diff --git a/android/bazel.go b/android/bazel.go
index 342b840..97226c6 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -485,11 +485,12 @@
 		"conscrypt",          // b/210751803, we don't handle path property for filegroups
 		"conscrypt-for-host", // b/210751803, we don't handle path property for filegroups
 
-		"host-libprotobuf-java-lite",  // b/217236083, java_library cannot have deps without srcs
-		"host-libprotobuf-java-micro", // b/217236083, java_library cannot have deps without srcs
-		"host-libprotobuf-java-nano",  // b/217236083, java_library cannot have deps without srcs
-		"error_prone_core",            // b/217236083, java_library cannot have deps without srcs
-		"bouncycastle-host",           // b/217236083, java_library cannot have deps without srcs
+		"host-libprotobuf-java-lite",   // b/217236083, java_library cannot have deps without srcs
+		"host-libprotobuf-java-micro",  // b/217236083, java_library cannot have deps without srcs
+		"host-libprotobuf-java-nano",   // b/217236083, java_library cannot have deps without srcs
+		"error_prone_core",             // b/217236083, java_library cannot have deps without srcs
+		"bouncycastle-host",            // b/217236083, java_library cannot have deps without srcs
+		"mockito-robolectric-prebuilt", // b/217236083, java_library cannot have deps without srcs
 
 		"apex_manifest_proto_java", // b/215230097, we don't handle .proto files in java_library srcs attribute
 
@@ -559,6 +560,8 @@
 		"dex2oat-script", // depends on unconverted modules: dex2oat
 
 		"error_prone_checkerframework_dataflow_nullaway", // TODO(b/219908977): "Error in fail: deps not allowed without srcs; move to runtime_deps?"
+
+		"libprotobuf-java-nano", // b/220869005, depends on non-public_current SDK
 	}
 
 	// Per-module denylist of cc_library modules to only generate the static
diff --git a/android/hooks.go b/android/hooks.go
index bded764..5e3a4a7 100644
--- a/android/hooks.go
+++ b/android/hooks.go
@@ -15,7 +15,10 @@
 package android
 
 import (
+	"fmt"
+	"path"
 	"reflect"
+	"runtime"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
@@ -88,7 +91,19 @@
 
 func (l *loadHookContext) CreateModule(factory ModuleFactory, props ...interface{}) Module {
 	inherited := []interface{}{&l.Module().base().commonProperties}
-	module := l.bp.CreateModule(ModuleFactoryAdaptor(factory), append(inherited, props...)...).(Module)
+
+	var typeName string
+	if typeNameLookup, ok := ModuleTypeByFactory()[reflect.ValueOf(factory)]; ok {
+		typeName = typeNameLookup
+	} else {
+		factoryPtr := reflect.ValueOf(factory).Pointer()
+		factoryFunc := runtime.FuncForPC(factoryPtr)
+		filePath, _ := factoryFunc.FileLine(factoryPtr)
+		typeName = fmt.Sprintf("%s_%s", path.Base(filePath), factoryFunc.Name())
+	}
+	typeName = typeName + "_loadHookModule"
+
+	module := l.bp.CreateModule(ModuleFactoryAdaptor(factory), typeName, append(inherited, props...)...).(Module)
 
 	if l.Module().base().variableProperties != nil && module.base().variableProperties != nil {
 		src := l.Module().base().variableProperties
diff --git a/android/register.go b/android/register.go
index 10e14e0..c505833 100644
--- a/android/register.go
+++ b/android/register.go
@@ -59,6 +59,7 @@
 
 var moduleTypes []moduleType
 var moduleTypesForDocs = map[string]reflect.Value{}
+var moduleTypeByFactory = map[reflect.Value]string{}
 
 type singleton struct {
 	// True if this should be registered as a pre-singleton, false otherwise.
@@ -140,6 +141,7 @@
 // RegisterModuleType was a lambda.
 func RegisterModuleTypeForDocs(name string, factory reflect.Value) {
 	moduleTypesForDocs[name] = factory
+	moduleTypeByFactory[factory] = name
 }
 
 func RegisterSingletonType(name string, factory SingletonFactory) {
@@ -228,6 +230,10 @@
 	return moduleTypesForDocs
 }
 
+func ModuleTypeByFactory() map[reflect.Value]string {
+	return moduleTypeByFactory
+}
+
 // Interface for registering build components.
 //
 // Provided to allow registration of build components to be shared between the runtime
diff --git a/bp2build/android_app_conversion_test.go b/bp2build/android_app_conversion_test.go
index 42c1a54..b6095b2 100644
--- a/bp2build/android_app_conversion_test.go
+++ b/bp2build/android_app_conversion_test.go
@@ -94,3 +94,42 @@
 			}),
 		}})
 }
+
+func TestAndroidAppArchVariantSrcs(t *testing.T) {
+	runAndroidAppTestCase(t, bp2buildTestCase{
+		description:                "Android app - arch variant srcs",
+		moduleTypeUnderTest:        "android_app",
+		moduleTypeUnderTestFactory: java.AndroidAppFactory,
+		filesystem: map[string]string{
+			"arm.java":            "",
+			"x86.java":            "",
+			"res/res.png":         "",
+			"AndroidManifest.xml": "",
+		},
+		blueprint: `
+android_app {
+        name: "TestApp",
+        sdk_version: "current",
+        arch: {
+			arm: {
+				srcs: ["arm.java"],
+			},
+			x86: {
+				srcs: ["x86.java"],
+			}
+		}
+}
+`,
+		expectedBazelTargets: []string{
+			makeBazelTarget("android_binary", "TestApp", attrNameToString{
+				"srcs": `select({
+        "//build/bazel/platforms/arch:arm": ["arm.java"],
+        "//build/bazel/platforms/arch:x86": ["x86.java"],
+        "//conditions:default": [],
+    })`,
+				"manifest":       `"AndroidManifest.xml"`,
+				"resource_files": `["res/res.png"]`,
+				"deps":           `["//prebuilts/sdk:public_current_android_sdk_java_import"]`,
+			}),
+		}})
+}
diff --git a/java/droidstubs.go b/java/droidstubs.go
index 272cf1e..2921c3e 100644
--- a/java/droidstubs.go
+++ b/java/droidstubs.go
@@ -477,7 +477,9 @@
 		Flag("--format=v2").
 		FlagWithArg("--repeat-errors-max ", "10").
 		FlagWithArg("--hide ", "UnresolvedImport").
-		FlagWithArg("--hide ", "InvalidNullability")
+		FlagWithArg("--hide ", "InvalidNullability").
+		// b/223382732
+		FlagWithArg("--hide ", "ChangedDefault")
 
