diff --git a/Android.bp b/Android.bp
index d32c957..886d63d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -56,6 +56,7 @@
         "android/prebuilt.go",
         "android/proto.go",
         "android/register.go",
+        "android/singleton.go",
         "android/testing.go",
         "android/util.go",
         "android/variable.go",
diff --git a/android/androidmk.go b/android/androidmk.go
index 19d5ea6..aff43fa 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -53,13 +53,13 @@
 
 type AndroidMkExtraFunc func(w io.Writer, outputFile Path)
 
-func AndroidMkSingleton() blueprint.Singleton {
+func AndroidMkSingleton() Singleton {
 	return &androidMkSingleton{}
 }
 
 type androidMkSingleton struct{}
 
-func (c *androidMkSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
+func (c *androidMkSingleton) GenerateBuildActions(ctx SingletonContext) {
 	config := ctx.Config().(Config)
 
 	if !config.EmbeddedInMake() {
@@ -68,10 +68,8 @@
 
 	var androidMkModulesList []Module
 
-	ctx.VisitAllModules(func(module blueprint.Module) {
-		if amod, ok := module.(Module); ok {
-			androidMkModulesList = append(androidMkModulesList, amod)
-		}
+	ctx.VisitAllModules(func(module Module) {
+		androidMkModulesList = append(androidMkModulesList, module)
 	})
 
 	sort.Sort(AndroidModulesByName{androidMkModulesList, ctx})
@@ -86,14 +84,13 @@
 		ctx.Errorf(err.Error())
 	}
 
-	ctx.Build(pctx, blueprint.BuildParams{
-		Rule:     blueprint.Phony,
-		Outputs:  []string{transMk.String()},
-		Optional: true,
+	ctx.Build(pctx, BuildParams{
+		Rule:   blueprint.Phony,
+		Output: transMk,
 	})
 }
 
-func translateAndroidMk(ctx blueprint.SingletonContext, mkFile string, mods []Module) error {
+func translateAndroidMk(ctx SingletonContext, mkFile string, mods []Module) error {
 	buf := &bytes.Buffer{}
 
 	fmt.Fprintln(buf, "LOCAL_MODULE_MAKEFILE := $(lastword $(MAKEFILE_LIST))")
@@ -145,7 +142,7 @@
 	return ioutil.WriteFile(mkFile, buf.Bytes(), 0666)
 }
 
-func translateAndroidMkModule(ctx blueprint.SingletonContext, w io.Writer, mod blueprint.Module) error {
+func translateAndroidMkModule(ctx SingletonContext, w io.Writer, mod blueprint.Module) error {
 	provider, ok := mod.(AndroidMkDataProvider)
 	if !ok {
 		return nil
diff --git a/android/api_levels.go b/android/api_levels.go
index 2c4ae1a..bdfbc43 100644
--- a/android/api_levels.go
+++ b/android/api_levels.go
@@ -16,22 +16,19 @@
 
 import (
 	"encoding/json"
-	"path/filepath"
-
-	"github.com/google/blueprint"
 )
 
 func init() {
 	RegisterSingletonType("api_levels", ApiLevelsSingleton)
 }
 
-func ApiLevelsSingleton() blueprint.Singleton {
+func ApiLevelsSingleton() Singleton {
 	return &apiLevelsSingleton{}
 }
 
 type apiLevelsSingleton struct{}
 
-func createApiLevelsJson(ctx blueprint.SingletonContext, file string,
+func createApiLevelsJson(ctx SingletonContext, file WritablePath,
 	apiLevelsMap map[string]int) {
 
 	jsonStr, err := json.Marshal(apiLevelsMap)
@@ -39,21 +36,21 @@
 		ctx.Errorf(err.Error())
 	}
 
-	ctx.Build(pctx, blueprint.BuildParams{
+	ctx.Build(pctx, BuildParams{
 		Rule:        WriteFile,
-		Description: "generate " + filepath.Base(file),
-		Outputs:     []string{file},
+		Description: "generate " + file.Base(),
+		Output:      file,
 		Args: map[string]string{
 			"content": string(jsonStr[:]),
 		},
 	})
 }
 
-func GetApiLevelsJson(ctx PathContext) Path {
+func GetApiLevelsJson(ctx PathContext) WritablePath {
 	return PathForOutput(ctx, "api_levels.json")
 }
 
-func (a *apiLevelsSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
+func (a *apiLevelsSingleton) GenerateBuildActions(ctx SingletonContext) {
 	baseApiLevel := 9000
 	apiLevelsMap := map[string]int{
 		"G":     9,
@@ -74,5 +71,5 @@
 	}
 
 	apiLevelsJson := GetApiLevelsJson(ctx)
-	createApiLevelsJson(ctx, apiLevelsJson.String(), apiLevelsMap)
+	createApiLevelsJson(ctx, apiLevelsJson, apiLevelsMap)
 }
diff --git a/android/makevars.go b/android/makevars.go
index 024e015..d323613 100644
--- a/android/makevars.go
+++ b/android/makevars.go
@@ -21,7 +21,6 @@
 	"os"
 	"strconv"
 
-	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 )
 
@@ -66,7 +65,7 @@
 
 type MakeVarsProvider func(ctx MakeVarsContext)
 
-func RegisterMakeVarsProvider(pctx blueprint.PackageContext, provider MakeVarsProvider) {
+func RegisterMakeVarsProvider(pctx PackageContext, provider MakeVarsProvider) {
 	makeVarsProviders = append(makeVarsProviders, makeVarsProvider{pctx, provider})
 }
 
@@ -76,14 +75,14 @@
 	RegisterSingletonType("makevars", makeVarsSingletonFunc)
 }
 
-func makeVarsSingletonFunc() blueprint.Singleton {
+func makeVarsSingletonFunc() Singleton {
 	return &makeVarsSingleton{}
 }
 
 type makeVarsSingleton struct{}
 
 type makeVarsProvider struct {
-	pctx blueprint.PackageContext
+	pctx PackageContext
 	call MakeVarsProvider
 }
 
@@ -91,8 +90,8 @@
 
 type makeVarsContext struct {
 	config Config
-	ctx    blueprint.SingletonContext
-	pctx   blueprint.PackageContext
+	ctx    SingletonContext
+	pctx   PackageContext
 	vars   []makeVarsVariable
 }
 
@@ -105,7 +104,7 @@
 	strict bool
 }
 
-func (s *makeVarsSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
+func (s *makeVarsSingleton) GenerateBuildActions(ctx SingletonContext) {
 	config := ctx.Config().(Config)
 
 	if !config.EmbeddedInMake() {
diff --git a/android/module.go b/android/module.go
index 66859fa..0eb4820 100644
--- a/android/module.go
+++ b/android/module.go
@@ -17,6 +17,7 @@
 import (
 	"fmt"
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"github.com/google/blueprint"
@@ -78,7 +79,7 @@
 	blueprint.BaseModuleContext
 
 	// Deprecated: use ModuleContext.Build instead.
-	ModuleBuild(pctx blueprint.PackageContext, params ModuleBuildParams)
+	ModuleBuild(pctx PackageContext, params ModuleBuildParams)
 
 	ExpandSources(srcFiles, excludes []string) Paths
 	ExpandSourcesSubDir(srcFiles, excludes []string, subDir string) Paths
@@ -115,15 +116,15 @@
 	VisitDepsDepthFirstIf(pred func(Module) bool, visit func(Module))
 	WalkDeps(visit func(Module, Module) bool)
 
-	Variable(pctx blueprint.PackageContext, name, value string)
-	Rule(pctx blueprint.PackageContext, name string, params blueprint.RuleParams, argNames ...string) blueprint.Rule
+	Variable(pctx PackageContext, name, value string)
+	Rule(pctx PackageContext, name string, params blueprint.RuleParams, argNames ...string) blueprint.Rule
 	// Similar to blueprint.ModuleContext.Build, but takes Paths instead of []string,
 	// and performs more verification.
-	Build(pctx blueprint.PackageContext, params BuildParams)
+	Build(pctx PackageContext, params BuildParams)
 
