InspectionCompanions as nested classes

+ Generate inspection companions as MyClass$InspectionCompanion instead
  of MyClass$$InspectionCompanion. This allows the discovery of custom
  inspection companions written as nested classes.
+ Rename GeneratedInspectionCompanionProvider to
  StaticInspectionCompanionProvider to more clearly articulate how it
  function in the new world.
+ StaticInspectionCompanionProvider now explicitly checks if a class it
  discovered implements InspectionCompanion, and returns null instead of
  throwing a ClassCastException.
+ The annotation processor checks for the existence of a nested class
  named InspectionCompanion, and fails the build if a class has both a
  custom InspectionCompanion and @InspectableProperty annotations.

Test: atest --host view-inspector-annotation-processor-test
Bug: 126913705
Change-Id: Ic0d2100ec22420e36f9db44e56c66fe9146eeb0c
diff --git a/api/current.txt b/api/current.txt
index 1d5318c..486c19a 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -53452,11 +53452,6 @@
 
 package android.view.inspector {
 
-  public class GeneratedInspectionCompanionProvider implements android.view.inspector.InspectionCompanionProvider {
-    ctor public GeneratedInspectionCompanionProvider();
-    method @Nullable public <T> android.view.inspector.InspectionCompanion<T> provide(@NonNull Class<T>);
-  }
-
   public interface InspectionCompanion<T> {
     method @Nullable public default String getNodeName();
     method public void mapProperties(@NonNull android.view.inspector.PropertyMapper);
@@ -53537,6 +53532,11 @@
     ctor public PropertyReader.PropertyTypeMismatchException(int, @NonNull String, @NonNull String);
   }
 
+  public class StaticInspectionCompanionProvider implements android.view.inspector.InspectionCompanionProvider {
+    ctor public StaticInspectionCompanionProvider();
+    method @Nullable public <T> android.view.inspector.InspectionCompanion<T> provide(@NonNull Class<T>);
+  }
+
   public final class WindowInspector {
     method @NonNull public static java.util.List<android.view.View> getGlobalWindowViews();
   }
diff --git a/core/java/android/view/inspector/GeneratedInspectionCompanionProvider.java b/core/java/android/view/inspector/StaticInspectionCompanionProvider.java
similarity index 76%
rename from core/java/android/view/inspector/GeneratedInspectionCompanionProvider.java
rename to core/java/android/view/inspector/StaticInspectionCompanionProvider.java
index d4b7e85..42a892d 100644
--- a/core/java/android/view/inspector/GeneratedInspectionCompanionProvider.java
+++ b/core/java/android/view/inspector/StaticInspectionCompanionProvider.java
@@ -20,15 +20,15 @@
 import android.annotation.Nullable;
 
 /**
- * An inspection companion provider that loads pre-generated inspection companions
+ * An inspection companion provider that finds companions as inner classes or generated code.
  *
  * @see android.processor.view.inspector.PlatformInspectableProcessor
  */
-public class GeneratedInspectionCompanionProvider implements InspectionCompanionProvider {
+public class StaticInspectionCompanionProvider implements InspectionCompanionProvider {
     /**
-     * The suffix used for the generated class
+     * The suffix used for the generated classes and inner classes
      */
-    private static final String COMPANION_SUFFIX = "$$InspectionCompanion";
+    private static final String COMPANION_SUFFIX = "$InspectionCompanion";
 
     @Override
     @Nullable
@@ -39,7 +39,12 @@
         try {
             final Class<InspectionCompanion<T>> companionClass =
                     (Class<InspectionCompanion<T>>) cls.getClassLoader().loadClass(companionName);
-            return companionClass.newInstance();
+
+            if (InspectionCompanion.class.isAssignableFrom(companionClass)) {
+                return companionClass.newInstance();
+            } else {
+                return null;
+            }
         } catch (ClassNotFoundException e) {
             return null;
         } catch (IllegalAccessException e) {
diff --git a/tools/processors/view_inspector/src/java/android/processor/view/inspector/InspectionCompanionGenerator.java b/tools/processors/view_inspector/src/java/android/processor/view/inspector/InspectionCompanionGenerator.java
index 44d88bb..6f6c1aa 100644
--- a/tools/processors/view_inspector/src/java/android/processor/view/inspector/InspectionCompanionGenerator.java
+++ b/tools/processors/view_inspector/src/java/android/processor/view/inspector/InspectionCompanionGenerator.java
@@ -97,7 +97,7 @@
     /**
      * The suffix of the generated class name after the class's binary name.
      */
-    private static final String GENERATED_CLASS_SUFFIX = "$$InspectionCompanion";
+    private static final String GENERATED_CLASS_SUFFIX = "$InspectionCompanion";
 
