next
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The React Framework
196 lines (195 loc) • 6.76 kB
JavaScript
import { InvariantError } from '../../shared/lib/invariant-error';
/**
* This is a utility function to make scheduling sequential tasks that run back to back easier.
* We schedule on the same queue (setImmediate) at the same time to ensure no other events can sneak in between.
*/ export function prerenderAndAbortInSequentialTasks(prerender, abort) {
if (process.env.NEXT_RUNTIME === 'edge') {
throw Object.defineProperty(new InvariantError('`prerenderAndAbortInSequentialTasks` should not be called in edge runtime.'), "__NEXT_ERROR_CODE", {
value: "E538",
enumerable: false,
configurable: true
});
} else {
return new Promise((resolve, reject)=>{
let pendingResult;
setImmediate(()=>{
try {
pendingResult = prerender();
pendingResult.catch(()=>{});
} catch (err) {
reject(err);
}
});
setImmediate(()=>{
abort();
resolve(pendingResult);
});
});
}
}
/**
* Like `prerenderAndAbortInSequentialTasks`, but with another task between `prerender` and `abort`,
* which allows us to move a part of the render into a separate task.
*/ export function prerenderAndAbortInSequentialTasksWithStages(prerender, advanceStage, abort) {
if (process.env.NEXT_RUNTIME === 'edge') {
throw Object.defineProperty(new InvariantError('`prerenderAndAbortInSequentialTasksWithStages` should not be called in edge runtime.'), "__NEXT_ERROR_CODE", {
value: "E778",
enumerable: false,
configurable: true
});
} else {
return new Promise((resolve, reject)=>{
let pendingResult;
setImmediate(()=>{
try {
pendingResult = prerender();
pendingResult.catch(()=>{});
} catch (err) {
reject(err);
}
});
setImmediate(()=>{
advanceStage();
});
setImmediate(()=>{
abort();
resolve(pendingResult);
});
});
}
}
// React's RSC prerender function will emit an incomplete flight stream when using `prerender`. If the connection
// closes then whatever hanging chunks exist will be errored. This is because prerender (an experimental feature)
// has not yet implemented a concept of resume. For now we will simulate a paused connection by wrapping the stream
// in one that doesn't close even when the underlying is complete.
export class ReactServerResult {
constructor(stream){
this._stream = stream;
}
tee() {
if (this._stream === null) {
throw Object.defineProperty(new Error('Cannot tee a ReactServerResult that has already been consumed'), "__NEXT_ERROR_CODE", {
value: "E106",
enumerable: false,
configurable: true
});
}
const tee = this._stream.tee();
this._stream = tee[0];
return tee[1];
}
consume() {
if (this._stream === null) {
throw Object.defineProperty(new Error('Cannot consume a ReactServerResult that has already been consumed'), "__NEXT_ERROR_CODE", {
value: "E470",
enumerable: false,
configurable: true
});
}
const stream = this._stream;
this._stream = null;
return stream;
}
}
export async function createReactServerPrerenderResult(underlying) {
const chunks = [];
const { prelude } = await underlying;
const reader = prelude.getReader();
while(true){
const { done, value } = await reader.read();
if (done) {
return new ReactServerPrerenderResult(chunks);
} else {
chunks.push(value);
}
}
}
export async function createReactServerPrerenderResultFromRender(underlying) {
const chunks = [];
const reader = underlying.getReader();
while(true){
const { done, value } = await reader.read();
if (done) {
break;
} else {
chunks.push(value);
}
}
return new ReactServerPrerenderResult(chunks);
}
export class ReactServerPrerenderResult {
assertChunks(expression) {
if (this._chunks === null) {
throw Object.defineProperty(new InvariantError(`Cannot \`${expression}\` on a ReactServerPrerenderResult that has already been consumed.`), "__NEXT_ERROR_CODE", {
value: "E593",
enumerable: false,
configurable: true
});
}
return this._chunks;
}
consumeChunks(expression) {
const chunks = this.assertChunks(expression);
this.consume();
return chunks;
}
consume() {
this._chunks = null;
}
constructor(chunks){
this._chunks = chunks;
}
asUnclosingStream() {
const chunks = this.assertChunks('asUnclosingStream()');
return createUnclosingStream(chunks);
}
consumeAsUnclosingStream() {
const chunks = this.consumeChunks('consumeAsUnclosingStream()');
return createUnclosingStream(chunks);
}
asStream() {
const chunks = this.assertChunks('asStream()');
return createClosingStream(chunks);
}
consumeAsStream() {
const chunks = this.consumeChunks('consumeAsStream()');
return createClosingStream(chunks);
}
}
function createUnclosingStream(chunks) {
let i = 0;
return new ReadableStream({
async pull (controller) {
if (i < chunks.length) {
controller.enqueue(chunks[i++]);
}
// we intentionally keep the stream open. The consumer will clear
// out chunks once finished and the remaining memory will be GC'd
// when this object goes out of scope
}
});
}
function createClosingStream(chunks) {
let i = 0;
return new ReadableStream({
async pull (controller) {
if (i < chunks.length) {
controller.enqueue(chunks[i++]);
} else {
controller.close();
}
}
});
}
export async function processPrelude(unprocessedPrelude) {
const [prelude, peek] = unprocessedPrelude.tee();
const reader = peek.getReader();
const firstResult = await reader.read();
reader.cancel();
const preludeIsEmpty = firstResult.done === true;
return {
prelude,
preludeIsEmpty
};
}
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