stream: Pass 'buffer' encoding to decoded writables

Since the encoding is no longer relevant once it is decoded to a Buffer,
it is confusing and incorrect to pass the encoding as 'utf8' or whatever
in those cases.

Closes #6119

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
index a26f711c1d..601f5b713f 100644
--- a/lib/_stream_writable.js
+++ b/lib/_stream_writable.js
@@ -196,6 +196,8 @@ function decodeChunk(state, chunk, encoding) {
 // If we return false, then we need a drain event, so set that flag.
 function writeOrBuffer(stream, state, chunk, encoding, cb) {
   chunk = decodeChunk(state, chunk, encoding);
+  if (Buffer.isBuffer(chunk))
+    encoding = 'buffer';
   var len = state.objectMode ? 1 : chunk.length;
 
   state.length += len;