hooks: assert that we've got s.hookManager instead of dyingavar/assert-hook-manager-not-defined

Before this when running with my nascent UserCreateTag in Go code we'd
die in auth_test.go with:

    TestAuthBeforeLimit: auth_test.go:380:
                Error Trace:    auth_test.go:380
                Error:          Received unexpected error:
                                rpc error: code = Internal desc =
                                panic: runtime error: invalid memory
                                address or nil pointer dereference
                Test:           TestAuthBeforeLimit

Now we'll emit the better error message of:

    rpc error: code = Internal desc = panic: The hookManager must be
    set up already! Did you migrate non-hook-supporting code from Ruby
    to Go?

To reproduce run:

    go test -v ./internal/gitaly/server/ -run 'TestAuth' -count=1

See [1] for more background details & further explanation, add a
comment pointing to it to aid future debugging.

1. https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2911#note_468836913

1 files changed, 4 insertions, 0 deletions

diff --git a/internal/gitaly/service/operations/update_with_hooks.go b/internal/gitaly/service/operations/update_with_hooks.go
index ba90634bc..615f8217e 100644
--- a/internal/gitaly/service/operations/update_with_hooks.go
+++ b/internal/gitaly/service/operations/update_with_hooks.go
@@ -62,6 +62,10 @@ func (s *Server) updateReferenceWithHooks(ctx context.Context, repo *gitalypb.Re
 	changes := fmt.Sprintf("%s %s %s\n", oldrev, newrev, reference)
 	var stdout, stderr bytes.Buffer
 
+	if s.hookManager == nil {
+		// See https://gitlab.com/gitlab-org/gitaly/-/merge_requests/2911#note_468836913
+		panic("The hookManager must be set up already! Did you migrate non-hook-supporting code from Ruby to Go?")
+	}
 	if err := s.hookManager.PreReceiveHook(ctx, repo, env, strings.NewReader(changes), &stdout, &stderr); err != nil {
 		msg := hookErrorFromStdoutAndStderr(stdout.String(), stderr.String())
 		return preReceiveError{message: msg}