Fix handling of existing imports in containerd

This change fixes the handling of existing imports in containerd
config files. Without this fix the existing imports were dropped
and replaced with the import directive for the generated drop-in
file.

Signed-off-by: Evan Lezar <[email protected]>

Author: elezar

cmd/nvidia-ctk/runtime/configure/configure_test.go

@@ -43,6 +43,36 @@ func TestConfigureLifecycle(t *testing.T) {
 		assertConditions   func(*testing.T, string) error
 	}{
 		// Containerd v2 test cases
+		{
+			description: "containerd: config exists with imports",
+			args: []string{
+				"--runtime", "containerd",
+				"--config", "{{ .testRoot }}/etc/containerd/config.toml",
+				"--drop-in-config", "{{ .testRoot }}/etc/containerd/conf.d/99-nvidia.toml",
+			},
+			prepareEnvironment: func(t *testing.T, testRoot string) error {
+				configPath := filepath.Join(testRoot, "etc/containerd/config.toml")
+				require.NoError(t, os.MkdirAll(filepath.Dir(configPath), 0755))
+
+				initialConfig := `version = 2
+imports = ["/foo/bar/*.toml"]
+`
+				return os.WriteFile(configPath, []byte(initialConfig), 0600)
+			},
+			assertConditions: func(t *testing.T, testRoot string) error {
+				mainConfig := filepath.Join(testRoot, "etc/containerd/config.toml")
+				content, err := os.ReadFile(mainConfig)
+				require.NoError(t, err)
+
+				expectedTemplate := `imports = ["/foo/bar/*.toml", "{{ .testRoot }}/etc/containerd/conf.d/*.toml"]
+version = 2
+`
+				expected := strings.ReplaceAll(expectedTemplate, "{{ .testRoot }}", testRoot)
+
+				require.Equal(t, expected, string(content))
+				return nil
+			},
+		},
 		{
 			description: "containerd: v2 config does not exist with drop-in",
 			args: []string{

pkg/config/engine/containerd/config_drop_in.go

@@ -173,12 +173,35 @@ func (c *topLevelConfig) removeVersion() {
 	c.config.Delete("version")
 }
 
+func (c *topLevelConfig) getCurrentImports() []string {
+	rawImports := c.config.Get("imports")
+	if rawImports == nil {
+		return nil
+	}
+
+	if importsStringSlice, ok := rawImports.([]string); ok {
+		return importsStringSlice
+	}
+
+	importsAnySlice, ok := rawImports.([]any)
+	if !ok {
+		return nil
+	}
+	var importsStringSlice []string
+	for _, importAny := range importsAnySlice {
+		importString, ok := importAny.(string)
+		if !ok {
+			continue
+		}
+		importsStringSlice = append(importsStringSlice, importString)
+	}
+
+	return importsStringSlice
+}
+
 func (c *topLevelConfig) ensureImports(dropInFilename string) {
 	config := c.config.Tree
-	var currentImports []string
-	if ci, ok := c.config.Get("imports").([]string); ok {
-		currentImports = ci
-	}
+	currentImports := c.getCurrentImports()
 
 	requiredImport := c.importPattern(dropInFilename)
 	for _, currentImport := range currentImports {

pkg/config/engine/containerd/config_drop_in_test.go

@@ -0,0 +1,74 @@
+/**
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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 containerd
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/pkg/config/toml"
+)
+
+func TestEnsureImports(t *testing.T) {
+	testCases := []struct {
+		description     string
+		configMap       map[string]any
+		path            string
+		expectedImports []string
+	}{
+		{
+			description:     "empty",
+			path:            "/another/path/file.toml",
+			expectedImports: []string{"/another/path/*.toml"},
+		},
+		{
+			description: "existing imports as string slice",
+			configMap: map[string]any{
+				"imports": []string{"/foo/bar/*.toml"},
+			},
+			path:            "/another/path/file.toml",
+			expectedImports: []string{"/foo/bar/*.toml", "/another/path/*.toml"},
+		},
+		{
+			description: "existing imports as any slice",
+			configMap: map[string]any{
+				"imports": []any{"/foo/bar/*.toml"},
+			},
+			path:            "/another/path/file.toml",
+			expectedImports: []string{"/foo/bar/*.toml", "/another/path/*.toml"},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.description, func(t *testing.T) {
+			cut := topLevelConfig{
+				config: &Config{
+					Tree: func() *toml.Tree {
+						t, _ := toml.FromMap(tc.configMap).Load()
+						return t
+					}(),
+				},
+			}
+
+			cut.ensureImports("/another/path/file.toml")
+			require.EqualValues(t, tc.expectedImports, cut.config.Get("imports"))
+		})
+	}
+
+}