-	PrimaryModule() blueprint.Module
-	FinalModule() blueprint.Module
-	VisitAllModuleVariants(visit func(blueprint.Module))
+	PrimaryModule() Module
+	FinalModule() Module
+	VisitAllModuleVariants(visit func(Module))
 
 	GetMissingDependencies() []string
 }
@@ -325,8 +326,8 @@
 
 	// Used by buildTargetSingleton to create checkbuild and per-directory build targets
 	// Only set on the final variant of each module
-	installTarget    string
-	checkbuildTarget string
+	installTarget    WritablePath
+	checkbuildTarget WritablePath
 	blueprintDir     string
 
 	hooks hooks
@@ -464,36 +465,35 @@
 	return false
 }
 
-func (a *ModuleBase) generateModuleTarget(ctx blueprint.ModuleContext) {
+func (a *ModuleBase) generateModuleTarget(ctx ModuleContext) {
 	allInstalledFiles := Paths{}
 	allCheckbuildFiles := Paths{}
-	ctx.VisitAllModuleVariants(func(module blueprint.Module) {
-		a := module.(Module).base()
+	ctx.VisitAllModuleVariants(func(module Module) {
+		a := module.base()
 		allInstalledFiles = append(allInstalledFiles, a.installFiles...)
 		allCheckbuildFiles = append(allCheckbuildFiles, a.checkbuildFiles...)
 	})
 
-	deps := []string{}
+	var deps Paths
 
 	if len(allInstalledFiles) > 0 {
-		name := ctx.ModuleName() + "-install"
-		ctx.Build(pctx, blueprint.BuildParams{
+		name := PathForPhony(ctx, ctx.ModuleName()+"-install")
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{name},
-			Implicits: allInstalledFiles.Strings(),
-			Optional:  ctx.Config().(Config).EmbeddedInMake(),
+			Output:    name,
+			Implicits: allInstalledFiles,
+			Default:   !ctx.Config().(Config).EmbeddedInMake(),
 		})
 		deps = append(deps, name)
 		a.installTarget = name
 	}
 
 	if len(allCheckbuildFiles) > 0 {
-		name := ctx.ModuleName() + "-checkbuild"
-		ctx.Build(pctx, blueprint.BuildParams{
+		name := PathForPhony(ctx, ctx.ModuleName()+"-checkbuild")
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{name},
-			Implicits: allCheckbuildFiles.Strings(),
-			Optional:  true,
+			Output:    name,
+			Implicits: allCheckbuildFiles,
 		})
 		deps = append(deps, name)
 		a.checkbuildTarget = name
@@ -505,11 +505,10 @@
 			suffix = "-soong"
 		}
 
-		ctx.Build(pctx, blueprint.BuildParams{
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{ctx.ModuleName() + suffix},
+			Output:    PathForPhony(ctx, ctx.ModuleName()+suffix),
 			Implicits: deps,
-			Optional:  true,
 		})
 
 		a.blueprintDir = ctx.ModuleDir()
@@ -525,23 +524,23 @@
 	}
 }
 
-func (a *ModuleBase) GenerateBuildActions(ctx blueprint.ModuleContext) {
-	androidCtx := &androidModuleContext{
+func (a *ModuleBase) GenerateBuildActions(blueprintCtx blueprint.ModuleContext) {
+	ctx := &androidModuleContext{
 		module:                 a.module,
-		ModuleContext:          ctx,
-		androidBaseContextImpl: a.androidBaseContextFactory(ctx),
-		installDeps:            a.computeInstallDeps(ctx),
+		ModuleContext:          blueprintCtx,
+		androidBaseContextImpl: a.androidBaseContextFactory(blueprintCtx),
+		installDeps:            a.computeInstallDeps(blueprintCtx),
 		installFiles:           a.installFiles,
-		missingDeps:            ctx.GetMissingDependencies(),
+		missingDeps:            blueprintCtx.GetMissingDependencies(),
 	}
 
 	desc := "//" + ctx.ModuleDir() + ":" + ctx.ModuleName() + " "
 	var suffix []string
-	if androidCtx.Os().Class != Device && androidCtx.Os().Class != Generic {
-		suffix = append(suffix, androidCtx.Os().String())
+	if ctx.Os().Class != Device && ctx.Os().Class != Generic {
+		suffix = append(suffix, ctx.Os().String())
 	}
-	if !androidCtx.PrimaryArch() {
-		suffix = append(suffix, androidCtx.Arch().ArchType.String())
+	if !ctx.PrimaryArch() {
+		suffix = append(suffix, ctx.Arch().ArchType.String())
 	}
 
 	ctx.Variable(pctx, "moduleDesc", desc)
@@ -553,13 +552,13 @@
 	ctx.Variable(pctx, "moduleDescSuffix", s)
 
 	if a.Enabled() {
-		a.module.GenerateAndroidBuildActions(androidCtx)
+		a.module.GenerateAndroidBuildActions(ctx)
 		if ctx.Failed() {
 			return
 		}
 
-		a.installFiles = append(a.installFiles, androidCtx.installFiles...)
-		a.checkbuildFiles = append(a.checkbuildFiles, androidCtx.checkbuildFiles...)
+		a.installFiles = append(a.installFiles, ctx.installFiles...)
+		a.checkbuildFiles = append(a.checkbuildFiles, ctx.checkbuildFiles...)
 	}
 
 	if a == ctx.FinalModule().(Module).base() {
@@ -569,7 +568,7 @@
 		}
 	}
 
-	a.buildParams = androidCtx.buildParams
+	a.buildParams = ctx.buildParams
 }
 
 type androidBaseContextImpl struct {
@@ -594,7 +593,7 @@
 }
 
 func (a *androidModuleContext) ninjaError(desc string, outputs []string, err error) {
-	a.ModuleContext.Build(pctx, blueprint.BuildParams{
+	a.ModuleContext.Build(pctx.PackageContext, blueprint.BuildParams{
 		Rule:        ErrorRule,
 		Description: desc,
 		Outputs:     outputs,
@@ -606,17 +605,14 @@
 	return
 }
 
-func (a *androidModuleContext) ModuleBuild(pctx blueprint.PackageContext, params ModuleBuildParams) {
+func (a *androidModuleContext) ModuleBuild(pctx PackageContext, params ModuleBuildParams) {
 	a.Build(pctx, BuildParams(params))
 }
 
-func (a *androidModuleContext) Build(pctx blueprint.PackageContext, params BuildParams) {
-	if a.config.captureBuild {
-		a.buildParams = append(a.buildParams, params)
-	}
-
+func convertBuildParams(params BuildParams) blueprint.BuildParams {
 	bparams := blueprint.BuildParams{
 		Rule:            params.Rule,
+		Description:     params.Description,
 		Deps:            params.Deps,
 		Outputs:         params.Outputs.Strings(),
 		ImplicitOutputs: params.ImplicitOutputs.Strings(),
@@ -627,10 +623,6 @@
 		Optional:        !params.Default,
 	}
 
-	if params.Description != "" {
-		bparams.Description = "${moduleDesc}" + params.Description + "${moduleDescSuffix}"
-	}
-
 	if params.Depfile != nil {
 		bparams.Depfile = params.Depfile.String()
 	}
@@ -647,6 +639,30 @@
 		bparams.Implicits = append(bparams.Implicits, params.Implicit.String())
 	}
 
