http: align OutgoingMessage.writable with streams

Should be a computed value that looks at finished and
destroyed state.

Fixes: nodejs#33643

lib/_http_outgoing.js

@@ -69,6 +69,7 @@ const HIGH_WATER_MARK = getDefaultHighWaterMark();
 const { CRLF, debug } = common;
 
 const kCorked = Symbol('corked');
+const kWritable = Symbol('writable');
 
 function nop() {}
 
@@ -97,7 +98,6 @@ function OutgoingMessage() {
   // TCP socket and HTTP Parser and thus handle the backpressure.
   this.outputSize = 0;
 
-  this.writable = true;
   this.destroyed = false;
 
   this._last = false;
@@ -127,6 +127,18 @@ function OutgoingMessage() {
 ObjectSetPrototypeOf(OutgoingMessage.prototype, Stream.prototype);
 ObjectSetPrototypeOf(OutgoingMessage, Stream);
 
+ObjectDefineProperty(OutgoingMessage.prototype, 'writable', {
+  get() {
+    // TODO (ronag): Add errored state? write/end might error/destroy one
+    // tick later.
+    return this[kWritable] !== false && !this.destroyed && !this.finished;
+  },
+  set(val) {
+    // Backwards compatible.
+    this[kWritable] = !!val;
+  }
+});
+
 ObjectDefineProperty(OutgoingMessage.prototype, 'writableFinished', {
   get() {
     return (

test/parallel/test-http-outgoing-destroy.js

@@ -8,8 +8,10 @@ const OutgoingMessage = http.OutgoingMessage;
 {
   const msg = new OutgoingMessage();
   assert.strictEqual(msg.destroyed, false);
+  assert.strictEqual(msg.writable, true);
   msg.destroy();
   assert.strictEqual(msg.destroyed, true);
+  assert.strictEqual(msg.writable, false);
   let callbackCalled = false;
   msg.write('asd', common.mustCall((err) => {
     assert.strictEqual(err.code, 'ERR_STREAM_DESTROYED');

test/parallel/test-http-outgoing-finish.js

@@ -73,4 +73,5 @@ function write(out) {
       console.log(`ok - ${name} endCb`);
     });
   }));
+  assert.strictEqual(out.writable, false);
 }

test/parallel/test-http-outgoing-writableFinished.js

@@ -22,11 +22,14 @@ server.on('listening', common.mustCall(function() {
     path: '/'
   });
 
+  assert.strictEqual(clientRequest.writable, true);
   assert.strictEqual(clientRequest.writableFinished, false);
   clientRequest
     .on('finish', common.mustCall(() => {
+      assert.strictEqual(clientRequest.writable, false);
       assert.strictEqual(clientRequest.writableFinished, true);
     }))
     .end();
+  assert.strictEqual(clientRequest.writable, false);
   assert.strictEqual(clientRequest.writableFinished, false);
 }));