http2: makes response.writeHead return the response

Fixes: #25935

PR-URL: #25974
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

doc/api/http2.md

@@ -3284,15 +3284,23 @@ should be sent. See the [`'checkContinue'`][] event on `Http2Server` and
 #### response.writeHead(statusCode[, statusMessage][, headers])
 <!-- YAML
 added: v8.4.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/25974
+    description: Return `this` from `writeHead()` to allow chaining with
+                 `end()`.
 -->
 
 * `statusCode` {number}
 * `statusMessage` {string}
 * `headers` {Object}
+* Returns: {http2.Http2ServerResponse}
 
 Sends a response header to the request. The status code is a 3-digit HTTP
 status code, like `404`. The last argument, `headers`, are the response headers.
 
+Returns a reference to the `Http2ServerResponse`, so that calls can be chained.
+
 For compatibility with [HTTP/1][], a human-readable `statusMessage` may be
 passed as the second argument. However, because the `statusMessage` has no
 meaning within HTTP/2, the argument will have no effect and a process warning

lib/internal/http2/compat.js

@@ -593,10 +593,8 @@ class Http2ServerResponse extends Stream {
     if (this[kStream].headersSent)
       throw new ERR_HTTP2_HEADERS_SENT();
 
-    // If the stream is destroyed, we return false,
-    // like require('http').
     if (this.stream.destroyed)
-      return false;
+      return this;
 
     if (typeof statusMessage === 'string')
       statusMessageWarn();
@@ -621,6 +619,8 @@ class Http2ServerResponse extends Stream {
 
     state.statusCode = statusCode;
     this[kBeginSend]();
+
+    return this;
   }
 
   write(chunk, encoding, cb) {

test/parallel/test-http2-compat-serverresponse-writehead-array.js

@@ -12,10 +12,11 @@ const server = h2.createServer();
 server.listen(0, common.mustCall(() => {
   const port = server.address().port;
   server.once('request', common.mustCall((request, response) => {
-    response.writeHead(200, [
+    const returnVal = response.writeHead(200, [
       ['foo', 'bar'],
       ['ABC', 123]
     ]);
+    assert.strictEqual(returnVal, response);
     response.end(common.mustCall(() => { server.close(); }));
   }));
 

test/parallel/test-http2-compat-serverresponse-writehead.js

@@ -13,7 +13,11 @@ server.listen(0, common.mustCall(function() {
   const port = server.address().port;
   server.once('request', common.mustCall(function(request, response) {
     response.setHeader('foo-bar', 'def456');
-    response.writeHead(418, { 'foo-bar': 'abc123' }); // Override
+
+    // Override
+    const returnVal = response.writeHead(418, { 'foo-bar': 'abc123' });
+
+    assert.strictEqual(returnVal, response);
 
     common.expectsError(() => { response.writeHead(300); }, {
       code: 'ERR_HTTP2_HEADERS_SENT'