+	return bparams
+}
+
+func (a *androidModuleContext) Variable(pctx PackageContext, name, value string) {
+	a.ModuleContext.Variable(pctx.PackageContext, name, value)
+}
+
+func (a *androidModuleContext) Rule(pctx PackageContext, name string, params blueprint.RuleParams,
+	argNames ...string) blueprint.Rule {
+
+	return a.ModuleContext.Rule(pctx.PackageContext, name, params, argNames...)
+}
+
+func (a *androidModuleContext) Build(pctx PackageContext, params BuildParams) {
+	if a.config.captureBuild {
+		a.buildParams = append(a.buildParams, params)
+	}
+
+	bparams := convertBuildParams(params)
+
+	if bparams.Description != "" {
+		bparams.Description = "${moduleDesc}" + params.Description + "${moduleDescSuffix}"
+	}
+
 	if a.missingDeps != nil {
 		a.ninjaError(bparams.Description, bparams.Outputs,
 			fmt.Errorf("module %s missing dependencies: %s\n",
@@ -654,7 +670,7 @@
 		return
 	}
 
-	a.ModuleContext.Build(pctx, bparams)
+	a.ModuleContext.Build(pctx.PackageContext, bparams)
 }
 
 func (a *androidModuleContext) GetMissingDependencies() []string {
@@ -751,6 +767,20 @@
 	})
 }
 
+func (a *androidModuleContext) VisitAllModuleVariants(visit func(Module)) {
+	a.ModuleContext.VisitAllModuleVariants(func(module blueprint.Module) {
+		visit(module.(Module))
+	})
+}
+
+func (a *androidModuleContext) PrimaryModule() Module {
+	return a.ModuleContext.PrimaryModule().(Module)
+}
+
+func (a *androidModuleContext) FinalModule() Module {
+	return a.ModuleContext.FinalModule().(Module)
+}
+
 func (a *androidBaseContextImpl) Target() Target {
 	return a.target
 }
@@ -1027,7 +1057,7 @@
 	RegisterSingletonType("buildtarget", BuildTargetSingleton)
 }
 
-func BuildTargetSingleton() blueprint.Singleton {
+func BuildTargetSingleton() Singleton {
 	return &buildTargetSingleton{}
 }
 
@@ -1038,29 +1068,28 @@
 
 type buildTargetSingleton struct{}
 
-func (c *buildTargetSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
-	checkbuildDeps := []string{}
+func (c *buildTargetSingleton) GenerateBuildActions(ctx SingletonContext) {
+	var checkbuildDeps Paths
 
-	mmTarget := func(dir string) string {
-		return "MODULES-IN-" + strings.Replace(filepath.Clean(dir), "/", "-", -1)
+	mmTarget := func(dir string) WritablePath {
+		return PathForPhony(ctx,
+			"MODULES-IN-"+strings.Replace(filepath.Clean(dir), "/", "-", -1))
 	}
 
-	modulesInDir := make(map[string][]string)
+	modulesInDir := make(map[string]Paths)
 
-	ctx.VisitAllModules(func(module blueprint.Module) {
-		if a, ok := module.(Module); ok {
-			blueprintDir := a.base().blueprintDir
-			installTarget := a.base().installTarget
-			checkbuildTarget := a.base().checkbuildTarget
+	ctx.VisitAllModules(func(module Module) {
+		blueprintDir := module.base().blueprintDir
+		installTarget := module.base().installTarget
+		checkbuildTarget := module.base().checkbuildTarget
 
-			if checkbuildTarget != "" {
-				checkbuildDeps = append(checkbuildDeps, checkbuildTarget)
-				modulesInDir[blueprintDir] = append(modulesInDir[blueprintDir], checkbuildTarget)
-			}
+		if checkbuildTarget != nil {
+			checkbuildDeps = append(checkbuildDeps, checkbuildTarget)
+			modulesInDir[blueprintDir] = append(modulesInDir[blueprintDir], checkbuildTarget)
+		}
 
-			if installTarget != "" {
-				modulesInDir[blueprintDir] = append(modulesInDir[blueprintDir], installTarget)
-			}
+		if installTarget != nil {
+			modulesInDir[blueprintDir] = append(modulesInDir[blueprintDir], installTarget)
 		}
 	})
 
@@ -1070,11 +1099,10 @@
 	}
 
 	// Create a top-level checkbuild target that depends on all modules
-	ctx.Build(pctx, blueprint.BuildParams{
+	ctx.Build(pctx, BuildParams{
 		Rule:      blueprint.Phony,
-		Outputs:   []string{"checkbuild" + suffix},
+		Output:    PathForPhony(ctx, "checkbuild"+suffix),
 		Implicits: checkbuildDeps,
-		Optional:  true,
 	})
 
 	// Make will generate the MODULES-IN-* targets
@@ -1082,6 +1110,15 @@
 		return
 	}
 
+	sortedKeys := func(m map[string]Paths) []string {
+		s := make([]string, 0, len(m))
+		for k := range m {
+			s = append(s, k)
+		}
+		sort.Strings(s)
+		return s
+	}
+
 	// Ensure ancestor directories are in modulesInDir
 	dirs := sortedKeys(modulesInDir)
 	for _, dir := range dirs {
@@ -1108,28 +1145,26 @@
 	// depends on the MODULES-IN-* targets of all of its subdirectories that contain Android.bp
 	// files.
 	for _, dir := range dirs {
-		ctx.Build(pctx, blueprint.BuildParams{
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{mmTarget(dir)},
+			Output:    mmTarget(dir),
 			Implicits: modulesInDir[dir],
 			// HACK: checkbuild should be an optional build, but force it
 			// enabled for now in standalone builds
-			Optional: ctx.Config().(Config).EmbeddedInMake(),
+			Default: !ctx.Config().(Config).EmbeddedInMake(),
 		})
 	}
 
 	// Create (host|host-cross|target)-<OS> phony rules to build a reduced checkbuild.
 	osDeps := map[OsType]Paths{}
-	ctx.VisitAllModules(func(module blueprint.Module) {
-		if a, ok := module.(Module); ok {
-			if a.Enabled() {
-				os := a.Target().Os
-				osDeps[os] = append(osDeps[os], a.base().checkbuildFiles...)
-			}
+	ctx.VisitAllModules(func(module Module) {
+		if module.Enabled() {
+			os := module.Target().Os
+			osDeps[os] = append(osDeps[os], module.base().checkbuildFiles...)
 		}
 	})
 
-	osClass := make(map[string][]string)
+	osClass := make(map[string]Paths)
 	for os, deps := range osDeps {
 		var className string
 
@@ -1144,25 +1179,23 @@
 			continue
 		}
 
-		name := className + "-" + os.Name
+		name := PathForPhony(ctx, className+"-"+os.Name)
 		osClass[className] = append(osClass[className], name)
 
-		ctx.Build(pctx, blueprint.BuildParams{
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{name},
-			Implicits: deps.Strings(),
-			Optional:  true,
+			Output:    name,
+			Implicits: deps,
 		})
 	}
 
 	// Wrap those into host|host-cross|target phony rules
 	osClasses := sortedKeys(osClass)
 	for _, class := range osClasses {
-		ctx.Build(pctx, blueprint.BuildParams{
+		ctx.Build(pctx, BuildParams{
 			Rule:      blueprint.Phony,
-			Outputs:   []string{class},
+			Output:    PathForPhony(ctx, class),
 			Implicits: osClass[class],
-			Optional:  true,
 		})
 	}
 }
diff --git a/android/package_ctx.go b/android/package_ctx.go
index d32e82b..1626f76 100644
--- a/android/package_ctx.go
+++ b/android/package_ctx.go
@@ -22,14 +22,14 @@
 	"github.com/google/blueprint/pathtools"
 )
 
-// AndroidPackageContext is a wrapper for blueprint.PackageContext that adds
+// PackageContext is a wrapper for blueprint.PackageContext that adds
 // some android-specific helper functions.
-type AndroidPackageContext struct {
+type PackageContext struct {
 	blueprint.PackageContext
 }
 
-func NewPackageContext(pkgPath string) AndroidPackageContext {
-	return AndroidPackageContext{blueprint.NewPackageContext(pkgPath)}
+func NewPackageContext(pkgPath string) PackageContext {
+	return PackageContext{blueprint.NewPackageContext(pkgPath)}
 }
 
