Refactored UI to allow for default values and value overrides. Also g…

…et better error messages for missing env values

.env.sample

@@ -1,4 +1,5 @@
 MY_APP_EMAIL=[email protected]
 #MY_APP_PASSWORD=password
 MY_APP_PASSWORD=password2
-MY_APP_ENDPOINT=some-endpoint
+MY_APP_ENDPOINT=some-endpoint
+MY_APP_URL=https://some.exmpale.org/foo?token=bar

README.md

@@ -7,14 +7,21 @@ A minimalistic approach to [spf13/viper](https://github.com/spf13/viper).
 ## Features
 - Read `ENV` variables into a `struct`
 - Read a `.env` file into a `struct`
-- `< 100` source lines of code
+- `< 110` source lines of code
 - [No dependencies](go.mod)
 
 Only string fields are supported. 
 
 ## Usage
 
 ```go
+package main
+
+import (
+	"github.com/nobloat/tinyviper"
+	"fmt"
+)
+
 type Config struct {
 	UserConfig struct {
 		Email    string `env:"MY_APP_EMAIL"`
@@ -25,8 +32,8 @@ type Config struct {
 }
 
 func main() {
-  //cfg, err := NewEnvConfig[Config]()  //Read from env
-  cfg, err := NewEnvFileConfig[Config](".env.sample") //Read from .env file
+  cfg := Config{}
+  cfg, err := tinyviper.LoadFromResolver(&cfg, tinyviper.EnvResolver{}, tinyviper.NewEnvFileResolver(".env.sample"))
   if err != nil {
     panic(err)
   }

tinyviper.go

@@ -11,67 +11,69 @@ import (
 type Resolver interface {
 	Get(key string) string
 }
-
 type EnvResolver struct{}
-
 type EnvFileResolver struct {
 	Variables map[string]string
 }
 
-func NewEnvFileResolver(filename string) (*EnvFileResolver, error) {
+func (e EnvFileResolver) Get(key string) string {
+	return e.Variables[key]
+}
+func (e EnvResolver) Get(key string) string {
+	return os.Getenv(key)
+}
+
+type multiResolver struct {
+	resolvers []Resolver
+}
+
+func NewEnvFileResolver(filename string) *EnvFileResolver {
 	readFile, err := os.Open(filename)
 	if err != nil {
-		return nil, err
+		return nil
 	}
+	defer readFile.Close()
 	r := &EnvFileResolver{make(map[string]string, 0)}
 	fileScanner := bufio.NewScanner(readFile)
 	fileScanner.Split(bufio.ScanLines)
 	for fileScanner.Scan() {
 		text := fileScanner.Text()
-		parts := strings.Split(text, "=")
-		if len(parts) != 2 || strings.HasPrefix(text, "#") {
+		index := strings.Index(text, "=")
+		if index == -1 || strings.HasPrefix(text, "#") {
 			continue
 		}
-		r.Variables[strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
+		r.Variables[text[0:index]] = strings.Trim(text[index+1:], " \"'")
 	}
-	return r, readFile.Close()
-}
-
-func (e EnvFileResolver) Get(key string) string {
-	return e.Variables[key]
-}
-
-func (e EnvResolver) Get(key string) string {
-	return os.Getenv(key)
+	return r
 }
 
-func NewEnvConfig[T any]() (*T, error) {
-	cfg := new(T)
-	res := EnvResolver{}
-	err := ReflectStruct(cfg, res)
-	if err != nil {
-		return nil, err
+func (m multiResolver) Get(key string) string {
+	for _, r := range m.resolvers {
+		v := r.Get(key)
+		if r.Get(key) != "" {
+			return v
+		}
 	}
-	return cfg, nil
+	return ""
 }
 
-func NewEnvFileConfig[T any](filename string) (*T, error) {
-	cfg := new(T)
-	res, err := NewEnvFileResolver(filename)
+func LoadFromResolver[T any](cfg *T, resolver ...Resolver) error {
+	res := multiResolver{resolvers: resolver}
