transport: Add an Unwrap method to ConnectionError (#5148)

Author: thallgren

internal/transport/transport.go

@@ -741,6 +741,12 @@ func (e ConnectionError) Origin() error {
 	return e.err
 }
 
+// Unwrap returns the original error of this connection error or nil when the
+// origin is nil.
+func (e ConnectionError) Unwrap() error {
+	return e.err
+}
+
 var (
 	// ErrConnClosing indicates that the transport is closing.
 	ErrConnClosing = connectionErrorf(true, nil, "transport is closing")

internal/transport/transport_test.go

@@ -27,6 +27,7 @@ import (
 	"io"
 	"math"
 	"net"
+	"os"
 	"runtime"
 	"strconv"
 	"strings"
@@ -2404,3 +2405,10 @@ func (s) TestClientDecodeHeaderStatusErr(t *testing.T) {
 		})
 	}
 }
+
+func TestConnectionError_Unwrap(t *testing.T) {
+	err := connectionErrorf(false, os.ErrNotExist, "unwrap me")
+	if !errors.Is(err, os.ErrNotExist) {
+		t.Error("ConnectionError does not unwrap")
+	}
+}