Optional yaml and json config files

arg.go

@@ -102,14 +102,23 @@ func (a *Arg) Set(value interface{}) error {
 	err := fmt.Errorf("incompatible set of type %T for arg $%v/-%v type %v", value, a.Env, a.Flag, a.ArgType)
 	switch a.ArgType {
 	case INT:
-		i, ok := value.(int)
-		if ok {
-			a.Value = i
-			err = nil
-		} else if s, ok := value.(string); !ok {
-		} else if i, err = strconv.Atoi(s); err == nil {
-			a.Value = i
+		switch value.(type) {
+		case int:
+			a.Value = value.(int)
 			err = nil
+		case string:
+			s := value.(string)
+			var i int
+			if i, err = strconv.Atoi(s); err == nil {
+				a.Value = i
+				err = nil
+			}
+		case float64:
+			f := value.(float64)
+			if f-float64(int(f)) == 0 {
+				a.Value = int(f)
+				err = nil
+			}
 		}
 	case STRING:
 		i, ok := value.(string)

argset.go

@@ -1,20 +1,28 @@
 package args
 
 import (
+	"encoding/json"
 	"errors"
 	"flag"
+	"fmt"
+	"io/ioutil"
 	"os"
+	"strings"
 	"time"
+
+	yaml "gopkg.in/yaml.v2"
 )
 
 type ArgSet struct {
-	parsed bool
-	args   []*Arg
+	parsed      bool
+	args        []*Arg
+	configFiles []string
 }
 
-func NewArgSet() *ArgSet {
+func NewArgSet(configFiles ...string) *ArgSet {
 	return &ArgSet{
-		args: []*Arg{},
+		args:        []*Arg{},
+		configFiles: configFiles,
 	}
 }
 
@@ -45,6 +53,9 @@ func (as *ArgSet) Parse() error {
 	if err := as.setValueFromDefaults(); err != nil {
 		return err
 	}
+	if err := as.setValueFromFiles(); err != nil {
+		return err
+	}
 	if err := as.setValueFromEnv(); err != nil {
 		return err
 	}
@@ -122,3 +133,39 @@ func (as *ArgSet) setValueFromFlags() error {
 	}
 	return err
 }
+
+func (as *ArgSet) setValueFromFiles() error {
+	for _, file := range as.configFiles {
+		if err := as.setValueFromFile(file); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (as *ArgSet) setValueFromFile(path string) error {
+	b, err := ioutil.ReadFile(path)
+	if err != nil {
+		return err
+	}
+	var config map[string]interface{}
+	if strings.HasSuffix(path, ".json") {
+		err = json.Unmarshal(b, &config)
+	} else if strings.HasSuffix(path, ".yaml") {
+		err = yaml.Unmarshal(b, &config)
+	} else {
+		err = fmt.Errorf("unknown config file suffix: %s", path)
+	}
+	if err != nil {
+		return err
+	}
+	for i := range as.args {
+		key := as.args[i].Flag
+		if v, ok := config[key]; ok {
+			if err := as.args[i].Set(v); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

argset_test.go

@@ -1,7 +1,10 @@
 package args
 
 import (
+	"fmt"
+	"io/ioutil"
 	"os"
+	"path"
 	"testing"
 	"time"
 )
@@ -68,6 +71,11 @@ func TestParseFloatTime(t *testing.T) {
 }
 
 func TestGet(t *testing.T) {
+	was := os.Args
+	defer func() {
+		os.Args = was
+	}()
+	os.Args = []string{"exec", "-testkey1", "5"}
 	as := NewArgSet()
 	as.Append(INT, "testkey1", "help", 1)
 	as.Append(INT, "testkey2", "help", 2)
@@ -79,3 +87,68 @@ func TestGet(t *testing.T) {
 		t.Errorf("cannot get parsed at %q", "testkey1")
 	}
 }
+
+func TestSetValueFromFileYAML(t *testing.T) {
+	was := os.Args
+	defer func() {
+		os.Args = was
+	}()
+	os.Args = []string{"exec"}
+	testSetValueFromFile(t, "yaml", `
+   1: 5
+   2: hello
+   3: 5m
+   4: true
+   5: 2019-01-01
+   6: 5.5
+   `)
+	testSetValueFromFile(t, "json", `
+   {
+      "1": 5,
+      "2": "hello",
+      "3": "5m",
+      "4": true,
+      "5": "2019-01-01",
+      "6": 5.5
+   }
+   `)
+}
+
+func testSetValueFromFile(t *testing.T, suffix, content string) {
+	d, err := ioutil.TempDir(os.TempDir(), "prefix")
+	defer os.RemoveAll(d)
+	f, err := os.Create(path.Join(d, "conf."+suffix))
+	if err != nil {
+		t.Fatal(err)
+	}
+	fmt.Fprintln(f, content)
+	f.Close()
+	as := NewArgSet(f.Name())
+	as.Append(INT, "1", "help", 1)
+	as.Append(STRING, "2", "help", "world")
+	as.Append(DURATION, "3", "help", time.Hour)
+	as.Append(BOOL, "4", "help", false)
+	as.Append(TIME, "5", "help", time.Now())
+	as.Append(FLOAT, "6", "help", 1.1)
+	if err := as.Parse(); err != nil {
+		t.Fatal(err)
+	}
+	if v := as.Get("1").GetInt(); v != 5 {
+		t.Fatal(v)
+	}
+	if v := as.Get("2").GetString(); v != "hello" {
+		t.Fatal(v)
+	}
+	if v := as.Get("3").GetDuration(); v != time.Minute*5 {
+		t.Fatal(v)
+	}
+	if v := as.Get("4").GetBool(); v != true {
+		t.Fatal(v)
+	}
+	if v := as.Get("5").GetTime(); v != time.Date(2019, 1, 1, 0, 0, 0, 0, time.UTC) {
+		t.Fatal(v)
+	}
+	if v := as.Get("6").GetFloat(); v != 5.5 {
+		t.Fatal(v)
+	}
+}