channel: Remove the WithTrigger wrapper type.

At one point I needed this for something, but I can no longer find any use of
it so I am removing it from the package.

channel/channel_test.go

@@ -200,46 +200,3 @@ func TestHeaderTypeMismatch(t *testing.T) {
 		}
 	}
 }
-
-func TestWithTrigger(t *testing.T) {
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			r, w := io.Pipe()
-			triggered := false
-			ch := WithTrigger(test.framing(r, w), func() {
-				triggered = true
-			})
-
-			// Send a message to the channel, then close it.
-			const message = `["fools", "rush", "in"]`
-			done := make(chan struct{})
-			go func() {
-				defer close(done)
-				t.Log("Sending...")
-				if err := ch.Send([]byte(message)); err != nil {
-					t.Errorf("Send failed: %v", err)
-				}
-				t.Logf("Close: err=%v", ch.Close())
-			}()
-
-			// Read messages from the channel till it closes, then check that
-			// the trigger was correctly invoked.
-			for {
-				msg, err := ch.Recv()
-				if err == io.EOF {
-					t.Log("Recv: returned io.EOF")
-					break
-				} else if err != nil {
-					t.Errorf("Recv: unexpected error: %v", err)
-					break
-				}
-				t.Logf("Recv: msg=%q", string(msg))
-			}
-
-			<-done
-			if !triggered {
-				t.Error("After channel close: trigger not called")
-			}
-		})
-	}
-}

channel/types.go

@@ -9,30 +9,6 @@ import (
 // message-framing discipline.
 type Framing func(io.Reader, io.WriteCloser) Channel
 
-// WithTrigger returns a Channel that delegates I/O operations to ch, and when
-// a Recv operation on ch returns io.EOF it synchronously calls the trigger.
-func WithTrigger(ch Channel, trigger func()) Channel {
-	return triggered{ch: ch, trigger: trigger}
-}
-
-type triggered struct {
-	ch      Channel
-	trigger func()
-}
-
-// Recv implements part of the channel.Channel interface. It delegates to the
-// wrapped channel and calls the trigger when the delegate returns io.EOF.
-func (c triggered) Recv() ([]byte, error) {
-	msg, err := c.ch.Recv()
-	if err == io.EOF {
-		c.trigger()
-	}
-	return msg, err
-}
-
-func (c triggered) Send(msg []byte) error { return c.ch.Send(msg) }
-func (c triggered) Close() error          { return c.ch.Close() }
-
 type direct struct {
 	send chan<- []byte
 	recv <-chan []byte