 	return cmd
 }
diff --git a/java/java.go b/java/java.go
index 0a35908..895ce7a 100644
--- a/java/java.go
+++ b/java/java.go
@@ -2011,8 +2011,16 @@
 }
 
 func (m *Library) convertLibraryAttrsBp2Build(ctx android.TopDownMutatorContext) *javaLibraryAttributes {
-	//TODO(b/209577426): Support multiple arch variants
-	srcs := bazel.MakeLabelListAttribute(android.BazelLabelForModuleSrcExcludes(ctx, m.properties.Srcs, m.properties.Exclude_srcs))
+	var srcs bazel.LabelListAttribute
+	archVariantProps := m.GetArchVariantProperties(ctx, &CommonProperties{})
+	for axis, configToProps := range archVariantProps {
+		for config, _props := range configToProps {
+			if archProps, ok := _props.(*CommonProperties); ok {
+				archSrcs := android.BazelLabelForModuleSrcExcludes(ctx, archProps.Srcs, archProps.Exclude_srcs)
+				srcs.SetSelectValue(axis, config, archSrcs)
+			}
+		}
+	}
 
 	javaSrcPartition := "java"
 	protoSrcPartition := "proto"
diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index d108a0d..d8b88b2 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -50,15 +50,12 @@
 	soongNsPrefix = "SOONG_CONFIG_"
 
 	// And here are the functions and variables:
-	cfnGetCfg          = baseName + ".cfg"
-	cfnMain            = baseName + ".product_configuration"
-	cfnBoardMain       = baseName + ".board_configuration"
-	cfnPrintVars       = baseName + ".printvars"
-	cfnWarning         = baseName + ".warning"
-	cfnLocalAppend     = baseName + ".local_append"
-	cfnLocalSetDefault = baseName + ".local_set_default"
-	cfnInherit         = baseName + ".inherit"
-	cfnSetListDefault  = baseName + ".setdefault"
+	cfnGetCfg         = baseName + ".cfg"
+	cfnMain           = baseName + ".product_configuration"
+	cfnBoardMain      = baseName + ".board_configuration"
+	cfnPrintVars      = baseName + ".printvars"
+	cfnInherit        = baseName + ".inherit"
+	cfnSetListDefault = baseName + ".setdefault"
 )
 
 const (
@@ -571,11 +568,7 @@
 	case "=", ":=":
 		asgn.flavor = asgnSet
 	case "+=":
-		if asgn.previous == nil && !asgn.lhs.isPreset() {
-			asgn.flavor = asgnMaybeAppend
-		} else {
-			asgn.flavor = asgnAppend
-		}
+		asgn.flavor = asgnAppend
 	case "?=":
 		asgn.flavor = asgnMaybeSet
 	default:
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 556dcaa..35c54d2 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -901,6 +901,43 @@
 `,
 	},
 	{
+		desc:   "assigment setdefaults",
+		mkname: "product.mk",
+		in: `
+# All of these should have a setdefault because they're self-referential and not defined before
+PRODUCT_LIST1 = a $(PRODUCT_LIST1)
+PRODUCT_LIST2 ?= a $(PRODUCT_LIST2)
+PRODUCT_LIST3 += a
+
+# Now doing them again should not have a setdefault because they've already been set
+PRODUCT_LIST1 = a $(PRODUCT_LIST1)
+PRODUCT_LIST2 ?= a $(PRODUCT_LIST2)
+PRODUCT_LIST3 += a
+`,
+		expected: `# All of these should have a setdefault because they're self-referential and not defined before
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  rblf.setdefault(handle, "PRODUCT_LIST1")
+  cfg["PRODUCT_LIST1"] = (["a"] +
+      cfg.get("PRODUCT_LIST1", []))
+  if cfg.get("PRODUCT_LIST2") == None:
+    rblf.setdefault(handle, "PRODUCT_LIST2")
+    cfg["PRODUCT_LIST2"] = (["a"] +
+        cfg.get("PRODUCT_LIST2", []))
+  rblf.setdefault(handle, "PRODUCT_LIST3")
+  cfg["PRODUCT_LIST3"] += ["a"]
+  # Now doing them again should not have a setdefault because they've already been set
+  cfg["PRODUCT_LIST1"] = (["a"] +
+      cfg["PRODUCT_LIST1"])
+  if cfg.get("PRODUCT_LIST2") == None:
+    cfg["PRODUCT_LIST2"] = (["a"] +
+        cfg["PRODUCT_LIST2"])
+  cfg["PRODUCT_LIST3"] += ["a"]
+`,
+	},
+	{
 		desc:   "soong namespace assignments",
 		mkname: "product.mk",
 		in: `
diff --git a/mk2rbc/node.go b/mk2rbc/node.go
index 5d98d7b..9d5af91 100644
--- a/mk2rbc/node.go
+++ b/mk2rbc/node.go
@@ -184,10 +184,9 @@
 
