Add rules to handle asset resources.

AAPT2 ignores assets in overlay resource inputs, so separate rules are
required to extract and merge assets from dependencies.

Test: app_test.go
Test: Added assets to Settings-core for testing
Test: Confirmed Settings.apk contains them with this change.
Fixes: 146655310
Change-Id: Iab8bc61b719541dae64f0e3502bc9cb45a353687
diff --git a/java/aapt2.go b/java/aapt2.go
index cfe0dea..04e4de5 100644
--- a/java/aapt2.go
+++ b/java/aapt2.go
@@ -147,10 +147,16 @@
 		RspfileContent: "$in",
 	})
 
+var mergeAssetsRule = pctx.AndroidStaticRule("mergeAssets",
+	blueprint.RuleParams{
+		Command:     `${config.MergeZipsCmd} ${out} ${in}`,
+		CommandDeps: []string{"${config.MergeZipsCmd}"},
+	})
+
 func aapt2Link(ctx android.ModuleContext,
 	packageRes, genJar, proguardOptions, rTxt, extraPackages android.WritablePath,
 	flags []string, deps android.Paths,
-	compiledRes, compiledOverlay android.Paths, splitPackages android.WritablePaths) {
+	compiledRes, compiledOverlay, assetPackages android.Paths, splitPackages android.WritablePaths) {
 
 	genDir := android.PathForModuleGen(ctx, "aapt2", "R")
 
@@ -186,12 +192,25 @@
 	}
 
 	implicitOutputs := append(splitPackages, proguardOptions, genJar, rTxt, extraPackages)
+	linkOutput := packageRes
+
+	// AAPT2 ignores assets in overlays. Merge them after linking.
+	if len(assetPackages) > 0 {
+		linkOutput = android.PathForModuleOut(ctx, "aapt2", "package-res.apk")
+		inputZips := append(android.Paths{linkOutput}, assetPackages...)
+		ctx.Build(pctx, android.BuildParams{
+			Rule:        mergeAssetsRule,
+			Inputs:      inputZips,
+			Output:      packageRes,
+			Description: "merge assets from dependencies",
+		})
+	}
 
 	ctx.Build(pctx, android.BuildParams{
 		Rule:            aapt2LinkRule,
 		Description:     "aapt2 link",
 		Implicits:       deps,
-		Output:          packageRes,
+		Output:          linkOutput,
 		ImplicitOutputs: implicitOutputs,
 		Args: map[string]string{
 			"flags":           strings.Join(flags, " "),
diff --git a/java/aar.go b/java/aar.go
index ae064e5..c0b39b6 100644
--- a/java/aar.go
+++ b/java/aar.go
@@ -15,11 +15,12 @@
 package java
 
 import (
-	"android/soong/android"
 	"fmt"
 	"path/filepath"
 	"strings"
 
+	"android/soong/android"
+
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 )
@@ -31,6 +32,7 @@
 	ExportedRRODirs() []rroDir
 	ExportedStaticPackages() android.Paths
 	ExportedManifests() android.Paths
+	ExportedAssets() android.OptionalPath
 }
 
 func init() {
@@ -92,6 +94,7 @@
 	extraAaptPackagesFile   android.Path
 	mergedManifestFile      android.Path
 	noticeFile              android.OptionalPath
+	assetPackage            android.OptionalPath
 	isLibrary               bool
 	useEmbeddedNativeLibs   bool
 	useEmbeddedDex          bool
@@ -123,6 +126,10 @@
 	return a.transitiveManifestPaths
 }
 
+func (a *aapt) ExportedAssets() android.OptionalPath {
+	return a.assetPackage
+}
+
 func (a *aapt) aapt2Flags(ctx android.ModuleContext, sdkContext sdkContext,
 	manifestPath android.Path) (compileFlags, linkFlags []string, linkDeps android.Paths,
 	resDirs, overlayDirs []globbedResourceDir, rroDirs []rroDir, resZips android.Paths) {
@@ -215,9 +222,15 @@
 	}
 }
 
+var extractAssetsRule = pctx.AndroidStaticRule("extractAssets",
+	blueprint.RuleParams{
+		Command:     `${config.Zip2ZipCmd} -i ${in} -o ${out} "assets/**/*"`,
+		CommandDeps: []string{"${config.Zip2ZipCmd}"},
+	})
+
 func (a *aapt) buildActions(ctx android.ModuleContext, sdkContext sdkContext, extraLinkFlags ...string) {
 
