http2: add writable* properties to compat api

added writableHighWaterMark, writableLength, and writableFinished
properties with test.
Refs: #29829
PR-URL: #33506
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: rexagod

lib/internal/http2/compat.js

@@ -519,6 +519,18 @@ class Http2ServerResponse extends Stream {
 returnthis[kStream].writableCorked;
 }
 
+getwritableHighWaterMark(){
+returnthis[kStream].writableHighWaterMark;
+}
+
+getwritableFinished(){
+returnthis[kStream].writableFinished;
+}
+
+getwritableLength(){
+returnthis[kStream].writableLength;
+}
+
 setstatusCode(code){
 code|=0;
 if(code>=100&&code<200)

test/parallel/test-http2-res-writable-properties.js

@@ -0,0 +1,30 @@
+'use strict';
+constcommon=require('../common');
+if(!common.hasCrypto){common.skip('missing crypto');}
+constassert=require('assert');
+consthttp2=require('http2');
+
+constserver=http2.createServer(common.mustCall((req,res)=>{
+consthwm=req.socket.writableHighWaterMark;
+assert.strictEqual(res.writableHighWaterMark,hwm);
+assert.strictEqual(res.writableLength,0);
+res.write('');
+constlen=res.writableLength;
+res.write('asd');
+assert.strictEqual(res.writableLength,len+3);
+res.end();
+res.on('finish',common.mustCall(()=>{
+assert.strictEqual(res.writableLength,0);
+assert.ok(res.writableFinished,'writableFinished is not truthy');
+server.close();
+}));
+}));
+
+server.listen(0,common.mustCall(()=>{
+constclient=http2.connect(`http://localhost:${server.address().port}`);
+constrequest=client.request();
+request.on('data',common.mustCall());
+request.on('end',common.mustCall(()=>{
+client.close();
+}));
+}));