http: add writeInformation to send arbitrary 1xx status codes

doc/api/http.md

@@ -2702,6 +2702,35 @@ been transmitted are equal or not.
 Attempting to set a header field name or value that contains invalid characters
 will result in a [`TypeError`][] being thrown.
 
+### `response.writeInformation(statusCode[, headers][, callback])`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `statusCode` {number} An HTTP 1xx informational status code, between `100`
+  and `199` inclusive, excluding `101` (Switching Protocols) which is only
+  available through the [`'upgrade'`][] event.
+* `headers` {Object|Array} An optional set of headers to send with the
+  informational response. Accepts the same shapes as
+  [`response.writeHead()`][].
+* `callback` {Function} Optional, called once the message has been written
+  to the socket.
+
+Sends an arbitrary HTTP/1.1 1xx informational response to the client. This
+is a generic equivalent of [`response.writeContinue()`][],
+[`response.writeProcessing()`][] and [`response.writeEarlyHints()`][], and
+can be called multiple times before the final response. After the final
+response headers have been sent (via [`response.writeHead()`][] or an
+implicit header), calling this method throws `ERR_HTTP_HEADERS_SENT`.
+
+Clients receive these responses via the [`'information'`][information event]
+event on `http.ClientRequest`.
+
+```js
+response.writeInformation(110, { 'X-Progress': '50%' });
+```
+
 ### `response.writeProcessing()`
 
 <!-- YAML
@@ -4712,7 +4741,9 @@ const agent2 = new http.Agent({ proxyEnv: process.env });
 [`response.write()`]: #responsewritechunk-encoding-callback
 [`response.write(data, encoding)`]: #responsewritechunk-encoding-callback
 [`response.writeContinue()`]: #responsewritecontinue
+[`response.writeEarlyHints()`]: #responsewriteearlyhintshints-callback
 [`response.writeHead()`]: #responsewriteheadstatuscode-statusmessage-headers
+[`response.writeProcessing()`]: #responsewriteprocessing
 [`server.close()`]: #serverclosecallback
 [`server.headersTimeout`]: #serverheaderstimeout
 [`server.keepAliveTimeoutBuffer`]: #serverkeepalivetimeoutbuffer
@@ -4733,4 +4764,5 @@ const agent2 = new http.Agent({ proxyEnv: process.env });
 [`writable.destroyed`]: stream.md#writabledestroyed
 [`writable.uncork()`]: stream.md#writableuncork
 [`writable.write()`]: stream.md#writablewritechunk-encoding-callback
+[information event]: #event-information
 [initial delay]: net.md#socketsetkeepaliveenable-initialdelay

