function decodeText(input?: Uint8Array) {
+  return new TextDecoder().decode(input)
+}
+
+export function createTransformStream<Input, Output>({
+  flush,
+  transform,
+}: {
+  flush?: (
+    controller: TransformStreamDefaultController<Output>
+  ) => Promise<void> | void
+  transform?: (
+    chunk: Input,
+    controller: TransformStreamDefaultController<Output>
+  ) => Promise<void> | void
+}): TransformStream<Input, Output> {
+  const source = new TransformStream()
+  const sink = new TransformStream()
+  const reader = source.readable.getReader()
+  const writer = sink.writable.getWriter()
+
+  const controller = {
+    enqueue(chunk: Output) {
+      writer.write(chunk)
+    },
+
+    error(reason: Error) {
+      writer.abort(reason)
+      reader.cancel()
+    },
+
+    terminate() {
+      writer.close()
+      reader.cancel()
+    },
+
+    get desiredSize() {
+      return writer.desiredSize
+    },
+  }
+
+  ;(async () => {
+    try {
+      while (true) {
+        const { done, value } = await reader.read()
+
+        if (done) {
+          const maybePromise = flush?.(controller)
+          if (maybePromise) {
+            await maybePromise
+          }
+          writer.close()
+          return
+        }
+
+        if (transform) {
+          const maybePromise = transform(value, controller)
+          if (maybePromise) {
+            await maybePromise
+          }
+        } else {
+          controller.enqueue(value)
+        }
+      }
+    } catch (err) {
+      writer.abort(err)
+    }
+  })()
+
+  return {
+    readable: sink.readable,
+    writable: source.writable,
+  }
+}
+
+export function createBufferedTransformStream(): TransformStream<
+  Uint8Array,
+  Uint8Array
+> {
+  let bufferedString = ''
+  let pendingFlush: Promise<void> | null = null
+
+  const flushBuffer = (controller: TransformStreamDefaultController) => {
+    if (!pendingFlush) {
+      pendingFlush = new Promise((resolve) => {
+        setTimeout(() => {
+          controller.enqueue(encodeText(bufferedString))
+          bufferedString = ''
+          pendingFlush = null
+          resolve()
+        }, 0)
+      })
+    }
+    return pendingFlush
+  }
+
+  return createTransformStream({
+    transform(chunk, controller) {
+      bufferedString += decodeText(chunk)
+      flushBuffer(controller)
+    },
+
+    flush() {
+      if (pendingFlush) {
+        return pendingFlush
+      }
+    },
+  })
+}
+
+export function createFlushEffectStream(
+  handleFlushEffect: () => Promise<string>
+): TransformStream<Uint8Array, Uint8Array> {
+  return createTransformStream({
+    async transform(chunk, controller) {
+      const extraChunk = await handleFlushEffect()
+      // those should flush together at once
+      controller.enqueue(encodeText(extraChunk + decodeText(chunk)))
+    },
+  })
+}
+
+export async function renderToStream({
+  ReactDOMServer,
+  element,
+  suffix,
+  dataStream,
+  generateStaticHTML,
+  flushEffectHandler,
+}: {
+  ReactDOMServer: typeof import('react-dom/server')
+  element: React.ReactElement
+  suffix?: string
+  dataStream?: ReadableStream<Uint8Array>
+  generateStaticHTML: boolean
+  flushEffectHandler?: () => Promise<string>
+}): Promise<ReadableStream<Uint8Array>> {
+  const closeTag = '</body></html>'
+  const suffixUnclosed = suffix ? suffix.split(closeTag)[0] : null
+  const renderStream: ReadableStream<Uint8Array> & {
+    allReady?: Promise<void>
+  } = await (ReactDOMServer as any).renderToReadableStream(element)
+
+  if (generateStaticHTML) {
+    await renderStream.allReady
+  }
+
+  const transforms: Array<TransformStream<Uint8Array, Uint8Array>> = [
+    createBufferedTransformStream(),
+    flushEffectHandler ? createFlushEffectStream(flushEffectHandler) : null,
+    suffixUnclosed != null ? createPrefixStream(suffixUnclosed) : null,
+    dataStream ? createInlineDataStream(dataStream) : null,
+    suffixUnclosed != null ? createSuffixStream(closeTag) : null,
+  ].filter(Boolean) as any
+
+  return transforms.reduce(
+    (readable, transform) => pipeThrough(readable, transform),
+    renderStream
+  )
+}
+
+export function createSuffixStream(
+  suffix: string
+): TransformStream<Uint8Array, Uint8Array> {
+  return createTransformStream({
+    flush(controller) {
+      if (suffix) {
+        controller.enqueue(encodeText(suffix))
+      }
+    },
+  })
+}
+
+export function createPrefixStream(
+  prefix: string
+): TransformStream<Uint8Array, Uint8Array> {
+  let prefixFlushed = false
+  let prefixPrefixFlushFinished: Promise<void> | null = null
