Separate metadata provider from apex contents provider

The platform_compat_config_singleton only needs access to the metadata
so this separates that method into its own interface, distinct from the
one needed by the apex. This also adds a test to ensure that the merging
still works.

Bug: 182402754
Test: m nothing
Change-Id: I5212239786810e5fc5eb99831b1122db93d1329f

java/platform_compat_config_test.go

@@ -0,0 +1,53 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// 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 java
+
+import (
+	"testing"
+
+	"android/soong/android"
+)
+
+func TestPlatformCompatConfig(t *testing.T) {
+	result := emptyFixtureFactory.RunTest(t,
+		PrepareForTestWithPlatformCompatConfig,
+		android.FixtureWithRootAndroidBp(`
+			platform_compat_config {
+				name: "myconfig2",
+			}
+			platform_compat_config {
+				name: "myconfig1",
+			}
+			platform_compat_config {
+				name: "myconfig3",
+			}
+		`),
+	)
+
+	checkMergedCompatConfigInputs(t, result, "myconfig",
+		"out/soong/.intermediates/myconfig1/myconfig1_meta.xml",
+		"out/soong/.intermediates/myconfig2/myconfig2_meta.xml",
+		"out/soong/.intermediates/myconfig3/myconfig3_meta.xml",
+	)
+}
+
+// Check that the merged file create by platform_compat_config_singleton has the correct inputs.
+func checkMergedCompatConfigInputs(t *testing.T, result *android.TestResult, message string, expectedPaths ...string) {
+	sourceGlobalCompatConfig := result.SingletonForTests("platform_compat_config_singleton")
+	allOutputs := sourceGlobalCompatConfig.AllOutputs()
+	android.AssertIntEquals(t, message+": output len", 1, len(allOutputs))
+	output := sourceGlobalCompatConfig.Output(allOutputs[0])
+	android.AssertPathsRelativeToTopEquals(t, message+": inputs", expectedPaths, output.Implicits)
+}