feat[v4]: add starting watching files manually

README.md

@@ -3,13 +3,13 @@
 ## Installation
 
 ```shell
-go get github.com/Clarilab/envi/v3
+go get github.com/Clarilab/envi/v4
 ```
 
 ## Importing
 
 ```go
-import "github.com/Clarilab/envi/v3"
+import "github.com/Clarilab/envi/v4"
 ```
 
 ## Usage
@@ -91,7 +91,7 @@ Load loads all config files and environment variables into the input struct.
 Supported types are JSON, YAML and text files, as well as strings on the struct root level.
 
 If you want to watch a file for changes, the "watch" tag has to be set to true and the underlying struct
-has to implement the envi.FileWatcher interface.
+has to implement the envi.FileWatcher interface. To actually start watching the files, the StartWatching() method must be called.
 
 While using the "default" tag, the "env" tag can be omitted. If not omitted, the value from the
 environment variable will be used.

envi.go

@@ -34,14 +34,24 @@ type FileWatcher interface {
 }
 
 type fileWatcherInstance struct {
-	watcher *fsnotify.Watcher
-	cancel  context.CancelFunc
+	field     reflect.Value
+	unmarshal unmarshalFunc
+	cancel    context.CancelFunc
+	close     func() error
+}
+
+func (f *fileWatcherInstance) setCancel(cancel context.CancelFunc) {
+	f.cancel = cancel
+}
+
+func (f *fileWatcherInstance) setClose(close func() error) {
+	f.close = close
 }
 
 // Envi holds references to all active file watchers.
 type Envi struct {
 	errorChan    chan error
-	fileWatchers map[string]fileWatcherInstance
+	fileWatchers map[string]*fileWatcherInstance
 }
 
 // Errors returns an error channel where filewatcher errors are sent to.
@@ -58,7 +68,7 @@ func (e *Envi) Close() error {
 	for filePath, instance := range e.fileWatchers {
 		instance.cancel()
 
-		if err := instance.watcher.Close(); err != nil {
+		if err := instance.close(); err != nil {
 			errs = append(errs, fmt.Errorf("failed to close watcher for file %s with error: %w", filePath, err))
 		}
 	}
@@ -74,7 +84,7 @@ func (e *Envi) Close() error {
 func New() *Envi {
 	return &Envi{
 		errorChan:    make(chan error, 100),
-		fileWatchers: make(map[string]fileWatcherInstance, 0),
+		fileWatchers: make(map[string]*fileWatcherInstance, 0),
 	}
 }
 
@@ -213,10 +223,7 @@ func (e *Envi) loadConfig(config any) error {
 			}
 
 			if watchTag == "true" {
-				err = e.watchFile(field, path, unmarshalFunc)
-				if err != nil {
-					return fmt.Errorf(errMsg, err)
-				}
+				e.addFileWatcher(field, path, unmarshalFunc)
 			}
 		case reflect.String:
 			tagVal := getStructTag(t.Field(i), tagEnv)
@@ -238,6 +245,19 @@ func (e *Envi) loadConfig(config any) error {
 	return nil
 }
 
+// StartWatching starts watching all files with enabled file watching.
+func (e *Envi) StartWatching() error {
+	const errMsg = "error while starting file watching: %w"
+
+	for path, watcher := range e.fileWatchers {
+		if err := e.watchFile(watcher, path); err != nil {
+			return fmt.Errorf(errMsg, err)
+		}
+	}
+
+	return nil
+}
+
 func unmarshalText(data []byte, v any) error {
 	val := strings.Trim(string(data), "\n")
 
@@ -330,8 +350,15 @@ func handleDefaults(field reflect.Value) error {
 	return nil
 }
 
-func (e *Envi) watchFile(field reflect.Value, path string, unmarshal unmarshalFunc) error {
-	const errMsg = "error while watching file: %w"
+func (e *Envi) addFileWatcher(field reflect.Value, path string, unmarshal unmarshalFunc) {
+	e.fileWatchers[path] = &fileWatcherInstance{
+		field:     field,
+		unmarshal: unmarshal,
+	}
+}
+
+func (e *Envi) watchFile(instance *fileWatcherInstance, path string) error {
+	const errMsg = "error while starting file watcher: %w"
 
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -340,12 +367,10 @@ func (e *Envi) watchFile(field reflect.Value, path string, unmarshal unmarshalFu
 
 	ctx, cancel := context.WithCancel(context.Background())
 
-	e.fileWatchers[path] = fileWatcherInstance{
-		watcher: watcher,
-		cancel:  cancel,
-	}
+	instance.setCancel(cancel)
+	instance.setClose(watcher.Close)
 
-	go e.fileWatcher(ctx, watcher, field, path, unmarshal)
+	go e.fileWatcher(ctx, watcher, instance.field, path, instance.unmarshal)
 
 	err = watcher.Add(filepath.Dir(path)) // needs to be the directory of the file to ensure working on linux systems
 	if err != nil {
@@ -356,6 +381,7 @@ func (e *Envi) watchFile(field reflect.Value, path string, unmarshal unmarshalFu
 
 	return nil
 }
+
 func validate(e any) []error {
 	v := reflect.ValueOf(e)
 	t := reflect.TypeOf(e)

envi_test.go

@@ -7,7 +7,7 @@ import (
 	"sync/atomic"
 	"testing"
 
-	"github.com/Clarilab/envi/v3"
+	"github.com/Clarilab/envi/v4"
 )
 
 // !!! Attention: The tests in this file are not meant to be run in parallel because of the t.Setenv usage !!!
@@ -205,6 +205,11 @@ func Test_Filewatcher(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	err = enviClient.StartWatching()
+	if err != nil {
+		t.Fatal(err)
+	}
+
 	if err := os.WriteFile(
 		"test.yaml",
 		[]byte(fmt.Sprintf("%s: %s", "PETER", "PANUS")),

go.mod

@@ -1,4 +1,4 @@
-module github.com/Clarilab/envi/v3
+module github.com/Clarilab/envi/v4
 
 go 1.22