-	transitiveStaticLibs, transitiveStaticLibManifests, staticRRODirs, libDeps, libFlags, sdkLibraries :=
+	transitiveStaticLibs, transitiveStaticLibManifests, staticRRODirs, assetPackages, libDeps, libFlags, sdkLibraries :=
 		aaptLibs(ctx, sdkContext)
 
 	// App manifest file
@@ -317,7 +330,20 @@
 	}
 
 	aapt2Link(ctx, packageRes, srcJar, proguardOptionsFile, rTxt, extraPackages,
-		linkFlags, linkDeps, compiledRes, compiledOverlay, splitPackages)
+		linkFlags, linkDeps, compiledRes, compiledOverlay, assetPackages, splitPackages)
+
+	// Extract assets from the resource package output so that they can be used later in aapt2link
+	// for modules that depend on this one.
+	if android.PrefixedStringInList(linkFlags, "-A ") || len(assetPackages) > 0 {
+		assets := android.PathForModuleOut(ctx, "assets.zip")
+		ctx.Build(pctx, android.BuildParams{
+			Rule:        extractAssetsRule,
+			Input:       packageRes,
+			Output:      assets,
+			Description: "extract assets from built resource file",
+		})
+		a.assetPackage = android.OptionalPathForPath(assets)
+	}
 
 	a.aaptSrcJar = srcJar
 	a.exportPackage = packageRes
@@ -331,7 +357,7 @@
 
 // aaptLibs collects libraries from dependencies and sdk_version and converts them into paths
 func aaptLibs(ctx android.ModuleContext, sdkContext sdkContext) (transitiveStaticLibs, transitiveStaticLibManifests android.Paths,
-	staticRRODirs []rroDir, deps android.Paths, flags []string, sdkLibraries []string) {
+	staticRRODirs []rroDir, assets, deps android.Paths, flags []string, sdkLibraries []string) {
 
 	var sharedLibs android.Paths
 
@@ -369,6 +395,9 @@
 				transitiveStaticLibs = append(transitiveStaticLibs, exportPackage)
 				transitiveStaticLibManifests = append(transitiveStaticLibManifests, aarDep.ExportedManifests()...)
 				sdkLibraries = append(sdkLibraries, aarDep.ExportedSdkLibs()...)
+				if aarDep.ExportedAssets().Valid() {
+					assets = append(assets, aarDep.ExportedAssets().Path())
+				}
 
 			outer:
 				for _, d := range aarDep.ExportedRRODirs() {
@@ -398,7 +427,7 @@
 	transitiveStaticLibManifests = android.FirstUniquePaths(transitiveStaticLibManifests)
 	sdkLibraries = android.FirstUniqueStrings(sdkLibraries)
 
-	return transitiveStaticLibs, transitiveStaticLibManifests, staticRRODirs, deps, flags, sdkLibraries
+	return transitiveStaticLibs, transitiveStaticLibManifests, staticRRODirs, assets, deps, flags, sdkLibraries
 }
 
 type AndroidLibrary struct {
@@ -568,6 +597,11 @@
 	return android.Paths{a.manifest}
 }
 
+// TODO(jungjw): Decide whether we want to implement this.
+func (a *AARImport) ExportedAssets() android.OptionalPath {
+	return android.OptionalPath{}
+}
+
 func (a *AARImport) Prebuilt() *android.Prebuilt {
 	return &a.prebuilt
 }
@@ -656,7 +690,7 @@
 	linkFlags = append(linkFlags, "--manifest "+a.manifest.String())
 	linkDeps = append(linkDeps, a.manifest)
 
-	transitiveStaticLibs, staticLibManifests, staticRRODirs, libDeps, libFlags, sdkLibraries :=
+	transitiveStaticLibs, staticLibManifests, staticRRODirs, transitiveAssets, libDeps, libFlags, sdkLibraries :=
 		aaptLibs(ctx, sdkContext(a))
 
 	_ = staticLibManifests
@@ -669,7 +703,7 @@
 	overlayRes := append(android.Paths{flata}, transitiveStaticLibs...)
 