 // configErrorWrapper can be used with Path functions when a Context is not
@@ -39,7 +39,7 @@
 // The most common use here will be with VariableFunc, where only a config is
 // provided, and an error should be returned.
 type configErrorWrapper struct {
-	pctx   AndroidPackageContext
+	pctx   PackageContext
 	config Config
 	errors []error
 }
@@ -61,13 +61,43 @@
 	return nil
 }
 
+// VariableFunc wraps blueprint.PackageContext.VariableFunc, converting the interface{} config
+// argument to a Config.
+func (p PackageContext) VariableFunc(name string,
+	f func(Config) (string, error)) blueprint.Variable {
+
+	return p.PackageContext.VariableFunc(name, func(config interface{}) (string, error) {
+		return f(config.(Config))
+	})
+}
+
+// PoolFunc wraps blueprint.PackageContext.PoolFunc, converting the interface{} config
+// argument to a Config.
+func (p PackageContext) PoolFunc(name string,
+	f func(Config) (blueprint.PoolParams, error)) blueprint.Pool {
+
+	return p.PackageContext.PoolFunc(name, func(config interface{}) (blueprint.PoolParams, error) {
+		return f(config.(Config))
+	})
+}
+
+// RuleFunc wraps blueprint.PackageContext.RuleFunc, converting the interface{} config
+// argument to a Config.
+func (p PackageContext) RuleFunc(name string,
+	f func(Config) (blueprint.RuleParams, error), argNames ...string) blueprint.Rule {
+
+	return p.PackageContext.RuleFunc(name, func(config interface{}) (blueprint.RuleParams, error) {
+		return f(config.(Config))
+	}, argNames...)
+}
+
 // SourcePathVariable returns a Variable whose value is the source directory
 // appended with the supplied path. It may only be called during a Go package's
 // initialization - either from the init() function or as part of a
 // package-scoped variable's initialization.
-func (p AndroidPackageContext) SourcePathVariable(name, path string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) SourcePathVariable(name, path string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		p := safePathForSource(ctx, path)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]
@@ -80,9 +110,9 @@
 // appended with the supplied paths, joined with separator. It may only be
 // called during a Go package's initialization - either from the init()
 // function or as part of a package-scoped variable's initialization.
-func (p AndroidPackageContext) SourcePathsVariable(name, separator string, paths ...string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) SourcePathsVariable(name, separator string, paths ...string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		var ret []string
 		for _, path := range paths {
 			p := safePathForSource(ctx, path)
@@ -100,14 +130,14 @@
 // The environment variable is not required to point to a path inside the source tree.
 // It may only be called during a Go package's initialization - either from the init() function or
 // as part of a package-scoped variable's initialization.
-func (p AndroidPackageContext) SourcePathVariableWithEnvOverride(name, path, env string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) SourcePathVariableWithEnvOverride(name, path, env string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		p := safePathForSource(ctx, path)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]
 		}
-		return config.(Config).GetenvWithDefault(env, p.String()), nil
+		return config.GetenvWithDefault(env, p.String()), nil
 	})
 }
 
@@ -115,8 +145,8 @@
 // in the bin directory for host targets. It may only be called during a Go
 // package's initialization - either from the init() function or as part of a
 // package-scoped variable's initialization.
-func (p AndroidPackageContext) HostBinToolVariable(name, path string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
+func (p PackageContext) HostBinToolVariable(name, path string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
 		po, err := p.HostBinToolPath(config, path)
 		if err != nil {
 			return "", err
@@ -125,8 +155,8 @@
 	})
 }
 
-func (p AndroidPackageContext) HostBinToolPath(config interface{}, path string) (Path, error) {
-	ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) HostBinToolPath(config Config, path string) (Path, error) {
+	ctx := &configErrorWrapper{p, config, []error{}}
 	pa := PathForOutput(ctx, "host", ctx.config.PrebuiltOS(), "bin", path)
 	if len(ctx.errors) > 0 {
 		return nil, ctx.errors[0]
@@ -138,9 +168,9 @@
 // tool in the frameworks directory for host targets. It may only be called
 // during a Go package's initialization - either from the init() function or as
 // part of a package-scoped variable's initialization.
-func (p AndroidPackageContext) HostJavaToolVariable(name, path string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) HostJavaToolVariable(name, path string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		p := PathForOutput(ctx, "host", ctx.config.PrebuiltOS(), "framework", path)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]
@@ -149,8 +179,8 @@
 	})
 }
 
-func (p AndroidPackageContext) HostJavaToolPath(config interface{}, path string) (Path, error) {
-	ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) HostJavaToolPath(config Config, path string) (Path, error) {
+	ctx := &configErrorWrapper{p, config, []error{}}
 	pa := PathForOutput(ctx, "host", ctx.config.PrebuiltOS(), "framework", path)
 	if len(ctx.errors) > 0 {
 		return nil, ctx.errors[0]
@@ -162,9 +192,9 @@
 // directory appended with the supplied path. It may only be called during a Go
 // package's initialization - either from the init() function or as part of a
 // package-scoped variable's initialization.
-func (p AndroidPackageContext) IntermediatesPathVariable(name, path string) blueprint.Variable {
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+func (p PackageContext) IntermediatesPathVariable(name, path string) blueprint.Variable {
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		p := PathForIntermediates(ctx, path)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]
@@ -177,11 +207,11 @@
 // list of present source paths prefixed with the supplied prefix. It may only
 // be called during a Go package's initialization - either from the init()
 // function or as part of a package-scoped variable's initialization.
-func (p AndroidPackageContext) PrefixedExistentPathsForSourcesVariable(
+func (p PackageContext) PrefixedExistentPathsForSourcesVariable(
 	name, prefix string, paths []string) blueprint.Variable {
 
-	return p.VariableFunc(name, func(config interface{}) (string, error) {
-		ctx := &configErrorWrapper{p, config.(Config), []error{}}
+	return p.VariableFunc(name, func(config Config) (string, error) {
+		ctx := &configErrorWrapper{p, config, []error{}}
 		paths := ExistentPathsForSources(ctx, "", paths)
 		if len(ctx.errors) > 0 {
 			return "", ctx.errors[0]
@@ -196,7 +226,7 @@
 }
 
 // AndroidStaticRule wraps blueprint.StaticRule and provides a default Pool if none is specified
-func (p AndroidPackageContext) AndroidStaticRule(name string, params blueprint.RuleParams,
+func (p PackageContext) AndroidStaticRule(name string, params blueprint.RuleParams,
 	argNames ...string) blueprint.Rule {
 	return p.AndroidRuleFunc(name, func(Config) (blueprint.RuleParams, error) {
 		return params, nil
@@ -204,16 +234,16 @@
 }
 
 // AndroidGomaStaticRule wraps blueprint.StaticRule but uses goma's parallelism if goma is enabled
-func (p AndroidPackageContext) AndroidGomaStaticRule(name string, params blueprint.RuleParams,
+func (p PackageContext) AndroidGomaStaticRule(name string, params blueprint.RuleParams,
 	argNames ...string) blueprint.Rule {
 	return p.StaticRule(name, params, argNames...)
 }
 
-func (p AndroidPackageContext) AndroidRuleFunc(name string,
+func (p PackageContext) AndroidRuleFunc(name string,
 	f func(Config) (blueprint.RuleParams, error), argNames ...string) blueprint.Rule {
-	return p.PackageContext.RuleFunc(name, func(config interface{}) (blueprint.RuleParams, error) {
-		params, err := f(config.(Config))
-		if config.(Config).UseGoma() && params.Pool == nil {
+	return p.RuleFunc(name, func(config Config) (blueprint.RuleParams, error) {
+		params, err := f(config)
+		if config.UseGoma() && params.Pool == nil {
 			// When USE_GOMA=true is set and the rule is not supported by goma, restrict jobs to the
 			// local parallelism value
 			params.Pool = localPool
diff --git a/android/paths.go b/android/paths.go
index 4adaa2d..b2ee627 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -449,6 +449,10 @@
 	return p.path
 }
 
