Use per-app package list to avoid unnecessary dexpreopt.

Starting from aosp/2594905, dexpreopt depends on
`$PRODUCT_OUT/product_packages.txt`. When PRODUCT_PACKAGES changes,
dexpreopt has to rerun for all apps. This is not ideal.

After this change, dexpreopt uses a per-app product_packages.txt that is
filtered by the app's dependencies, and it uses `rsync --checksum` to
prevent the file's mtime from being changed if the contents don't change.
This avoids unnecessary dexpreopt reruns.

Bug: 288218403
Test: m
Test: Change PRODUCT_PACKAGES and see no dexpreopt reruns.
Change-Id: I5788a9ee987dfd0abfd7d91cbcef748452290004

dexpreopt/class_loader_context.go

@@ -310,7 +310,7 @@ func (clcMap ClassLoaderContextMap) addContext(ctx android.ModuleInstallPathCont
 	// Nested class loader context shouldn't have conditional part (it is allowed only at the top level).
 	for ver, _ := range nestedClcMap {
 		if ver != AnySdkVersion {
-			clcPaths := ComputeClassLoaderContextDependencies(nestedClcMap)
+			_, clcPaths := ComputeClassLoaderContextDependencies(nestedClcMap)
 			return fmt.Errorf("nested class loader context shouldn't have conditional part: %+v", clcPaths)
 		}
 	}
@@ -553,27 +553,28 @@ func validateClassLoaderContextRec(sdkVer int, clcs []*ClassLoaderContext) (bool
 	return true, nil
 }
 
-// Returns a slice of build paths for all possible dependencies that the class loader context may
-// refer to.
+// Returns a slice of library names and a slice of build paths for all possible dependencies that
+// the class loader context may refer to.
 // Perform a depth-first preorder traversal of the class loader context tree for each SDK version.
-func ComputeClassLoaderContextDependencies(clcMap ClassLoaderContextMap) android.Paths {
-	var paths android.Paths
+func ComputeClassLoaderContextDependencies(clcMap ClassLoaderContextMap) (names []string, paths android.Paths) {
 	for _, clcs := range clcMap {
-		hostPaths := ComputeClassLoaderContextDependenciesRec(clcs)
-		paths = append(paths, hostPaths...)
+		currentNames, currentPaths := ComputeClassLoaderContextDependenciesRec(clcs)
+		names = append(names, currentNames...)
+		paths = append(paths, currentPaths...)
 	}
-	return android.FirstUniquePaths(paths)
+	return android.FirstUniqueStrings(names), android.FirstUniquePaths(paths)
 }
 
 // Helper function for ComputeClassLoaderContextDependencies() that handles recursion.
-func ComputeClassLoaderContextDependenciesRec(clcs []*ClassLoaderContext) android.Paths {
-	var paths android.Paths
+func ComputeClassLoaderContextDependenciesRec(clcs []*ClassLoaderContext) (names []string, paths android.Paths) {
 	for _, clc := range clcs {
-		subPaths := ComputeClassLoaderContextDependenciesRec(clc.Subcontexts)
+		subNames, subPaths := ComputeClassLoaderContextDependenciesRec(clc.Subcontexts)
+		names = append(names, clc.Name)
 		paths = append(paths, clc.Host)
+		names = append(names, subNames...)
 		paths = append(paths, subPaths...)
 	}
-	return paths
+	return names, paths
 }
 
 // Class loader contexts that come from Make via JSON dexpreopt.config. JSON CLC representation is

dexpreopt/class_loader_context_test.go

@@ -97,10 +97,11 @@ func TestCLC(t *testing.T) {
 
 	fixClassLoaderContext(m)
 
-	var havePaths android.Paths
+	var actualNames []string
+	var actualPaths android.Paths
 	var haveUsesLibsReq, haveUsesLibsOpt []string
 	if valid && validationError == nil {
-		havePaths = ComputeClassLoaderContextDependencies(m)
+		actualNames, actualPaths = ComputeClassLoaderContextDependencies(m)
 		haveUsesLibsReq, haveUsesLibsOpt = m.UsesLibs()
 	}
 
@@ -112,19 +113,26 @@ func TestCLC(t *testing.T) {
 	})
 
