If the extension is empty, do not append the dot when building the path

This allows to append "" to the viper.SupportedExts, while still set
the config type, and have viper not append anything instead of
appending just a dot.

viper.go

@@ -1874,10 +1874,16 @@ func (v *Viper) getConfigFile() (string, error) {
 func (v *Viper) searchInPath(in string) (filename string) {
 	jww.DEBUG.Println("Searching for config in ", in)
 	for _, ext := range SupportedExts {
-		jww.DEBUG.Println("Checking for", filepath.Join(in, v.configName+"."+ext))
+		configFilePlusExt := ""
-		if b, _ := exists(v.fs, filepath.Join(in, v.configName+"."+ext)); b {
+		if ext != "" {
-			jww.DEBUG.Println("Found: ", filepath.Join(in, v.configName+"."+ext))
+			configFilePlusExt = v.configName + "." + ext
-			return filepath.Join(in, v.configName+"."+ext)
+		} else {
+			configFilePlusExt = v.configName
+		}
+		jww.DEBUG.Println("Checking for", filepath.Join(in, configFilePlusExt))
+		if b, _ := exists(v.fs, filepath.Join(in, configFilePlusExt)); b {
+			jww.DEBUG.Println("Found: ", filepath.Join(in, configFilePlusExt))
+			return filepath.Join(in, configFilePlusExt)
 		}
 	}
 

viper_test.go

@@ -1112,6 +1112,26 @@ func TestSub(t *testing.T) {
 	assert.Equal(t, (*Viper)(nil), subv)
 }
 
+func TestEmptyExtension(t *testing.T) {
+	v := New()
+	fs := afero.NewMemMapFs()
+	v.SetFs(fs)
+	v.SetConfigName("config")
+	v.SetConfigType("json")
+	v.AddConfigPath("/etc/app/")
+	SupportedExts = append(SupportedExts, "")
+
+	err := afero.WriteFile(fs, "/etc/app/config", jsonExample, 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = v.ReadInConfig()
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 var hclWriteExpected = []byte(`"foos" = {
   "foo" = {
     "key" = 1