 const (
 	// Assignment flavors
-	asgnSet         assignmentFlavor = iota // := or =
-	asgnMaybeSet    assignmentFlavor = iota // ?= and variable may be unset
-	asgnAppend      assignmentFlavor = iota // += and variable has been set before
-	asgnMaybeAppend assignmentFlavor = iota // += and variable may be unset
+	asgnSet      assignmentFlavor = iota // := or =
+	asgnMaybeSet assignmentFlavor = iota // ?=
+	asgnAppend   assignmentFlavor = iota // +=
 )
 
 type assignmentNode struct {
@@ -215,6 +214,20 @@
 	}
 }
 
+func (asgn *assignmentNode) isSelfReferential() bool {
+	if asgn.flavor == asgnAppend {
+		return true
+	}
+	isSelfReferential := false
+	asgn.value.transform(func(expr starlarkExpr) starlarkExpr {
+		if ref, ok := expr.(*variableRefExpr); ok && ref.ref.name() == asgn.lhs.name() {
+			isSelfReferential = true
+		}
+		return nil
+	})
+	return isSelfReferential
+}
+
 type exprNode struct {
 	expr starlarkExpr
 }
diff --git a/mk2rbc/variable.go b/mk2rbc/variable.go
index 6805744..3241a38 100644
--- a/mk2rbc/variable.go
+++ b/mk2rbc/variable.go
@@ -97,29 +97,27 @@
 		gctx.newLine()
 	}
 
+	// If we are not sure variable has been assigned before, emit setdefault
+	needsSetDefault := asgn.previous == nil && !pcv.isPreset() && asgn.isSelfReferential()
+
 	switch asgn.flavor {
 	case asgnSet:
-		isSelfReferential := false
-		asgn.value.transform(func(expr starlarkExpr) starlarkExpr {
-			if ref, ok := expr.(*variableRefExpr); ok && ref.ref.name() == pcv.name() {
-				isSelfReferential = true
-			}
-			return nil
-		})
-		if isSelfReferential {
+		if needsSetDefault {
 			emitSetDefault()
 		}
 		emitAssignment()
 	case asgnAppend:
-		emitAppend()
-	case asgnMaybeAppend:
-		// If we are not sure variable has been assigned before, emit setdefault
-		emitSetDefault()
+		if needsSetDefault {
+			emitSetDefault()
+		}
 		emitAppend()
 	case asgnMaybeSet:
 		gctx.writef("if cfg.get(%q) == None:", pcv.nam)
 		gctx.indentLevel++
 		gctx.newLine()
+		if needsSetDefault {
+			emitSetDefault()
+		}
 		emitAssignment()
 		gctx.indentLevel--
 	}
@@ -134,7 +132,7 @@
 }
 
 func (pcv productConfigVariable) emitDefined(gctx *generationContext) {
-	gctx.writef("g.get(%q) != None", pcv.name())
+	gctx.writef("cfg.get(%q) != None", pcv.name())
 }
 
 type otherGlobalVariable struct {
@@ -159,20 +157,30 @@
 		value.emit(gctx)
 	}
 
+	// If we are not sure variable has been assigned before, emit setdefault
+	needsSetDefault := asgn.previous == nil && !scv.isPreset() && asgn.isSelfReferential()
+
 	switch asgn.flavor {
 	case asgnSet:
+		if needsSetDefault {
+			gctx.writef("g.setdefault(%q, %s)", scv.name(), scv.defaultValueString())
+			gctx.newLine()
+		}
 		emitAssignment()
 	case asgnAppend:
-		emitAppend()
-	case asgnMaybeAppend:
-		// If we are not sure variable has been assigned before, emit setdefault
-		gctx.writef("g.setdefault(%q, %s)", scv.name(), scv.defaultValueString())
-		gctx.newLine()
+		if needsSetDefault {
+			gctx.writef("g.setdefault(%q, %s)", scv.name(), scv.defaultValueString())
+			gctx.newLine()
+		}
 		emitAppend()
 	case asgnMaybeSet:
 		gctx.writef("if g.get(%q) == None:", scv.nam)
 		gctx.indentLevel++
 		gctx.newLine()
+		if needsSetDefault {
+			gctx.writef("g.setdefault(%q, %s)", scv.name(), scv.defaultValueString())
+			gctx.newLine()
+		}
 		emitAssignment()
 		gctx.indentLevel--
 	}
@@ -204,7 +212,7 @@
 
 func (lv localVariable) emitSet(gctx *generationContext, asgn *assignmentNode) {
 	switch asgn.flavor {
-	case asgnSet:
+	case asgnSet, asgnMaybeSet:
 		gctx.writef("%s = ", lv)
 		asgn.value.emitListVarCopy(gctx)
 	case asgnAppend:
@@ -216,14 +224,6 @@
 			value = &toStringExpr{expr: value}
 		}
 		value.emit(gctx)
-	case asgnMaybeAppend:
-		gctx.writef("%s(%q, ", cfnLocalAppend, lv)
-		asgn.value.emit(gctx)
-		gctx.write(")")
-	case asgnMaybeSet:
-		gctx.writef("%s(%q, ", cfnLocalSetDefault, lv)
-		asgn.value.emit(gctx)
-		gctx.write(")")
 	}
 }
 
diff --git a/rust/config/allowed_list.go b/rust/config/allowed_list.go
index 14fcb02..bc36b20 100644
--- a/rust/config/allowed_list.go
+++ b/rust/config/allowed_list.go
@@ -24,6 +24,7 @@
 		"packages/modules/DnsResolver",
 		"packages/modules/Uwb",
 		"packages/modules/Virtualization",
+		"platform_testing/tests/codecoverage/native/rust",
 		"prebuilts/rust",
 		"system/core/libstats/pull_rust",
 		"system/extras/profcollectd",
diff --git a/scripts/hiddenapi/Android.bp b/scripts/hiddenapi/Android.bp
index 7ffda62..8a47c5d 100644
--- a/scripts/hiddenapi/Android.bp
+++ b/scripts/hiddenapi/Android.bp
@@ -69,10 +69,37 @@
     },
 }
 