     /**
      * The null resource ID, copied to avoid a host dependency on platform code.
diff --git a/tools/processors/view_inspector/src/java/android/processor/view/inspector/PlatformInspectableProcessor.java b/tools/processors/view_inspector/src/java/android/processor/view/inspector/PlatformInspectableProcessor.java
index 01d9430..fd142c6 100644
--- a/tools/processors/view_inspector/src/java/android/processor/view/inspector/PlatformInspectableProcessor.java
+++ b/tools/processors/view_inspector/src/java/android/processor/view/inspector/PlatformInspectableProcessor.java
@@ -34,6 +34,7 @@
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.Modifier;
 import javax.lang.model.element.TypeElement;
+import javax.lang.model.util.ElementFilter;
 
 
 /**
@@ -127,13 +128,38 @@
 
             final InspectableClassModel model = modelMap.computeIfAbsent(
                     classElement.get().getQualifiedName().toString(),
-                    k -> new InspectableClassModel(ClassName.get(classElement.get())));
+                    k -> {
+                        if (hasNestedInspectionCompanion(classElement.get())) {
+                            fail(
+                                    String.format(
+                                            "Class %s already has an inspection companion.",
+                                            classElement.get().getQualifiedName().toString()),
+                                    element);
+                        }
+                        return new InspectableClassModel(ClassName.get(classElement.get()));
+                    });
 
             processor.process(element, model);
         }
     }
 
     /**
+     * Determine if a class has a nested class named {@code InspectionCompanion}.
+     *
+     * @param typeElement A type element representing the class to check
+     * @return f the class contains a class named {@code InspectionCompanion}
+     */
+    private static boolean hasNestedInspectionCompanion(TypeElement typeElement) {
+        for (TypeElement nestedClass : ElementFilter.typesIn(typeElement.getEnclosedElements())) {
+            if (nestedClass.getSimpleName().toString().equals("InspectionCompanion")) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
      * Get the nearest enclosing class if there is one.
      *
      * If {@param element} represents a class, it will be returned wrapped in an optional.
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/FieldProperty.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/FieldProperty.java.txt
index a44c43e..9a0fe5b 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/FieldProperty.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/FieldProperty.java.txt
@@ -12,7 +12,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntEnum.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntEnum.java.txt
index 764aa8b..b491de1 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntEnum.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntEnum.java.txt
@@ -13,7 +13,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntFlag.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntFlag.java.txt
index 75f2813..7d18058 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntFlag.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/IntFlag.java.txt
@@ -12,7 +12,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NestedClass.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NestedClass.java.txt
index 0cac462..dc27abb 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NestedClass.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NestedClass.java.txt
@@ -11,7 +11,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class Outer$Inner$$InspectionCompanion implements InspectionCompanion<Outer.Inner> {
+public final class Outer$Inner$InspectionCompanion implements InspectionCompanion<Outer.Inner> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NoAttributeId.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NoAttributeId.java.txt
index ce0f867..738bcd3 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NoAttributeId.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NoAttributeId.java.txt
@@ -11,7 +11,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NodeName.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NodeName.java.txt
index f7357fe..82dd66e 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NodeName.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/NodeName.java.txt
@@ -12,7 +12,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SimpleProperties.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SimpleProperties.java.txt
index 556d8dd..08ea696 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SimpleProperties.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SimpleProperties.java.txt
@@ -12,7 +12,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */
diff --git a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SuppliedAttributeId.java.txt b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SuppliedAttributeId.java.txt
index d72cdd5..3bfa78a 100644
--- a/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SuppliedAttributeId.java.txt
+++ b/tools/processors/view_inspector/test/resources/android/processor/view/inspector/InspectionCompanionGeneratorTest/SuppliedAttributeId.java.txt
@@ -11,7 +11,7 @@
  * Generated by {@link android.processor.view.inspector.InspectionCompanionGenerator}
  * on behalf of {@link android.processor.view.inspector.InspectionCompanionGeneratorTest}.
  */
-public final class TestNode$$InspectionCompanion implements InspectionCompanion<TestNode> {
+public final class TestNode$InspectionCompanion implements InspectionCompanion<TestNode> {
     /**
      * Set by {@link #mapProperties(PropertyMapper)} once properties have been mapped.
      */