 	aapt2Link(ctx, a.exportPackage, srcJar, proguardOptionsFile, rTxt, a.extraAaptPackagesFile,
-		linkFlags, linkDeps, nil, overlayRes, nil)
+		linkFlags, linkDeps, nil, overlayRes, transitiveAssets, nil)
 }
 
 var _ Dependency = (*AARImport)(nil)
diff --git a/java/app_test.go b/java/app_test.go
index 9bdef4e..3612112 100644
--- a/java/app_test.go
+++ b/java/app_test.go
@@ -323,6 +323,107 @@
 	}
 }
 
+func TestLibraryAssets(t *testing.T) {
+	bp := `
+			android_app {
+				name: "foo",
+				sdk_version: "current",
+				static_libs: ["lib1", "lib2", "lib3"],
+			}
+
+			android_library {
+				name: "lib1",
+				sdk_version: "current",
+				asset_dirs: ["assets_a"],
+			}
+
+			android_library {
+				name: "lib2",
+				sdk_version: "current",
+			}
+
+			android_library {
+				name: "lib3",
+				sdk_version: "current",
+				static_libs: ["lib4"],
+			}
+
+			android_library {
+				name: "lib4",
+				sdk_version: "current",
+				asset_dirs: ["assets_b"],
+			}
+		`
+
+	testCases := []struct {
+		name          string
+		assetFlag     string
+		assetPackages []string
+	}{
+		{
+			name: "foo",
+			// lib1 has its own asset. lib3 doesn't have any, but provides lib4's transitively.
+			assetPackages: []string{
+				buildDir + "/.intermediates/foo/android_common/aapt2/package-res.apk",
+				buildDir + "/.intermediates/lib1/android_common/assets.zip",
+				buildDir + "/.intermediates/lib3/android_common/assets.zip",
+			},
+		},
+		{
+			name:      "lib1",
+			assetFlag: "-A assets_a",
+		},
+		{
+			name: "lib2",
+		},
+		{
+			name: "lib3",
+			assetPackages: []string{
+				buildDir + "/.intermediates/lib3/android_common/aapt2/package-res.apk",
+				buildDir + "/.intermediates/lib4/android_common/assets.zip",
+			},
+		},
+		{
+			name:      "lib4",
+			assetFlag: "-A assets_b",
+		},
+	}
+	ctx := testApp(t, bp)
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			m := ctx.ModuleForTests(test.name, "android_common")
+
+			// Check asset flag in aapt2 link flags
+			var aapt2link android.TestingBuildParams
+			if len(test.assetPackages) > 0 {
+				aapt2link = m.Output("aapt2/package-res.apk")
+			} else {
+				aapt2link = m.Output("package-res.apk")
+			}
+			aapt2Flags := aapt2link.Args["flags"]
+			if test.assetFlag != "" {
+				if !strings.Contains(aapt2Flags, test.assetFlag) {
+					t.Errorf("Can't find asset flag %q in aapt2 link flags %q", test.assetFlag, aapt2Flags)
+				}
+			} else {
+				if strings.Contains(aapt2Flags, " -A ") {
+					t.Errorf("aapt2 link flags %q contain unexpected asset flag", aapt2Flags)
+				}
+			}
+
+			// Check asset merge rule.
+			if len(test.assetPackages) > 0 {
+				mergeAssets := m.Output("package-res.apk")
+				if !reflect.DeepEqual(test.assetPackages, mergeAssets.Inputs.Strings()) {
+					t.Errorf("Unexpected mergeAssets inputs: %v, expected: %v",
+						mergeAssets.Inputs.Strings(), test.assetPackages)
+				}
+			}
+		})
+	}
+}
+
 func TestAndroidResources(t *testing.T) {
 	testCases := []struct {
 		name                       string
diff --git a/java/testing.go b/java/testing.go
index 08bae44..3a2fe43 100644
--- a/java/testing.go
+++ b/java/testing.go
@@ -48,6 +48,8 @@
 		"api/test-current.txt":   nil,
 		"api/test-removed.txt":   nil,
 		"framework/aidl/a.aidl":  nil,
+		"assets_a/a":             nil,
+		"assets_b/b":             nil,
 
 		"prebuilts/ndk/current/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++_shared.so": nil,