+python_library_host {
+    name: "signature_trie",
+    srcs: ["signature_trie.py"],
+}
+
+python_test_host {
+    name: "signature_trie_test",
+    main: "signature_trie_test.py",
+    srcs: ["signature_trie_test.py"],
+    libs: ["signature_trie"],
+    version: {
+        py2: {
+            enabled: false,
+        },
+        py3: {
+            enabled: true,
+            embedded_launcher: true,
+        },
+    },
+    test_options: {
+        unit_test: true,
+    },
+}
+
 python_binary_host {
     name: "verify_overlaps",
     main: "verify_overlaps.py",
     srcs: ["verify_overlaps.py"],
+    libs: [
+        "signature_trie",
+    ],
     version: {
         py2: {
             enabled: false,
@@ -91,6 +118,9 @@
         "verify_overlaps.py",
         "verify_overlaps_test.py",
     ],
+    libs: [
+        "signature_trie",
+    ],
     version: {
         py2: {
             enabled: false,
diff --git a/scripts/hiddenapi/signature_trie.py b/scripts/hiddenapi/signature_trie.py
new file mode 100644
index 0000000..2ea8c49
--- /dev/null
+++ b/scripts/hiddenapi/signature_trie.py
@@ -0,0 +1,256 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2022 The Android Open Source Project
+#
+# 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.
+"""Verify that one set of hidden API flags is a subset of another."""
+import dataclasses
+import typing
+
+from itertools import chain
+
+
+@dataclasses.dataclass()
+class Node:
+
+    def values(self, selector):
+        """Get the values from a set of selected nodes.
+
+        :param selector: a function that can be applied to a key in the nodes
+            attribute to determine whether to return its values.
+
+        :return: A list of iterables of all the values associated with
+            this node and its children.
+        """
+        raise NotImplementedError("Please Implement this method")
+
+    def append_values(self, values, selector):
+        """Append the values associated with this node and its children.
+
+        For each item (key, child) in nodes the child node's values are returned
+        if and only if the selector returns True when called on its key. A child
+        node's values are all the values associated with it and all its
+        descendant nodes.
+
+        :param selector: a function that can be applied to a key in the nodes
+        attribute to determine whether to return its values.
+        :param values: a list of a iterables of values.
+        """
+        raise NotImplementedError("Please Implement this method")
+
+
+# pylint: disable=line-too-long
+@dataclasses.dataclass()
+class InteriorNode(Node):
+    """An interior node in a trie.
+
+    Each interior node has a dict that maps from an element of a signature to
+    either another interior node or a leaf. Each interior node represents either
+    a package, class or nested class. Class members are represented by a Leaf.
+
+    Associating the set of flags [public-api] with the signature
+    "Ljava/lang/Object;->String()Ljava/lang/String;" will cause the following
+    nodes to be created:
+    Node()
+    ^- package:java -> Node()
+       ^- package:lang -> Node()
+           ^- class:Object -> Node()
+              ^- member:String()Ljava/lang/String; -> Leaf([public-api])
+
+    Associating the set of flags [blocked,core-platform-api] with the signature
+    "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;"
+    will cause the following nodes to be created:
+    Node()
+    ^- package:java -> Node()
+       ^- package:lang -> Node()
+           ^- class:Character -> Node()
+              ^- class:UnicodeScript -> Node()
+                 ^- member:of(I)Ljava/lang/Character$UnicodeScript;
+                    -> Leaf([blocked,core-platform-api])
+    """
+
+    # pylint: enable=line-too-long
+
+    # A dict from an element of the signature to the Node/Leaf containing the
+    # next element/value.
+    nodes: typing.Dict[str, Node] = dataclasses.field(default_factory=dict)
+
+    # pylint: disable=line-too-long
+    @staticmethod
+    def signature_to_elements(signature):
+        """Split a signature or a prefix into a number of elements:
+
+        1. The packages (excluding the leading L preceding the first package).
+        2. The class names, from outermost to innermost.
+        3. The member signature.
+        e.g.
+        Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
+        will be broken down into these elements:
+        1. package:java
+        2. package:lang
+        3. class:Character
+        4. class:UnicodeScript
+        5. member:of(I)Ljava/lang/Character$UnicodeScript;
+        """
+        # Remove the leading L.
+        #  - java/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
+        text = signature.removeprefix("L")
+        # Split the signature between qualified class name and the class member
+        # signature.
+        #  0 - java/lang/Character$UnicodeScript
+        #  1 - of(I)Ljava/lang/Character$UnicodeScript;
+        parts = text.split(";->")
+        member = parts[1:]
+        # Split the qualified class name into packages, and class name.
+        #  0 - java
+        #  1 - lang
+        #  2 - Character$UnicodeScript
+        elements = parts[0].split("/")
+        packages = elements[0:-1]
+        class_name = elements[-1]
+        if class_name in ("*", "**"):  # pylint: disable=no-else-return
+            # Cannot specify a wildcard and target a specific member
+            if len(member) != 0:
+                raise Exception(f"Invalid signature {signature}: contains "
+                                f"wildcard {class_name} and "
