Better parsing of the csv output's arguments

1. don't use external libraries that we want to remove to do it
2. error out on non existing keys in the argument
3. don't print ot stdout if `file_name` is not provided in the argument
but there is an argument

stats/csv/config.go

@@ -21,12 +21,11 @@
 package csv
 
 import (
+	"fmt"
 	"strings"
 	"time"
 
-	"github.com/kubernetes/helm/pkg/strvals"
 	"github.com/loadimpact/k6/lib/types"
-	"github.com/mitchellh/mapstructure"
 	"gopkg.in/guregu/null.v3"
 )
 
@@ -37,13 +36,6 @@ type Config struct {
 	SaveInterval types.NullDuration `json:"save_interval" envconfig:"K6_CSV_SAVE_INTERVAL"`
 }
 
-// config is a duplicate of ConfigFields as we can not mapstructure.Decode into
-// null types so we duplicate the struct with primitive types to Decode into
-type config struct {
-	FileName     string `json:"file_name" mapstructure:"file_name" envconfig:"K6_CSV_FILENAME"`
-	SaveInterval string `json:"save_interval" mapstructure:"save_interval" envconfig:"K6_CSV_SAVE_INTERVAL"`
-}
-
 // NewConfig creates a new Config instance with default values for some fields.
 func NewConfig() Config {
 	return Config{
@@ -73,26 +65,24 @@ func ParseArg(arg string) (Config, error) {
 		return c, nil
 	}
 
-	params, err := strvals.Parse(arg)
-
-	if err != nil {
-		return c, err
-	}
-
-	if v, ok := params["save_interval"].(string); ok {
-		err = c.SaveInterval.UnmarshalText([]byte(v))
-		if err != nil {
-			return c, err
+	pairs := strings.Split(arg, ",")
+	for _, pair := range pairs {
+		r := strings.SplitN(pair, "=", 2)
+		if len(r) != 2 {
+			return c, fmt.Errorf("couldn't parse %q as argument for csv output", arg)
+		}
+		switch r[0] {
+		case "save_interval":
+			err := c.SaveInterval.UnmarshalText([]byte(r[1]))
+			if err != nil {
+				return c, err
+			}
+		case "file_name":
+			c.FileName = null.StringFrom(r[1])
+		default:
+			return c, fmt.Errorf("unknown key %q as argument for csv output", r[0])
 		}
 	}
 
-	var cfg config
-	err = mapstructure.Decode(params, &cfg)
-	if err != nil {
-		return c, err
-	}
-
-	c.FileName = null.StringFrom(cfg.FileName)
-
 	return c, nil
 }

stats/csv/config_test.go

@@ -75,32 +75,46 @@ func TestApply(t *testing.T) {
 }
 
 func TestParseArg(t *testing.T) {
-	args := []string{
-		"test_file.csv",
-		"file_name=test.csv,save_interval=5s",
-	}
-
-	expected := []Config{
-		{
-			FileName:     null.StringFrom("test_file.csv"),
-			SaveInterval: types.NullDurationFrom(1 * time.Second),
+	cases := map[string]struct {
+		config      Config
+		expectedErr bool
+	}{
+		"test_file.csv": {
+			config: Config{
+				FileName:     null.StringFrom("test_file.csv"),
+				SaveInterval: types.NullDurationFrom(1 * time.Second),
+			},
 		},
-		{
-			FileName:     null.StringFrom("test.csv"),
-			SaveInterval: types.NullDurationFrom(5 * time.Second),
+		"save_interval=5s": {
+			config: Config{
+				SaveInterval: types.NullDurationFrom(5 * time.Second),
+			},
+		},
+		"file_name=test.csv,save_interval=5s": {
+			config: Config{
+				FileName:     null.StringFrom("test.csv"),
+				SaveInterval: types.NullDurationFrom(5 * time.Second),
+			},
+		},
+		"filename=test.csv,save_interval=5s": {
+			expectedErr: true,
 		},
 	}
 
-	for i := range args {
-		arg := args[i]
-		expected := expected[i]
+	for arg, testCase := range cases {
+		arg := arg
+		testCase := testCase
 
-		t.Run(expected.FileName.String+"_"+expected.SaveInterval.String(), func(t *testing.T) {
+		t.Run(arg, func(t *testing.T) {
 			config, err := ParseArg(arg)
 
-			assert.Nil(t, err)
-			assert.Equal(t, expected.FileName.String, config.FileName.String)
-			assert.Equal(t, expected.SaveInterval.String(), config.SaveInterval.String())
+			if testCase.expectedErr {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+			}
+			assert.Equal(t, testCase.config.FileName.String, config.FileName.String)
+			assert.Equal(t, testCase.config.SaveInterval.String(), config.SaveInterval.String())
 		})
 	}
 }