stream: always invoke callback before emitting error

Ensure the callback is always invoked before emitting
the error in both sync and async case.

PR-URL: #29293
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: ronag

doc/api/stream.md

@@ -571,7 +571,8 @@ The `writable.write()` method writes some data to the stream, and calls the
 supplied `callback` once the data has been fully handled. If an error
 occurs, the `callback` *may or may not* be called with the error as its
 first argument. To reliably detect write errors, add a listener for the
-`'error'` event.
+`'error'` event. If `callback` is called with an error, it will be called
+before the `'error'` event is emitted.
 
 The return value is `true` if the internal buffer is less than the
 `highWaterMark` configured when the stream was created after admitting `chunk`.

lib/_stream_writable.js

@@ -158,6 +158,11 @@ function WritableState(options, stream, isDuplex) {
   // Should .destroy() be called after 'finish' (and potentially 'end')
   this.autoDestroy = !!(options && options.autoDestroy);
 
+  // Indicates whether the stream has errored. When true all write() calls
+  // should return false. This is needed since when autoDestroy
+  // is disabled we need a way to tell whether the stream has failed.
+  this.errored = false;
+
   // Count buffered requests
   this.bufferedRequestCount = 0;
 
@@ -401,7 +406,7 @@ function writeOrBuffer(stream, state, isBuf, chunk, encoding, cb) {
   if (!ret)
     state.needDrain = true;
 
-  if (state.writing || state.corked) {
+  if (state.writing || state.corked || state.errored) {
     var last = state.lastBufferedRequest;
     state.lastBufferedRequest = {
       chunk,
@@ -420,7 +425,9 @@ function writeOrBuffer(stream, state, isBuf, chunk, encoding, cb) {
     doWrite(stream, state, false, len, chunk, encoding, cb);
   }
 
-  return ret;
+  // Return false if errored or destroyed in order to break
+  // any synchronous while(stream.write(data)) loops.
+  return ret && !state.errored && !state.destroyed;
 }
 
 function doWrite(stream, state, writev, len, chunk, encoding, cb) {
@@ -437,18 +444,11 @@ function doWrite(stream, state, writev, len, chunk, encoding, cb) {
   state.sync = false;
 }
 
-function onwriteError(stream, state, sync, er, cb) {
+function onwriteError(stream, state, er, cb) {
   --state.pendingcb;
 
-  if (sync) {
-    // Defer the callback if we are being called synchronously
-    // to avoid piling up things on the stack
-    process.nextTick(cb, er);
-  } else {
-    // The caller expect this to happen before if
-    // it is async
-    cb(er);
-  }
+  cb(er);
+  // This can emit error, but error must always follow cb.
   errorOrDestroy(stream, er);
 }
 
@@ -465,9 +465,14 @@ function onwrite(stream, er) {
   state.length -= state.writelen;
   state.writelen = 0;
 
-  if (er)
-    onwriteError(stream, state, sync, er, cb);
-  else {
+  if (er) {
+    state.errored = true;
+    if (sync) {
+      process.nextTick(onwriteError, stream, state, er, cb);
+    } else {
+      onwriteError(stream, state, er, cb);
+    }
+  } else {
     // Check if we're actually ready to finish, but don't emit yet
     var finished = needFinish(state) || stream.destroyed;
 
@@ -622,7 +627,7 @@ Object.defineProperty(Writable.prototype, 'writableLength', {
 function needFinish(state) {
   return (state.ending &&
           state.length === 0 &&
-          !state.errorEmitted &&
+          !state.errored &&
           state.bufferedRequest === null &&
           !state.finished &&
           !state.writing);

lib/internal/streams/destroy.js

@@ -27,6 +27,10 @@ function destroy(err, cb) {
   const r = this._readableState;
   const w = this._writableState;
 
