Add an api_files property in java_api_library

java_api_contribution is useful to java_api_library when the api files
are not colocated.

If they are colocated (e.g. in Multi-tree assembled api_surfaces
directory), it is useful to refer to them directly without nedding to
create a java_api_contribution module.

Test: In build/soong, go test ./java
Change-Id: I5b4e557068a1e5c71a80c76452030e72ec83a696

java/java.go

@@ -1567,8 +1567,14 @@ type JavaApiLibraryProperties struct {
 	Api_surface *string
 
 	// list of Java API contribution modules that consists this API surface
+	// This is a list of Soong modules
 	Api_contributions []string
 
+	// list of api.txt files relative to this directory that contribute to the
+	// API surface.
+	// This is a list of relative paths
+	Api_files []string
+
 	// List of flags to be passed to the javac compiler to generate jar file
 	Javacflags []string
 }
@@ -1665,6 +1671,13 @@ func (al *ApiLibrary) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 		srcFiles = append(srcFiles, android.PathForSource(ctx, provider.ApiFile.String()))
 	})
 
+	// Add the api_files inputs
+	for _, api := range al.properties.Api_files {
+		// Use MaybeExistentPathForSource since the api file might not exist during analysis.
+		// This will be provided by the orchestrator in the combined execution.
+		srcFiles = append(srcFiles, android.MaybeExistentPathForSource(ctx, ctx.ModuleDir(), api))
+	}
+
 	cmd := metalavaStubCmd(ctx, rule, srcFiles, homeDir)
 
 	al.stubsFlags(ctx, cmd, stubsDir)

java/java_test.go

@@ -1863,6 +1863,7 @@ func TestJavaApiLibraryAndProviderLink(t *testing.T) {
 			name: "bar2",
 			api_surface: "system",
 			api_contributions: ["foo1", "foo2"],
+			api_files: ["api1/current.txt", "api2/current.txt"]
 		}
 		`,
 		map[string][]byte{
@@ -1880,7 +1881,7 @@ func TestJavaApiLibraryAndProviderLink(t *testing.T) {
 		},
 		{
 			moduleName:         "bar2",
-			sourceTextFileDirs: []string{"a/foo1.txt", "b/foo2.txt"},
+			sourceTextFileDirs: []string{"a/foo1.txt", "b/foo2.txt", "api1/current.txt", "api2/current.txt"},
 		},
 	}
 	for _, c := range testcases {