+                                f"member signature {member[0]}")
+            wildcard = [class_name]
+            # Assemble the parts into a single list, adding prefixes to identify
+            # the different parts.
+            #  0 - package:java
+            #  1 - package:lang
+            #  2 - *
+            return list(chain(["package:" + x for x in packages], wildcard))
+        else:
+            # Split the class name into outer / inner classes
+            #  0 - Character
+            #  1 - UnicodeScript
+            classes = class_name.split("$")
+            # Assemble the parts into a single list, adding prefixes to identify
+            # the different parts.
+            #  0 - package:java
+            #  1 - package:lang
+            #  2 - class:Character
+            #  3 - class:UnicodeScript
+            #  4 - member:of(I)Ljava/lang/Character$UnicodeScript;
+            return list(
+                chain(["package:" + x for x in packages],
+                      ["class:" + x for x in classes],
+                      ["member:" + x for x in member]))
+
+    # pylint: enable=line-too-long
+
+    def add(self, signature, value):
+        """Associate the value with the specific signature.
+
+        :param signature: the member signature
+        :param value: the value to associated with the signature
+        :return: n/a
+        """
+        # Split the signature into elements.
+        elements = self.signature_to_elements(signature)
+        # Find the Node associated with the deepest class.
+        node = self
+        for element in elements[:-1]:
+            if element in node.nodes:
+                node = node.nodes[element]
+            else:
+                next_node = InteriorNode()
+                node.nodes[element] = next_node
+                node = next_node
+        # Add a Leaf containing the value and associate it with the member
+        # signature within the class.
+        last_element = elements[-1]
+        if not last_element.startswith("member:"):
+            raise Exception(
+                f"Invalid signature: {signature}, does not identify a "
+                "specific member")
+        if last_element in node.nodes:
+            raise Exception(f"Duplicate signature: {signature}")
+        node.nodes[last_element] = Leaf(value)
+
+    def get_matching_rows(self, pattern):
+        """Get the values (plural) associated with the pattern.
+
+        e.g. If the pattern is a full signature then this will return a list
+        containing the value associated with that signature.
+
+        If the pattern is a class then this will return a list containing the
+        values associated with all members of that class.
+
+        If the pattern is a package then this will return a list containing the
+        values associated with all the members of all the classes in that
+        package and sub-packages.
+
+        If the pattern ends with "*" then the preceding part is treated as a
+        package and this will return a list containing the values associated
+        with all the members of all the classes in that package.
+
+        If the pattern ends with "**" then the preceding part is treated
+        as a package and this will return a list containing the values
+        associated with all the members of all the classes in that package and
+        all sub-packages.
+
+        :param pattern: the pattern which could be a complete signature or a
+        class, or package wildcard.
+        :return: an iterable containing all the values associated with the
+        pattern.
+        """
+        elements = self.signature_to_elements(pattern)
+        node = self
+
+        # Include all values from this node and all its children.
+        selector = lambda x: True
+
+        last_element = elements[-1]
+        if last_element in ("*", "**"):
+            elements = elements[:-1]
+            if last_element == "*":
+                # Do not include values from sub-packages.
+                selector = lambda x: not x.startswith("package:")
+
+        for element in elements:
+            if element in node.nodes:
+                node = node.nodes[element]
+            else:
+                return []
+        return chain.from_iterable(node.values(selector))
+
+    def values(self, selector):
+        values = []
+        self.append_values(values, selector)
+        return values
+
+    def append_values(self, values, selector):
+        for key, node in self.nodes.items():
+            if selector(key):
+                node.append_values(values, lambda x: True)
+
+
+
+@dataclasses.dataclass()
+class Leaf(Node):
+    """A leaf of the trie"""
+
+    # The value associated with this leaf.
+    value: typing.Any
+
+    def values(self, selector):
+        return [[self.value]]
+
+    def append_values(self, values, selector):
+        values.append([self.value])
+
+
+def signature_trie():
+    return InteriorNode()
diff --git a/scripts/hiddenapi/signature_trie_test.py b/scripts/hiddenapi/signature_trie_test.py
new file mode 100755
index 0000000..2dc79d0
--- /dev/null
+++ b/scripts/hiddenapi/signature_trie_test.py
@@ -0,0 +1,192 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2022 The Android Open Source Project
+#
+# 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.
+"""Unit tests for verify_overlaps_test.py."""
+import io
+import unittest
+
+from signature_trie import InteriorNode
+from signature_trie import signature_trie
+
+
+class TestSignatureToElements(unittest.TestCase):
+
+    @staticmethod
+    def signature_to_elements(signature):
