ignore missing drop-in files to avoid creating an empty configuration

config/jsonschema/schema_test.go

@@ -147,7 +147,7 @@ func TestJsonSchemaValidation(t *testing.T) {
 
 	extensionMatcher := regexp.MustCompile(`\.(conf|toml|yaml|json)$`)
 	version2Matcher := regexp.MustCompile(`"version":\s*"2`)
-	exclusions := regexp.MustCompile(`[\\/](rsyslogd\.conf|utf.*\.conf)$`)
+	exclusions := regexp.MustCompile(`[\\/](rsyslogd\.conf|utf.*\.conf|drop-in-example\.conf)$`)
 	testCount := 0
 
 	err := filepath.Walk("../../examples/", func(filename string, info fs.FileInfo, err error) error {

examples/drop-in-example.conf

@@ -0,0 +1,2 @@
+[Service]
+Environment=RESTIC_PASSWORD_FILE=%d/restic-repo-password

examples/linux.yaml

@@ -98,7 +98,7 @@ longrun:
 self:
     inherit: default
     status-file: /tmp/status.json
-    # systemd-drop-in-files: [ drop-in-example.conf ]
+    systemd-drop-in-files: [ drop-in-example.conf ]
     backup:
         extended-status: true
         source: ./

systemd/drop_ins.go

@@ -4,8 +4,10 @@
 
 import (
 	"bufio"
+	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -23,6 +25,18 @@
 	return fmt.Sprintf("%s.resticprofile.conf", strings.TrimSuffix(basename, ext))
 }
 
+func (u Unit) DropInFileExists(file string) bool {
+	if _, err := u.fs.Stat(file); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			clog.Errorf("drop-in file %q not found", file)
+			return false
+		}
+		clog.Error(err)
+		return false
+	}
+	return true
+}
+
 func (u Unit) IsTimerDropIn(file string) bool {
 	if f, err := u.fs.Open(file); err == nil {
 		defer func() { _ = f.Close() }()

systemd/drop_ins_test.go

@@ -0,0 +1,68 @@
+//go:build !darwin && !windows
+
+package systemd
+
+import (
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestDropInFileExists(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name          string
+		file          string
+		setupFs       func() afero.Fs
+		expectedValue bool
+	}{
+		{
+			name: "file exists",
+			file: "/path/to/file",
+			setupFs: func() afero.Fs {
+				testFs := afero.NewMemMapFs()
+				_, err := testFs.Create("/path/to/file")
+				require.NoError(t, err)
+				return testFs
+			},
+			expectedValue: true,
+		},
+		{
+			name: "directory",
+			file: "/path/to/dir",
+			setupFs: func() afero.Fs {
+				testFs := afero.NewMemMapFs()
+				err := testFs.Mkdir("/path/to/dir", 0755)
+				require.NoError(t, err)
+				return testFs
+			},
+			expectedValue: true,
+		},
+		{
+			name: "file does not exist",
+			file: "/path/to/nonexistent",
+			setupFs: func() afero.Fs {
+				testFs := afero.NewMemMapFs()
+				return testFs
+			},
+			expectedValue: false,
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			testFs := tc.setupFs()
+
+			unit := Unit{
+				fs: testFs,
+			}
+
+			result := unit.DropInFileExists(tc.file)
+			assert.Equal(t, tc.expectedValue, result)
+		})
+	}
+}

systemd/generate.go

@@ -220,9 +220,11 @@ func (u Unit) Generate(config Config) error {
 		_ = u.fs.Chown(filePathName, u.user.Uid, u.user.Gid)
 	}
 
+	existingFiles := collect.All(config.DropInFiles, u.DropInFileExists)
+
 	dropIns := map[string][]string{
-		GetTimerFileDropInDir(config.Title, config.SubTitle):   collect.All(config.DropInFiles, u.IsTimerDropIn),
-		GetServiceFileDropInDir(config.Title, config.SubTitle): collect.All(config.DropInFiles, collect.Not(u.IsTimerDropIn)),
+		GetTimerFileDropInDir(config.Title, config.SubTitle):   collect.All(existingFiles, u.IsTimerDropIn),
+		GetServiceFileDropInDir(config.Title, config.SubTitle): collect.All(existingFiles, collect.Not(u.IsTimerDropIn)),
 	}
 	for dropInDir, dropInFiles := range dropIns {
 		dropInDir = filepath.Join(systemdUserDir, dropInDir)