Enable droidstubs to export "exportable" artifacts

This change adds support for the droidstubs module to export the
"exportable" artifacts via OutputFiles(tag string) method, while
supporting the current behavior of exporting "everything" artifacts via
a tag. With the support, a rdep module can depend on the "exportable"
(and "runtime" in the long run) artifacts by prepending the stubs type
in the tag. For instance, given that the currently supported tag
{.annotations.zip} exports the everything annotations.zip file,
{.exportable.annotations.zip} tag will export the exportable
annotations.zip file. For an unsupported combination (e.g. all runtime
stubs related artifacts as of now), an error will be thrown.

Test: m nothing --no-skip-soong-tests
Bug: 315490657
Change-Id: Idcefd9cdc02d323306fb8d7be2a2b34f67501f56

java/droidstubs.go

@@ -36,6 +36,7 @@ const (
 	Everything StubsType = iota
 	Runtime
 	Exportable
+	Unavailable
 )
 
 func (s StubsType) String() string {
@@ -270,21 +271,55 @@ func DroidstubsHostFactory() android.Module {
 	return module
 }
 
+func getStubsTypeAndTag(tag string) (StubsType, string, error) {
+	if len(tag) == 0 {
+		return Everything, "", nil
+	}
+	if tag[0] != '.' {
+		return Unavailable, "", fmt.Errorf("tag must begin with \".\"")
+	}
+
+	stubsType := Everything
+	// Check if the tag has a stubs type prefix (e.g. ".exportable")
+	for st := Everything; st <= Exportable; st++ {
+		if strings.HasPrefix(tag, "."+st.String()) {
+			stubsType = st
+		}
+	}
+
+	return stubsType, strings.TrimPrefix(tag, "."+stubsType.String()), nil
+}
+
+// Droidstubs' tag supports specifying with the stubs type.
+// While supporting the pre-existing tags, it also supports tags with
+// the stubs type prefix. Some examples are shown below:
+// {.annotations.zip} - pre-existing behavior. Returns the path to the
+// annotation zip.
+// {.exportable} - Returns the path to the exportable stubs src jar.
+// {.exportable.annotations.zip} - Returns the path to the exportable
+// annotations zip file.
+// {.runtime.api_versions.xml} - Runtime stubs does not generate api versions
+// xml file. For unsupported combinations, the default everything output file
+// is returned.
 func (d *Droidstubs) OutputFiles(tag string) (android.Paths, error) {
-	switch tag {
+	stubsType, prefixRemovedTag, err := getStubsTypeAndTag(tag)
+	if err != nil {
+		return nil, err
+	}
+	switch prefixRemovedTag {
 	case "":
-		return android.Paths{d.stubsSrcJar}, nil
+		return d.StubsSrcJarWithStubsType(stubsType)
 	case ".docs.zip":
-		return android.Paths{d.docZip}, nil
+		return d.DocZipWithStubsType(stubsType)
 	case ".api.txt", android.DefaultDistTag:
 		// This is the default dist path for dist properties that have no tag property.
-		return android.Paths{d.apiFile}, nil
+		return d.ApiFilePathWithStubsType(stubsType)
 	case ".removed-api.txt":
-		return android.Paths{d.removedApiFile}, nil
+		return d.RemovedApiFilePathWithStubsType(stubsType)
 	case ".annotations.zip":
-		return android.Paths{d.annotationsZip}, nil
+		return d.AnnotationsZipWithStubsType(stubsType)
 	case ".api_versions.xml":
-		return android.Paths{d.apiVersionsXml}, nil
+		return d.ApiVersionsXmlFilePathWithStubsType(stubsType)
 	default:
 		return nil, fmt.Errorf("unsupported module reference tag %q", tag)
 	}
@@ -294,18 +329,96 @@ func (d *Droidstubs) AnnotationsZip() android.Path {
 	return d.annotationsZip
 }
 
+func (d *Droidstubs) ExportableAnnotationsZip() android.Path {
+	return d.exportableAnnotationsZip
+}
+
+func (d *Droidstubs) AnnotationsZipWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.AnnotationsZip()}, nil
+	case Exportable:
+		return android.Paths{d.ExportableAnnotationsZip()}, nil
+	default:
+		return nil, fmt.Errorf("annotations zip not supported for the stub type %s", stubsType.String())
+	}
+}
+
 func (d *Droidstubs) ApiFilePath() android.Path {
 	return d.apiFile
 }
 
+func (d *Droidstubs) ExportableApiFilePath() android.Path {
+	return d.exportableApiFile
+}
+
+func (d *Droidstubs) ApiFilePathWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.ApiFilePath()}, nil
+	case Exportable:
+		return android.Paths{d.ExportableApiFilePath()}, nil
+	default:
+		return nil, fmt.Errorf("api file path not supported for the stub type %s", stubsType.String())
+	}
+}
+
+func (d *Droidstubs) ApiVersionsXmlFilePathWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.apiVersionsXml}, nil
+	default:
+		return nil, fmt.Errorf("api versions xml file path not supported for the stub type %s", stubsType.String())
+	}
+}
+
+func (d *Droidstubs) DocZipWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.docZip}, nil
+	default:
+		return nil, fmt.Errorf("docs zip not supported for the stub type %s", stubsType.String())
+	}
+}
+
 func (d *Droidstubs) RemovedApiFilePath() android.Path {
 	return d.removedApiFile
 }
 
+func (d *Droidstubs) ExportableRemovedApiFilePath() android.Path {
+	return d.exportableRemovedApiFile
+}
+
+func (d *Droidstubs) RemovedApiFilePathWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.RemovedApiFilePath()}, nil
+	case Exportable:
+		return android.Paths{d.ExportableRemovedApiFilePath()}, nil
+	default:
+		return nil, fmt.Errorf("removed api file path not supported for the stub type %s", stubsType.String())
+	}
+}
+
 func (d *Droidstubs) StubsSrcJar() android.Path {
 	return d.stubsSrcJar
 }
 
+func (d *Droidstubs) ExportableStubsSrcJar() android.Path {
+	return d.exportableStubsSrcJar
+}
+
+func (d *Droidstubs) StubsSrcJarWithStubsType(stubsType StubsType) (android.Paths, error) {
+	switch stubsType {
+	case Everything:
+		return android.Paths{d.StubsSrcJar()}, nil
+	case Exportable:
+		return android.Paths{d.ExportableStubsSrcJar()}, nil
+	default:
+		return nil, fmt.Errorf("stubs srcjar not supported for the stub type %s", stubsType.String())
+	}
+}
+
 func (d *Droidstubs) CurrentApiTimestamp() android.Path {
 	return d.checkCurrentApiTimestamp
 }