feat(migrations): Add migration for inputs.snmp_legacy (#14123)

migrations/all/inputs_snmp_legacy.go

@@ -0,0 +1,5 @@
+//go:build !custom || (migrations && (inputs || inputs.snmp_legacy))
+
+package all
+
+import _ "github.com/influxdata/telegraf/migrations/inputs_snmp_legacy" // register migration

migrations/inputs_snmp_legacy/migration.go

@@ -0,0 +1,21 @@
+package inputs_snmp_legacy
+
+import (
+	"github.com/influxdata/toml/ast"
+
+	"github.com/influxdata/telegraf/migrations"
+)
+
+const msg = `
+    This plugin cannot be migrated automatically and requires manual intervention!
+`
+
+// Migration function
+func migrate(_ *ast.Table) ([]byte, string, error) {
+	return nil, msg, nil
+}
+
+// Register the migration function for the plugin type
+func init() {
+	migrations.AddPluginMigration("inputs.snmp_legacy", migrate)
+}

migrations/inputs_snmp_legacy/migration_test.go

@@ -0,0 +1,23 @@
+package inputs_snmp_legacy_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/influxdata/telegraf/config"
+	_ "github.com/influxdata/telegraf/migrations/inputs_snmp_legacy" // register migration
+)
+
+func TestNoMigration(t *testing.T) {
+	input := []byte(`
+[[inputs.snmp_legacy]]
+  address = "192.168.2.2:161"
+`)
+
+	output, n, err := config.ApplyMigrations(input)
+	require.NoError(t, err)
+	require.Empty(t, strings.TrimSpace(string(output)))
+	require.Equal(t, uint64(1), n)
+}