+func (p basePath) String() string {
+	return p.path
+}
+
 // SourcePath is a Path representing a file path rooted from SrcDir
 type SourcePath struct {
 	basePath
@@ -885,6 +889,13 @@
 	return validateSafePath(ctx, pathComponents...)
 }
 
+func PathForPhony(ctx PathContext, phony string) WritablePath {
+	if strings.ContainsAny(phony, "$/") {
+		reportPathError(ctx, "Phony target contains invalid character ($ or /): %s", phony)
+	}
+	return OutputPath{basePath{phony, pathConfig(ctx), ""}}
+}
+
 type testPath struct {
 	basePath
 }
diff --git a/android/register.go b/android/register.go
index 81a266d..78ae481 100644
--- a/android/register.go
+++ b/android/register.go
@@ -44,7 +44,7 @@
 
 type ModuleFactory func() Module
 
-// ModuleFactoryAdaptor Wraps a ModuleFactory into a blueprint.ModuleFactory by converting an Module
+// ModuleFactoryAdaptor wraps a ModuleFactory into a blueprint.ModuleFactory by converting a Module
 // into a blueprint.Module and a list of property structs
 func ModuleFactoryAdaptor(factory ModuleFactory) blueprint.ModuleFactory {
 	return func() (blueprint.Module, []interface{}) {
@@ -53,16 +53,27 @@
 	}
 }
 
+type SingletonFactory func() Singleton
+
+// SingletonFactoryAdaptor wraps a SingletonFactory into a blueprint.SingletonFactory by converting
+// a Singleton into a blueprint.Singleton
+func SingletonFactoryAdaptor(factory SingletonFactory) blueprint.SingletonFactory {
+	return func() blueprint.Singleton {
+		singleton := factory()
+		return singletonAdaptor{singleton}
+	}
+}
+
 func RegisterModuleType(name string, factory ModuleFactory) {
 	moduleTypes = append(moduleTypes, moduleType{name, ModuleFactoryAdaptor(factory)})
 }
 
-func RegisterSingletonType(name string, factory blueprint.SingletonFactory) {
-	singletons = append(singletons, singleton{name, factory})
+func RegisterSingletonType(name string, factory SingletonFactory) {
+	singletons = append(singletons, singleton{name, SingletonFactoryAdaptor(factory)})
 }
 
-func RegisterPreSingletonType(name string, factory blueprint.SingletonFactory) {
-	preSingletons = append(preSingletons, singleton{name, factory})
+func RegisterPreSingletonType(name string, factory SingletonFactory) {
+	preSingletons = append(preSingletons, singleton{name, SingletonFactoryAdaptor(factory)})
 }
 
 type Context struct {
diff --git a/android/singleton.go b/android/singleton.go
new file mode 100644
index 0000000..f2f575f
--- /dev/null
+++ b/android/singleton.go
@@ -0,0 +1,162 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+import (
+	"github.com/google/blueprint"
+	"github.com/google/blueprint/pathtools"
+)
+
+// SingletonContext
+type SingletonContext interface {
+	// TODO(ccross): make this return an android.Config
+	Config() interface{}
+
+	ModuleName(module blueprint.Module) string
+	ModuleDir(module blueprint.Module) string
+	ModuleSubDir(module blueprint.Module) string
+	ModuleType(module blueprint.Module) string
+	BlueprintFile(module blueprint.Module) string
+
+	ModuleErrorf(module blueprint.Module, format string, args ...interface{})
+	Errorf(format string, args ...interface{})
+	Failed() bool
+
+	Variable(pctx PackageContext, name, value string)
+	Rule(pctx PackageContext, name string, params RuleParams, argNames ...string) blueprint.Rule
+	Build(pctx PackageContext, params BuildParams)
+	RequireNinjaVersion(major, minor, micro int)
+
+	// SetNinjaBuildDir sets the value of the top-level "builddir" Ninja variable
+	// that controls where Ninja stores its build log files.  This value can be
+	// set at most one time for a single build, later calls are ignored.
+	SetNinjaBuildDir(pctx PackageContext, value string)
+
+	// Eval takes a string with embedded ninja variables, and returns a string
+	// with all of the variables recursively expanded. Any variables references
+	// are expanded in the scope of the PackageContext.
+	Eval(pctx PackageContext, ninjaStr string) (string, error)
+
+	VisitAllModules(visit func(Module))
+	VisitAllModulesIf(pred func(Module) bool, visit func(Module))
+	VisitDepsDepthFirst(module Module, visit func(Module))
+	VisitDepsDepthFirstIf(module Module, pred func(Module) bool,
+		visit func(Module))
+
+	VisitAllModuleVariants(module Module, visit func(Module))
+
+	PrimaryModule(module Module) Module
+	FinalModule(module Module) Module
+
+	AddNinjaFileDeps(deps ...string)
+
+	// GlobWithDeps returns a list of files that match the specified pattern but do not match any
+	// of the patterns in excludes.  It also adds efficient dependencies to rerun the primary
+	// builder whenever a file matching the pattern as added or removed, without rerunning if a
+	// file that does not match the pattern is added to a searched directory.
+	GlobWithDeps(pattern string, excludes []string) ([]string, error)
+
+	Fs() pathtools.FileSystem
+}
+
+type singletonAdaptor struct {
+	Singleton
+}
+
+func (s singletonAdaptor) GenerateBuildActions(ctx blueprint.SingletonContext) {
+	s.Singleton.GenerateBuildActions(singletonContextAdaptor{ctx})
+}
+
+type Singleton interface {
+	GenerateBuildActions(SingletonContext)
+}
+
+type singletonContextAdaptor struct {
+	blueprint.SingletonContext
+}
+
+func (s singletonContextAdaptor) Variable(pctx PackageContext, name, value string) {
+	s.SingletonContext.Variable(pctx.PackageContext, name, value)
+}
+
+func (s singletonContextAdaptor) Rule(pctx PackageContext, name string, params RuleParams, argNames ...string) blueprint.Rule {
+	return s.SingletonContext.Rule(pctx.PackageContext, name, params.RuleParams, argNames...)
+}
+
+func (s singletonContextAdaptor) Build(pctx PackageContext, params BuildParams) {
+	bparams := convertBuildParams(params)
+	s.SingletonContext.Build(pctx.PackageContext, bparams)
+
+}
+
+func (s singletonContextAdaptor) SetNinjaBuildDir(pctx PackageContext, value string) {
+	s.SingletonContext.SetNinjaBuildDir(pctx.PackageContext, value)
+}
+
+func (s singletonContextAdaptor) Eval(pctx PackageContext, ninjaStr string) (string, error) {
+	return s.SingletonContext.Eval(pctx.PackageContext, ninjaStr)
+}
+
+// visitAdaptor wraps a visit function that takes an android.Module parameter into
+// a function that takes an blueprint.Module parameter and only calls the visit function if the
+// blueprint.Module is an android.Module.
+func visitAdaptor(visit func(Module)) func(blueprint.Module) {
+	return func(module blueprint.Module) {
+		if aModule, ok := module.(Module); ok {
+			visit(aModule)
+		}
+	}
+}
+
+// predAdaptor wraps a pred function that takes an android.Module parameter
+// into a function that takes an blueprint.Module parameter and only calls the visit function if the
+// blueprint.Module is an android.Module, otherwise returns false.
+func predAdaptor(pred func(Module) bool) func(blueprint.Module) bool {
+	return func(module blueprint.Module) bool {
+		if aModule, ok := module.(Module); ok {
+			return pred(aModule)
+		} else {
+			return false
+		}
+	}
+}
+
+func (s singletonContextAdaptor) VisitAllModules(visit func(Module)) {
+	s.SingletonContext.VisitAllModules(visitAdaptor(visit))
+}
+
+func (s singletonContextAdaptor) VisitAllModulesIf(pred func(Module) bool, visit func(Module)) {
+	s.SingletonContext.VisitAllModulesIf(predAdaptor(pred), visitAdaptor(visit))
+}
+
+func (s singletonContextAdaptor) VisitDepsDepthFirst(module Module, visit func(Module)) {
+	s.SingletonContext.VisitDepsDepthFirst(module, visitAdaptor(visit))
+}
+
+func (s singletonContextAdaptor) VisitDepsDepthFirstIf(module Module, pred func(Module) bool, visit func(Module)) {
+	s.SingletonContext.VisitDepsDepthFirstIf(module, predAdaptor(pred), visitAdaptor(visit))
+}
+
+func (s singletonContextAdaptor) VisitAllModuleVariants(module Module, visit func(Module)) {
+	s.SingletonContext.VisitAllModuleVariants(module, visitAdaptor(visit))
+}
+
+func (s singletonContextAdaptor) PrimaryModule(module Module) Module {
+	return s.SingletonContext.PrimaryModule(module).(Module)
+}
+
+func (s singletonContextAdaptor) FinalModule(module Module) Module {
+	return s.SingletonContext.FinalModule(module).(Module)
+}
diff --git a/cc/androidmk.go b/cc/androidmk.go
index 065d0aa..44e977f 100644
--- a/cc/androidmk.go
+++ b/cc/androidmk.go
@@ -318,7 +318,7 @@
 	ret.Class = "SHARED_LIBRARIES"
 
