refactor: move dialer's errorwrapper in i/errorsx (#417)

Part of https://github.com/ooni/probe/issues/1505

internal/errorsx/dialer.go

@@ -0,0 +1,65 @@
+package errorsx
+
+import (
+	"context"
+	"net"
+)
+
+// Dialer establishes network connections.
+type Dialer interface {
+	// DialContext behaves like net.Dialer.DialContext.
+	DialContext(ctx context.Context, network, address string) (net.Conn, error)
+}
+
+// ErrorWrapperDialer is a dialer that performs err wrapping.
+type ErrorWrapperDialer struct {
+	Dialer
+}
+
+// DialContext implements Dialer.DialContext
+func (d *ErrorWrapperDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	conn, err := d.Dialer.DialContext(ctx, network, address)
+	err = SafeErrWrapperBuilder{
+		Error:     err,
+		Operation: ConnectOperation,
+	}.MaybeBuild()
+	if err != nil {
+		return nil, err
+	}
+	return &errorWrapperConn{Conn: conn}, nil
+}
+
+// errorWrapperConn is a net.Conn that performs error wrapping.
+type errorWrapperConn struct {
+	net.Conn
+}
+
+// Read implements net.Conn.Read
+func (c *errorWrapperConn) Read(b []byte) (n int, err error) {
+	n, err = c.Conn.Read(b)
+	err = SafeErrWrapperBuilder{
+		Error:     err,
+		Operation: ReadOperation,
+	}.MaybeBuild()
+	return
+}
+
+// Write implements net.Conn.Write
+func (c *errorWrapperConn) Write(b []byte) (n int, err error) {
+	n, err = c.Conn.Write(b)
+	err = SafeErrWrapperBuilder{
+		Error:     err,
+		Operation: WriteOperation,
+	}.MaybeBuild()
+	return
+}
+
+// Close implements net.Conn.Close
+func (c *errorWrapperConn) Close() (err error) {
+	err = c.Conn.Close()
+	err = SafeErrWrapperBuilder{
+		Error:     err,
+		Operation: CloseOperation,
+	}.MaybeBuild()
+	return
+}

internal/errorsx/dialer_test.go

@@ -0,0 +1,83 @@
+package errorsx
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/netxmocks"
+)
+
+func TestErrorWrapperFailure(t *testing.T) {
+	ctx := context.Background()
+	d := &ErrorWrapperDialer{Dialer: &netxmocks.Dialer{
+		MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
+			return nil, io.EOF
+		},
+	}}
+	conn, err := d.DialContext(ctx, "tcp", "www.google.com:443")
+	if conn != nil {
+		t.Fatal("expected a nil conn here")
+	}
+	errorWrapperCheckErr(t, err, ConnectOperation)
+}
+
+func errorWrapperCheckErr(t *testing.T, err error, op string) {
+	if !errors.Is(err, io.EOF) {
+		t.Fatal("expected another error here")
+	}
+	var errWrapper *ErrWrapper
+	if !errors.As(err, &errWrapper) {
+		t.Fatal("cannot cast to ErrWrapper")
+	}
+	if errWrapper.Operation != op {
+		t.Fatal("unexpected Operation")
+	}
+	if errWrapper.Failure != FailureEOFError {
+		t.Fatal("unexpected failure")
+	}
+}
+
+func TestErrorWrapperSuccess(t *testing.T) {
+	ctx := context.Background()
+	d := &ErrorWrapperDialer{Dialer: &netxmocks.Dialer{
+		MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
+			return &netxmocks.Conn{
+				MockRead: func(b []byte) (int, error) {
+					return 0, io.EOF
+				},
+				MockWrite: func(b []byte) (int, error) {
+					return 0, io.EOF
+				},
+				MockClose: func() error {
+					return io.EOF
+				},
+				MockLocalAddr: func() net.Addr {
+					return &net.TCPAddr{Port: 12345}
+				},
+			}, nil
+		},
+	}}
+	conn, err := d.DialContext(ctx, "tcp", "www.google.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if conn == nil {
+		t.Fatal("expected non-nil conn here")
+	}
+	count, err := conn.Read(nil)
+	errorWrapperCheckIOResult(t, count, err, ReadOperation)
+	count, err = conn.Write(nil)
+	errorWrapperCheckIOResult(t, count, err, WriteOperation)
+	err = conn.Close()
+	errorWrapperCheckErr(t, err, CloseOperation)
+}
+
+func errorWrapperCheckIOResult(t *testing.T, count int, err error, op string) {
+	if count != 0 {
+		t.Fatal("expected nil count here")
+	}
+	errorWrapperCheckErr(t, err, op)
+}