PipeListenerDialer.Close should be called once

PipeListenerDialer.Close will return unix.EINVAL if it is called more
than once. This is to emulate the behavior of other standard listeners.

Also:

  * PipeListenerDialer.Accept will return (nil, unix.EINVAL) if the
    listener is closed. This roughly matches with behavior described in
    accept(2).

  * PipeListenerDialer.Dial will also return (nil, unix.EINVAL) if the
    address passed does not match the one passed to New. It will also
    return (nil, unix.ECONNREFUSED) if the listener is closed. This
    roughly matches the behavior described in connect(2) and unix(7).

  * The custom errors ErrBadAddress and ErrClosed are removed.

4 files changed, 38 insertions, 13 deletions

diff --git a/go.mod b/go.mod
index e6f2ddd..e9bef6d 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module go.awhk.org/pipeln
 
 go 1.15
 
-require github.com/stretchr/testify v1.7.0
+require (
+	github.com/stretchr/testify v1.7.0
+	golang.org/x/sys v0.0.0-20210316092937-0b90fd5c4c48
+)
diff --git a/go.sum b/go.sum
index acb88a4..c5d38b3 100644
--- a/go.sum
+++ b/go.sum
@@ -5,6 +5,8 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+golang.org/x/sys v0.0.0-20210316092937-0b90fd5c4c48 h1:70qalHWW1n9yoI8B8zEQxFJO/D6NUWIX8SNmJO+rvNw=
+golang.org/x/sys v0.0.0-20210316092937-0b90fd5c4c48/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
diff --git a/pipeln.go b/pipeln.go
index c836f28..29c6523 100644
--- a/pipeln.go
+++ b/pipeln.go
@@ -4,13 +4,9 @@ package pipeln
 
 import (
 	"context"
-	"errors"
 	"net"
-)
 
-var (
-	ErrBadAddress = errors.New("bad address")
-	ErrClosed     = errors.New("closed listener")
+	"golang.org/x/sys/unix"
 )
 
 type addr struct {
@@ -34,6 +30,7 @@ type PipeListenerDialer struct {
 	addr  string
 	conns chan net.Conn
 	done  chan struct{}
+	ok    bool
 }
 
 var _ net.Listener = &PipeListenerDialer{}
@@ -43,7 +40,7 @@ func (ln *PipeListenerDialer) Accept() (net.Conn, error) {
 	case conn := <-ln.conns:
 		return conn, nil
 	case <-ln.done:
-		return nil, ErrClosed
+		return nil, unix.EINVAL
 	}
 }
 
@@ -52,20 +49,24 @@ func (ln *PipeListenerDialer) Addr() net.Addr {
 }
 
 func (ln *PipeListenerDialer) Close() error {
+	if !ln.ok {
+		return unix.EINVAL
+	}
 	close(ln.done)
+	ln.ok = false
 	return nil
 }
 
 func (ln *PipeListenerDialer) Dial(_, addr string) (net.Conn, error) {
 	if addr != ln.addr {
-		return nil, ErrBadAddress
+		return nil, unix.EINVAL
 	}
 	s, c := net.Pipe()
 	select {
 	case ln.conns <- s:
 		return c, nil
 	case <-ln.done:
-		return nil, ErrClosed
+		return nil, unix.ECONNREFUSED
 	}
 }
 
@@ -78,5 +79,5 @@ func (ln *PipeListenerDialer) DialContextAddr(_ context.Context, addr string) (n
 }
 
 func New(addr string) *PipeListenerDialer {
-	return &PipeListenerDialer{addr, make(chan net.Conn), make(chan struct{})}
+	return &PipeListenerDialer{addr, make(chan net.Conn), make(chan struct{}), true}
 }
diff --git a/pipeln_test.go b/pipeln_test.go
index e5de8d0..9673fcc 100644
--- a/pipeln_test.go
+++ b/pipeln_test.go
@@ -9,6 +9,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"golang.org/x/sys/unix"
 )
 
 func Test(t *testing.T) {
@@ -22,9 +23,27 @@ func Test(t *testing.T) {
 	go srv.Serve(ln)
 
 	client := http.Client{Transport: &http.Transport{Dial: ln.Dial}}
-	resp, err := client.Get("http://test/endpoint")
-	require.NoError(t, err)
-	assert.Equal(t, http.StatusOK, resp.StatusCode)
+
+	t.Run("OK", func(t *testing.T) {
+		resp, err := client.Get("http://test/endpoint")
+		require.NoError(t, err)
+		assert.Equal(t, http.StatusOK, resp.StatusCode)
+	})
+
+	t.Run("Address Mismatch", func(t *testing.T) {
+		_, err := client.Get("http://other-test/endpoint")
+		assert.ErrorIs(t, err, unix.EINVAL)
+	})
 
 	srv.Shutdown(context.Background())
+
+	t.Run("Remote Connection Closed", func(t *testing.T) {
+		_, err := client.Get("http://test/endpoint")
+		assert.ErrorIs(t, err, unix.ECONNREFUSED)
+	})
+
+	t.Run("Already-closed Listener", func(t *testing.T) {
+		srv = http.Server{Handler: mux}
+		assert.ErrorIs(t, srv.Serve(ln), unix.EINVAL)
+	})
 }