+        return InteriorNode.signature_to_elements(signature)
+
+    def test_nested_inner_classes(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "class:ProcessBuilder",
+            "class:Redirect",
+            "class:1",
+            "member:<init>()V",
+        ]
+        signature = "Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_basic_member(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "class:Object",
+            "member:hashCode()I",
+        ]
+        signature = "Ljava/lang/Object;->hashCode()I"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_double_dollar_class(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "class:CharSequence",
+            "class:",
+            "class:ExternalSyntheticLambda0",
+            "member:<init>(Ljava/lang/CharSequence;)V",
+        ]
+        signature = "Ljava/lang/CharSequence$$ExternalSyntheticLambda0;" \
+                    "-><init>(Ljava/lang/CharSequence;)V"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_no_member(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "class:CharSequence",
+            "class:",
+            "class:ExternalSyntheticLambda0",
+        ]
+        signature = "Ljava/lang/CharSequence$$ExternalSyntheticLambda0"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_wildcard(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "*",
+        ]
+        signature = "java/lang/*"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_recursive_wildcard(self):
+        elements = [
+            "package:java",
+            "package:lang",
+            "**",
+        ]
+        signature = "java/lang/**"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_no_packages_wildcard(self):
+        elements = [
+            "*",
+        ]
+        signature = "*"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_no_packages_recursive_wildcard(self):
+        elements = [
+            "**",
+        ]
+        signature = "**"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_non_standard_class_name(self):
+        elements = [
+            "package:javax",
+            "package:crypto",
+            "class:extObjectInputStream",
+        ]
+        signature = "Ljavax/crypto/extObjectInputStream"
+        self.assertEqual(elements, self.signature_to_elements(signature))
+
+    def test_invalid_pattern_wildcard_and_member(self):
+        pattern = "Ljava/lang/*;->hashCode()I"
+        with self.assertRaises(Exception) as context:
+            self.signature_to_elements(pattern)
+        self.assertIn("contains wildcard * and member signature hashCode()I",
+                      str(context.exception))
+
+
+class TestGetMatchingRows(unittest.TestCase):
+    extractInput = """
+Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
+Ljava/lang/Character;->serialVersionUID:J
+Ljava/lang/Object;->hashCode()I
+Ljava/lang/Object;->toString()Ljava/lang/String;
+Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V
+Ljava/util/zip/ZipFile;-><clinit>()V
+"""
+
+    def read_trie(self):
+        trie = signature_trie()
+        with io.StringIO(self.extractInput.strip()) as f:
+            for line in iter(f.readline, ""):
+                line = line.rstrip()
+                trie.add(line, line)
+        return trie
+
+    def check_patterns(self, pattern, expected):
+        trie = self.read_trie()
+        self.check_node_patterns(trie, pattern, expected)
+
+    def check_node_patterns(self, node, pattern, expected):
+        actual = list(node.get_matching_rows(pattern))
+        actual.sort()
+        self.assertEqual(expected, actual)
+
+    def test_member_pattern(self):
+        self.check_patterns("java/util/zip/ZipFile;-><clinit>()V",
+                            ["Ljava/util/zip/ZipFile;-><clinit>()V"])
+
+    def test_class_pattern(self):
+        self.check_patterns("java/lang/Object", [
+            "Ljava/lang/Object;->hashCode()I",
+            "Ljava/lang/Object;->toString()Ljava/lang/String;",
+        ])
+
+    # pylint: disable=line-too-long
+    def test_nested_class_pattern(self):
+        self.check_patterns("java/lang/Character", [
+            "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;",
+            "Ljava/lang/Character;->serialVersionUID:J",
+        ])
+
+    def test_wildcard(self):
+        self.check_patterns("java/lang/*", [
+            "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;",
+            "Ljava/lang/Character;->serialVersionUID:J",
+            "Ljava/lang/Object;->hashCode()I",
+            "Ljava/lang/Object;->toString()Ljava/lang/String;",
+            "Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V",
+        ])
+
+    def test_recursive_wildcard(self):
+        self.check_patterns("java/**", [
+            "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;",
+            "Ljava/lang/Character;->serialVersionUID:J",
+            "Ljava/lang/Object;->hashCode()I",
+            "Ljava/lang/Object;->toString()Ljava/lang/String;",
+            "Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V",
+            "Ljava/util/zip/ZipFile;-><clinit>()V",
+        ])
+
+    # pylint: enable=line-too-long
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=2)
diff --git a/scripts/hiddenapi/verify_overlaps.py b/scripts/hiddenapi/verify_overlaps.py
index 4cd7e63..e5214df 100755
--- a/scripts/hiddenapi/verify_overlaps.py
+++ b/scripts/hiddenapi/verify_overlaps.py
@@ -13,239 +13,14 @@
 # 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.
-"""Verify that one set of hidden API flags is a subset of another.
-"""
+"""Verify that one set of hidden API flags is a subset of another."""
 