 	ret.Extra = append(ret.Extra, func(w io.Writer, outputFile android.Path) {
-		path, file := filepath.Split(c.installPath)
+		path, file := filepath.Split(c.installPath.String())
 		stem := strings.TrimSuffix(file, filepath.Ext(file))
 		fmt.Fprintln(w, "LOCAL_SYSTEM_SHARED_LIBRARIES :=")
 		fmt.Fprintln(w, "LOCAL_MODULE_SUFFIX := "+outputFile.Ext())
diff --git a/cc/cmakelists.go b/cc/cmakelists.go
index 13a2e8e..9b32182 100644
--- a/cc/cmakelists.go
+++ b/cc/cmakelists.go
@@ -23,8 +23,6 @@
 	"path"
 	"path/filepath"
 	"strings"
-
-	"github.com/google/blueprint"
 )
 
 // This singleton generates CMakeLists.txt files. It does so for each blueprint Android.bp resulting in a cc.Module
@@ -35,7 +33,7 @@
 	android.RegisterSingletonType("cmakelists_generator", cMakeListsGeneratorSingleton)
 }
 
-func cMakeListsGeneratorSingleton() blueprint.Singleton {
+func cMakeListsGeneratorSingleton() android.Singleton {
 	return &cmakelistsGeneratorSingleton{}
 }
 
@@ -57,14 +55,14 @@
 // This is done to ease investigating bug reports.
 var outputDebugInfo = false
 
-func (c *cmakelistsGeneratorSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
+func (c *cmakelistsGeneratorSingleton) GenerateBuildActions(ctx android.SingletonContext) {
 	if getEnvVariable(envVariableGenerateCMakeLists, ctx) != envVariableTrue {
 		return
 	}
 
 	outputDebugInfo = (getEnvVariable(envVariableGenerateDebugInfo, ctx) == envVariableTrue)
 
-	ctx.VisitAllModules(func(module blueprint.Module) {
+	ctx.VisitAllModules(func(module android.Module) {
 		if ccModule, ok := module.(*Module); ok {
 			if compiledModule, ok := ccModule.compiler.(CompiledInterface); ok {
 				generateCLionProject(compiledModule, ctx, ccModule)
@@ -81,7 +79,7 @@
 	return
 }
 
-func getEnvVariable(name string, ctx blueprint.SingletonContext) string {
+func getEnvVariable(name string, ctx android.SingletonContext) string {
 	// Using android.Config.Getenv instead of os.getEnv to guarantee soong will
 	// re-run in case this environment variable changes.
 	return ctx.Config().(android.Config).Getenv(name)
@@ -116,7 +114,7 @@
 	return nil
 }
 
-func generateCLionProject(compiledModule CompiledInterface, ctx blueprint.SingletonContext, ccModule *Module) {
+func generateCLionProject(compiledModule CompiledInterface, ctx android.SingletonContext, ccModule *Module) {
 	srcs := compiledModule.Srcs()
 	if len(srcs) == 0 {
 		return
@@ -287,7 +285,7 @@
 	return flag
 }
 
-func parseCompilerParameters(params []string, ctx blueprint.SingletonContext, f *os.File) compilerParameters {
+func parseCompilerParameters(params []string, ctx android.SingletonContext, f *os.File) compilerParameters {
 	var compilerParameters = makeCompilerParameters()
 
 	for i, str := range params {
@@ -388,7 +386,7 @@
 	c1.flags = append(c1.flags, c2.flags...)
 }
 
-func evalVariable(ctx blueprint.SingletonContext, str string) (string, error) {
+func evalVariable(ctx android.SingletonContext, str string) (string, error) {
 	evaluated, err := ctx.Eval(pctx, str)
 	if err == nil {
 		return evaluated, nil
@@ -396,7 +394,7 @@
 	return "", err
 }
 
-func getCMakeListsForModule(module *Module, ctx blueprint.SingletonContext) string {
+func getCMakeListsForModule(module *Module, ctx android.SingletonContext) string {
 	return filepath.Join(getAndroidSrcRootDirectory(ctx),
 		cLionOutputProjectsDirectory,
 		path.Dir(ctx.BlueprintFile(module)),
@@ -406,7 +404,7 @@
 		cMakeListsFilename)
 }
 
-func getAndroidSrcRootDirectory(ctx blueprint.SingletonContext) string {
+func getAndroidSrcRootDirectory(ctx android.SingletonContext) string {
 	srcPath, _ := filepath.Abs(android.PathForSource(ctx).String())
 	return srcPath
 }
diff --git a/cc/config/global.go b/cc/config/global.go
index 4322436..8881b4b 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -216,14 +216,14 @@
 		[]string{"libnativehelper/include_deprecated"})
 
 	pctx.SourcePathVariable("ClangDefaultBase", ClangDefaultBase)
-	pctx.VariableFunc("ClangBase", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("LLVM_PREBUILTS_BASE"); override != "" {
+	pctx.VariableFunc("ClangBase", func(config android.Config) (string, error) {
+		if override := config.Getenv("LLVM_PREBUILTS_BASE"); override != "" {
 			return override, nil
 		}
 		return "${ClangDefaultBase}", nil
 	})
-	pctx.VariableFunc("ClangVersion", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("LLVM_PREBUILTS_VERSION"); override != "" {
+	pctx.VariableFunc("ClangVersion", func(config android.Config) (string, error) {
+		if override := config.Getenv("LLVM_PREBUILTS_VERSION"); override != "" {
 			return override, nil
 		}
 		return ClangDefaultVersion, nil
@@ -231,8 +231,8 @@
 	pctx.StaticVariable("ClangPath", "${ClangBase}/${HostPrebuiltTag}/${ClangVersion}")
 	pctx.StaticVariable("ClangBin", "${ClangPath}/bin")
 
-	pctx.VariableFunc("ClangShortVersion", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("LLVM_RELEASE_VERSION"); override != "" {
+	pctx.VariableFunc("ClangShortVersion", func(config android.Config) (string, error) {
+		if override := config.Getenv("LLVM_RELEASE_VERSION"); override != "" {
 			return override, nil
 		}
 		return ClangDefaultShortVersion, nil
@@ -258,8 +258,8 @@
 			"frameworks/rs/script_api/include",
 		})
 
