Add support for sdk extensions in prebuilt_apis

This makes it possible to pass an extensions_dir containing finalized
module APIs to prebuilt_apis. The extension versions are compared to the
api level versions to figure out what the "latest" finalized API is for
each module. This is done using the base_sdk_extension_version, such
that any extension higher than than base_sdk_extension_version is
assumed to be finalized after any of the existing api level versions.

Bug: 220086085
Test: prebuilt_apis_test.go
Test: existing module in prebuilts/sdk
Change-Id: Ib792f84202d436f594ba5e8716c6a187f9cd60dc
diff --git a/java/prebuilt_apis_test.go b/java/prebuilt_apis_test.go
index 79f4225..75422ad 100644
--- a/java/prebuilt_apis_test.go
+++ b/java/prebuilt_apis_test.go
@@ -20,9 +20,14 @@
 	"testing"
 
 	"android/soong/android"
+
 	"github.com/google/blueprint"
 )
 
+func intPtr(v int) *int {
+	return &v
+}
+
 func TestPrebuiltApis_SystemModulesCreation(t *testing.T) {
 	result := android.GroupFixturePreparers(
 		prepareForJavaTest,
@@ -54,3 +59,34 @@
 	sort.Strings(expected)
 	android.AssertArrayString(t, "sdk system modules", expected, sdkSystemModules)
 }
+
+func TestPrebuiltApis_WithExtensions(t *testing.T) {
+	runTestWithBaseExtensionLevel := func(v int) (foo_input string, bar_input string) {
+		result := android.GroupFixturePreparers(
+			prepareForJavaTest,
+			android.FixtureModifyProductVariables(func(variables android.FixtureProductVariables) {
+				variables.Platform_base_sdk_extension_version = intPtr(v)
+			}),
+			FixtureWithPrebuiltApisAndExtensions(map[string][]string{
+				"31":      {"foo"},
+				"32":      {"foo", "bar"},
+				"current": {"foo", "bar"},
+			}, map[string][]string{
+				"1": {"foo"},
+				"2": {"foo", "bar"},
+			}),
+		).RunTest(t)
+		foo_input = result.ModuleForTests("foo.api.public.latest", "").Rule("generator").Implicits[0].String()
+		bar_input = result.ModuleForTests("bar.api.public.latest", "").Rule("generator").Implicits[0].String()
+		return
+	}
+	// Here, the base extension level is 1, so extension level 2 is the latest
+	foo_input, bar_input := runTestWithBaseExtensionLevel(1)
+	android.AssertStringEquals(t, "Expected latest = extension level 2", "prebuilts/sdk/extensions/2/public/api/foo.txt", foo_input)
+	android.AssertStringEquals(t, "Expected latest = extension level 2", "prebuilts/sdk/extensions/2/public/api/bar.txt", bar_input)
+
+	// Here, the base extension level is 2, so 2 is not later than 32.
+	foo_input, bar_input = runTestWithBaseExtensionLevel(2)
+	android.AssertStringEquals(t, "Expected latest = api level 32", "prebuilts/sdk/32/public/api/foo.txt", foo_input)
+	android.AssertStringEquals(t, "Expected latest = api level 32", "prebuilts/sdk/32/public/api/bar.txt", bar_input)
+}