config updated to improve setting values, writing changes and test coverage

internal/config/config.go

@@ -4,7 +4,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"log/slog"
+	"maps"
 	"reflect"
+	"slices"
 	"strings"
 
 	"github.com/spf13/viper"
@@ -65,23 +67,31 @@ func LoadFromViper(conf *JobSearchConfig) {
 		if keyType == reflect.Invalid {
 			continue
 		}
-		var err error
-		switch keyType {
-		case reflect.String:
-			err = conf.SetValue(key, viper.GetString(key))
-		case reflect.Int:
-			err = conf.SetValue(key, viper.GetInt(key))
-		case reflect.Bool:
-			err = conf.SetValue(key, viper.GetBool(key))
-		default:
+		value, ok := viperValue(key, keyType)
+		if !ok {
 			slog.Error(fmt.Sprintf("unknown key type: %s", keyType))
+			continue
 		}
-		if err != nil {
+		if err := conf.SetValue(key, value); err != nil {
 			slog.Warn("ignoring invalid config value", "key", key, "err", err)
 		}
 	}
 }
 
+// viperValue reads key from Viper as a value of kind. ok is false for a kind
+// LoadFromViper doesn't handle.
+func viperValue(key string, kind reflect.Kind) (value any, ok bool) {
+	switch kind {
+	case reflect.String:
+		return viper.GetString(key), true
+	case reflect.Int:
+		return viper.GetInt(key), true
+	case reflect.Bool:
+		return viper.GetBool(key), true
+	}
+	return nil, false
+}
+
 // LoadToViper sets every key of conf as a Viper default.
 func LoadToViper(conf JobSearchConfig) {
 	flatMap := conf.Flatten()
@@ -91,12 +101,13 @@ func LoadToViper(conf JobSearchConfig) {
 }
 
 // String formats the configuration one "key = value <type>" line per key, with
-// dotted keys.
+// dotted keys, sorted by key.
 func (conf JobSearchConfig) String() string {
 	var sb strings.Builder
-	for k, v := range conf.Flatten() {
+	flat := conf.Flatten()
+	for _, k := range slices.Sorted(maps.Keys(flat)) {
 		typ, _ := conf.TypeOf(k)
-		fmt.Fprint(&sb, k, " = ", v, " <", typ, ">\n")
+		fmt.Fprint(&sb, k, " = ", flat[k], " <", typ, ">\n")
 	}
 	return sb.String()
 }