push.go: initialize nil opts with the zero PushOptions inside InitPushExtWithOptions

This makes the InitPushExtWithOptions code more maintainable because of removed checks for nil opts.

push.go

@@ -179,6 +179,10 @@ func InitPushExt(pushURL string, interval time.Duration, extraLabels string, wri
 // It is OK calling InitPushExtWithOptions multiple times with different writeMetrics -
 // in this case all the metrics generated by writeMetrics callbacks are written to pushURL.
 func InitPushExtWithOptions(ctx context.Context, pushURL string, interval time.Duration, writeMetrics func(w io.Writer), opts *PushOptions) error {
+	if opts == nil {
+		opts = &PushOptions{}
+	}
+
 	// validate pushURL
 	pu, err := url.Parse(pushURL)
 	if err != nil {
@@ -197,33 +201,25 @@ func InitPushExtWithOptions(ctx context.Context, pushURL string, interval time.D
 	}
 
 	// validate ExtraLabels
-	var extraLabels string
-	if opts != nil {
-		extraLabels = opts.ExtraLabels
-	}
+	extraLabels := opts.ExtraLabels
 	if err := validateTags(extraLabels); err != nil {
 		return fmt.Errorf("invalid extraLabels=%q: %w", extraLabels, err)
 	}
 
 	// validate Headers
 	headers := make(http.Header)
-	if opts != nil {
-		for _, h := range opts.Headers {
-			n := strings.IndexByte(h, ':')
-			if n < 0 {
-				return fmt.Errorf("missing `:` delimiter in the header %q", h)
-			}
-			name := strings.TrimSpace(h[:n])
-			value := strings.TrimSpace(h[n+1:])
-			headers.Add(name, value)
+	for _, h := range opts.Headers {
+		n := strings.IndexByte(h, ':')
+		if n < 0 {
+			return fmt.Errorf("missing `:` delimiter in the header %q", h)
 		}
+		name := strings.TrimSpace(h[:n])
+		value := strings.TrimSpace(h[n+1:])
+		headers.Add(name, value)
 	}
 
 	// validate DisableCompression
-	disableCompression := false
-	if opts != nil {
-		disableCompression = opts.DisableCompression
-	}
+	disableCompression := opts.DisableCompression
 
 	// Initialize metrics for the given pushURL
 	pushURLRedacted := pu.Redacted()