Provide support for preparing tests with prebuilt_apis

Adds general support for generating a set of prebuilt apis for a set of
releases and modules. Plus some wrappers for common use cases.

This temporarily will delete any existing conflicting files and replace
them so that it can be used in tests without first removing
javaMockFS(). The future update that removes javaMockFS() will also
remove that workaround.

Bug: 182638834
Test: m nothing
Change-Id: If4e2118f2384b9866cf3f85a5afec1e2e4f9ac95

java/testing.go

@@ -77,6 +77,71 @@ var javaSdkLibraryFiles = android.MockFS{
 	"api/system-server-removed.txt": nil,
 }
 
+// FixtureWithLastReleaseApis creates a preparer that creates prebuilt versions of the specified
+// modules for the `last` API release. By `last` it just means last in the list of supplied versions
+// and as this only provides one version it can be any value.
+//
+// This uses FixtureWithPrebuiltApis under the covers so the limitations of that apply to this.
+func FixtureWithLastReleaseApis(moduleNames ...string) android.FixturePreparer {
+	return FixtureWithPrebuiltApis(map[string][]string{
+		"30": moduleNames,
+	})
+}
+
+// PrepareForTestWithPrebuiltsOfCurrentApi is a preparer that creates prebuilt versions of the
+// standard modules for the current version.
+//
+// This uses FixtureWithPrebuiltApis under the covers so the limitations of that apply to this.
+var PrepareForTestWithPrebuiltsOfCurrentApi = FixtureWithPrebuiltApis(map[string][]string{
+	"current": {},
+	// Can't have current on its own as it adds a prebuilt_apis module but doesn't add any
+	// .txt files which causes the prebuilt_apis module to fail.
+	"30": {},
+})
+
+// FixtureWithPrebuiltApis creates a preparer that will define prebuilt api modules for the
+// specified releases and modules.
+//
+// The supplied map keys are the releases, e.g. current, 29, 30, etc. The values are a list of
+// modules for that release. Due to limitations in the prebuilt_apis module which this preparer
+// uses the set of releases must include at least one numbered release, i.e. it cannot just include
+// "current".
+//
+// This defines a file in the mock file system in a predefined location (prebuilts/sdk/Android.bp)
+// and so only one instance of this can be used in each fixture.
+func FixtureWithPrebuiltApis(release2Modules map[string][]string) android.FixturePreparer {
+	mockFS := android.MockFS{}
+	path := "prebuilts/sdk/Android.bp"
+
+	bp := fmt.Sprintf(`
+			prebuilt_apis {
+				name: "sdk",
+				api_dirs: ["%s"],
+				imports_sdk_version: "none",
+				imports_compile_dex: true,
+			}
+		`, strings.Join(android.SortedStringKeys(release2Modules), `", "`))
+
+	for release, modules := range release2Modules {
+		libs := append([]string{"android", "core-for-system-modules"}, modules...)
+		mockFS.Merge(prebuiltApisFilesForLibs([]string{release}, libs))
+	}
+	return android.GroupFixturePreparers(
+		// A temporary measure to discard the definitions provided by default by javaMockFS() to allow
+		// the changes that use this preparer to fix tests to be separated from the change to remove
+		// javaMockFS().
+		android.FixtureModifyMockFS(func(fs android.MockFS) {
+			for k, _ := range fs {
+				if strings.HasPrefix(k, "prebuilts/sdk/") {
+					delete(fs, k)
+				}
+			}
+		}),
+		android.FixtureAddTextFile(path, bp),
+		android.FixtureMergeMockFs(mockFS),
+	)
+}
+
 func javaMockFS() android.MockFS {
 	mockFS := android.MockFS{
 		"prebuilts/sdk/tools/core-lambda-stubs.jar": nil,