cmd/pkgserver: make report argument optional

This allows serving metadata only without a populated report. This also removes the out-of-bounds read on args when no arguments are passed.

Signed-off-by: Ophestra <cat@gensokyo.uk>

cmd/pkgserver/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"log"
 	"net/http"
@@ -31,31 +32,43 @@ func main() {
 	msg := message.New(log.Default())
 
 	c := command.New(os.Stderr, log.Printf, "pkgserver", func(args []string) error {
-		reportPath := args[0]
-		baseDir, err := check.NewAbs(flagBaseDir)
-		if err != nil {
-			return err
-		}
-		cache, err := pkg.Open(ctx, msg, 0, baseDir)
-		if err != nil {
-			return err
-		}
-		defer cache.Close()
-		report, err := rosa.OpenReport(reportPath)
-		if err != nil {
-			return err
+		var (
+			cache  *pkg.Cache
+			report *rosa.Report
+		)
+		switch len(args) {
+		case 0:
+			break
+
+		case 1:
+			baseDir, err := check.NewAbs(flagBaseDir)
+			if err != nil {
+				return err
+			}
+
+			cache, err = pkg.Open(ctx, msg, 0, baseDir)
+			if err != nil {
+				return err
+			}
+			defer cache.Close()
+
+			report, err = rosa.OpenReport(args[0])
+			if err != nil {
+				return err
+			}
+
+		default:
+			return errors.New("pkgserver requires 1 argument")
+
 		}
+
 		var index packageIndex
-		if err = index.populate(cache, report); err != nil {
+		if err := index.populate(cache, report); err != nil {
 			return err
 		}
 		uiRoutes(http.DefaultServeMux)
 		apiRoutes(http.DefaultServeMux, &index)
-		err = http.ListenAndServe(fmt.Sprintf(":%d", flagPort), nil)
-		if err != nil {
-			return err
-		}
-		return nil
+		return http.ListenAndServe(fmt.Sprintf(":%d", flagPort), nil)
 	}).Flag(
 		&flagBaseDir,
 		"b", command.StringFlag(""),