allow locale to work with a fs.FS

Signed-off-by: jkoberg <jkoberg@owncloud.com>

locale.go

@@ -8,6 +8,7 @@ package gotext
 import (
 	"bytes"
 	"encoding/gob"
+	"io/fs"
 	"os"
 	"path"
 	"sync"
@@ -60,6 +61,9 @@ type Locale struct {
 
 	// Sync Mutex
 	sync.RWMutex
+
+	// optional fs to use
+	fs fs.FS
 }
 
 // NewLocale creates and initializes a new Locale object for a given language.
@@ -72,27 +76,34 @@ func NewLocale(p, l string) *Locale {
 	}
 }
 
+// NewLocaleFS returns a Locale working with a fs.FS
+func NewLocaleFS(p, l string, filesystem fs.FS) *Locale {
+	loc := NewLocale(p, l)
+	loc.fs = filesystem
+	return loc
+}
+
 func (l *Locale) findExt(dom, ext string) string {
 	filename := path.Join(l.path, l.lang, "LC_MESSAGES", dom+"."+ext)
-	if _, err := os.Stat(filename); err == nil {
+	if l.fileExists(filename) {
 		return filename
 	}
 
 	if len(l.lang) > 2 {
 		filename = path.Join(l.path, l.lang[:2], "LC_MESSAGES", dom+"."+ext)
-		if _, err := os.Stat(filename); err == nil {
+		if l.fileExists(filename) {
 			return filename
 		}
 	}
 
 	filename = path.Join(l.path, l.lang, dom+"."+ext)
-	if _, err := os.Stat(filename); err == nil {
+	if l.fileExists(filename) {
 		return filename
 	}
 
 	if len(l.lang) > 2 {
 		filename = path.Join(l.path, l.lang[:2], dom+"."+ext)
-		if _, err := os.Stat(filename); err == nil {
+		if l.fileExists(filename) {
 			return filename
 		}
 	}
@@ -100,6 +111,20 @@ func (l *Locale) findExt(dom, ext string) string {
 	return ""
 }
 
+func (l *Locale) fileExists(filename string) bool {
+	if l.fs != nil {
+		f, err := l.fs.Open(filename)
+		if err != nil {
+			return false
+		}
+		_, err = f.Stat()
+		return err == nil
+
+	}
+	_, err := os.Stat(filename)
+	return err == nil
+}
+
 // AddDomain creates a new domain for a given locale object and initializes the Po object.
 // If the domain exists, it gets reloaded.
 func (l *Locale) AddDomain(dom string) {
@@ -107,13 +132,13 @@ func (l *Locale) AddDomain(dom string) {
 
 	file := l.findExt(dom, "po")
 	if file != "" {
-		poObj = NewPo()
+		poObj = NewPoFS(l.fs)
 		// Parse file.
 		poObj.ParseFile(file)
 	} else {
 		file = l.findExt(dom, "mo")
 		if file != "" {
-			poObj = NewMo()
+			poObj = NewMoFS(l.fs)
 			// Parse file.
 			poObj.ParseFile(file)
 		} else {

mo.go

@@ -8,6 +8,7 @@ package gotext
 import (
 	"bytes"
 	"encoding/binary"
+	"io/fs"
 )
 
 const (
@@ -52,6 +53,7 @@ type Mo struct {
 	Language    string
 	PluralForms string
 	domain      *Domain
+	fs          fs.FS
 }
 
 //NewMo should always be used to instantiate a new Mo object
@@ -62,6 +64,13 @@ func NewMo() *Mo {
 	return mo
 }
 
+// NewMoFS works like NewMO but adds an optional fs.FS
+func NewMoFS(filesystem fs.FS) *Mo {
+	mo := NewMo()
+	mo.fs = filesystem
+	return mo
+}
+
 func (mo *Mo) GetDomain() *Domain {
 	return mo.domain
 }
@@ -92,7 +101,7 @@ func (mo *Mo) UnmarshalBinary(data []byte) error {
 }
 
 func (mo *Mo) ParseFile(f string) {
-	data, err := getFileData(f)
+	data, err := getFileData(f, mo.fs)
 	if err != nil {
 		return
 	}

po.go

@@ -6,6 +6,7 @@
 package gotext
 
 import (
+	"io/fs"
 	"strconv"
 	"strings"
 )
@@ -41,6 +42,7 @@ type Po struct {
 	PluralForms string
 
 	domain *Domain
+	fs     fs.FS
 }
 
 type parseState int
@@ -61,6 +63,13 @@ func NewPo() *Po {
 	return po
 }
 
+// NewPoFS works like NewPO but adds an optional fs.FS
+func NewPoFS(filesystem fs.FS) *Po {
+	po := NewPo()
+	po.fs = filesystem
+	return po
+}
+
 func (po *Po) GetDomain() *Domain {
 	return po.domain
 }
@@ -118,7 +127,7 @@ func (po *Po) UnmarshalBinary(data []byte) error {
 }
 
 func (po *Po) ParseFile(f string) {
-	data, err := getFileData(f)
+	data, err := getFileData(f, po.fs)
 	if err != nil {
 		return
 	}

translator.go

@@ -7,6 +7,7 @@ package gotext
 
 import (
 	"errors"
+	"io/fs"
 	"io/ioutil"
 	"os"
 )
@@ -66,7 +67,11 @@ func (te *TranslatorEncoding) GetTranslator() Translator {
 }
 
 //getFileData reads a file and returns the byte slice after doing some basic sanity checking
-func getFileData(f string) ([]byte, error) {
+func getFileData(f string, filesystem fs.FS) ([]byte, error) {
+	if filesystem != nil {
+		return fs.ReadFile(filesystem, f)
+	}
+
 	// Check if file exists
 	info, err := os.Stat(f)
 	if err != nil {