-	pctx.VariableFunc("CcWrapper", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("CC_WRAPPER"); override != "" {
+	pctx.VariableFunc("CcWrapper", func(config android.Config) (string, error) {
+		if override := config.Getenv("CC_WRAPPER"); override != "" {
 			return override + " ", nil
 		}
 		return "", nil
diff --git a/cc/config/tidy.go b/cc/config/tidy.go
index a2fa5a2..76a5f9e 100644
--- a/cc/config/tidy.go
+++ b/cc/config/tidy.go
@@ -25,8 +25,8 @@
 	// Global tidy checks include only google*, performance*,
 	// and misc-macro-parentheses, but not google-readability*
 	// or google-runtime-references.
-	pctx.VariableFunc("TidyDefaultGlobalChecks", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("DEFAULT_GLOBAL_TIDY_CHECKS"); override != "" {
+	pctx.VariableFunc("TidyDefaultGlobalChecks", func(config android.Config) (string, error) {
+		if override := config.Getenv("DEFAULT_GLOBAL_TIDY_CHECKS"); override != "" {
 			return override, nil
 		}
 		return strings.Join([]string{
@@ -41,8 +41,8 @@
 
 	// There are too many clang-tidy warnings in external and vendor projects.
 	// Enable only some google checks for these projects.
-	pctx.VariableFunc("TidyExternalVendorChecks", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("DEFAULT_EXTERNAL_VENDOR_TIDY_CHECKS"); override != "" {
+	pctx.VariableFunc("TidyExternalVendorChecks", func(config android.Config) (string, error) {
+		if override := config.Getenv("DEFAULT_EXTERNAL_VENDOR_TIDY_CHECKS"); override != "" {
 			return override, nil
 		}
 		return strings.Join([]string{
diff --git a/cc/config/x86_darwin_host.go b/cc/config/x86_darwin_host.go
index 8d805c9..dbaa6fa 100644
--- a/cc/config/x86_darwin_host.go
+++ b/cc/config/x86_darwin_host.go
@@ -107,25 +107,25 @@
 )
 
 func init() {
-	pctx.VariableFunc("macSdkPath", func(config interface{}) (string, error) {
-		xcodeselect := config.(android.Config).HostSystemTool("xcode-select")
+	pctx.VariableFunc("macSdkPath", func(config android.Config) (string, error) {
+		xcodeselect := config.HostSystemTool("xcode-select")
 		bytes, err := exec.Command(xcodeselect, "--print-path").Output()
 		return strings.TrimSpace(string(bytes)), err
 	})
-	pctx.VariableFunc("macSdkRoot", func(config interface{}) (string, error) {
-		return xcrunSdk(config.(android.Config), "--show-sdk-path")
+	pctx.VariableFunc("macSdkRoot", func(config android.Config) (string, error) {
+		return xcrunSdk(config, "--show-sdk-path")
 	})
 	pctx.StaticVariable("macMinVersion", "10.8")
-	pctx.VariableFunc("MacArPath", func(config interface{}) (string, error) {
-		return xcrun(config.(android.Config), "--find", "ar")
+	pctx.VariableFunc("MacArPath", func(config android.Config) (string, error) {
+		return xcrun(config, "--find", "ar")
 	})
 
-	pctx.VariableFunc("MacStripPath", func(config interface{}) (string, error) {
-		return xcrun(config.(android.Config), "--find", "strip")
+	pctx.VariableFunc("MacStripPath", func(config android.Config) (string, error) {
+		return xcrun(config, "--find", "strip")
 	})
 
-	pctx.VariableFunc("MacToolPath", func(config interface{}) (string, error) {
-		path, err := xcrun(config.(android.Config), "--find", "ld")
+	pctx.VariableFunc("MacToolPath", func(config android.Config) (string, error) {
+		path, err := xcrun(config, "--find", "ld")
 		return filepath.Dir(path), err
 	})
 
diff --git a/cc/library.go b/cc/library.go
index 192496a..cf10617 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -85,9 +85,6 @@
 	VariantIsShared bool `blueprint:"mutated"`
 	// This variant is static
 	VariantIsStatic bool `blueprint:"mutated"`
-	// Location of the static library in the sysroot. Empty if the library is
-	// not included in the NDK.
-	NdkSysrootPath string `blueprint:"mutated"`
 }
 
 type FlagExporterProperties struct {
@@ -246,6 +243,10 @@
 	// Source Abi Diff
 	sAbiDiff android.OptionalPath
 
+	// Location of the static library in the sysroot. Empty if the library is
+	// not included in the NDK.
+	ndkSysrootPath android.Path
+
 	// Decorated interafaces
 	*baseCompiler
 	*baseLinker
@@ -742,7 +743,7 @@
 			Input:       file,
 		})
 
-		library.MutatedProperties.NdkSysrootPath = installPath.String()
+		library.ndkSysrootPath = installPath
 	}
 }
 
diff --git a/cc/ndk_headers.go b/cc/ndk_headers.go
index bfbf0f5..d7c2a06 100644
--- a/cc/ndk_headers.go
+++ b/cc/ndk_headers.go
@@ -74,7 +74,7 @@
 
 	properties headerProperies
 
-	installPaths []string
+	installPaths android.Paths
 	licensePath  android.ModuleSrcPath
 }
 
@@ -139,7 +139,7 @@
 				"expected header install path (%q) not equal to actual install path %q",
 				installPath, installedPath))
 		}
-		m.installPaths = append(m.installPaths, installPath.String())
+		m.installPaths = append(m.installPaths, installPath)
 	}
 
 	if len(m.installPaths) == 0 {
@@ -186,7 +186,7 @@
 
 	properties preprocessedHeaderProperies
 
-	installPaths []string
+	installPaths android.Paths
 	licensePath  android.ModuleSrcPath
 }
 
@@ -208,7 +208,7 @@
 		installDir := getHeaderInstallDir(ctx, header, String(m.properties.From), String(m.properties.To))
 		installPath := installDir.Join(ctx, header.Base())
 		installPaths = append(installPaths, installPath)
-		m.installPaths = append(m.installPaths, installPath.String())
+		m.installPaths = append(m.installPaths, installPath)
 	}
 
 	if len(m.installPaths) == 0 {
diff --git a/cc/ndk_library.go b/cc/ndk_library.go
index 96a90fb..e69128c 100644
--- a/cc/ndk_library.go
+++ b/cc/ndk_library.go
@@ -98,7 +98,7 @@
 	properties libraryProperties
 
 	versionScriptPath android.ModuleGenPath
-	installPath       string
+	installPath       android.Path
 }
 
 // OMG GO
@@ -344,7 +344,7 @@
 
 	installDir := getNdkInstallBase(ctx).Join(ctx, fmt.Sprintf(
 		"platforms/android-%s/arch-%s/usr/%s", apiLevel, arch, libDir))
-	stub.installPath = ctx.InstallFile(installDir, path.Base(), path).String()
+	stub.installPath = ctx.InstallFile(installDir, path.Base(), path)
 }
 
 func newStubLibrary() *Module {
diff --git a/cc/ndk_sysroot.go b/cc/ndk_sysroot.go
index e213965..4324458 100644
--- a/cc/ndk_sysroot.go
+++ b/cc/ndk_sysroot.go
@@ -53,8 +53,6 @@
 // TODO(danalbert): Write `ndk_static_library` rule.
 
 import (
-	"github.com/google/blueprint"
-
 	"android/soong/android"
 )
 
@@ -76,32 +74,32 @@
 	return getNdkInstallBase(ctx).Join(ctx, "sysroot")
 }
 
-func getNdkSysrootTimestampFile(ctx android.PathContext) android.Path {
+func getNdkSysrootTimestampFile(ctx android.PathContext) android.WritablePath {
 	return android.PathForOutput(ctx, "ndk.timestamp")
 }
 
