MM-54314: Return the error correctly from config parse failure (#649)

https://mattermost.atlassian.net/browse/MM-54314

Co-authored-by: Alejandro García Montoro <[email protected]>

defaults/json.go

@@ -10,19 +10,24 @@ import (
 // This function will try to read from given path, if it is empty will try
 // fallback path. If it fails on fallback, it will set value to it's defaults
 func ReadFromJSON(path, fallbackPath string, value interface{}) error {
+	if err := Set(value); err != nil {
+		return err
+	}
+
 	if path != "" {
 		if err := readJSON(path, &value); err != nil {
-			return err
+			return fmt.Errorf("failed to read from path %s: %w", path, err)
 		}
 		return nil
 	}
 
-	if err := readJSON(fallbackPath, value); err == nil {
+	// If the fallback path doesn't exist, return.
+	if _, err := os.Stat(fallbackPath); err != nil && os.IsNotExist(err) {
 		return nil
 	}
 
-	if err := Set(value); err != nil {
-		return err
+	if err := readJSON(fallbackPath, value); err != nil {
+		return fmt.Errorf("failed to read from fallback path %s: %w", fallbackPath, err)
 	}
 
 	return nil

defaults/json_test.go

@@ -0,0 +1,42 @@
+package defaults
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type testCFG struct {
+	Setting string `default:"hi"`
+	Another int    `default:"1"`
+}
+
+func TestReadFromJSON(t *testing.T) {
+	cfg := testCFG{}
+	f, err := os.CreateTemp("", "loadtest")
+	require.NoError(t, err)
+	defer os.Remove(f.Name()) // clean up
+
+	// Ensuring that a bad config throws an error
+	_, err = f.Write([]byte(`{"setting": "hello" "another": 1}`))
+	require.NoError(t, err)
+	require.NoError(t, f.Close())
+
+	require.Error(t, ReadFromJSON("", f.Name(), &cfg))
+
+	cfg = testCFG{}
+	f1, err := os.CreateTemp("", "loadtest")
+	require.NoError(t, err)
+	defer os.Remove(f1.Name()) // clean up
+
+	// Ensuring default values get correctly overridden
+	_, err = f1.Write([]byte(`{"setting": "hello"}`))
+	require.NoError(t, err)
+	require.NoError(t, f1.Close())
+
+	require.NoError(t, ReadFromJSON("", f1.Name(), &cfg))
+	assert.Equal(t, 1, cfg.Another)
+	assert.Equal(t, "hello", cfg.Setting)
+}

loadtest/user/userentity/helper_test.go

@@ -8,17 +8,50 @@ import (
 
 	"github.com/mattermost/mattermost-load-test-ng/defaults"
 	"github.com/mattermost/mattermost-load-test-ng/loadtest/store/memstore"
+	"github.com/mattermost/mattermost-load-test-ng/logger"
 
 	"github.com/stretchr/testify/require"
 )
 
+type ratesDistribution struct {
+	Rate       float64 `default:"1.0" validate:"range:[0,)"`
+	Percentage float64 `default:"1.0" validate:"range:[0,1]"`
+}
+type userControllerType string
+
 type config struct {
 	ConnectionConfiguration struct {
 		ServerURL     string `default:"http://localhost:8065" validate:"url"`
 		WebSocketURL  string `default:"ws://localhost:8065" validate:"url"`
 		AdminEmail    string `default:"[email protected]" validate:"email"`
 		AdminPassword string `default:"Sys@dmin-sample1" validate:"notempty"`
 	}
+	UserControllerConfiguration struct {
+		Type              userControllerType  `default:"simulative" validate:"oneof:{simple,simulative,noop,cluster,generative}"`
+		RatesDistribution []ratesDistribution `default_len:"1"`
+		ServerVersion     string
+	}
+	InstanceConfiguration struct {
+		NumTeams                    int64   `default:"2" validate:"range:[0,]"`
+		NumChannels                 int64   `default:"10" validate:"range:[0,]"`
+		NumPosts                    int64   `default:"0" validate:"range:[0,]"`
+		NumReactions                int64   `default:"0" validate:"range:[0,]"`
+		NumAdmins                   int64   `default:"0" validate:"range:[0,]"`
+		PercentReplies              float64 `default:"0.5" validate:"range:[0,1]"`
+		PercentRepliesInLongThreads float64 `default:"0.05" validate:"range:[0,1]"`
+		PercentUrgentPosts          float64 `default:"0.001" validate:"range:[0,1]"`
+		PercentPublicChannels       float64 `default:"0.2" validate:"range:[0,1]"`
+		PercentPrivateChannels      float64 `default:"0.1" validate:"range:[0,1]"`
+		PercentDirectChannels       float64 `default:"0.6" validate:"range:[0,1]"`
+		PercentGroupChannels        float64 `default:"0.1" validate:"range:[0,1]"`
+	}
+	UsersConfiguration struct {
+		UsersFilePath      string
+		InitialActiveUsers int `default:"0" validate:"range:[0,$MaxActiveUsers]"`
+		MaxActiveUsers     int `default:"2000" validate:"range:(0,]"`
+		AvgSessionsPerUser int `default:"1" validate:"range:[1,]"`
+	}
+	LogSettings logger.Settings
 }
 
 type TestHelper struct {