Change format from JSON to CSV

README.md

@@ -94,8 +94,7 @@ $ NUM_WORKERS=4 ./example
 Workers: 4
 ```
 
-You should use a JSON array of strings (value will be converted if
-necessary) in the case of multiple values:
+You can provide multiple values using the CSV (RFC 4180) format:
 
 ```go
 var args struct {
@@ -106,7 +105,7 @@ fmt.Println("Workers:", args.Workers)
 ```
 
 ```
-$ WORKERS='["1", "99"]' ./example
+$ WORKERS='1,99' ./example
 Workers: [1 99]
 ```
 

parse.go

@@ -2,7 +2,7 @@ package arg
 
 import (
 	"encoding"
-	"encoding/json"
+	"encoding/csv"
 	"errors"
 	"fmt"
 	"os"
@@ -278,18 +278,12 @@ func process(specs []*spec, args []string) error {
 			if value, found := os.LookupEnv(spec.env); found {
 				var err error
 				if spec.multiple {
-					// expect a JSON array of strings in an environment
+					// expect a CSV string in an environment
 					// variable in the case of multiple values
-					var values []string
-					err = json.Unmarshal([]byte(value), &values)
-					if err != nil {
-						return fmt.Errorf(
-							"error processing environment variable %s (it should be a JSON array of strings):\n%v",
-							spec.env,
-							err,
-						)
+					values, err := csv.NewReader(strings.NewReader(value)).Read()
+					if err == nil {
+						err = setSlice(spec.dest, values, !spec.separate)
 					}
-					err = setSlice(spec.dest, values, !spec.separate)
 				} else {
 					err = scalar.ParseValue(spec.dest, value)
 				}

parse_test.go

@@ -584,16 +584,16 @@ func TestEnvironmentVariableSliceArgumentString(t *testing.T)  {
 	var args struct {
 		Foo []string `arg:"env"`
 	}
-	setenv(t, "FOO", "[\"bar\", \"baz\"]")
+	setenv(t, "FOO", "bar,\"baz, qux\"")
 	MustParse(&args)
-	assert.Equal(t, []string{"bar", "baz"}, args.Foo)
+	assert.Equal(t, []string{"bar", "baz, qux"}, args.Foo)
 }
 
 func TestEnvironmentVariableSliceArgumentInteger(t *testing.T)  {
 	var args struct {
 		Foo []int `arg:"env"`
 	}
-	setenv(t, "FOO", "[\"1\", \"99\"]")
+	setenv(t, "FOO", "1,99")
 	MustParse(&args)
 	assert.Equal(t, []int{1, 99}, args.Foo)
 }
@@ -602,7 +602,7 @@ func TestEnvironmentVariableSliceArgumentFloat(t *testing.T)  {
 	var args struct {
 		Foo []float32 `arg:"env"`
 	}
-	setenv(t, "FOO", "[\"1.1\", \"99.9\"]")
+	setenv(t, "FOO", "1.1,99.9")
 	MustParse(&args)
 	assert.Equal(t, []float32{1.1, 99.9}, args.Foo)
 }
@@ -611,20 +611,11 @@ func TestEnvironmentVariableSliceArgumentBool(t *testing.T)  {
 	var args struct {
 		Foo []bool `arg:"env"`
 	}
-	setenv(t, "FOO", "[\"true\", \"false\", \"0\", \"1\"]")
+	setenv(t, "FOO", "true,false,0,1")
 	MustParse(&args)
 	assert.Equal(t, []bool{true, false, false, true}, args.Foo)
 }
 
-func TestEnvironmentVariableSliceArgumentError(t *testing.T) {
-	var args struct {
-		Foo []int `arg:"env"`
-	}
-	setenv(t, "FOO", "[1, 99]")
-	err := Parse(&args)
-	assert.Error(t, err)
-}
-
 type textUnmarshaler struct {
 	val int
 }