+  return createTransformStream({
+    transform(chunk, controller) {
+      controller.enqueue(chunk)
+      if (!prefixFlushed && prefix) {
+        prefixFlushed = true
+        prefixPrefixFlushFinished = new Promise((res) => {
+          // NOTE: streaming flush
+          // Enqueue prefix part before the major chunks are enqueued so that
+          // prefix won't be flushed too early to interrupt the data stream
+          setTimeout(() => {
+            controller.enqueue(encodeText(prefix))
+            res()
+          })
+        })
+      }
+    },
+    flush(controller) {
+      if (prefixPrefixFlushFinished) return prefixPrefixFlushFinished
+      if (!prefixFlushed && prefix) {
+        prefixFlushed = true
+        controller.enqueue(encodeText(prefix))
+      }
+    },
+  })
+}
+
+export function createInlineDataStream(
+  dataStream: ReadableStream<Uint8Array>
+): TransformStream<Uint8Array, Uint8Array> {
+  let dataStreamFinished: Promise<void> | null = null
+  return createTransformStream({
+    transform(chunk, controller) {
+      controller.enqueue(chunk)
+
+      if (!dataStreamFinished) {
+        const dataStreamReader = dataStream.getReader()
+
+        // NOTE: streaming flush
+        // We are buffering here for the inlined data stream because the
+        // "shell" stream might be chunkenized again by the underlying stream
+        // implementation, e.g. with a specific high-water mark. To ensure it's
+        // the safe timing to pipe the data stream, this extra tick is
+        // necessary.
+        dataStreamFinished = new Promise((res) =>
+          setTimeout(async () => {
+            try {
+              while (true) {
+                const { done, value } = await dataStreamReader.read()
+                if (done) {
+                  return res()
+                }
+                controller.enqueue(value)
+              }
+            } catch (err) {
+              controller.error(err)
+            }
+            res()
+          }, 0)
+        )
+      }
+    },
+    flush() {
+      if (dataStreamFinished) {
+        return dataStreamFinished
+      }
+    },
+  })
+}
diff --git a/packages/next/server/render.tsx b/packages/next/server/render.tsx
index e80cf62991cc7..c13d5ff65c128 100644
--- a/packages/next/server/render.tsx
+++ b/packages/next/server/render.tsx
@@ -64,7 +64,17 @@ import {
 } from '../lib/load-custom-routes'
 import RenderResult from './render-result'
 import isError from '../lib/is-error'
-import { readableStreamTee } from './web/utils'
+import {
+  readableStreamTee,
+  encodeText,
+  decodeText,
+  pipeThrough,
+  streamFromArray,
+  streamToString,
+  chainStreams,
+  createBufferedTransformStream,
+  renderToStream,
+} from './node-web-streams-helper'
 import { ImageConfigContext } from '../shared/lib/image-config-context'
 import { FlushEffectsContext } from '../shared/lib/flush-effects'
 
@@ -1637,335 +1647,3 @@ function serializeError(
     statusCode: 500,
   }
 }
-
-function createTransformStream<Input, Output>({
-  flush,
-  transform,
-}: {
-  flush?: (
-    controller: TransformStreamDefaultController<Output>
-  ) => Promise<void> | void
-  transform?: (
-    chunk: Input,
-    controller: TransformStreamDefaultController<Output>
-  ) => Promise<void> | void
-}): TransformStream<Input, Output> {
-  const source = new TransformStream()
-  const sink = new TransformStream()
-  const reader = source.readable.getReader()
-  const writer = sink.writable.getWriter()
-
-  const controller = {
-    enqueue(chunk: Output) {
-      writer.write(chunk)
-    },
-
-    error(reason: Error) {
-      writer.abort(reason)
-      reader.cancel()
-    },
-
-    terminate() {
-      writer.close()
-      reader.cancel()
-    },
-
-    get desiredSize() {
-      return writer.desiredSize
-    },
-  }
-
-  ;(async () => {
-    try {
-      while (true) {
-        const { done, value } = await reader.read()
-
-        if (done) {
-          const maybePromise = flush?.(controller)
-          if (maybePromise) {
-            await maybePromise
-          }
-          writer.close()
-          return
-        }
-
-        if (transform) {
-          const maybePromise = transform(value, controller)
-          if (maybePromise) {
-            await maybePromise
-          }
-        } else {
-          controller.enqueue(value)
-        }
-      }
-    } catch (err) {
-      writer.abort(err)
-    }
-  })()
-
-  return {
-    readable: sink.readable,
-    writable: source.writable,
-  }
-}
-
-function createBufferedTransformStream(): TransformStream<
