Fix library order in class loader context to agree with PackageManager.

PackageManager adds compatibility libraries for different SDK versions
in descending order, and Soong should do the same.

Bug: 132357300

Test: lunch aosp_cf_x86_phone-userdebug && m \
  && launch_cvd \
  && adb wait-for-device \
  && adb logcat | grep -E 'ClassLoaderContext [a-z ]+ mismatch'

  [no messages "ClassLoaderContext classpath element mismatch"]

Change-Id: Ib1d981808ae4022b2c6e73f407a003e8b8e9c7d6

dexpreopt/class_loader_context.go

@@ -16,6 +16,7 @@ package dexpreopt
 
 import (
 	"fmt"
+	"sort"
 	"strconv"
 	"strings"
 
@@ -238,8 +239,8 @@ var OptionalCompatUsesLibs30 = []string{
 	AndroidTestMock,
 }
 var CompatUsesLibs29 = []string{
-	AndroidHidlBase,
 	AndroidHidlManager,
+	AndroidHidlBase,
 }
 var OptionalCompatUsesLibs = append(android.CopyOf(OptionalCompatUsesLibs28), OptionalCompatUsesLibs30...)
 var CompatUsesLibs = android.CopyOf(CompatUsesLibs29)
@@ -462,7 +463,26 @@ func validateClassLoaderContextRec(sdkVer int, clcs []*ClassLoaderContext) (bool
 // Perform a depth-first preorder traversal of the class loader context tree for each SDK version.
 // Return the resulting string and a slice of on-host build paths to all library dependencies.
 func ComputeClassLoaderContext(clcMap ClassLoaderContextMap) (clcStr string, paths android.Paths) {
-	for _, sdkVer := range android.SortedIntKeys(clcMap) { // determinisitc traversal order
+	// CLC for different SDK versions should come in specific order that agrees with PackageManager.
+	// Since PackageManager processes SDK versions in ascending order and prepends compatibility
+	// libraries at the front, the required order is descending, except for AnySdkVersion that has
+	// numerically the largest order, but must be the last one. Example of correct order: [30, 29,
+	// 28, AnySdkVersion]. There are Soong tests to ensure that someone doesn't change this by
+	// accident, but there is no way to guard against changes in the PackageManager, except for
+	// grepping logcat on the first boot for absence of the following messages:
+	//
+	//   `logcat | grep -E 'ClassLoaderContext [a-z ]+ mismatch`
+	//
+	versions := make([]int, 0, len(clcMap))
+	for ver, _ := range clcMap {
+		if ver != AnySdkVersion {
+			versions = append(versions, ver)
+		}
+	}
+	sort.Sort(sort.Reverse(sort.IntSlice(versions))) // descending order
+	versions = append(versions, AnySdkVersion)
+
+	for _, sdkVer := range versions {
 		sdkVerStr := fmt.Sprintf("%d", sdkVer)
 		if sdkVer == AnySdkVersion {
 			sdkVerStr = "any" // a special keyword that means any SDK version

dexpreopt/class_loader_context_test.go

@@ -209,6 +209,48 @@ func TestCLCNestedConditional(t *testing.T) {
 	checkError(t, err, "nested class loader context shouldn't have conditional part")
 }
 
+// Test for SDK version order in conditional CLC: no matter in what order the libraries are added,
+// they end up in the order that agrees with PackageManager.
+func TestCLCSdkVersionOrder(t *testing.T) {
+	ctx := testContext()
+	m := make(ClassLoaderContextMap)
+	m.AddContextForSdk(ctx, 28, "a", buildPath(ctx, "a"), installPath(ctx, "a"), nil)
+	m.AddContextForSdk(ctx, 29, "b", buildPath(ctx, "b"), installPath(ctx, "b"), nil)
+	m.AddContextForSdk(ctx, 30, "c", buildPath(ctx, "c"), installPath(ctx, "c"), nil)
+	m.AddContextForSdk(ctx, AnySdkVersion, "d", buildPath(ctx, "d"), installPath(ctx, "d"), nil)
+
+	valid, validationError := validateClassLoaderContext(m)
+
+	fixClassLoaderContext(m)
+
+	var haveStr string
+	if valid && validationError == nil {
+		haveStr, _ = ComputeClassLoaderContext(m)
+	}
+
+	// Test that validation is successful (all paths are known).
+	t.Run("validate", func(t *testing.T) {
+		if !(valid && validationError == nil) {
+			t.Errorf("invalid class loader context")
+		}
+	})
+
+	// Test that class loader context structure is correct.
+	t.Run("string", func(t *testing.T) {
+		wantStr := " --host-context-for-sdk 30 PCL[out/c.jar]" +
+			" --target-context-for-sdk 30 PCL[/system/c.jar]" +
+			" --host-context-for-sdk 29 PCL[out/b.jar]" +
+			" --target-context-for-sdk 29 PCL[/system/b.jar]" +
+			" --host-context-for-sdk 28 PCL[out/a.jar]" +
+			" --target-context-for-sdk 28 PCL[/system/a.jar]" +
+			" --host-context-for-sdk any PCL[out/d.jar]" +
+			" --target-context-for-sdk any PCL[/system/d.jar]"
+		if wantStr != haveStr {
+			t.Errorf("\nwant class loader context: %s\nhave class loader context: %s", wantStr, haveStr)
+		}
+	})
+}
+
 func checkError(t *testing.T, have error, want string) {
 	if have == nil {
 		t.Errorf("\nwant error: '%s'\nhave: none", want)

java/app_test.go

@@ -2896,8 +2896,8 @@ func TestUsesLibraries(t *testing.T) {
 
 	// Test conditional context for target SDK version 29.
 	if w := `--target-context-for-sdk 29` +
-		` PCL[/system/framework/android.hidl.base-V1.0-java.jar]` +
+		` PCL[/system/framework/android.hidl.manager-V1.0-java.jar]` +
-		`#PCL[/system/framework/android.hidl.manager-V1.0-java.jar] `; !strings.Contains(cmd, w) {
+		`#PCL[/system/framework/android.hidl.base-V1.0-java.jar] `; !strings.Contains(cmd, w) {
 		t.Errorf("wanted %q in %q", w, cmd)
 	}