terraform: refresh returning nil should delete from state

terraform/context.go

@@ -820,7 +820,11 @@ func (c *Context) refreshWalkFn() depgraph.WalkFunc {
 		rs.Type = r.State.Type
 
 		c.sl.Lock()
-		c.state.Resources[r.Id] = rs
+		if rs.ID == "" {
+			delete(c.state.Resources, r.Id)
+		} else {
+			c.state.Resources[r.Id] = rs
+		}
 		c.sl.Unlock()
 
 		for _, h := range c.hooks {

terraform/context_test.go

@@ -1639,6 +1639,37 @@ func TestContextRefresh(t *testing.T) {
 	}
 }
 
+func TestContextRefresh_delete(t *testing.T) {
+	p := testProvider("aws")
+	c := testConfig(t, "refresh-basic")
+	ctx := testContext(t, &ContextOpts{
+		Config: c,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		State: &State{
+			Resources: map[string]*ResourceState{
+				"aws_instance.web": &ResourceState{
+					ID:   "foo",
+					Type: "aws_instance",
+				},
+			},
+		},
+	})
+
+	p.RefreshFn = nil
+	p.RefreshReturn = nil
+
+	s, err := ctx.Refresh()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if len(s.Resources) > 0 {
+		t.Fatal("resources should be empty")
+	}
+}
+
 func TestContextRefresh_ignoreUncreated(t *testing.T) {
 	p := testProvider("aws")
 	c := testConfig(t, "refresh-basic")