diff --git a/android/defaults.go b/android/defaults.go
index 6a908ea..81e340e 100644
--- a/android/defaults.go
+++ b/android/defaults.go
@@ -35,6 +35,9 @@
 	defaultsProperties            defaultsProperties
 	defaultableProperties         []interface{}
 	defaultableVariableProperties interface{}
+
+	// The optional hook to call after any defaults have been applied.
+	hook DefaultableHook
 }
 
 func (d *DefaultableModuleBase) defaults() *defaultsProperties {
@@ -46,6 +49,16 @@
 	d.defaultableVariableProperties = variableProperties
 }
 
+func (d *DefaultableModuleBase) SetDefaultableHook(hook DefaultableHook) {
+	d.hook = hook
+}
+
+func (d *DefaultableModuleBase) callHookIfAvailable(ctx DefaultableHookContext) {
+	if d.hook != nil {
+		d.hook(ctx)
+	}
+}
+
 // Interface that must be supported by any module to which defaults can be applied.
 type Defaultable interface {
 	// Get a pointer to the struct containing the Defaults property.
@@ -57,6 +70,15 @@
 	// Apply defaults from the supplied Defaults to the property structures supplied to
 	// setProperties(...).
 	applyDefaults(TopDownMutatorContext, []Defaults)
+
+	// Set the hook to be called after any defaults have been applied.
+	//
+	// Should be used in preference to a AddLoadHook when the behavior of the load
+	// hook is dependent on properties supplied in the Android.bp file.
+	SetDefaultableHook(hook DefaultableHook)
+
+	// Call the hook if specified.
+	callHookIfAvailable(context DefaultableHookContext)
 }
 
 type DefaultableModule interface {
@@ -75,6 +97,15 @@
 	module.AddProperties(module.defaults())
 }
 
+// A restricted subset of context methods, similar to LoadHookContext.
+type DefaultableHookContext interface {
+	EarlyModuleContext
+
+	CreateModule(ModuleFactory, ...interface{}) Module
+}
+
+type DefaultableHook func(ctx DefaultableHookContext)
+
 // The Defaults_visibility property.
 type DefaultsVisibilityProperties struct {
 
@@ -268,25 +299,29 @@
 }
 
 func defaultsMutator(ctx TopDownMutatorContext) {
-	if defaultable, ok := ctx.Module().(Defaultable); ok && len(defaultable.defaults().Defaults) > 0 {
-		var defaultsList []Defaults
-		seen := make(map[Defaults]bool)
+	if defaultable, ok := ctx.Module().(Defaultable); ok {
+		if len(defaultable.defaults().Defaults) > 0 {
+			var defaultsList []Defaults
+			seen := make(map[Defaults]bool)
 
-		ctx.WalkDeps(func(module, parent Module) bool {
-			if ctx.OtherModuleDependencyTag(module) == DefaultsDepTag {
-				if defaults, ok := module.(Defaults); ok {
-					if !seen[defaults] {
-						seen[defaults] = true
-						defaultsList = append(defaultsList, defaults)
-						return len(defaults.defaults().Defaults) > 0
+			ctx.WalkDeps(func(module, parent Module) bool {
+				if ctx.OtherModuleDependencyTag(module) == DefaultsDepTag {
+					if defaults, ok := module.(Defaults); ok {
+						if !seen[defaults] {
+							seen[defaults] = true
+							defaultsList = append(defaultsList, defaults)
+							return len(defaults.defaults().Defaults) > 0
+						}
+					} else {
+						ctx.PropertyErrorf("defaults", "module %s is not an defaults module",
+							ctx.OtherModuleName(module))
 					}
-				} else {
-					ctx.PropertyErrorf("defaults", "module %s is not an defaults module",
-						ctx.OtherModuleName(module))
 				}
-			}
-			return false
-		})
-		defaultable.applyDefaults(ctx, defaultsList)
+				return false
+			})
+			defaultable.applyDefaults(ctx, defaultsList)
+		}
+
+		defaultable.callHookIfAvailable(ctx)
 	}
 }
diff --git a/android/hooks.go b/android/hooks.go
index 47f69d1..f43a007 100644
--- a/android/hooks.go
+++ b/android/hooks.go
@@ -39,6 +39,12 @@
 	moduleFactories() map[string]blueprint.ModuleFactory
 }
 
+// Add a hook that will be called once the module has been loaded, i.e. its
+// properties have been initialized from the Android.bp file.
+//
+// Consider using SetDefaultableHook to register a hook for any module that implements
+// DefaultableModule as the hook is called after any defaults have been applied to the
+// module which could reduce duplication and make it easier to use.
 func AddLoadHook(m blueprint.Module, hook func(LoadHookContext)) {
 	blueprint.AddLoadHook(m, func(ctx blueprint.LoadHookContext) {
 		actx := &loadHookContext{
diff --git a/android/mutator.go b/android/mutator.go
index 79a8506..77d5f43 100644
--- a/android/mutator.go
+++ b/android/mutator.go
@@ -82,10 +82,6 @@
 var preArch = []RegisterMutatorFunc{
 	RegisterNamespaceMutator,
 
