Add support for flushing headers

docs/api/response.md

@@ -289,3 +289,7 @@ this.response.etag = crypto.createHash('md5').update(this.body).digest('hex');
 ### response.vary(field)
 
  Vary on `field`.
+
+### response.flushHeaders()
+
+ Flush any set headers, and begin the body.

lib/application.js

@@ -181,7 +181,7 @@ function respond(ctx) {
  if (false === ctx.respond) return;
 
  const res = ctx.res;
- if (res.headersSent || !ctx.writable) return;
+ if (!ctx.writable) return;
 
  let body = ctx.body;
  const code = ctx.status;
@@ -194,15 +194,19 @@ function respond(ctx) {
  }
 
  if ('HEAD' == ctx.method) {
- if (isJSON(body)) ctx.length = Buffer.byteLength(JSON.stringify(body));
+ if (!res.headersSent && isJSON(body)) {
+ ctx.length = Buffer.byteLength(JSON.stringify(body));
+ }
  return res.end();
  }
 
  // status body
  if (null == body) {
- ctx.type = 'text';
  body = ctx.message || String(code);
- ctx.length = Buffer.byteLength(body);
+ if (!res.headersSent) {
+ ctx.type = 'text';
+ ctx.length = Buffer.byteLength(body);
+ }
  return res.end(body);
  }
 
@@ -213,6 +217,8 @@ function respond(ctx) {
 
  // body: json
  body = JSON.stringify(body);
- ctx.length = Buffer.byteLength(body);
+ if (!res.headersSent) {
+ ctx.length = Buffer.byteLength(body);
+ }
  res.end(body);
 }

lib/context.js

@@ -149,6 +149,7 @@ delegate(proto, 'response')
  .method('vary')
  .method('set')
  .method('append')
+ .method('flushHeaders')
  .access('status')
  .access('message')
  .access('body')

lib/response.js

@@ -80,6 +80,7 @@ module.exports = {
  set status(code) {
  assert('number' == typeof code, 'status code must be a number');
  assert(statuses[code], `invalid status code: ${code}`);
+ assert(!this.res.headersSent, 'headers have already been sent');
  this._explicitStatus = true;
  this.res.statusCode = code;
  this.res.statusMessage = statuses[code];
@@ -130,6 +131,8 @@ module.exports = {
  const original = this._body;
  this._body = val;
 
+ if (this.res.headersSent) return;
+
  // no content
  if (null == val) {
  if (!statuses.empty[this.status]) this.status = 204;
@@ -521,5 +524,12 @@ module.exports = {
  'message',
  'header'
  ]);
+ },
+
+ /**
+ * Flush any set headers, and begin the body
+ */
+ flushHeaders() {
+ this.res.writeHead(this.res.statusCode);
  }
 };

test/application/respond.js

@@ -234,7 +234,12 @@ describe('app.respond', () => {
  ctx.status = 200;
  res.setHeader('Content-Type', 'text/html');
  res.write('Hello');
- setTimeout(() => res.end('Goodbye'), 0);
+ return new Promise(resolve => {
+ setTimeout(() => {
+ res.end('Goodbye');
+ resolve();
+ }, 0);
+ });
  });
 
  const server = app.listen();

test/response/flushHeaders.js

@@ -0,0 +1,98 @@
+
+'use strict';
+
+const request = require('supertest');
+const assert = require('assert');
+const Koa = require('../..');
+
+describe('ctx.flushHeaders()', () => {
+ it('should set headersSent', done => {
+ const app = new Koa();
+
+ app.use((ctx, next) => {
+ ctx.body = 'Body';
+ ctx.status = 200;
+ ctx.flushHeaders();
+ assert(ctx.res.headersSent);
+ });
+
+ const server = app.listen();
+
+ request(server)
+ .get('/')
+ .expect(200)
+ .expect('Body', done);
+ });
+
+ it('should allow a response afterwards', done => {
+ const app = new Koa();
+
+ app.use((ctx, next) => {
+ ctx.status = 200;
+ ctx.res.setHeader('Content-Type', 'text/plain');
+ ctx.flushHeaders();
+ ctx.body = 'Body';
+ });
+
+ const server = app.listen();
+ request(server)
+ .get('/')
+ .expect(200)
+ .expect('Content-Type', 'text/plain')
+ .expect('Body', done);
+ });
+
+ it('should send the correct status code', done => {
+ const app = new Koa();
+
+ app.use((ctx, next) => {
+ ctx.status = 401;
+ ctx.res.setHeader('Content-Type', 'text/plain');
+ ctx.flushHeaders();
+ ctx.body = 'Body';
+ });
+
+ const server = app.listen();
+ request(server)
+ .get('/')
+ .expect(401)
+ .expect('Content-Type', 'text/plain')
+ .expect('Body', done);
+ });
+
+ it('should fail to set the headers after flushHeaders', done => {
+ const app = new Koa();
+
+ app.use((ctx, next) => {
+ ctx.status = 401;
+ ctx.res.setHeader('Content-Type', 'text/plain');
+ ctx.flushHeaders();
+ ctx.body = '';
+ try {
+ ctx.set('X-Shouldnt-Work', 'Value');
+ } catch (err) {
+ ctx.body += 'ctx.set fail ';
+ }
+ try {
+ ctx.status = 200;
+ } catch (err) {
+ ctx.body += 'ctx.status fail ';
+ }
+ try {
+ ctx.length = 10;
+ } catch (err) {
+ ctx.body += 'ctx.length fail';
+ }
+ });
+
+ const server = app.listen();
+ request(server)
+ .get('/')
+ .expect(401)
+ .expect('Content-Type', 'text/plain')
+ .expect('ctx.set fail ctx.status fail ctx.length fail', (err, res) => {
+ assert(res.headers['x-shouldnt-work'] === undefined, 'header set after flushHeaders');
+ done(err);
+ });
+ });
+});