+  if (w && err) {
+    w.errored = true;
+  }
+
   if ((w && w.destroyed) || (r && r.destroyed)) {
     if (cb) {
       cb(err);
@@ -50,10 +54,12 @@ function destroy(err, cb) {
   this._destroy(err || null, (err) => {
     const emitClose = (w && w.emitClose) || (r && r.emitClose);
     if (cb) {
+      // Invoke callback before scheduling emitClose so that callback
+      // can schedule before.
+      cb(err);
       if (emitClose) {
         process.nextTick(emitCloseNT, this);
       }
-      cb(err);
     } else if (needError(this, err)) {
       process.nextTick(emitClose ? emitErrorCloseNT : emitErrorNT, this, err);
     } else if (emitClose) {
@@ -91,6 +97,7 @@ function undestroy() {
 
   if (w) {
     w.destroyed = false;
+    w.errored = false;
     w.ended = false;
     w.ending = false;
     w.finalCalled = false;
@@ -110,6 +117,10 @@ function errorOrDestroy(stream, err) {
   const r = stream._readableState;
   const w = stream._writableState;
 
+  if (w & err) {
+    w.errored = true;
+  }
+
   if ((r && r.autoDestroy) || (w && w.autoDestroy))
     stream.destroy(err);
   else if (needError(stream, err))

test/parallel/test-http2-reset-flood.js

@@ -67,7 +67,10 @@ const worker = new Worker(__filename).on('message', common.mustCall((port) => {
       h2header.writeIntBE(1, 0, 3);  // Length: 1
       h2header.writeIntBE(i, 5, 4);  // Stream ID
       // 0x88 = :status: 200
-      conn.write(Buffer.concat([h2header, Buffer.from([0x88])]));
+      if (!conn.write(Buffer.concat([h2header, Buffer.from([0x88])]))) {
+        process.nextTick(writeRequests);
+        break;
+      }
     }
   }
 

test/parallel/test-stream-writable-destroy.js

@@ -16,6 +16,20 @@ const assert = require('assert');
   assert.strictEqual(write.destroyed, true);
 }
 
+{
+  const write = new Writable({
+    write(chunk, enc, cb) {
+      this.destroy(new Error('asd'));
+      cb();
+    }
+  });
+
+  write.on('error', common.mustCall());
+  write.on('finish', common.mustNotCall());
+  write.end('asd');
+  assert.strictEqual(write.destroyed, true);
+}
+
 {
   const write = new Writable({
     write(chunk, enc, cb) { cb(); }

test/parallel/test-stream-writable-write-cb-error.js

@@ -0,0 +1,58 @@
+'use strict';
+const common = require('../common');
+const { Writable } = require('stream');
+const assert = require('assert');
+
+// Ensure callback is always invoked before
+// error is emitted. Regardless if error was
+// sync or async.
+
+{
+  let callbackCalled = false;
+  // Sync Error
+  const writable = new Writable({
+    write: common.mustCall((buf, enc, cb) => {
+      cb(new Error());
+    })
+  });
+  writable.on('error', common.mustCall(() => {
+    assert.strictEqual(callbackCalled, true);
+  }));
+  writable.write('hi', common.mustCall(() => {
+    callbackCalled = true;
+  }));
+}
+
+{
+  let callbackCalled = false;
+  // Async Error
+  const writable = new Writable({
+    write: common.mustCall((buf, enc, cb) => {
+      process.nextTick(cb, new Error());
+    })
+  });
+  writable.on('error', common.mustCall(() => {
+    assert.strictEqual(callbackCalled, true);
+  }));
+  writable.write('hi', common.mustCall(() => {
+    callbackCalled = true;
+  }));
+}
+
+{
+  // Sync Error
+  const writable = new Writable({
+    write: common.mustCall((buf, enc, cb) => {
+      cb(new Error());
+    })
+  });
+
+  writable.on('error', common.mustCall());
+
+  let cnt = 0;
+  // Ensure we don't live lock on sync error
+  while (writable.write('a'))
+    cnt++;
+
+  assert.strictEqual(cnt, 0);
+}

test/parallel/test-wrap-js-stream-exceptions.js

@@ -16,4 +16,8 @@ const socket = new JSStreamWrap(new Duplex({
   })
 }));
 
-assert.throws(() => socket.end('foo'), /Error: write EPROTO/);
+socket.end('foo');
+socket.on('error', common.expectsError({
+  type: Error,
+  message: 'write EPROTO'
+}));