feat: add nerdctl-container support for client

Signed-off-by: Wei Zhang <[email protected]>

Author: zwpaper

client/connhelper/nerdctlcontainer/nerdctlcontainer.go

@@ -0,0 +1,49 @@
+// Package nerdctlcontainer provides connhelper for nerdctl-container://<container>
+package nerdctlcontainer
+
+import (
+	"context"
+	"net"
+	"net/url"
+
+	"github.com/docker/cli/cli/connhelper/commandconn"
+	"github.com/moby/buildkit/client/connhelper"
+	"github.com/pkg/errors"
+)
+
+func init() {
+	connhelper.Register("nerdctl-container", Helper)
+}
+
+// Helper returns helper for connecting to a Nerdctl container.
+// Requires BuildKit v0.5.0 or later in the container.
+func Helper(u *url.URL) (*connhelper.ConnectionHelper, error) {
+	sp, err := SpecFromURL(u)
+	if err != nil {
+		return nil, err
+	}
+	return &connhelper.ConnectionHelper{
+		ContextDialer: func(ctx context.Context, addr string) (net.Conn, error) {
+			// using background context because context remains active for the duration of the process, after dial has completed
+			return commandconn.New(context.Background(), "nerdctl", []string{"exec", "-i", sp.Container, "buildctl", "dial-stdio"}...)
+		},
+	}, nil
+}
+
+// Spec
+type Spec struct {
+	Container string
+}
+
+// SpecFromURL creates Spec from URL.
+// URL is like nerdctl-container://<container>
+// Only <container> part is mandatory.
+func SpecFromURL(u *url.URL) (*Spec, error) {
+	sp := Spec{
+		Container: u.Hostname(),
+	}
+	if sp.Container == "" {
+		return nil, errors.New("url lacks container name")
+	}
+	return &sp, nil
+}

client/connhelper/nerdctlcontainer/nerdctlcontainer_test.go

@@ -0,0 +1,30 @@
+package nerdctlcontainer
+
+import (
+	"net/url"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestSpecFromURL(t *testing.T) {
+	cases := map[string]*Spec{
+		"nerdctl-container://containername": {
+			Container: "containername",
+		},
+		"nerdctl-container://": nil,
+	}
+	for s, expected := range cases {
+		u, err := url.Parse(s)
+		if err != nil {
+			t.Fatal(err)
+		}
+		got, err := SpecFromURL(u)
+		if expected != nil {
+			require.NoError(t, err)
+			require.EqualValues(t, expected, got, s)
+		} else {
+			require.Error(t, err, s)
+		}
+	}
+}