Validate configuration

Validating passed Config prevents a panic or rendering invalid markdown.

Signed-off-by: Anna Kapuscinska <anna@isovalent.com>

pkg/metricsmd/config.go

@@ -4,6 +4,7 @@
 package metricsmd
 
 import (
+	"fmt"
 	"log/slog"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -33,3 +34,16 @@ type Config struct {
 	CommentStyle     CommentStyle
 	HeadingLevel     int // must be between 0 and 4
 }
+
+func validateConfig(config *Config) error {
+	if config.Targets == nil {
+		return fmt.Errorf("config.Targets must be set")
+	}
+	if config.InitMetrics == nil {
+		return fmt.Errorf("config.InitMetrics must be set")
+	}
+	if config.HeadingLevel < 0 || config.HeadingLevel > 4 {
+		return fmt.Errorf("config.HeadingLevel must be between 0 and 4")
+	}
+	return nil
+}

pkg/metricsmd/print.go

@@ -19,7 +19,11 @@ import (
 // NewCmd creates a Cobra command for generating metrics reference docs.
 // It's intended to be used as an add-on to applications that have a Cobra CLI
 // and expose Prometheus metrics.
-func NewCmd(vp *viper.Viper, log *slog.Logger, config *Config) *cobra.Command {
+func NewCmd(vp *viper.Viper, log *slog.Logger, config *Config) (*cobra.Command, error) {
+	err := validateConfig(config)
+	if err != nil {
+		return nil, err
+	}
 	cmd := &cobra.Command{
 		Use:         "metrics-docs",
 		Hidden:      true,
@@ -71,5 +75,5 @@ please do not edit directly.
 			return nil
 		},
 	}
-	return cmd
+	return cmd, nil
 }