Fix issues with bp transformation

Returning nil from transformPropertySet in order to remove it did
not work because it ends up comparing as (*bpPropertySet, nil) and
not an untyped nil which causes the test against nil to fail.

This change adds tests to check that returning nil will delete a
property/property set from the containing property set and fixes the
code so that it passes the tests. It extracts common code to transform
a property set and its contents as well as code for creating new
property sets.

Bug: 148933848
Bug: 153306490
Test: m nothing
Merged-In: I35dc3c39c76e701821891622615c09b094cf697f
Change-Id: I35dc3c39c76e701821891622615c09b094cf697f

sdk/bp_test.go

@@ -0,0 +1,69 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package sdk
+
+import (
+	"testing"
+
+	"android/soong/android"
+)
+
+type removeFredTransformation struct {
+	identityTransformation
+}
+
+func (t removeFredTransformation) transformProperty(name string, value interface{}, tag android.BpPropertyTag) (interface{}, android.BpPropertyTag) {
+	if name == "fred" {
+		return nil, nil
+	}
+	return value, tag
+}
+
+func (t removeFredTransformation) transformPropertySet(name string, propertySet *bpPropertySet, tag android.BpPropertyTag) (*bpPropertySet, android.BpPropertyTag) {
+	if name == "fred" {
+		return nil, nil
+	}
+	return propertySet, tag
+}
+
+func TestTransformRemoveProperty(t *testing.T) {
+
+	helper := &TestHelper{t}
+
+	set := newPropertySet()
+	set.AddProperty("name", "name")
+	set.AddProperty("fred", "12")
+
+	set.transformContents(removeFredTransformation{})
+
+	contents := &generatedContents{}
+	outputPropertySet(contents, set)
+	helper.AssertTrimmedStringEquals("removing property failed", "name: \"name\",\\n", contents.content.String())
+}
+
+func TestTransformRemovePropertySet(t *testing.T) {
+
+	helper := &TestHelper{t}
+
+	set := newPropertySet()
+	set.AddProperty("name", "name")
+	set.AddPropertySet("fred")
+
+	set.transformContents(removeFredTransformation{})
+
+	contents := &generatedContents{}
+	outputPropertySet(contents, set)
+	helper.AssertTrimmedStringEquals("removing property set failed", "name: \"name\",\\n", contents.content.String())
+}