Add a parameter to disable configuration file automatic creation (#45)

* added server ConfigurationFile flag "create_file"

* add IsNotExist error handling to file open

* Changed to use "Open" instead of "Touch" with flags

parser/parser.go

@@ -104,9 +104,10 @@ func (cp ConfigurationParser) String() string {
 // ConfigurationFile defines a configuration file for the server startup. These
 // will be looped over and modified before the server finishes booting.
 type ConfigurationFile struct {
-	FileName string                         `json:"file"`
-	Parser   ConfigurationParser            `json:"parser"`
-	Replace  []ConfigurationFileReplacement `json:"replace"`
+	FileName        string                         `json:"file"`
+	Parser          ConfigurationParser            `json:"parser"`
+	Replace         []ConfigurationFileReplacement `json:"replace"`
+	AllowCreateFile bool                           `json:"create_file"` // assumed true by unmarshal as it was the original behaviour
 
 	// Tracks Wings' configuration so that we can quickly get values
 	// out of it when variables request it.
@@ -137,6 +138,17 @@ func (f *ConfigurationFile) UnmarshalJSON(data []byte) error {
 		f.Replace = []ConfigurationFileReplacement{}
 	}
 
+	// test if "create_file" exists, if not just assume true
+	if val, exists := m["create_file"]; exists && val != nil {
+		if err := json.Unmarshal(*val, &f.AllowCreateFile); err != nil {
+			log.WithField("file", f.FileName).WithField("error", err).Warn("create_file unmarshal failed")
+			f.AllowCreateFile = true
+		}
+	} else {
+		log.WithField("file", f.FileName).Debug("create_file not specified assumed true")
+		f.AllowCreateFile = true
+	}
+
 	return nil
 }
 

server/config_parser.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"os"
 	"runtime"
 
 	"fmt"
@@ -43,9 +44,19 @@ func (s *Server) UpdateConfigurationFiles() {
 
 		pool.Submit(func() {
 			filename := replaceParserConfigPathVariables(f.FileName, s.Config().EnvVars)
-			file, err := s.Filesystem().UnixFS().Touch(filename, ufs.O_RDWR|ufs.O_CREATE, 0o644)
+			file, err := func() (ufs.File, error) {
+				if f.AllowCreateFile {
+					return s.Filesystem().UnixFS().Touch(filename, ufs.O_RDWR|ufs.O_CREATE, 0o644)
+				}
+				return s.Filesystem().UnixFS().Open(filename)
+			}()
 			if err != nil {
-				s.Log().WithField("file_name", f.FileName).WithField("error", err).Error("failed to open file for configuration")
+				log := s.Log().WithField("file_name", filename)
+				if os.IsNotExist(err) && !f.AllowCreateFile {
+					log.Debug("file not created")
+				} else {
+					log.WithField("error", err).Error("failed to open file for configuration")
+				}
 				return
 			}
 			defer file.Close()