-	// Create an association between prebuilt modules and their corresponding source
-	// modules (if any).
-	RegisterPrebuiltsPreArchMutators,
-
 	// Check the visibility rules are valid.
 	//
 	// This must run after the package renamer mutators so that any issues found during
@@ -114,8 +110,19 @@
 	RegisterVisibilityRuleChecker,
 
 	// Apply properties from defaults modules to the referencing modules.
+	//
+	// Any mutators that are added before this will not see any modules created by
+	// a DefaultableHook.
 	RegisterDefaultsPreArchMutators,
 
+	// Create an association between prebuilt modules and their corresponding source
+	// modules (if any).
+	//
+	// Must be run after defaults mutators to ensure that any modules created by
+	// a DefaultableHook can be either a prebuilt or a source module with a matching
+	// prebuilt.
+	RegisterPrebuiltsPreArchMutators,
+
 	// Gather the visibility rules for all modules for us during visibility enforcement.
 	//
 	// This must come after the defaults mutators to ensure that any visibility supplied
diff --git a/android/visibility_test.go b/android/visibility_test.go
index 8dd6a8f..4cf41a6 100644
--- a/android/visibility_test.go
+++ b/android/visibility_test.go
@@ -903,6 +903,69 @@
 				}`),
 		},
 	},
+	{
+		name: "ensure visibility properties are checked for correctness",
+		fs: map[string][]byte{
+			"top/Blueprints": []byte(`
+				mock_parent {
+					name: "parent",
+					visibility: ["//top/nested"],
+					child: {
+						name: "libchild",
+						visibility: ["top/other"],
+					},
+				}`),
+		},
+		expectedErrors: []string{
+			`module "parent": child.visibility: invalid visibility pattern "top/other"`,
+		},
+	},
+	{
+		name: "invalid visibility added to child detected during gather phase",
+		fs: map[string][]byte{
+			"top/Blueprints": []byte(`
+				mock_parent {
+					name: "parent",
+					visibility: ["//top/nested"],
+					child: {
+						name: "libchild",
+						invalid_visibility: ["top/other"],
+					},
+				}`),
+		},
+		expectedErrors: []string{
+			// That this error is reported against the child not the parent shows it was
+			// not being detected in the parent which is correct as invalid_visibility is
+			// purposely not added to the list of visibility properties to check, and was
+			// in fact detected in the child in the gather phase. Contrast this error message
+			// with the preceding one.
+			`module "libchild" \(created by module "parent"\): visibility: invalid visibility pattern "top/other"`,
+		},
+	},
+	{
+		name: "automatic visibility inheritance enabled",
+		fs: map[string][]byte{
+			"top/Blueprints": []byte(`
+				mock_parent {
+					name: "parent",
+					visibility: ["//top/nested"],
+					child: {
+						name: "libchild",
+						visibility: ["//top/other"],
+					},
+				}`),
+			"top/nested/Blueprints": []byte(`
+				mock_library {
+					name: "libnested",
+					deps: ["libchild"],
+				}`),
+			"top/other/Blueprints": []byte(`
+				mock_library {
+					name: "libother",
+					deps: ["libchild"],
+				}`),
+		},
+	},
 }
 
 func TestVisibility(t *testing.T) {
@@ -936,6 +999,7 @@
 
 	ctx := NewTestArchContext()
 	ctx.RegisterModuleType("mock_library", newMockLibraryModule)
+	ctx.RegisterModuleType("mock_parent", newMockParentFactory)
 	ctx.RegisterModuleType("mock_defaults", defaultsFactory)
 
 	// Order of the following method calls is significant.
@@ -996,3 +1060,42 @@
 	InitDefaultsModule(m)
 	return m
 }
+
+type mockParentProperties struct {
+	Child struct {
+		Name *string
+
+		// Visibility to pass to the child module.
+		Visibility []string
+
+		// Purposely not validated visibility to pass to the child.
+		Invalid_visibility []string
+	}
+}
+
+type mockParent struct {
+	ModuleBase
+	DefaultableModuleBase
+	properties mockParentProperties
+}
+
+func (p *mockParent) GenerateAndroidBuildActions(ModuleContext) {
+}
+
+func newMockParentFactory() Module {
+	m := &mockParent{}
+	m.AddProperties(&m.properties)
+	InitAndroidArchModule(m, HostAndDeviceSupported, MultilibCommon)
+	InitDefaultableModule(m)
+	AddVisibilityProperty(m, "child.visibility", &m.properties.Child.Visibility)
+
+	m.SetDefaultableHook(func(ctx DefaultableHookContext) {
+		visibility := m.properties.Child.Visibility
+		visibility = append(visibility, m.properties.Child.Invalid_visibility...)
+		ctx.CreateModule(newMockLibraryModule, &struct {
+			Name       *string
+			Visibility []string
+		}{m.properties.Child.Name, visibility})
+	})
+	return m
+}
diff --git a/apex/apex.go b/apex/apex.go
index d196e95..03df0fb 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -228,7 +228,6 @@
 		"netd_aidl_interface-unstable-java",
 		"netd_event_listener_interface-java",
 		"netlink-client",
-		"networkstack-aidl-interfaces-unstable-java",
 		"networkstack-client",
 		"sap-api-java-static",
 		"services.net",
@@ -680,7 +679,6 @@
 		"netd_aidl_interface-unstable-java",
 		"netd_event_listener_interface-java",
 		"netlink-client",
-		"networkstack-aidl-interfaces-unstable-java",
 		"networkstack-client",
 		"services.net",
 		"wifi-lite-protos",
@@ -2099,8 +2097,8 @@
 							//
 							// Always include if we are a host-apex however since those won't have any
 							// system libraries.
-							if !android.DirectlyInAnyApex(ctx, cc.Name()) && !android.InList(cc.Name(), a.requiredDeps) {
-								a.requiredDeps = append(a.requiredDeps, cc.Name())
+							if !android.DirectlyInAnyApex(ctx, cc.Name()) && !android.InList(cc.BaseModuleName(), a.requiredDeps) {
+								a.requiredDeps = append(a.requiredDeps, cc.BaseModuleName())
 							}
 							requireNativeLibs = append(requireNativeLibs, cc.OutputFile().Path().Base())
 							// Don't track further
diff --git a/apex/apex_test.go b/apex/apex_test.go
index ce39b39..dc69862 100644
--- a/apex/apex_test.go
+++ b/apex/apex_test.go
@@ -4530,12 +4530,12 @@
 	ctx.RegisterModuleType("apex", BundleFactory)
 	ctx.RegisterModuleType("apex_key", ApexKeyFactory)
 	ctx.RegisterModuleType("filegroup", android.FileGroupFactory)
+	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
 	cc.RegisterRequiredBuildComponentsForTest(ctx)
 	java.RegisterJavaBuildComponents(ctx)
 	java.RegisterSystemModulesBuildComponents(ctx)
 	java.RegisterAppBuildComponents(ctx)
 	java.RegisterDexpreoptBootJarsComponents(ctx)
-	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
 	ctx.PostDepsMutators(android.RegisterOverridePostDepsMutators)
 	ctx.PreDepsMutators(RegisterPreDepsMutators)
 	ctx.PostDepsMutators(RegisterPostDepsMutators)
diff --git a/cc/config/arm64_device.go b/cc/config/arm64_device.go
index 5575baa..9383463 100644
--- a/cc/config/arm64_device.go
+++ b/cc/config/arm64_device.go
@@ -92,7 +92,6 @@
 
 	pctx.StaticVariable("Arm64Ldflags", strings.Join(arm64Ldflags, " "))
 	pctx.StaticVariable("Arm64Lldflags", strings.Join(arm64Lldflags, " "))
-	pctx.StaticVariable("Arm64IncludeFlags", bionicHeaders("arm64"))
 
 	pctx.StaticVariable("Arm64ClangCflags", strings.Join(ClangFilterUnknownCflags(arm64Cflags), " "))
 	pctx.StaticVariable("Arm64ClangLdflags", strings.Join(ClangFilterUnknownCflags(arm64Ldflags), " "))
@@ -164,7 +163,7 @@
 }
 
 func (t *toolchainArm64) IncludeFlags() string {
-	return "${config.Arm64IncludeFlags}"
+	return ""
 }
 
 func (t *toolchainArm64) ClangTriple() string {
diff --git a/cc/config/arm_device.go b/cc/config/arm_device.go
index d37e486..f01c638 100644
--- a/cc/config/arm_device.go
+++ b/cc/config/arm_device.go
@@ -175,7 +175,6 @@
 
 	pctx.StaticVariable("ArmLdflags", strings.Join(armLdflags, " "))
 	pctx.StaticVariable("ArmLldflags", strings.Join(armLldflags, " "))
-	pctx.StaticVariable("ArmIncludeFlags", bionicHeaders("arm"))
 
 	// Clang cflags
 	pctx.StaticVariable("ArmToolchainClangCflags", strings.Join(ClangFilterUnknownCflags(armToolchainCflags), " "))
@@ -269,7 +268,7 @@
 }
 
 func (t *toolchainArm) IncludeFlags() string {
-	return "${config.ArmIncludeFlags}"
+	return ""
 }
 
 func (t *toolchainArm) ClangTriple() string {
diff --git a/cc/config/global.go b/cc/config/global.go
index 923dd29..4e51ae9 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -265,16 +265,6 @@
 
 var HostPrebuiltTag = pctx.VariableConfigMethod("HostPrebuiltTag", android.Config.PrebuiltOS)
 
-func bionicHeaders(kernelArch string) string {
-	return strings.Join([]string{
-		"-isystem bionic/libc/include",
-		"-isystem bionic/libc/kernel/uapi",
-		"-isystem bionic/libc/kernel/uapi/asm-" + kernelArch,
-		"-isystem bionic/libc/kernel/android/scsi",
-		"-isystem bionic/libc/kernel/android/uapi",
-	}, " ")
-}
-
 func envOverrideFunc(envVar, defaultVal string) func(ctx android.PackageVarContext) string {
 	return func(ctx android.PackageVarContext) string {
 		if override := ctx.Config().Getenv(envVar); override != "" {
diff --git a/cc/config/x86_64_device.go b/cc/config/x86_64_device.go
index bcfae5d..1e25a3b 100644
--- a/cc/config/x86_64_device.go
+++ b/cc/config/x86_64_device.go
@@ -103,7 +103,6 @@
 
 	pctx.StaticVariable("X86_64Ldflags", strings.Join(x86_64Ldflags, " "))
 	pctx.StaticVariable("X86_64Lldflags", strings.Join(x86_64Lldflags, " "))
-	pctx.StaticVariable("X86_64IncludeFlags", bionicHeaders("x86"))
 
 	// Clang cflags
 	pctx.StaticVariable("X86_64ClangCflags", strings.Join(ClangFilterUnknownCflags(x86_64Cflags), " "))
@@ -145,7 +144,7 @@
 }
 
 func (t *toolchainX86_64) IncludeFlags() string {
-	return "${config.X86_64IncludeFlags}"
+	return ""
 }
 
 func (t *toolchainX86_64) ClangTriple() string {
diff --git a/cc/config/x86_device.go b/cc/config/x86_device.go
index 64392dc..fe83098 100644
--- a/cc/config/x86_device.go
+++ b/cc/config/x86_device.go
@@ -114,7 +114,6 @@
 
 	pctx.StaticVariable("X86Ldflags", strings.Join(x86Ldflags, " "))
 	pctx.StaticVariable("X86Lldflags", strings.Join(x86Lldflags, " "))
-	pctx.StaticVariable("X86IncludeFlags", bionicHeaders("x86"))
 
 	// Clang cflags
 	pctx.StaticVariable("X86ClangCflags", strings.Join(ClangFilterUnknownCflags(x86ClangCflags), " "))
@@ -156,7 +155,7 @@
 }
 
 func (t *toolchainX86) IncludeFlags() string {
-	return "${config.X86IncludeFlags}"
+	return ""
 }
 
 func (t *toolchainX86) ClangTriple() string {
diff --git a/cc/config/x86_linux_bionic_host.go b/cc/config/x86_linux_bionic_host.go
index fb1cdeb..fa625e3 100644
--- a/cc/config/x86_linux_bionic_host.go
+++ b/cc/config/x86_linux_bionic_host.go
@@ -70,8 +70,6 @@
 	pctx.StaticVariable("LinuxBionicLdflags", strings.Join(linuxBionicLdflags, " "))
 	pctx.StaticVariable("LinuxBionicLldflags", strings.Join(linuxBionicLldflags, " "))
 
-	pctx.StaticVariable("LinuxBionicIncludeFlags", bionicHeaders("x86"))
-
 	// Use the device gcc toolchain for now
 	pctx.StaticVariable("LinuxBionicGccRoot", "${X86_64GccRoot}")
 }
@@ -97,7 +95,7 @@
 }
 
 func (t *toolchainLinuxBionic) IncludeFlags() string {
-	return "${config.LinuxBionicIncludeFlags}"
+	return ""
 }
 
 func (t *toolchainLinuxBionic) ClangTriple() string {
diff --git a/cc/testing.go b/cc/testing.go
index 53f0995..6119920 100644
--- a/cc/testing.go
+++ b/cc/testing.go
@@ -485,8 +485,8 @@
 	ctx.RegisterModuleType("filegroup", android.FileGroupFactory)
 	ctx.RegisterModuleType("vndk_prebuilt_shared", VndkPrebuiltSharedFactory)
 	ctx.RegisterModuleType("vndk_libraries_txt", VndkLibrariesTxtFactory)
-	RegisterRequiredBuildComponentsForTest(ctx)
 	ctx.PreArchMutators(android.RegisterDefaultsPreArchMutators)
+	RegisterRequiredBuildComponentsForTest(ctx)
 	ctx.RegisterSingletonType("vndk-snapshot", VndkSnapshotSingleton)
 	ctx.RegisterSingletonType("vendor-snapshot", VendorSnapshotSingleton)
 
diff --git a/java/droiddoc.go b/java/droiddoc.go
index 1c46a2b..879353d 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -1473,6 +1473,104 @@
 		cmd.ImplicitOutput(android.PathForModuleGen(ctx, o))
 	}
 
+	// Add options for the other optional tasks: API-lint and check-released.
+	// We generate separate timestamp files for them.
+
+	doApiLint := false
+	doCheckReleased := false
+
+	// Add API lint options.
+
+	if BoolDefault(d.properties.Check_api.Api_lint.Enabled, false) && !ctx.Config().IsPdkBuild() {
+		doApiLint = true
+
+		newSince := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Api_lint.New_since)
+		if newSince.Valid() {
+			cmd.FlagWithInput("--api-lint ", newSince.Path())
+		} else {
+			cmd.Flag("--api-lint")
+		}
+		d.apiLintReport = android.PathForModuleOut(ctx, "api_lint_report.txt")
+		cmd.FlagWithOutput("--report-even-if-suppressed ", d.apiLintReport) // TODO:  Change to ":api-lint"
+
+		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Api_lint.Baseline_file)
+		updatedBaselineOutput := android.PathForModuleOut(ctx, "api_lint_baseline.txt")
+		d.apiLintTimestamp = android.PathForModuleOut(ctx, "api_lint.timestamp")
+
+		// Note this string includes a special shell quote $' ... ', which decodes the "\n"s.
+		// However, because $' ... ' doesn't expand environmental variables, we can't just embed
+		// $PWD, so we have to terminate $'...', use "$PWD", then start $' ... ' again,
+		// which is why we have '"$PWD"$' in it.
+		//
+		// TODO: metalava also has a slightly different message hardcoded. Should we unify this
+		// message and metalava's one?
+		msg := `$'` + // Enclose with $' ... '
+			`************************************************************\n` +
+			`Your API changes are triggering API Lint warnings or errors.\n` +
+			`To make these errors go away, fix the code according to the\n` +
+			`error and/or warning messages above.\n` +
+			`\n` +
+			`If it is not possible to do so, there are workarounds:\n` +
+			`\n` +
+			`1. You can suppress the errors with @SuppressLint("<id>")\n`
+
+		if baselineFile.Valid() {
+			cmd.FlagWithInput("--baseline:api-lint ", baselineFile.Path())
+			cmd.FlagWithOutput("--update-baseline:api-lint ", updatedBaselineOutput)
+
+			msg += fmt.Sprintf(``+
+				`2. You can update the baseline by executing the following\n`+
+				`   command:\n`+
+				`       cp \\ \n`+
+				`       "'"$PWD"$'/%s" \\ \n`+
+				`       "'"$PWD"$'/%s" \n`+
+				`   To submit the revised baseline.txt to the main Android\n`+
+				`   repository, you will need approval.\n`, updatedBaselineOutput, baselineFile.Path())
+		} else {
+			msg += fmt.Sprintf(``+
+				`2. You can add a baseline file of existing lint failures\n`+
+				`   to the build rule of %s.\n`, d.Name())
+		}
+		// Note the message ends with a ' (single quote), to close the $' ... ' .
+		msg += `************************************************************\n'`
+
+		cmd.FlagWithArg("--error-message:api-lint ", msg)
+	}
+
+	// Add "check released" options. (Detect incompatible API changes from the last public release)
+
+	if apiCheckEnabled(ctx, d.properties.Check_api.Last_released, "last_released") &&
+		!ctx.Config().IsPdkBuild() {
+		doCheckReleased = true
+
+		if len(d.Javadoc.properties.Out) > 0 {
+			ctx.PropertyErrorf("out", "out property may not be combined with check_api")
+		}
+
+		apiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Last_released.Api_file))
+		removedApiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Last_released.Removed_api_file))
+		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Last_released.Baseline_file)
+		updatedBaselineOutput := android.PathForModuleOut(ctx, "last_released_baseline.txt")
+
+		d.checkLastReleasedApiTimestamp = android.PathForModuleOut(ctx, "check_last_released_api.timestamp")
+
+		cmd.FlagWithInput("--check-compatibility:api:released ", apiFile)
+		cmd.FlagWithInput("--check-compatibility:removed:released ", removedApiFile)
+
+		if baselineFile.Valid() {
+			cmd.FlagWithInput("--baseline:compatibility:released ", baselineFile.Path())
+			cmd.FlagWithOutput("--update-baseline:compatibility:released ", updatedBaselineOutput)
+		}
+
+		// Note this string includes quote ($' ... '), which decodes the "\n"s.
+		msg := `$'\n******************************\n` +
+			`You have tried to change the API from what has been previously released in\n` +
+			`an SDK.  Please fix the errors listed above.\n` +
+			`******************************\n'`
+
+		cmd.FlagWithArg("--error-message:compatibility:released ", msg)
+	}
+
 	if generateStubs {
 		rule.Command().
 			BuiltTool(ctx, "soong_zip").
@@ -1494,83 +1592,20 @@
 			FlagWithArg("-D ", d.metadataDir.String())
 	}
 
+	// TODO: We don't really need two separate API files, but this is a reminiscence of how
+	// we used to run metalava separately for API lint and the "last_released" check. Unify them.
+	if doApiLint {
+		rule.Command().Text("touch").Output(d.apiLintTimestamp)
+	}
+	if doCheckReleased {
+		rule.Command().Text("touch").Output(d.checkLastReleasedApiTimestamp)
+	}
+
 	rule.Restat()
 
 	zipSyncCleanupCmd(rule, srcJarDir)
 
-	rule.Build(pctx, ctx, "metalava", "metalava")
-
-	// Create rule for apicheck
-
-	if BoolDefault(d.properties.Check_api.Api_lint.Enabled, false) && !ctx.Config().IsPdkBuild() {
-		rule := android.NewRuleBuilder()
-		rule.Command().Text("( true")
-
-		srcJarDir := android.PathForModuleOut(ctx, "api_lint", "srcjars")
-		srcJarList := zipSyncCmd(ctx, rule, srcJarDir, d.Javadoc.srcJars)
-
-		cmd := metalavaCmd(ctx, rule, javaVersion, d.Javadoc.srcFiles, srcJarList,
-			deps.bootClasspath, deps.classpath, d.Javadoc.sourcepaths)
-
-		cmd.Flag(d.Javadoc.args).Implicits(d.Javadoc.argFiles)
-
-		newSince := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Api_lint.New_since)
-		if newSince.Valid() {
-			cmd.FlagWithInput("--api-lint ", newSince.Path())
-		} else {
-			cmd.Flag("--api-lint")
-		}
-		d.apiLintReport = android.PathForModuleOut(ctx, "api_lint_report.txt")
-		cmd.FlagWithOutput("--report-even-if-suppressed ", d.apiLintReport)
-
-		d.inclusionAnnotationsFlags(ctx, cmd)
-		d.mergeAnnoDirFlags(ctx, cmd)
-
-		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Api_lint.Baseline_file)
-		updatedBaselineOutput := android.PathForModuleOut(ctx, "api_lint_baseline.txt")
-		d.apiLintTimestamp = android.PathForModuleOut(ctx, "api_lint.timestamp")
-
-		msg := `` +
-			`************************************************************\n` +
-			`Your API changes are triggering API Lint warnings or errors.\n` +
-			`To make these errors go away, fix the code according to the\n` +
-			`error and/or warning messages above.\n` +
-			`\n` +
-			`If it's not possible to do so, there are workarounds:\n` +
-			`\n` +
-			`1. You can suppress the errors with @SuppressLint(\"<id>\")\n`
-
-		if baselineFile.Valid() {
-			cmd.FlagWithInput("--baseline ", baselineFile.Path())
-			cmd.FlagWithOutput("--update-baseline ", updatedBaselineOutput)
-
-			msg += fmt.Sprintf(``+
-				`2. You can update the baseline by executing the following\n`+
-				`   command:\n`+
-				`       cp \\ \n`+
-				`       \"$PWD/%s\" \\ \n`+
-				`       \"$PWD/%s\" \n`+
-				`   To submit the revised baseline.txt to the main Android\n`+
-				`   repository, you will need approval.\n`, updatedBaselineOutput, baselineFile.Path())
-		} else {
-			msg += fmt.Sprintf(``+
-				`2. You can add a baseline file of existing lint failures\n`+
-				`   to the build rule of %s.\n`, d.Name())
-		}
-		msg += `************************************************************\n`
-
-		zipSyncCleanupCmd(rule, srcJarDir)
-
-		rule.Command().
-			Text("touch").Output(d.apiLintTimestamp).
-			Text(") || (").
-			Text("echo").Flag("-e").Flag(`"` + msg + `"`).
-			Text("; exit 38").
-			Text(")")
-
-		rule.Build(pctx, ctx, "metalavaApiLint", "metalava API lint")
-
-	}
+	rule.Build(pctx, ctx, "metalava", "metalava merged")
 
 	if apiCheckEnabled(ctx, d.properties.Check_api.Current, "current") &&
 		!ctx.Config().IsPdkBuild() {
@@ -1584,7 +1619,7 @@
 		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Current.Baseline_file)
 
 		if baselineFile.Valid() {
-			ctx.PropertyErrorf("current API check can't have a baseline file. (module %s)", ctx.ModuleName())
+			ctx.PropertyErrorf("baseline_file", "current API check can't have a baseline file. (module %s)", ctx.ModuleName())
 		}
 
 		d.checkCurrentApiTimestamp = android.PathForModuleOut(ctx, "check_current_api.timestamp")
@@ -1592,8 +1627,8 @@
 		rule := android.NewRuleBuilder()
 
 		// Diff command line.
-		// -F matches the closest "opening" line, such as "package xxx{"
-		// and "  public class Yyy {".
+		// -F matches the closest "opening" line, such as "package android {"
+		// and "  public class Intent {".
 		diff := `diff -u -F '{ *$'`
 
 		rule.Command().Text("( true")
@@ -1652,60 +1687,6 @@
 		rule.Build(pctx, ctx, "metalavaCurrentApiUpdate", "update current API")
 	}
 
-	if apiCheckEnabled(ctx, d.properties.Check_api.Last_released, "last_released") &&
-		!ctx.Config().IsPdkBuild() {
-
-		if len(d.Javadoc.properties.Out) > 0 {
-			ctx.PropertyErrorf("out", "out property may not be combined with check_api")
-		}
-
-		apiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Last_released.Api_file))
-		removedApiFile := android.PathForModuleSrc(ctx, String(d.properties.Check_api.Last_released.Removed_api_file))
-		baselineFile := android.OptionalPathForModuleSrc(ctx, d.properties.Check_api.Last_released.Baseline_file)
-		updatedBaselineOutput := android.PathForModuleOut(ctx, "last_released_baseline.txt")
-
-		d.checkLastReleasedApiTimestamp = android.PathForModuleOut(ctx, "check_last_released_api.timestamp")
-
-		rule := android.NewRuleBuilder()
-
-		rule.Command().Text("( true")
-
-		srcJarDir := android.PathForModuleOut(ctx, "last-apicheck", "srcjars")
-		srcJarList := zipSyncCmd(ctx, rule, srcJarDir, d.Javadoc.srcJars)
-
-		cmd := metalavaCmd(ctx, rule, javaVersion, d.Javadoc.srcFiles, srcJarList,
-			deps.bootClasspath, deps.classpath, d.Javadoc.sourcepaths)
-
-		cmd.Flag(d.Javadoc.args).Implicits(d.Javadoc.argFiles).
-			FlagWithInput("--check-compatibility:api:released ", apiFile)
-
-		d.inclusionAnnotationsFlags(ctx, cmd)
-
-		cmd.FlagWithInput("--check-compatibility:removed:released ", removedApiFile)
-
-		d.mergeAnnoDirFlags(ctx, cmd)
-
-		if baselineFile.Valid() {
-			cmd.FlagWithInput("--baseline ", baselineFile.Path())
-			cmd.FlagWithOutput("--update-baseline ", updatedBaselineOutput)
-		}
-
-		zipSyncCleanupCmd(rule, srcJarDir)
-
-		msg := `\n******************************\n` +
-			`You have tried to change the API from what has been previously released in\n` +
-			`an SDK.  Please fix the errors listed above.\n` +
-			`******************************\n`
-		rule.Command().
-			Text("touch").Output(d.checkLastReleasedApiTimestamp).
-			Text(") || (").
-			Text("echo").Flag("-e").Flag(`"` + msg + `"`).
-			Text("; exit 38").
-			Text(")")
-
-		rule.Build(pctx, ctx, "metalavaLastApiCheck", "metalava check last API")
-	}
-
 	if String(d.properties.Check_nullability_warnings) != "" {
 		if d.nullabilityWarningsFile == nil {
 			ctx.PropertyErrorf("check_nullability_warnings",
diff --git a/java/sdk_library.go b/java/sdk_library.go
index d70f632..4d480ee 100644
--- a/java/sdk_library.go
+++ b/java/sdk_library.go
@@ -67,6 +67,9 @@
 	// The name of the api scope, e.g. public, system, test
 	name string
 
+	// The api scope that this scope extends.
+	extends *apiScope
+
 	// The name of the field in the dynamically created structure.
 	fieldName string
 
@@ -134,6 +137,7 @@
 	})
 	apiScopeSystem = initApiScope(&apiScope{
 		name:           "system",
+		extends:        apiScopePublic,
 		apiFilePrefix:  "system-",
 		moduleSuffix:   sdkSystemApiSuffix,
 		sdkVersion:     "system_current",
@@ -141,6 +145,7 @@
 	})
 	apiScopeTest = initApiScope(&apiScope{
 		name:           "test",
+		extends:        apiScopePublic,
 		apiFilePrefix:  "test-",
 		moduleSuffix:   sdkTestApiSuffix,
 		sdkVersion:     "test_current",
diff --git a/scripts/build-aml-prebuilts.sh b/scripts/build-aml-prebuilts.sh
index eef6149..c60eaa1 100755
--- a/scripts/build-aml-prebuilts.sh
+++ b/scripts/build-aml-prebuilts.sh
@@ -1,5 +1,15 @@
 #!/bin/bash -e
 
+# This is a wrapper around "m" that builds the given modules in multi-arch mode
+# for all architectures supported by Mainline modules. The make (kati) stage is
+# skipped, so the build targets in the arguments can only be Soong modules or
+# intermediate output files - make targets and normal installed paths are not
+# supported.
+#
+# This script is typically used with "sdk" or "module_export" modules, which
+# Soong will install in $OUT_DIR/soong/mainline-sdks (cf
+# PathForMainlineSdksInstall in android/paths.go).
+
 export OUT_DIR=${OUT_DIR:-out}
 
 if [ -e ${OUT_DIR}/soong/.soong.in_make ]; then
@@ -8,11 +18,16 @@
   # expected to be supplied by the .mk files, and that might cause errors in
   # "m --skip-make" below. We therefore default to a different out dir
   # location in that case.
-  AML_OUT_DIR=out-aml
+  AML_OUT_DIR=out/aml
   echo "Avoiding in-make OUT_DIR '${OUT_DIR}' - building in '${AML_OUT_DIR}' instead"
   OUT_DIR=${AML_OUT_DIR}
 fi
 
+if [ ! -e "build/envsetup.sh" ]; then
+  echo "$0 must be run from the top of the tree"
+  exit 1
+fi
+
 source build/envsetup.sh
 
 my_get_build_var() {
@@ -22,13 +37,13 @@
   OUT_DIR=${OUT_DIR}/get_build_var get_build_var "$@"
 }
 
-PLATFORM_SDK_VERSION=$(my_get_build_var PLATFORM_SDK_VERSION)
-PLATFORM_VERSION=$(my_get_build_var PLATFORM_VERSION)
-PLATFORM_VERSION_ALL_CODENAMES=$(my_get_build_var PLATFORM_VERSION_ALL_CODENAMES)
+readonly PLATFORM_SDK_VERSION="$(my_get_build_var PLATFORM_SDK_VERSION)"
+readonly PLATFORM_VERSION="$(my_get_build_var PLATFORM_VERSION)"
+PLATFORM_VERSION_ALL_CODENAMES="$(my_get_build_var PLATFORM_VERSION_ALL_CODENAMES)"
 
 # PLATFORM_VERSION_ALL_CODENAMES is a comma separated list like O,P. We need to
 # turn this into ["O","P"].
-PLATFORM_VERSION_ALL_CODENAMES=${PLATFORM_VERSION_ALL_CODENAMES/,/'","'}
+PLATFORM_VERSION_ALL_CODENAMES="${PLATFORM_VERSION_ALL_CODENAMES/,/'","'}"
 PLATFORM_VERSION_ALL_CODENAMES="[\"${PLATFORM_VERSION_ALL_CODENAMES}\"]"
 
 # Logic from build/make/core/goma.mk
@@ -46,11 +61,16 @@
   USE_GOMA=false
 fi
 
-SOONG_OUT=${OUT_DIR}/soong
+readonly SOONG_OUT=${OUT_DIR}/soong
 mkdir -p ${SOONG_OUT}
-SOONG_VARS=${SOONG_OUT}/soong.variables
+readonly SOONG_VARS=${SOONG_OUT}/soong.variables
 
-# We enable bionic linux builds as ART also needs prebuilts for it.
+# Aml_abis: true
+#   -  This flag configures Soong to compile for all architectures required for
+#      Mainline modules.
+# CrossHost: linux_bionic
+# CrossHostArch: x86_64
+#   -  Enable Bionic on host as ART needs prebuilts for it.
 cat > ${SOONG_VARS}.new << EOF
 {
     "Platform_sdk_version": ${PLATFORM_SDK_VERSION},
@@ -79,4 +99,6 @@
 # We use force building LLVM components flag (even though we actually don't
 # compile them) because we don't have bionic host prebuilts
 # for them.
-FORCE_BUILD_LLVM_COMPONENTS=true m --skip-make "$@"
+export FORCE_BUILD_LLVM_COMPONENTS=true
+
+m --skip-make "$@"
diff --git a/scripts/build-mainline-modules.sh b/scripts/build-mainline-modules.sh
index fc91c3d..770adc9 100755
--- a/scripts/build-mainline-modules.sh
+++ b/scripts/build-mainline-modules.sh
@@ -1,4 +1,4 @@
-#!/bin/bash -ex
+#!/bin/bash -e
 
 # Non exhaustive list of modules where we want prebuilts. More can be added as
 # needed.
@@ -23,42 +23,45 @@
 
 # We want to create apex modules for all supported architectures.
 PRODUCTS=(
-    aosp_arm
-    aosp_arm64
-    aosp_x86
-    aosp_x86_64
+  aosp_arm
+  aosp_arm64
+  aosp_x86
+  aosp_x86_64
 )
 
 if [ ! -e "build/make/core/Makefile" ]; then
-    echo "$0 must be run from the top of the tree"
-    exit 1
+  echo "$0 must be run from the top of the tree"
+  exit 1
 fi
 
+echo_and_run() {
+  echo "$*"
+  "$@"
+}
+
 OUT_DIR=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT= get_build_var OUT_DIR)
 DIST_DIR=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT= get_build_var DIST_DIR)
 
 for product in "${PRODUCTS[@]}"; do
-    build/soong/soong_ui.bash --make-mode $@ \
-        TARGET_PRODUCT=${product} \
-        ${MAINLINE_MODULES[@]}
+  echo_and_run build/soong/soong_ui.bash --make-mode $@ \
+    TARGET_PRODUCT=${product} \
+    ${MAINLINE_MODULES[@]}
 
-    PRODUCT_OUT=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT=${product} get_build_var PRODUCT_OUT)
-    TARGET_ARCH=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT=${product} get_build_var TARGET_ARCH)
-    rm -rf ${DIST_DIR}/${TARGET_ARCH}/
-    mkdir -p ${DIST_DIR}/${TARGET_ARCH}/
-    for module in "${MAINLINE_MODULES[@]}"; do
-      cp ${PWD}/${PRODUCT_OUT}/system/apex/${module}.apex ${DIST_DIR}/${TARGET_ARCH}/
-    done
+  PRODUCT_OUT=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT=${product} get_build_var PRODUCT_OUT)
+  TARGET_ARCH=$(source build/envsetup.sh > /dev/null; TARGET_PRODUCT=${product} get_build_var TARGET_ARCH)
+  rm -rf ${DIST_DIR}/${TARGET_ARCH}/
+  mkdir -p ${DIST_DIR}/${TARGET_ARCH}/
+  for module in "${MAINLINE_MODULES[@]}"; do
+    echo_and_run cp ${PWD}/${PRODUCT_OUT}/system/apex/${module}.apex ${DIST_DIR}/${TARGET_ARCH}/
+  done
 done
 
 
 # Create multi-archs SDKs in a different out directory. The multi-arch script
-# uses soong directly and therefore needs its own directory that doesn't clash
-# with make.
-export OUT_DIR=${OUT_DIR}/aml/
-for sdk in "${MODULES_SDK_AND_EXPORTS[@]}"; do
-    build/soong/scripts/build-aml-prebuilts.sh ${sdk}
-done
+# uses Soong in --skip-make mode which cannot use the same directory as normal
+# mode with make.
+export OUT_DIR=${OUT_DIR}/aml
+echo_and_run build/soong/scripts/build-aml-prebuilts.sh ${MODULES_SDK_AND_EXPORTS[@]}
 
 rm -rf ${DIST_DIR}/mainline-sdks
-cp -R ${OUT_DIR}/soong/mainline-sdks ${DIST_DIR}
+echo_and_run cp -R ${OUT_DIR}/soong/mainline-sdks ${DIST_DIR}