 	// Test that all expected build paths are gathered.
-	t.Run("paths", func(t *testing.T) {
-		wantPaths := []string{
+	t.Run("names and paths", func(t *testing.T) {
+		expectedNames := []string{
+			"a'", "a1", "a2", "a3", "android.hidl.base-V1.0-java", "android.hidl.manager-V1.0-java", "b",
+			"b1", "b2", "b3", "c", "c2", "d", "f",
+		}
+		expectedPaths := []string{
 			"out/soong/android.hidl.manager-V1.0-java.jar", "out/soong/android.hidl.base-V1.0-java.jar",
 			"out/soong/a.jar", "out/soong/b.jar", "out/soong/c.jar", "out/soong/d.jar",
 			"out/soong/a2.jar", "out/soong/b2.jar", "out/soong/c2.jar",
 			"out/soong/a1.jar", "out/soong/b1.jar",
 			"out/soong/f.jar", "out/soong/a3.jar", "out/soong/b3.jar",
 		}
-		actual := havePaths.Strings()
+		actualPathsStrs := actualPaths.Strings()
 		// The order does not matter.
-		sort.Strings(wantPaths)
-		sort.Strings(actual)
-		android.AssertArrayString(t, "", wantPaths, actual)
+		sort.Strings(expectedNames)
+		sort.Strings(actualNames)
+		android.AssertArrayString(t, "", expectedNames, actualNames)
+		sort.Strings(expectedPaths)
+		sort.Strings(actualPathsStrs)
+		android.AssertArrayString(t, "", expectedPaths, actualPathsStrs)
 	})
 
 	// Test the JSON passed to construct_context.py.

dexpreopt/dexpreopt.go

@@ -353,7 +353,7 @@ func dexpreoptCommand(ctx android.BuilderContext, globalSoong *GlobalSoongConfig
 		}
 
 		// Generate command that saves host and target class loader context in shell variables.
-		paths := ComputeClassLoaderContextDependencies(module.ClassLoaderContexts)
+		_, paths := ComputeClassLoaderContextDependencies(module.ClassLoaderContexts)
 		rule.Command().
 			Text(`eval "$(`).Tool(globalSoong.ConstructContext).
 			Text(` --target-sdk-version ${target_sdk_version}`).

java/app_test.go

@@ -2697,7 +2697,7 @@ func TestUsesLibraries(t *testing.T) {
 	cmd := app.Rule("dexpreopt").RuleParams.Command
 	android.AssertStringDoesContain(t, "dexpreopt app cmd context", cmd, "--context-json=")
 	android.AssertStringDoesContain(t, "dexpreopt app cmd product_packages", cmd,
-		"--product-packages=out/soong/target/product/test_device/product_packages.txt")
+		"--product-packages=out/soong/.intermediates/app/android_common/dexpreopt/product_packages.txt")
 }
 
 func TestDexpreoptBcp(t *testing.T) {

java/dexpreopt.go

@@ -16,6 +16,7 @@ package java
 
 import (
 	"path/filepath"
+	"sort"
 	"strings"
 
 	"android/soong/android"
@@ -390,11 +391,37 @@ func (d *dexpreopter) dexpreopt(ctx android.ModuleContext, dexJarFile android.Wr
 
 	globalSoong := dexpreopt.GetGlobalSoongConfig(ctx)
 
-	// "product_packages.txt" is generated by `build/make/core/Makefile`.
+	// The root "product_packages.txt" is generated by `build/make/core/Makefile`. It contains a list
+	// of all packages that are installed on the device. We use `grep` to filter the list by the app's
+	// dependencies to create a per-app list, and use `rsync --checksum` to prevent the file's mtime
+	// from being changed if the contents don't change. This avoids unnecessary dexpreopt reruns.
 	productPackages := android.PathForModuleInPartitionInstall(ctx, "", "product_packages.txt")
+	appProductPackages := android.PathForModuleOut(ctx, "dexpreopt", "product_packages.txt")
+	appProductPackagesStaging := appProductPackages.ReplaceExtension(ctx, "txt.tmp")
+	clcNames, _ := dexpreopt.ComputeClassLoaderContextDependencies(dexpreoptConfig.ClassLoaderContexts)
+	sort.Strings(clcNames) // The order needs to be deterministic.
+	productPackagesRule := android.NewRuleBuilder(pctx, ctx)
+	if len(clcNames) > 0 {
+		productPackagesRule.Command().
+			Text("grep -F -x").
+			FlagForEachArg("-e ", clcNames).
+			Input(productPackages).
+			FlagWithOutput("> ", appProductPackagesStaging).
+			Text("|| true")
+	} else {
+		productPackagesRule.Command().
+			Text("rm -f").Output(appProductPackagesStaging).
+			Text("&&").
+			Text("touch").Output(appProductPackagesStaging)
+	}
+	productPackagesRule.Command().
+		Text("rsync --checksum").
+		Input(appProductPackagesStaging).
+		Output(appProductPackages)
+	productPackagesRule.Restat().Build("product_packages", "dexpreopt product_packages")
 
 	dexpreoptRule, err := dexpreopt.GenerateDexpreoptRule(
-		ctx, globalSoong, global, dexpreoptConfig, productPackages)
+		ctx, globalSoong, global, dexpreoptConfig, appProductPackages)
 	if err != nil {
 		ctx.ModuleErrorf("error generating dexpreopt rule: %s", err.Error())
 		return