cmd/godoc: better error message for missing index files

Fixes #5024.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/8222045

diff --git a/src/cmd/godoc/godoc.go b/src/cmd/godoc/godoc.go
index 6f585fee8820de3aab9daff3eeb472170f9e862d..6f9e19d5f9799d0d863ac293e7b3551e2bbb6075 100644 (file)
--- a/src/cmd/godoc/godoc.go
+++ b/src/cmd/godoc/godoc.go
@@ -1517,6 +1517,8 @@ func readIndex(filenames string) error {
        matches, err := filepath.Glob(filenames)
        if err != nil {
                return err
+       } else if matches == nil {
+               return fmt.Errorf("no index files match %q", filenames)
        }
        sort.Strings(matches) // make sure files are in the right order
        files := make([]io.Reader, 0, len(matches))