 import argparse
 import csv
 import sys
 from itertools import chain
 
-#pylint: disable=line-too-long
-class InteriorNode:
-    """An interior node in a trie.
-
-    Each interior node has a dict that maps from an element of a signature to
-    either another interior node or a leaf. Each interior node represents either
-    a package, class or nested class. Class members are represented by a Leaf.
-
-    Associating the set of flags [public-api] with the signature
-    "Ljava/lang/Object;->String()Ljava/lang/String;" will cause the following
-    nodes to be created:
-    Node()
-    ^- package:java -> Node()
-       ^- package:lang -> Node()
-           ^- class:Object -> Node()
-              ^- member:String()Ljava/lang/String; -> Leaf([public-api])
-
-    Associating the set of flags [blocked,core-platform-api] with the signature
-    "Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;"
-    will cause the following nodes to be created:
-    Node()
-    ^- package:java -> Node()
-       ^- package:lang -> Node()
-           ^- class:Character -> Node()
-              ^- class:UnicodeScript -> Node()
-                 ^- member:of(I)Ljava/lang/Character$UnicodeScript;
-                    -> Leaf([blocked,core-platform-api])
-
-    Attributes:
-        nodes: a dict from an element of the signature to the Node/Leaf
-          containing the next element/value.
-    """
-    #pylint: enable=line-too-long
-
-    def __init__(self):
-        self.nodes = {}
-
-    #pylint: disable=line-too-long
-    def signatureToElements(self, signature):
-        """Split a signature or a prefix into a number of elements:
-        1. The packages (excluding the leading L preceding the first package).
-        2. The class names, from outermost to innermost.
-        3. The member signature.
-        e.g.
-        Ljava/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
-        will be broken down into these elements:
-        1. package:java
-        2. package:lang
-        3. class:Character
-        4. class:UnicodeScript
-        5. member:of(I)Ljava/lang/Character$UnicodeScript;
-        """
-        # Remove the leading L.
-        #  - java/lang/Character$UnicodeScript;->of(I)Ljava/lang/Character$UnicodeScript;
-        text = signature.removeprefix("L")
-        # Split the signature between qualified class name and the class member
-        # signature.
-        #  0 - java/lang/Character$UnicodeScript
-        #  1 - of(I)Ljava/lang/Character$UnicodeScript;
-        parts = text.split(";->")
-        member = parts[1:]
-        # Split the qualified class name into packages, and class name.
-        #  0 - java
-        #  1 - lang
-        #  2 - Character$UnicodeScript
-        elements = parts[0].split("/")
-        packages = elements[0:-1]
-        className = elements[-1]
-        if className in ("*" , "**"): #pylint: disable=no-else-return
-            # Cannot specify a wildcard and target a specific member
-            if len(member) != 0:
-                raise Exception(
-                    "Invalid signature %s: contains wildcard %s and member " \
-                    "signature %s"
-                    % (signature, className, member[0]))
-            wildcard = [className]
-            # Assemble the parts into a single list, adding prefixes to identify
-            # the different parts.
-            #  0 - package:java
-            #  1 - package:lang
-            #  2 - *
-            return list(
-                chain(["package:" + x for x in packages], wildcard))
-        else:
-            # Split the class name into outer / inner classes
-            #  0 - Character
-            #  1 - UnicodeScript
-            classes = className.split("$")
-            # Assemble the parts into a single list, adding prefixes to identify
-            # the different parts.
-            #  0 - package:java
-            #  1 - package:lang
-            #  2 - class:Character
-            #  3 - class:UnicodeScript
-            #  4 - member:of(I)Ljava/lang/Character$UnicodeScript;
-            return list(
-                chain(
-                    ["package:" + x for x in packages],
-                    ["class:" + x for x in classes],
-                    ["member:" + x for x in member]))
-    #pylint: enable=line-too-long
-
-    def add(self, signature, value):
-        """Associate the value with the specific signature.
-
-        :param signature: the member signature
-        :param value: the value to associated with the signature
-        :return: n/a
-        """
-        # Split the signature into elements.
-        elements = self.signatureToElements(signature)
-        # Find the Node associated with the deepest class.
-        node = self
-        for element in elements[:-1]:
-            if element in node.nodes:
-                node = node.nodes[element]
-            else:
-                next_node = InteriorNode()
-                node.nodes[element] = next_node
-                node = next_node
-        # Add a Leaf containing the value and associate it with the member
-        # signature within the class.
-        lastElement = elements[-1]
-        if not lastElement.startswith("member:"):
-            raise Exception(
-                "Invalid signature: %s, does not identify a specific member" %
-                signature)
-        if lastElement in node.nodes:
-            raise Exception("Duplicate signature: %s" % signature)
-        node.nodes[lastElement] = Leaf(value)
-
-    def getMatchingRows(self, pattern):
-        """Get the values (plural) associated with the pattern.
-
-        e.g. If the pattern is a full signature then this will return a list
-        containing the value associated with that signature.
-
-        If the pattern is a class then this will return a list containing the
-        values associated with all members of that class.
-
-        If the pattern is a package then this will return a list containing the
-        values associated with all the members of all the classes in that
-        package and sub-packages.
-
-        If the pattern ends with "*" then the preceding part is treated as a
-        package and this will return a list containing the values associated
-        with all the members of all the classes in that package.
-
-        If the pattern ends with "**" then the preceding part is treated
-        as a package and this will return a list containing the values
-        associated with all the members of all the classes in that package and
-        all sub-packages.
-
-        :param pattern: the pattern which could be a complete signature or a
-        class, or package wildcard.
-        :return: an iterable containing all the values associated with the
-        pattern.
-        """
-        elements = self.signatureToElements(pattern)
-        node = self
-        # Include all values from this node and all its children.
-        selector = lambda x: True
-        lastElement = elements[-1]
-        if lastElement in ("*", "**"):
-            elements = elements[:-1]
-            if lastElement == "*":
-                # Do not include values from sub-packages.
-                selector = lambda x: not x.startswith("package:")
-        for element in elements:
-            if element in node.nodes:
-                node = node.nodes[element]
-            else:
-                return []
-        return chain.from_iterable(node.values(selector))
-
-    def values(self, selector):
-        """:param selector: a function that can be applied to a key in the nodes
-        attribute to determine whether to return its values.
-
-        :return: A list of iterables of all the values associated with
-        this node and its children.
-        """
-        values = []
-        self.appendValues(values, selector)
-        return values
-
-    def appendValues(self, values, selector):
-        """Append the values associated with this node and its children to the
-        list.
-
-        For each item (key, child) in nodes the child node's values are returned
-        if and only if the selector returns True when called on its key. A child
-        node's values are all the values associated with it and all its
-        descendant nodes.
-
-        :param selector: a function that can be applied to a key in the nodes
-        attribute to determine whether to return its values.
-        :param values: a list of a iterables of values.
-        """
-        for key, node in self.nodes.items():
-            if selector(key):
-                node.appendValues(values, lambda x: True)
-
-
-class Leaf:
-    """A leaf of the trie
-
-    Attributes:
-        value: the value associated with this leaf.
-    """
-
-    def __init__(self, value):
-        self.value = value
-
-    def values(self, selector): #pylint: disable=unused-argument
-        """:return: A list of a list of the value associated with this node.
-        """
-        return [[self.value]]
-
-    def appendValues(self, values, selector): #pylint: disable=unused-argument
-        """Appends a list of the value associated with this node to the list.
-
-        :param values: a list of a iterables of values.
-        """
-        values.append([self.value])
+from signature_trie import signature_trie
 
 
 def dict_reader(csvfile):
@@ -259,7 +34,7 @@
 
 
 def read_flag_trie_from_stream(stream):
-    trie = InteriorNode()
+    trie = signature_trie()
     reader = dict_reader(stream)
     for row in reader:
         signature = row["signature"]
@@ -269,8 +44,7 @@
 
 def extract_subset_from_monolithic_flags_as_dict_from_file(
         monolithicTrie, patternsFile):
-    """Extract a subset of flags from the dict containing all the monolithic
-    flags.
+    """Extract a subset of flags from the dict of monolithic flags.
 