doc/api/http2.md

@@ -4848,6 +4848,30 @@ response.writeEarlyHints({
 });
 ```
 
+#### `response.writeInformation(statusCode[, headers])`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `statusCode` {number} An HTTP 1xx informational status code, between `100`
+  and `199` inclusive, excluding `101` (Switching Protocols) which is not
+  allowed in HTTP/2.
+* `headers` {Object} An optional object of headers to send with the
+  informational response.
+
+Sends an arbitrary HTTP 1xx informational response, equivalent in HTTP/2 to a
+`HEADERS` frame whose `:status` pseudo-header is a 1xx code. May be called
+multiple times before the final response. After the final response headers
+have been sent, this method is a no-op and returns `false`.
+
+This is the generic equivalent of [`response.writeContinue()`][] and
+[`response.writeEarlyHints()`][].
+
+```js
+response.writeInformation(110, { 'X-Progress': '50%' });
+```
+
 #### `response.writeHead(statusCode[, statusMessage][, headers])`
 
 <!-- YAML
@@ -5057,6 +5081,7 @@ you need to implement any fall-back behavior yourself.
 [`response.write()`]: #responsewritechunk-encoding-callback
 [`response.write(data, encoding)`]: http.md#responsewritechunk-encoding-callback
 [`response.writeContinue()`]: #responsewritecontinue
+[`response.writeEarlyHints()`]: #responsewriteearlyhintshints
 [`response.writeHead()`]: #responsewriteheadstatuscode-statusmessage-headers
 [`server.close()`]: #serverclosecallback
 [`server.maxHeadersCount`]: http.md#servermaxheaderscount

lib/_http_server.js

@@ -311,18 +311,66 @@ ServerResponse.prototype.detachSocket = function detachSocket(socket) {
   this.socket = null;
 };
 
+ServerResponse.prototype.writeInformation = function writeInformation(
+  statusCode, headers, cb) {
+  if (this._header) {
+    throw new ERR_HTTP_HEADERS_SENT('write');
+  }
+
+  validateInteger(statusCode, 'statusCode', 100, 199);
+  if (statusCode === 101) {
+    throw new ERR_HTTP_INVALID_STATUS_CODE(statusCode);
+  }
+
+  const statusMessage = STATUS_CODES[statusCode] || 'unknown';
+  let head = `HTTP/1.1 ${statusCode} ${statusMessage}\r\n`;
+
+  if (headers !== undefined && headers !== null) {
+    if (ArrayIsArray(headers)) {
+      if (headers.length && ArrayIsArray(headers[0])) {
+        for (let i = 0; i < headers.length; i++) {
+          const entry = headers[i];
+          head += processInformationHeader(entry[0], entry[1]);
+        }
+      } else {
+        if (headers.length % 2 !== 0) {
+          throw new ERR_INVALID_ARG_VALUE('headers', headers);
+        }
+        for (let i = 0; i < headers.length; i += 2) {
+          head += processInformationHeader(headers[i], headers[i + 1]);
+        }
+      }
+    } else {
+      validateObject(headers, 'headers');
+      const keys = ObjectKeys(headers);
+      for (let i = 0; i < keys.length; i++) {
+        const key = keys[i];
+        head += processInformationHeader(key, headers[key]);
+      }
+    }
+  }
+
+  head += '\r\n';
+
+  return this._writeRaw(head, 'ascii', cb);
+};
+
+function processInformationHeader(name, value) {
+  validateHeaderName(name);
+  validateHeaderValue(name, value);
+  return `${name}: ${value}\r\n`;
+}
+
 ServerResponse.prototype.writeContinue = function writeContinue(cb) {
-  this._writeRaw('HTTP/1.1 100 Continue\r\n\r\n', 'ascii', cb);
+  this.writeInformation(100, null, cb);
   this._sent100 = true;
 };
 
 ServerResponse.prototype.writeProcessing = function writeProcessing(cb) {
-  this._writeRaw('HTTP/1.1 102 Processing\r\n\r\n', 'ascii', cb);
+  this.writeInformation(102, null, cb);
 };
 
 ServerResponse.prototype.writeEarlyHints = function writeEarlyHints(hints, cb) {
-  let head = 'HTTP/1.1 103 Early Hints\r\n';
-
   validateObject(hints, 'hints');
 
   if (hints.link === null || hints.link === undefined) {
@@ -339,22 +387,16 @@ ServerResponse.prototype.writeEarlyHints = function writeEarlyHints(hints, cb) {
     throw new ERR_INVALID_CHAR('header content', 'Link');
   }
 
-  head += 'Link: ' + link + '\r\n';
-
+  const headers = { __proto__: null, Link: link };
   const keys = ObjectKeys(hints);
   for (let i = 0; i < keys.length; i++) {
     const key = keys[i];
     if (key !== 'link') {
-      validateHeaderName(key);
-      const value = hints[key];
-      validateHeaderValue(key, value);
-      head += key + ': ' + value + '\r\n';
+      headers[key] = hints[key];
     }
   }
 
-  head += '\r\n';
-
-  this._writeRaw(head, 'ascii', cb);
+  this.writeInformation(103, headers, cb);
 };
 
 ServerResponse.prototype._implicitHeader = function _implicitHeader() {

lib/internal/http2/compat.js

@@ -901,17 +901,39 @@ class Http2ServerResponse extends Stream {
     this[kStream].respond(headers, options);
   }
 
-  // TODO doesn't support callbacks
-  writeContinue() {
+  writeInformation(statusCode, headers) {
+    if (typeof statusCode !== 'number' ||
+        statusCode < 100 || statusCode > 199) {
+      throw new ERR_HTTP2_STATUS_INVALID(statusCode);
+    }
+    if (statusCode === 101) {
+      throw new ERR_HTTP2_STATUS_INVALID(statusCode);
+    }
+