-func NdkSingleton() blueprint.Singleton {
+func NdkSingleton() android.Singleton {
 	return &ndkSingleton{}
 }
 
 type ndkSingleton struct{}
 
-func (n *ndkSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
-	installPaths := []string{}
-	licensePaths := []string{}
-	ctx.VisitAllModules(func(module blueprint.Module) {
+func (n *ndkSingleton) GenerateBuildActions(ctx android.SingletonContext) {
+	var installPaths android.Paths
+	var licensePaths android.Paths
+	ctx.VisitAllModules(func(module android.Module) {
 		if m, ok := module.(android.Module); ok && !m.Enabled() {
 			return
 		}
 
 		if m, ok := module.(*headerModule); ok {
 			installPaths = append(installPaths, m.installPaths...)
-			licensePaths = append(licensePaths, m.licensePath.String())
+			licensePaths = append(licensePaths, m.licensePath)
 		}
 
 		if m, ok := module.(*preprocessedHeaderModule); ok {
 			installPaths = append(installPaths, m.installPaths...)
-			licensePaths = append(licensePaths, m.licensePath.String())
+			licensePaths = append(licensePaths, m.licensePath)
 		}
 
 		if m, ok := module.(*Module); ok {
@@ -110,30 +108,28 @@
 			}
 
 			if library, ok := m.linker.(*libraryDecorator); ok {
-				if library.MutatedProperties.NdkSysrootPath != "" {
-					installPaths = append(installPaths, library.MutatedProperties.NdkSysrootPath)
+				if library.ndkSysrootPath != nil {
+					installPaths = append(installPaths, library.ndkSysrootPath)
 				}
 			}
 		}
 	})
 
 	combinedLicense := getNdkInstallBase(ctx).Join(ctx, "NOTICE")
-	ctx.Build(pctx, blueprint.BuildParams{
+	ctx.Build(pctx, android.BuildParams{
 		Rule:        android.Cat,
 		Description: "combine licenses",
-		Outputs:     []string{combinedLicense.String()},
+		Output:      combinedLicense,
 		Inputs:      licensePaths,
-		Optional:    true,
 	})
 
-	depPaths := append(installPaths, combinedLicense.String())
+	depPaths := append(installPaths, combinedLicense)
 
 	// There's a dummy "ndk" rule defined in ndk/Android.mk that depends on
 	// this. `m ndk` will build the sysroots.
-	ctx.Build(pctx, blueprint.BuildParams{
+	ctx.Build(pctx, android.BuildParams{
 		Rule:      android.Touch,
-		Outputs:   []string{getNdkSysrootTimestampFile(ctx).String()},
+		Output:    getNdkSysrootTimestampFile(ctx),
 		Implicits: depPaths,
-		Optional:  true,
 	})
 }
diff --git a/java/config/config.go b/java/config/config.go
index 49481be..466563f 100644
--- a/java/config/config.go
+++ b/java/config/config.go
@@ -64,9 +64,9 @@
 
 	pctx.VariableConfigMethod("hostPrebuiltTag", android.Config.PrebuiltOS)
 
-	pctx.VariableFunc("JavaHome", func(config interface{}) (string, error) {
+	pctx.VariableFunc("JavaHome", func(config android.Config) (string, error) {
 		// This is set up and guaranteed by soong_ui
-		return config.(android.Config).Getenv("ANDROID_JAVA_HOME"), nil
+		return config.Getenv("ANDROID_JAVA_HOME"), nil
 	})
 
 	pctx.SourcePathVariable("JavaToolchain", "${JavaHome}/bin")
@@ -85,9 +85,9 @@
 	pctx.HostBinToolVariable("SoongZipCmd", "soong_zip")
 	pctx.HostBinToolVariable("MergeZipsCmd", "merge_zips")
 	pctx.HostBinToolVariable("Zip2ZipCmd", "zip2zip")
-	pctx.VariableFunc("DxCmd", func(config interface{}) (string, error) {
-		if config.(android.Config).IsEnvFalse("USE_D8") {
-			if config.(android.Config).UnbundledBuild() || config.(android.Config).IsPdkBuild() {
+	pctx.VariableFunc("DxCmd", func(config android.Config) (string, error) {
+		if config.IsEnvFalse("USE_D8") {
+			if config.UnbundledBuild() || config.IsPdkBuild() {
 				return "prebuilts/build-tools/common/bin/dx", nil
 			} else {
 				path, err := pctx.HostBinToolPath(config, "dx")
@@ -104,9 +104,9 @@
 			return path.String(), nil
 		}
 	})
-	pctx.VariableFunc("TurbineJar", func(config interface{}) (string, error) {
+	pctx.VariableFunc("TurbineJar", func(config android.Config) (string, error) {
 		turbine := "turbine.jar"
-		if config.(android.Config).UnbundledBuild() {
+		if config.UnbundledBuild() {
 			return "prebuilts/build-tools/common/framework/" + turbine, nil
 		} else {
 			path, err := pctx.HostJavaToolPath(config, turbine)
@@ -122,8 +122,8 @@
 
 	pctx.HostBinToolVariable("SoongJavacWrapper", "soong_javac_wrapper")
 
-	pctx.VariableFunc("JavacWrapper", func(config interface{}) (string, error) {
-		if override := config.(android.Config).Getenv("JAVAC_WRAPPER"); override != "" {
+	pctx.VariableFunc("JavacWrapper", func(config android.Config) (string, error) {
+		if override := config.Getenv("JAVAC_WRAPPER"); override != "" {
 			return override + " ", nil
 		}
 		return "", nil
diff --git a/java/config/error_prone.go b/java/config/error_prone.go
index 31cbf2c..862217f 100644
--- a/java/config/error_prone.go
+++ b/java/config/error_prone.go
@@ -14,6 +14,8 @@
 
 package config
 
+import "android/soong/android"
+
 var (
 	// These will be filled out by external/error_prone/soong/error_prone.go if it is available
 	ErrorProneJavacJar    string
@@ -25,7 +27,7 @@
 
 // Wrapper that grabs value of val late so it can be initialized by a later module's init function
 func errorProneVar(name string, val *string) {
-	pctx.VariableFunc(name, func(config interface{}) (string, error) {
+	pctx.VariableFunc(name, func(config android.Config) (string, error) {
 		return *val, nil
 	})
 }
diff --git a/java/gen.go b/java/gen.go
index b5973ec..7a0dcac 100644
--- a/java/gen.go
+++ b/java/gen.go
@@ -28,8 +28,6 @@
 	pctx.HostBinToolVariable("aidlCmd", "aidl")
 	pctx.SourcePathVariable("logtagsCmd", "build/tools/java-event-log-tags.py")
 	pctx.SourcePathVariable("mergeLogtagsCmd", "build/tools/merge-event-log-tags.py")
-
-	pctx.IntermediatesPathVariable("allLogtagsFile", "all-event-log-tags.txt")
 }
 
 var (
@@ -117,7 +115,7 @@
 	return outSrcFiles
 }
 
-func LogtagsSingleton() blueprint.Singleton {
+func LogtagsSingleton() android.Singleton {
 	return &logtagsSingleton{}
 }
 
@@ -127,18 +125,18 @@
 
 type logtagsSingleton struct{}
 
-func (l *logtagsSingleton) GenerateBuildActions(ctx blueprint.SingletonContext) {
+func (l *logtagsSingleton) GenerateBuildActions(ctx android.SingletonContext) {
 	var allLogtags android.Paths
-	ctx.VisitAllModules(func(module blueprint.Module) {
+	ctx.VisitAllModules(func(module android.Module) {
 		if logtags, ok := module.(logtagsProducer); ok {
 			allLogtags = append(allLogtags, logtags.logtags()...)
 		}
 	})
 
-	ctx.Build(pctx, blueprint.BuildParams{
+	ctx.Build(pctx, android.BuildParams{
 		Rule:        mergeLogtags,
 		Description: "merge logtags",
-		Outputs:     []string{"$allLogtagsFile"},
-		Inputs:      allLogtags.Strings(),
+		Output:      android.PathForIntermediates(ctx, "all-event-log-tags.txt"),
+		Inputs:      allLogtags,
 	})
 }