Add helper functions for getting output files from modules

Add OutputFileForModule and OutputFilesForModules to get paths from
OutputFileProducers.

Bug: 122332855
Test: m checkbuild
Change-Id: I2e9aeeb55987742077250390cdb804ba22e79442

android/module.go

@@ -1803,6 +1803,49 @@ type OutputFileProducer interface {
 	OutputFiles(tag string) (Paths, error)
 }
 
+// OutputFilesForModule returns the paths from an OutputFileProducer with the given tag.  On error, including if the
+// module produced zero paths, it reports errors to the ctx and returns nil.
+func OutputFilesForModule(ctx PathContext, module blueprint.Module, tag string) Paths {
+	paths, err := outputFilesForModule(ctx, module, tag)
+	if err != nil {
+		reportPathError(ctx, err)
+		return nil
+	}
+	return paths
+}
+
+// OutputFileForModule returns the path from an OutputFileProducer with the given tag.  On error, including if the
+// module produced zero or multiple paths, it reports errors to the ctx and returns nil.
+func OutputFileForModule(ctx PathContext, module blueprint.Module, tag string) Path {
+	paths, err := outputFilesForModule(ctx, module, tag)
+	if err != nil {
+		reportPathError(ctx, err)
+		return nil
+	}
+	if len(paths) > 1 {
+		reportPathErrorf(ctx, "got multiple output files from module %q, expected exactly one",
+			pathContextName(ctx, module))
+		return nil
+	}
+	return paths[0]
+}
+
+func outputFilesForModule(ctx PathContext, module blueprint.Module, tag string) (Paths, error) {
+	if outputFileProducer, ok := module.(OutputFileProducer); ok {
+		paths, err := outputFileProducer.OutputFiles(tag)
+		if err != nil {
+			return nil, fmt.Errorf("failed to get output file from module %q: %s",
+				pathContextName(ctx, module), err.Error())
+		}
+		if len(paths) == 0 {
+			return nil, fmt.Errorf("failed to get output files from module %q", pathContextName(ctx, module))
+		}
+		return paths, nil
+	} else {
+		return nil, fmt.Errorf("module %q is not an OutputFileProducer", pathContextName(ctx, module))
+	}
+}
+
 type HostToolProvider interface {
 	HostToolPath() OptionalPath
 }

android/paths.go

@@ -89,6 +89,15 @@ func reportPathErrorf(ctx PathContext, format string, args ...interface{}) {
 	}
 }
 
+func pathContextName(ctx PathContext, module blueprint.Module) string {
+	if x, ok := ctx.(interface{ ModuleName(blueprint.Module) string }); ok {
+		return x.ModuleName(module)
+	} else if x, ok := ctx.(interface{ OtherModuleName(blueprint.Module) string }); ok {
+		return x.OtherModuleName(module)
+	}
+	return "unknown"
+}
+
 type Path interface {
 	// Returns the path in string form
 	String() string