     const stream = this[kStream];
+
     if (stream.headersSent || this[kState].closed)
       return false;
-    stream.additionalHeaders({
-      [HTTP2_HEADER_STATUS]: HTTP_STATUS_CONTINUE,
-    });
+
+    const outHeaders = { __proto__: null };
+    if (headers !== undefined && headers !== null) {
+      validateObject(headers, 'headers');
+      const keys = ObjectKeys(headers);
+      for (let i = 0; i < keys.length; i++) {
+        outHeaders[keys[i]] = headers[keys[i]];
+      }
+    }
+    outHeaders[HTTP2_HEADER_STATUS] = statusCode;
+
+    stream.additionalHeaders(outHeaders);
     return true;
   }
 
+  // TODO doesn't support callbacks
+  writeContinue() {
+    return this.writeInformation(HTTP_STATUS_CONTINUE);
+  }
+
   writeEarlyHints(hints) {
     validateObject(hints, 'hints');
 
@@ -929,18 +951,9 @@ class Http2ServerResponse extends Stream {
       return false;
     }
 
-    const stream = this[kStream];
+    headers.Link = linkHeaderValue;
 
-    if (stream.headersSent || this[kState].closed)
-      return false;
-
-    stream.additionalHeaders({
-      ...headers,
-      [HTTP2_HEADER_STATUS]: HTTP_STATUS_EARLY_HINTS,
-      'Link': linkHeaderValue,
-    });
-
-    return true;
+    return this.writeInformation(HTTP_STATUS_EARLY_HINTS, headers);
   }
 }
 

test/parallel/test-http-information-headers.js

@@ -9,11 +9,7 @@ const countdown = new Countdown(2, () => server.close());
 
 const server = http.createServer(common.mustCallAtLeast((req, res) => {
   console.error('Server sending informational message #1...');
-  // These function calls may rewritten as necessary
-  // to call res.writeHead instead
-  res._writeRaw('HTTP/1.1 102 Processing\r\n');
-  res._writeRaw('Foo: Bar\r\n');
-  res._writeRaw('\r\n', common.mustCall());
+  res.writeInformation(102, { Foo: 'Bar' }, common.mustCall());
   console.error('Server sending full response...');
   res.writeHead(200, {
     'Content-Type': 'text/plain',

test/parallel/test-http-write-information.js

@@ -0,0 +1,94 @@
+'use strict';
+const common = require('../common');
+const assert = require('node:assert');
+const http = require('node:http');
+
+// Happy flow: arbitrary 1xx status with custom headers, observed by the
+// client's 'information' event.
+{
+  const server = http.createServer(common.mustCall((req, res) => {
+    res.writeInformation(110, { 'X-Progress': '50%', 'X-Stage': 'reading' });
+    res.writeInformation(199, [['X-Custom', 'one'], ['X-Custom-2', 'two']]);
+    res.end('done');
+  }));
+
+  server.listen(0, common.mustCall(() => {
+    const req = http.request({ port: server.address().port });
+
+    const seen = [];
+    req.on('information', (res) => {
+      seen.push({
+        statusCode: res.statusCode,
+        headers: res.headers,
+      });
+    });
+
+    req.on('response', common.mustCall((res) => {
+      assert.strictEqual(res.statusCode, 200);
+
+      assert.strictEqual(seen.length, 2);
+      assert.strictEqual(seen[0].statusCode, 110);
+      assert.strictEqual(seen[0].headers['x-progress'], '50%');
+      assert.strictEqual(seen[0].headers['x-stage'], 'reading');
+      assert.strictEqual(seen[1].statusCode, 199);
+      assert.strictEqual(seen[1].headers['x-custom'], 'one');
+      assert.strictEqual(seen[1].headers['x-custom-2'], 'two');
+
+      res.resume();
+      res.on('end', common.mustCall(() => server.close()));
+    }));
+
+    req.end();
+  }));
+}
+
+// Headers argument is optional / nullable.
+{
+  const server = http.createServer(common.mustCall((req, res) => {
+    res.writeInformation(150);
+    res.writeInformation(151, null);
+    res.end();
+  }));
+
+  server.listen(0, common.mustCall(() => {
+    const req = http.request({ port: server.address().port });
+    let count = 0;
+    req.on('information', () => count++);
+    req.on('response', common.mustCall((res) => {
+      assert.strictEqual(count, 2);
+      res.resume();
+      res.on('end', common.mustCall(() => server.close()));
+    }));
+    req.end();
+  }));
+}
+
+// Error cases.
+{
+  const server = http.createServer(common.mustCall((req, res) => {
+    assert.throws(() => res.writeInformation(101),
+                  { code: 'ERR_HTTP_INVALID_STATUS_CODE' });
+    assert.throws(() => res.writeInformation(99),
+                  { code: 'ERR_OUT_OF_RANGE' });
+    assert.throws(() => res.writeInformation(200),
+                  { code: 'ERR_OUT_OF_RANGE' });
+    assert.throws(() => res.writeInformation('100'),
+                  { code: 'ERR_INVALID_ARG_TYPE' });
+    assert.throws(() => res.writeInformation(150, { 'X-Bad\n': 'v' }),
+                  { code: 'ERR_INVALID_HTTP_TOKEN' });
+
+    res.writeHead(200);
+    assert.throws(() => res.writeInformation(150),
+                  { code: 'ERR_HTTP_HEADERS_SENT' });
+    res.end();
+  }));
+
+  server.listen(0, common.mustCall(() => {
+    const req = http.request({ port: server.address().port });
+    req.on('response', common.mustCall((res) => {
+      res.resume();
+      res.on('end', common.mustCall(() => server.close()));
+    }));
+    req.end();
+  }));
+}