-  Uint8Array,
-  Uint8Array
-> {
-  let bufferedString = ''
-  let pendingFlush: Promise<void> | null = null
-
-  const flushBuffer = (controller: TransformStreamDefaultController) => {
-    if (!pendingFlush) {
-      pendingFlush = new Promise((resolve) => {
-        setTimeout(() => {
-          controller.enqueue(encodeText(bufferedString))
-          bufferedString = ''
-          pendingFlush = null
-          resolve()
-        }, 0)
-      })
-    }
-    return pendingFlush
-  }
-
-  return createTransformStream({
-    transform(chunk, controller) {
-      bufferedString += decodeText(chunk)
-      flushBuffer(controller)
-    },
-
-    flush() {
-      if (pendingFlush) {
-        return pendingFlush
-      }
-    },
-  })
-}
-
-function createFlushEffectStream(
-  handleFlushEffect: () => Promise<string>
-): TransformStream<Uint8Array, Uint8Array> {
-  return createTransformStream({
-    async transform(chunk, controller) {
-      const extraChunk = await handleFlushEffect()
-      // those should flush together at once
-      controller.enqueue(encodeText(extraChunk + decodeText(chunk)))
-    },
-  })
-}
-
-async function renderToStream({
-  ReactDOMServer,
-  element,
-  suffix,
-  dataStream,
-  generateStaticHTML,
-  flushEffectHandler,
-}: {
-  ReactDOMServer: typeof import('react-dom/server')
-  element: React.ReactElement
-  suffix?: string
-  dataStream?: ReadableStream<Uint8Array>
-  generateStaticHTML: boolean
-  flushEffectHandler?: () => Promise<string>
-}): Promise<ReadableStream<Uint8Array>> {
-  const closeTag = '</body></html>'
-  const suffixUnclosed = suffix ? suffix.split(closeTag)[0] : null
-  const renderStream: ReadableStream<Uint8Array> & {
-    allReady?: Promise<void>
-  } = await (ReactDOMServer as any).renderToReadableStream(element)
-
-  if (generateStaticHTML) {
-    await renderStream.allReady
-  }
-
-  const transforms: Array<TransformStream<Uint8Array, Uint8Array>> = [
-    createBufferedTransformStream(),
-    flushEffectHandler ? createFlushEffectStream(flushEffectHandler) : null,
-    suffixUnclosed != null ? createPrefixStream(suffixUnclosed) : null,
-    dataStream ? createInlineDataStream(dataStream) : null,
-    suffixUnclosed != null ? createSuffixStream(closeTag) : null,
-  ].filter(Boolean) as any
-
-  return transforms.reduce(
-    (readable, transform) => pipeThrough(readable, transform),
-    renderStream
-  )
-}
-
-function encodeText(input: string) {
-  return new TextEncoder().encode(input)
-}
-
-function decodeText(input?: Uint8Array) {
-  return new TextDecoder().decode(input)
-}
-
-function createSuffixStream(
-  suffix: string
-): TransformStream<Uint8Array, Uint8Array> {
-  return createTransformStream({
-    flush(controller) {
-      if (suffix) {
-        controller.enqueue(encodeText(suffix))
-      }
-    },
-  })
-}
-
-function createPrefixStream(
-  prefix: string
-): TransformStream<Uint8Array, Uint8Array> {
-  let prefixFlushed = false
-  let prefixPrefixFlushFinished: Promise<void> | null = null
-  return createTransformStream({
-    transform(chunk, controller) {
-      controller.enqueue(chunk)
-      if (!prefixFlushed && prefix) {
-        prefixFlushed = true
-        prefixPrefixFlushFinished = new Promise((res) => {
-          // NOTE: streaming flush
-          // Enqueue prefix part before the major chunks are enqueued so that
-          // prefix won't be flushed too early to interrupt the data stream
-          setTimeout(() => {
-            controller.enqueue(encodeText(prefix))
-            res()
-          })
-        })
-      }
-    },
-    flush(controller) {
-      if (prefixPrefixFlushFinished) return prefixPrefixFlushFinished
-      if (!prefixFlushed && prefix) {
-        prefixFlushed = true
-        controller.enqueue(encodeText(prefix))
-      }
-    },
-  })
-}
-
-function createInlineDataStream(
-  dataStream: ReadableStream<Uint8Array>
-): TransformStream<Uint8Array, Uint8Array> {
-  let dataStreamFinished: Promise<void> | null = null
-  return createTransformStream({
-    transform(chunk, controller) {
-      controller.enqueue(chunk)
-
-      if (!dataStreamFinished) {
-        const dataStreamReader = dataStream.getReader()
-
-        // NOTE: streaming flush
-        // We are buffering here for the inlined data stream because the
-        // "shell" stream might be chunkenized again by the underlying stream
-        // implementation, e.g. with a specific high-water mark. To ensure it's
-        // the safe timing to pipe the data stream, this extra tick is
-        // necessary.
