fix: merge extension service config files by mountPath

Allow overwriting config file content.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>
Co-authored-by: Noel Georgi <git@frezbo.dev>

pkg/machinery/config/configpatcher/testdata/multidoc/config.yaml

@@ -9,3 +9,12 @@ machine:
 apiVersion: v1alpha1
 kind: SideroLinkConfig
 apiUrl: https://siderolink.api/join?jointoken=secret&user=alice
+---
+apiVersion: v1alpha1
+kind: ExtensionServiceConfig
+name: foo
+configFiles:
+    - content: hello
+      mountPath: /etc/foo
+environment:
+    - FOO=BAR

pkg/machinery/config/configpatcher/testdata/multidoc/expected.yaml

@@ -13,3 +13,15 @@ cluster: null
 apiVersion: v1alpha1
 kind: SideroLinkConfig
 apiUrl: https://siderolink.api/join?jointoken=secret&user=bob
+---
+apiVersion: v1alpha1
+kind: ExtensionServiceConfig
+name: foo
+configFiles:
+    - content: hello world
+      mountPath: /etc/foo
+    - content: another hello
+      mountPath: /etc/bar
+environment:
+    - FOO=BAR
+    - XXX=YYY

pkg/machinery/config/configpatcher/testdata/multidoc/strategic2.yaml

@@ -1,3 +1,14 @@
 apiVersion: v1alpha1
 kind: SideroLinkConfig
 apiUrl: https://siderolink.api/join?jointoken=secret&user=bob
+---
+apiVersion: v1alpha1
+kind: ExtensionServiceConfig
+name: foo
+configFiles:
+    - content: hello world
+      mountPath: /etc/foo
+    - content: another hello
+      mountPath: /etc/bar
+environment:
+    - XXX=YYY

pkg/machinery/config/types/runtime/extensions/service_config.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/siderolabs/talos/pkg/machinery/config/config"
 	"github.com/siderolabs/talos/pkg/machinery/config/internal/registry"
+	"github.com/siderolabs/talos/pkg/machinery/config/merge"
 	"github.com/siderolabs/talos/pkg/machinery/config/types/meta"
 	"github.com/siderolabs/talos/pkg/machinery/config/validation"
 )
@@ -53,12 +54,53 @@ type ServiceConfigV1Alpha1 struct {
 	ServiceName string `yaml:"name"`
 	//   description: |
 	//     The config files for the extension service.
-	ServiceConfigFiles []ConfigFile `yaml:"configFiles,omitempty"`
+	ServiceConfigFiles ConfigFileList `yaml:"configFiles,omitempty"`
 	//   description: |
 	//     The environment for the extension service.
 	ServiceEnvironment []string `yaml:"environment,omitempty"`
 }
 
+// ConfigFileList is a list of ConfigFiles.
+//
+//docgen:alias
+type ConfigFileList []ConfigFile
+
+// Merge the config files by mountPath.
+func (list *ConfigFileList) Merge(other any) error {
+	otherFiles, ok := other.(ConfigFileList)
+	if !ok {
+		return fmt.Errorf("unexpected type for config file merge %T", other)
+	}
+
+	for _, configFile := range otherFiles {
+		if err := list.mergeConfigFile(configFile); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (list *ConfigFileList) mergeConfigFile(configFile ConfigFile) error {
+	var existing *ConfigFile
+
+	for idx, cf := range *list {
+		if cf.ConfigFileMountPath == configFile.ConfigFileMountPath {
+			existing = &(*list)[idx]
+
+			break
+		}
+	}
+
+	if existing != nil {
+		return merge.Merge(existing, &configFile)
+	}
+
+	*list = append(*list, configFile)
+
+	return nil
+}
+
 // ConfigFile is a config file for extension services.
 type ConfigFile struct {
 	//   description: |

pkg/machinery/config/types/runtime/extensions/service_config_test.go

@@ -12,6 +12,7 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"github.com/siderolabs/talos/pkg/machinery/config/encoder"
+	"github.com/siderolabs/talos/pkg/machinery/config/merge"
 	"github.com/siderolabs/talos/pkg/machinery/config/types/runtime/extensions"
 )
 
@@ -38,3 +39,33 @@ func TestExtensionServiceConfigMarshalStability(t *testing.T) {
 
 	assert.Equal(t, expectedExtensionServiceConfigDocument, marshaled)
 }
+
+func TestExtensionServiceConfigMerge(t *testing.T) {
+	t.Parallel()
+
+	cfgLeft := extensions.NewServicesConfigV1Alpha1()
+	cfgLeft.ServiceName = "foo"
+	cfgLeft.ServiceConfigFiles = []extensions.ConfigFile{
+		{
+			ConfigFileContent:   "hello",
+			ConfigFileMountPath: "/etc/foo",
+		},
+	}
+
+	cfgRight := cfgLeft.DeepCopy()
+	cfgRight.ServiceConfigFiles[0].ConfigFileContent = "hello world"
+
+	cfgRight.ServiceConfigFiles = append(cfgRight.ServiceConfigFiles,
+		extensions.ConfigFile{
+			ConfigFileContent:   "bar",
+			ConfigFileMountPath: "/etc/bar",
+		},
+	)
+
+	require.NoError(t, merge.Merge(cfgLeft, cfgRight))
+
+	require.Len(t, cfgLeft.ConfigFiles(), 2)
+
+	assert.Equal(t, "hello world", cfgLeft.ConfigFiles()[0].Content())
+	assert.Equal(t, "bar", cfgLeft.ConfigFiles()[1].Content())
+}

website/content/v1.8/talos-guides/configuration/patching.md

@@ -50,6 +50,7 @@ There are some special rules:
   - `network.interfaces` section is merged with the value in the machine config if there is a match on `interface:` or `deviceSelector:` keys
   - `network.interfaces.vlans` section is merged with the value in the machine config if there is a match on the `vlanId:` key
   - `cluster.apiServer.auditPolicy` value is replaced on merge
+  - `ExtensionServiceConfig.configFiles` section is merged matching on `mountPath` (replacing `content` if matches)
 
 When patching a [multi-document machine configuration]({{< relref "../../reference/configuration" >}}), following rules apply: