terraform: fix crash if outputs with no state [GH-358]

terraform/context.go

@@ -498,7 +498,7 @@ func (c *walkContext) Walk() error {
 		// On Apply, we prune so that we don't do outputs if we destroyed
 		mod.prune()
 	}
-	if len(mod.Resources) == 0 {
+	if mod == nil || len(mod.Resources) == 0 {
 		return nil
 	}
 

terraform/context_test.go

@@ -3336,6 +3336,27 @@ func TestContextRefresh_modules(t *testing.T) {
 	}
 }
 
+// GH-70
+func TestContextRefresh_noState(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "refresh-no-state")
+	ctx := testContext(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+	})
+
+	p.RefreshFn = nil
+	p.RefreshReturn = &InstanceState{
+		ID: "foo",
+	}
+
+	if _, err := ctx.Refresh(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+}
+
 func TestContextRefresh_state(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "refresh-basic")

terraform/test-fixtures/refresh-no-state/main.tf

@@ -0,0 +1 @@
+output "foo" {}