-        dataStreamFinished = new Promise((res) =>
-          setTimeout(async () => {
-            try {
-              while (true) {
-                const { done, value } = await dataStreamReader.read()
-                if (done) {
-                  return res()
-                }
-                controller.enqueue(value)
-              }
-            } catch (err) {
-              controller.error(err)
-            }
-            res()
-          }, 0)
-        )
-      }
-    },
-    flush() {
-      if (dataStreamFinished) {
-        return dataStreamFinished
-      }
-    },
-  })
-}
-
-function pipeTo<T>(
-  readable: ReadableStream<T>,
-  writable: WritableStream<T>,
-  options?: { preventClose: boolean }
-) {
-  let resolver: () => void
-  const promise = new Promise<void>((resolve) => (resolver = resolve))
-
-  const reader = readable.getReader()
-  const writer = writable.getWriter()
-  function process() {
-    reader.read().then(({ done, value }) => {
-      if (done) {
-        if (options?.preventClose) {
-          writer.releaseLock()
-        } else {
-          writer.close()
-        }
-        resolver()
-      } else {
-        writer.write(value)
-        process()
-      }
-    })
-  }
-  process()
-  return promise
-}
-
-function pipeThrough<Input, Output>(
-  readable: ReadableStream<Input>,
-  transformStream: TransformStream<Input, Output>
-) {
-  pipeTo(readable, transformStream.writable)
-  return transformStream.readable
-}
-
-function chainStreams<T>(streams: ReadableStream<T>[]): ReadableStream<T> {
-  const { readable, writable } = new TransformStream()
-
-  let promise = Promise.resolve()
-  for (let i = 0; i < streams.length; ++i) {
-    promise = promise.then(() =>
-      pipeTo(streams[i], writable, {
-        preventClose: i + 1 < streams.length,
-      })
-    )
-  }
-
-  return readable
-}
-
-function streamFromArray(strings: string[]): ReadableStream<Uint8Array> {
-  // Note: we use a TransformStream here instead of instantiating a ReadableStream
-  // because the built-in ReadableStream polyfill runs strings through TextEncoder.
-  const { readable, writable } = new TransformStream()
-
-  const writer = writable.getWriter()
-  strings.forEach((str) => writer.write(encodeText(str)))
-  writer.close()
-
-  return readable
-}
-
-async function streamToString(
-  stream: ReadableStream<Uint8Array>
-): Promise<string> {
-  const reader = stream.getReader()
-  let bufferedString = ''
-
-  while (true) {
-    const { done, value } = await reader.read()
-
-    if (done) {
-      return bufferedString
-    }
-
-    bufferedString += decodeText(value)
-  }
-}
diff --git a/packages/next/server/web/utils.ts b/packages/next/server/web/utils.ts
index a795ec35e144e..864721bb3ab40 100644
--- a/packages/next/server/web/utils.ts
+++ b/packages/next/server/web/utils.ts
@@ -14,32 +14,6 @@ export async function* streamToIterator<T>(
   reader.releaseLock()
 }
 
-export function readableStreamTee<T = any>(
-  readable: ReadableStream<T>
-): [ReadableStream<T>, ReadableStream<T>] {
-  const transformStream = new TransformStream()
-  const transformStream2 = new TransformStream()
-  const writer = transformStream.writable.getWriter()
-  const writer2 = transformStream2.writable.getWriter()
-
-  const reader = readable.getReader()
-  function read() {
-    reader.read().then(({ done, value }) => {
-      if (done) {
-        writer.close()
-        writer2.close()
-        return
-      }
-      writer.write(value)
-      writer2.write(value)
-      read()
-    })
-  }
-  read()
-
-  return [transformStream.readable, transformStream2.readable]
-}
-
 export function notImplemented(name: string, method: string): any {
   throw new Error(
     `Failed to get the '${method}' property on '${name}': the property is not implemented`