+	missing := make([]string, 0)
+	missing, err := refelectStruct(cfg, res, missing)
 	if err != nil {
-		return nil, err
+		return err
 	}
-	err = ReflectStruct(cfg, res)
-	if err != nil {
-		return nil, err
+	if len(missing) > 0 {
+		return errors.New("missing config variables: " + strings.Join(missing, ","))
 	}
-	return cfg, nil
+	return nil
 }
 
-func ReflectStruct(object any, resolver Resolver) error {
+func refelectStruct(object any, resolver Resolver, missing []string) ([]string, error) {
 	v := reflect.ValueOf(object)
 	if v.Elem().Kind() != reflect.Struct {
-		return errors.New("type must be a struct")
+		return missing, errors.New("type must be a struct")
 	}
 	e := v.Elem()
 	t := e.Type()
@@ -81,22 +83,24 @@ func ReflectStruct(object any, resolver Resolver) error {
 		envName := tf.Tag.Get("env")
 		if envName != "" {
 			if tf.Type != reflect.TypeOf("") {
-				return errors.New("env annotated field must have type string")
+				return missing, errors.New("env annotated field must have type string")
 			}
 			if !ef.CanSet() {
-				return errors.New("env field must be public")
+				return missing, errors.New("env field must be public")
 			}
 			value := resolver.Get(envName)
-			if value == "" {
-				return errors.New("env variable " + envName + " is not set")
+			if value != "" {
+				ef.SetString(resolver.Get(envName))
+			} else if ef.String() == "" {
+				missing = append(missing, envName)
 			}
-			ef.SetString(resolver.Get(envName))
 		} else if t.Kind() == reflect.Struct {
-			err := ReflectStruct(ef.Addr().Interface(), resolver)
+			m, err := refelectStruct(ef.Addr().Interface(), resolver, missing)
 			if err != nil {
-				return err
+				return missing, err
 			}
+			missing = append(missing, m...)
 		}
 	}
-	return nil
+	return missing, nil
 }

tinyviper_test.go

@@ -11,23 +11,49 @@ type Config struct {
 		Password string `env:"MY_APP_PASSWORD"`
 	}
 	Endpoint string `env:"MY_APP_ENDPOINT"`
+	AppUrl   string `env:"MY_APP_URL"`
 }
 
-func TestConfig(t *testing.T) {
-	cfg, err := NewEnvFileConfig[Config](".env.sample")
+type testEnvResolver struct{}
+
+func (t testEnvResolver) Get(key string) string {
+	switch key {
+	case "MY_APP_EMAIL":
+		return "[email protected]"
+	case "MY_APP_PASSWORD":
+		return "[email protected]"
+	default:
+		return ""
+	}
+}
+
+func TestConfigErrors(t *testing.T) {
+	cfg := Config{}
+	err := LoadFromResolver(&cfg, testEnvResolver{})
+	if err == nil {
+		t.Fatalf("Expected error, got none")
+	}
+	if err.Error() != "missing config variables: MY_APP_ENDPOINT,MY_APP_URL" {
+		t.Error("Expected error, got wrong one: " + err.Error())
+	}
+}
+
+func TestConfigNew(t *testing.T) {
+	cfg := Config{}
+	err := LoadFromResolver(&cfg, EnvResolver{}, NewEnvFileResolver(".env.sample"))
 	if err != nil {
 		t.Error(err)
 	}
-
 	if cfg.UserConfig.Email != "[email protected]" {
 		t.Error(errors.New("unexpected email"))
 	}
-
 	if cfg.UserConfig.Password != "password2" {
 		t.Error(errors.New("unexpected password"))
 	}
-
 	if cfg.Endpoint != "some-endpoint" {
 		t.Error(errors.New("unexpected endpoint"))
 	}
+	if cfg.AppUrl != "https://some.exmpale.org/foo?token=bar" {
+		t.Error(errors.New("unexpected url"))
+	}
 }