Add error to arg getset

go/state/state.go

@@ -39,12 +39,16 @@ func(st State) WithCacheSize(cacheSize uint32) State {
 	return st
 }
 
-func(st *State) PutArg(input string) {
+func(st *State) PutArg(input string) error {
 	st.Arg = &input
+	return nil
 }
 
-func(st *State) PopArg() string {
+func(st *State) PopArg() (string, error) {
-	return *st.Arg
+	if st.Arg == nil {
+		return "", fmt.Errorf("arg is not set")
+	}
+	return *st.Arg, nil
 }
 
 func(st *State) Down(input string) {

go/vm/vm_test.go

@@ -16,6 +16,7 @@ import (
 var dynVal = "three"
 
 type TestResource struct {
+	state *state.State
 }
 
 func getOne(input []byte, ctx context.Context) (string, error) {
@@ -30,6 +31,15 @@ func getDyn(input []byte, ctx context.Context) (string, error) {
 	return dynVal, nil
 }
 
+type TestStatefulResolver struct {
+	state *state.State
+}
+
+
+func (r *TestResource) getEachArg(input []byte, ctx context.Context) (string, error) {
+	return r.state.PopArg()
+}
+
 func (r *TestResource) Get(sym string) (string, error) {
 	switch sym {
 	case "foo":
@@ -70,6 +80,8 @@ func (r *TestResource) FuncFor(sym string) (resource.EntryFunc, error) {
 		return getTwo, nil
 	case "dyn":
 		return getDyn, nil
+	case "arg":
+		return r.getEachArg, nil
 	}
 	return nil, fmt.Errorf("invalid function: '%s'", sym)
 }
@@ -92,7 +104,7 @@ func TestRun(t *testing.T) {
 	_ = r
 }
 
-func TestRunLoad(t *testing.T) {
+func TestRunLoadRender(t *testing.T) {
 	st := state.NewState(5)
 	st.Down("barbarbar")
 	rs := TestResource{}