Revert "http: headers(Distinct), trailers(Distinct) setters to be no-op"

This reverts commit 4d723c7fd6f8b2ecd0dbc1d6f0595645f6471928.

I'm not sure if we should re-apply this as a semver-major change or if
we should accept it as valid and add tests/documentation, but either
way, we have to revert it at least temporarily.

Closes: https://github.com/nodejs/node/issues/45510
PR-URL: https://github.com/nodejs/node/pull/45527
Fixes: https://github.com/nodejs/node/issues/45510
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Filip Skokan <panva.ip@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Robert Nagy <ronagy@icloud.com>

lib/_http_incoming.js

@@ -122,7 +122,9 @@ ObjectDefineProperty(IncomingMessage.prototype, 'headers', {
     }
     return this[kHeaders];
   },
-  set: function(val) {}
+  set: function(val) {
+    this[kHeaders] = val;
+  }
 });
 
 ObjectDefineProperty(IncomingMessage.prototype, 'headersDistinct', {
@@ -140,7 +142,9 @@ ObjectDefineProperty(IncomingMessage.prototype, 'headersDistinct', {
     }
     return this[kHeadersDistinct];
   },
-  set: function(val) {}
+  set: function(val) {
+    this[kHeadersDistinct] = val;
+  }
 });
 
 ObjectDefineProperty(IncomingMessage.prototype, 'trailers', {
@@ -158,7 +162,9 @@ ObjectDefineProperty(IncomingMessage.prototype, 'trailers', {
     }
     return this[kTrailers];
   },
-  set: function(val) {}
+  set: function(val) {
+    this[kTrailers] = val;
+  }
 });
 
 ObjectDefineProperty(IncomingMessage.prototype, 'trailersDistinct', {
@@ -176,7 +182,9 @@ ObjectDefineProperty(IncomingMessage.prototype, 'trailersDistinct', {
     }
     return this[kTrailersDistinct];
   },
-  set: function(val) {}
+  set: function(val) {
+    this[kTrailersDistinct] = val;
+  }
 });
 
 IncomingMessage.prototype.setTimeout = function setTimeout(msecs, callback) {

test/parallel/test-http-set-headers-distinct.js

@@ -1,54 +0,0 @@
-'use strict';
-
-const common = require('../common');
-const assert = require('assert');
-const { createServer, request } = require('http');
-
-const server = createServer(
-  common.mustCall((req, res) => {
-    req.headersDistinct = { 'x-req-a': ['zzz'] };
-
-    // headersDistinct setter should be a No-Op
-    assert.deepStrictEqual(req.headersDistinct, {
-      'transfer-encoding': [
-        'chunked',
-      ],
-      'connection': [
-        'keep-alive',
-      ],
-      'host': [
-        `127.0.0.1:${server.address().port}`,
-      ]
-    });
-
-    req.on('end', function() {
-      res.write('BODY');
-      res.end();
-    });
-
-    req.resume();
-  })
-);
-
-server.listen(
-  0,
-  common.mustCall(() => {
-    const req = request(
-      {
-        host: '127.0.0.1',
-        port: server.address().port,
-        path: '/',
-        method: 'POST',
-      },
-      common.mustCall((res) => {
-        res.on('end', function() {
-          server.close();
-        });
-        res.resume();
-      })
-    );
-
-    req.write('BODY');
-    req.end();
-  })
-);

test/parallel/test-set-incoming-message-header.js

@@ -4,23 +4,24 @@ require('../common');
 const { IncomingMessage } = require('http');
 const assert = require('assert');
 
-// Headers setter should be a No-Op
+// Headers setter function set a header correctly
 {
   const im = new IncomingMessage();
   im.headers = { key: 'value' };
-  assert.deepStrictEqual(im.headers, {});
+  assert.deepStrictEqual(im.headers, { key: 'value' });
 }
 
-// Trailers setter should be a No-Op
+// Trailers setter function set a header correctly
 {
   const im = new IncomingMessage();
   im.trailers = { key: 'value' };
-  assert.deepStrictEqual(im.trailers, {});
+  assert.deepStrictEqual(im.trailers, { key: 'value' });
 }
 
 // _addHeaderLines function set a header correctly
 {
   const im = new IncomingMessage();
+  im.headers = { key1: 'value1' };
   im._addHeaderLines(['key2', 'value2'], 2);
-  assert.deepStrictEqual(im.headers, { key2: 'value2' });
+  assert.deepStrictEqual(im.headers, { key1: 'value1', key2: 'value2' });
 }