     :param monolithicFlagsDict: the dict containing all the monolithic flags.
     :param patternsFile: a file containing a list of signature patterns that
@@ -284,8 +58,7 @@
 
 def extract_subset_from_monolithic_flags_as_dict_from_stream(
         monolithicTrie, stream):
-    """Extract a subset of flags from the trie containing all the monolithic
-    flags.
+    """Extract a subset of flags from the trie of monolithic flags.
 
     :param monolithicTrie: the trie containing all the monolithic flags.
     :param stream: a stream containing a list of signature patterns that define
@@ -295,7 +68,7 @@
     dict_signature_to_row = {}
     for pattern in stream:
         pattern = pattern.rstrip()
-        rows = monolithicTrie.getMatchingRows(pattern)
+        rows = monolithicTrie.get_matching_rows(pattern)
         for row in rows:
             signature = row["signature"]
             dict_signature_to_row[signature] = row
@@ -303,8 +76,10 @@
 
 
 def read_signature_csv_from_stream_as_dict(stream):
-    """Read the csv contents from the stream into a dict. The first column is
-    assumed to be the signature and used as the key.
+    """Read the csv contents from the stream into a dict.
+
+    The first column is assumed to be the signature and used as the
+    key.
 
     The whole row is stored as the value.
     :param stream: the csv contents to read
@@ -319,8 +94,10 @@
 
 
 def read_signature_csv_from_file_as_dict(csvFile):
-    """Read the csvFile into a dict. The first column is assumed to be the
-    signature and used as the key.
+    """Read the csvFile into a dict.
+
+    The first column is assumed to be the signature and used as the
+    key.
 
     The whole row is stored as the value.
     :param csvFile: the csv file to read
@@ -363,8 +140,7 @@
 def main(argv):
     args_parser = argparse.ArgumentParser(
         description="Verify that sets of hidden API flags are each a subset of "
-        "the monolithic flag file."
-    )
+        "the monolithic flag file.")
     args_parser.add_argument("monolithicFlags", help="The monolithic flag file")
     args_parser.add_argument(
         "modularFlags",
diff --git a/scripts/hiddenapi/verify_overlaps_test.py b/scripts/hiddenapi/verify_overlaps_test.py
index 22a1cdf..8cf2959 100755
--- a/scripts/hiddenapi/verify_overlaps_test.py
+++ b/scripts/hiddenapi/verify_overlaps_test.py
@@ -17,54 +17,9 @@
 import io
 import unittest
 
-from verify_overlaps import * #pylint: disable=unused-wildcard-import,wildcard-import
+from verify_overlaps import *  #pylint: disable=unused-wildcard-import,wildcard-import
 
 
-class TestSignatureToElements(unittest.TestCase):
-
-    def signatureToElements(self, signature):
-        return InteriorNode().signatureToElements(signature)
-
-    def test_signatureToElements_1(self):
-        expected = [
-            'package:java',
-            'package:lang',
-            'class:ProcessBuilder',
-            'class:Redirect',
-            'class:1',
-            'member:<init>()V',
-        ]
-        self.assertEqual(
-            expected,
-            self.signatureToElements(
-                'Ljava/lang/ProcessBuilder$Redirect$1;-><init>()V'))
-
-    def test_signatureToElements_2(self):
-        expected = [
-            'package:java',
-            'package:lang',
-            'class:Object',
-            'member:hashCode()I',
-        ]
-        self.assertEqual(
-            expected,
-            self.signatureToElements('Ljava/lang/Object;->hashCode()I'))
-
-    def test_signatureToElements_3(self):
-        expected = [
-            'package:java',
-            'package:lang',
-            'class:CharSequence',
-            'class:',
-            'class:ExternalSyntheticLambda0',
-            'member:<init>(Ljava/lang/CharSequence;)V',
-        ]
-        self.assertEqual(
-            expected,
-            self.signatureToElements(
-                'Ljava/lang/CharSequence$$ExternalSyntheticLambda0;'
-                '-><init>(Ljava/lang/CharSequence;)V'))
-
 #pylint: disable=line-too-long
 class TestDetectOverlaps(unittest.TestCase):
 
@@ -239,18 +194,6 @@
         }
         self.assertEqual(expected, subset)
 
-    def test_extract_subset_invalid_pattern_wildcard_and_member(self):
-        monolithic = self.read_flag_trie_from_string(
-            TestDetectOverlaps.extractInput)
-
-        patterns = 'Ljava/lang/*;->hashCode()I'
-
-        with self.assertRaises(Exception) as context:
-            self.extract_subset_from_monolithic_flags_as_dict_from_string(
-                monolithic, patterns)
-        self.assertTrue('contains wildcard * and member signature hashCode()I'
-                        in str(context.exception))
-
     def test_read_trie_duplicate(self):
         with self.assertRaises(Exception) as context:
             self.read_flag_trie_from_string("""
@@ -369,6 +312,8 @@
         mismatches = compare_signature_flags(monolithic, modular)
         expected = []
         self.assertEqual(expected, mismatches)
+
+
 #pylint: enable=line-too-long
 
 if __name__ == '__main__':