stream: refactor writable _write

lib/internal/streams/writable.js

@@ -443,22 +443,21 @@ Writable.prototype.pipe = function() {
 function _write(stream, chunk, encoding, cb) {
  const state = stream._writableState;
 
- if (typeof encoding === 'function') {
- cb = encoding;
- encoding = null;
- }
-
- if (!encoding)
- encoding = (state[kState] & kDefaultUTF8Encoding) !== 0 ? 'utf8' : state[kDefaultEncodingValue];
- else if (encoding !== 'buffer' && !Buffer.isEncoding(encoding))
- throw new ERR_UNKNOWN_ENCODING(encoding);
-
- if (cb == null || typeof cb !== 'function')
+ if (cb == null || typeof cb !== 'function') {
  cb = nop;
+ }
 
  if (chunk === null) {
  throw new ERR_STREAM_NULL_VALUES();
- } else if ((state[kState] & kObjectMode) === 0) {
+ }
+
+ if ((state[kState] & kObjectMode) === 0) {
+ if (!encoding) {
+ encoding = (state[kState] & kDefaultUTF8Encoding) !== 0 ? 'utf8' : state.defaultEncoding;
+ } else if (encoding !== 'buffer' && !Buffer.isEncoding(encoding)) {
+ throw new ERR_UNKNOWN_ENCODING(encoding);
+ }
+
  if (typeof chunk === 'string') {
  if ((state[kState] & kDecodeStrings) !== 0) {
  chunk = Buffer.from(chunk, encoding);
@@ -487,11 +486,17 @@ function _write(stream, chunk, encoding, cb) {
  errorOrDestroy(stream, err, true);
  return err;
  }
+
  state.pendingcb++;
  return writeOrBuffer(stream, state, chunk, encoding, cb);
 }
 
 Writable.prototype.write = function(chunk, encoding, cb) {
+ if (encoding != null && typeof encoding === 'function') {
+ cb = encoding;
+ encoding = null;
+ }
+
  return _write(this, chunk, encoding, cb) === true;
 };
 

test/parallel/test-stream-uint8array.js

@@ -38,7 +38,7 @@ const GHI = new Uint8Array([0x47, 0x48, 0x49]);
  assert(!(chunk instanceof Buffer));
  assert(chunk instanceof Uint8Array);
  assert.strictEqual(chunk, ABC);
- assert.strictEqual(encoding, 'utf8');
+ assert.strictEqual(encoding, undefined);
  cb();
  })
  });