Maintenance: improve error wrapping

internal/openvpn/command.go

@@ -2,6 +2,7 @@ package openvpn
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 
@@ -14,6 +15,8 @@ func (c *configurator) Start(ctx context.Context) (
 	return c.commander.Start(ctx, "openvpn", "--config", constants.OpenVPNConf)
 }
 
+var ErrVersionTooShort = errors.New("version output is too short")
+
 func (c *configurator) Version(ctx context.Context) (string, error) {
 	output, err := c.commander.Run(ctx, "openvpn", "--version")
 	if err != nil && err.Error() != "exit status 1" {
@@ -23,7 +26,7 @@ func (c *configurator) Version(ctx context.Context) (string, error) {
 	words := strings.Fields(firstLine)
 	const minWords = 2
 	if len(words) < minWords {
-		return "", fmt.Errorf("openvpn --version: first line is too short: %q", firstLine)
+		return "", fmt.Errorf("%w: %s", ErrVersionTooShort, firstLine)
 	}
 	return words[1], nil
 }

internal/openvpn/state.go

@@ -1,6 +1,7 @@
 package openvpn
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"sync"
@@ -43,6 +44,8 @@ func (l *looper) GetStatus() (status models.LoopStatus) {
 	return l.state.status
 }
 
+var ErrInvalidStatus = errors.New("invalid status")
+
 func (l *looper) SetStatus(status models.LoopStatus) (outcome string, err error) {
 	l.state.statusMu.Lock()
 	defer l.state.statusMu.Unlock()
@@ -78,8 +81,8 @@ func (l *looper) SetStatus(status models.LoopStatus) (outcome string, err error)
 		l.state.status = constants.Stopped
 		return status.String(), nil
 	default:
-		return "", fmt.Errorf("status %q can only be %q or %q",
-			status, constants.Running, constants.Stopped)
+		return "", fmt.Errorf("%w: %s: it can only be one of: %s, %s",
+			ErrInvalidStatus, status, constants.Running, constants.Stopped)
 	}
 }