streams: expose stream symbols

This is required for streams interop with e.g. readable-stream. Currently
readable-stream helpers will not work with normal node streams which is confusing
and bad for the ecosystem.

lib/internal/streams/destroy.js

@@ -11,7 +11,7 @@ const {
   Symbol,
 } = primordials;
 const {
-  kDestroyed,
+  kIsDestroyed,
   isDestroyed,
   isFinished,
   isServerRequest
@@ -325,7 +325,7 @@ function destroyer(stream, err) {
   }
 
   if (!stream.destroyed) {
-    stream[kDestroyed] = true;
+    stream[kIsDestroyed] = true;
   }
 }
 

lib/internal/streams/utils.js

@@ -6,9 +6,10 @@ const {
   SymbolIterator,
 } = primordials;
 
-const kDestroyed = Symbol('kDestroyed');
+const kIsDestroyed = Symbol('kIsDestroyed');
 const kIsErrored = Symbol('kIsErrored');
 const kIsReadable = Symbol('kIsReadable');
+const kIsWritable = Symbol('kIsWritable');
 const kIsDisturbed = Symbol('kIsDisturbed');
 
 function isReadableNodeStream(obj, strict = false) {
@@ -68,7 +69,7 @@ function isDestroyed(stream) {
   const wState = stream._writableState;
   const rState = stream._readableState;
   const state = wState || rState;
-  return !!(stream.destroyed || stream[kDestroyed] || state?.destroyed);
+  return !!(stream.destroyed || stream[kIsDestroyed] || state?.destroyed);
 }
 
 // Have been end():d.
@@ -126,6 +127,7 @@ function isReadable(stream) {
 }
 
 function isWritable(stream) {
+  if (stream && stream[kIsWritable] != null) return stream[kIsWritable];
   if (typeof stream?.writable !== 'boolean') return null;
   if (isDestroyed(stream)) return false;
   return isWritableNodeStream(stream) &&
@@ -262,13 +264,14 @@ function isErrored(stream) {
 }
 
 module.exports = {
-  kDestroyed,
-  isDisturbed,
+  kIsDestroyed,
   kIsDisturbed,
-  isErrored,
   kIsErrored,
-  isReadable,
   kIsReadable,
+  kIsWritable,
+  isDisturbed,
+  isErrored,
+  isReadable,
   isClosed,
   isDestroyed,
   isDuplexNodeStream,

lib/stream.js

@@ -51,9 +51,19 @@ const promises = require('stream/promises');
 const utils = require('internal/streams/utils');
 
 const Stream = module.exports = require('internal/streams/legacy').Stream;
+
+Stream.isDestroyed = utils.isDestroyed;
 Stream.isDisturbed = utils.isDisturbed;
 Stream.isErrored = utils.isErrored;
 Stream.isReadable = utils.isReadable;
+Stream.isWritable = utils.isWritable;
+
+Stream.kIsDestroyed = utils.kIsDestroyed;
+Stream.kIsErrored = utils.kIsErrored;
+Stream.kIsReadable = utils.kIsReadable;
+Stream.kIsWritable = utils.kIsWritable;
+Stream.kIsDisturbed = utils.kIsDisturbed;
+
 Stream.Readable = require('internal/streams/readable');
 for (const key of ObjectKeys(streamReturningOperators)) {
   const op = streamReturningOperators[key];