Fix nerdctl load stdin for pipes.

If stdin is received from a pipe, the size is still zero
and an error will not be not thrown now.

If stdin is empty, error will still be thrown.

Added tests

Signed-off-by: Manu Gupta <[email protected]>

Author: manugupt1

cmd/nerdctl/load.go

@@ -73,7 +73,7 @@ func loadAction(cmd *cobra.Command, _ []string) error {
 		if err != nil {
 			return err
 		}
-		if stdinStat.Size() == 0 {
+		if stdinStat.Size() == 0 && (stdinStat.Mode()&os.ModeNamedPipe) == 0 {
 			return errors.New("stdin is empty and input flag is not specified")
 		}
 	}

cmd/nerdctl/load_linux_test.go

@@ -0,0 +1,61 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/containerd/nerdctl/pkg/testutil"
+	"gotest.tools/v3/assert"
+)
+
+func TestLoadStdinFromPipe(t *testing.T) {
+	t.Parallel()
+	base := testutil.NewBase(t)
+
+	tmp := t.TempDir()
+	base.Cmd("pull", testutil.CommonImage).AssertOK()
+	base.Cmd("save", testutil.CommonImage, "-o", filepath.Join(tmp, "common.tar")).AssertOK()
+
+	cmdStr := strings.Join(base.Cmd("load").Command, " ")
+
+	f, err := os.OpenFile(filepath.Join(tmp, "load.sh"), os.O_CREATE|os.O_RDWR, 0777)
+	assert.NilError(t, err)
+
+	f.WriteString("#/bin/sh\n")
+	f.WriteString("set -euo pipefail\n")
+	f.WriteString(fmt.Sprintf("cat %s/common.tar | %s", tmp, cmdStr))
+	err = f.Close()
+	assert.NilError(t, err)
+
+	cmd := exec.Command("sh", "-euxc", filepath.Join(tmp, "load.sh"))
+	combined, err := cmd.CombinedOutput()
+	assert.NilError(t, err, "%s; %s", string(combined), cmd.String())
+	assert.Assert(t, strings.Contains(string(combined), "unpacking"))
+	base.Cmd("images").AssertOutContains(strings.Split(testutil.CommonImage, ":")[0])
+}
+
+func TestLoadStdinEmpty(t *testing.T) {
+	t.Parallel()
+	base := testutil.NewBase(t)
+	base.Cmd("load").AssertFail()
+}