Merge "Error Linter for Marking Activities and Services and Singleton" into main
diff --git a/packages/SystemUI/checks/Android.bp b/packages/SystemUI/checks/Android.bp
index addcaf4..04ac748 100644
--- a/packages/SystemUI/checks/Android.bp
+++ b/packages/SystemUI/checks/Android.bp
@@ -38,8 +38,9 @@
     defaults: ["AndroidLintCheckerTestDefaults"],
     srcs: ["tests/**/*.kt"],
     data: [
-        ":framework",
         ":androidx.annotation_annotation",
+        ":dagger2",
+        ":framework",
         ":kotlinx-coroutines-core",
     ],
     static_libs: [
diff --git a/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SingletonAndroidComponentDetector.kt b/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SingletonAndroidComponentDetector.kt
new file mode 100644
index 0000000..68ec1ee
--- /dev/null
+++ b/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SingletonAndroidComponentDetector.kt
@@ -0,0 +1,160 @@
+/*
+ * Copyright (C) 2024 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.
+ */
+
+package com.android.internal.systemui.lint
+
+import com.android.tools.lint.detector.api.AnnotationInfo
+import com.android.tools.lint.detector.api.AnnotationUsageInfo
+import com.android.tools.lint.detector.api.AnnotationUsageType
+import com.android.tools.lint.detector.api.Category
+import com.android.tools.lint.detector.api.Detector
+import com.android.tools.lint.detector.api.Implementation
+import com.android.tools.lint.detector.api.Issue
+import com.android.tools.lint.detector.api.JavaContext
+import com.android.tools.lint.detector.api.Scope
+import com.android.tools.lint.detector.api.Severity
+import com.android.tools.lint.detector.api.SourceCodeScanner
+import org.jetbrains.uast.UAnnotation
+import org.jetbrains.uast.UClass
+import org.jetbrains.uast.UElement
+import org.jetbrains.uast.UMethod
+
+/**
+ * Prevents binding Activities, Services, and BroadcastReceivers as Singletons in the Dagger graph.
+ *
+ * It is OK to mark a BroadcastReceiver as singleton as long as it is being constructed/injected and
+ * registered directly in the code. If instead it is declared in the manifest, and we let Android
+ * construct it for us, we also need to let Android destroy it for us, so don't allow marking it as
+ * singleton.
+ */
+class SingletonAndroidComponentDetector : Detector(), SourceCodeScanner {
+    override fun applicableAnnotations(): List<String> {
+        return listOf(
+            "com.android.systemui.dagger.SysUISingleton",
+        )
+    }
+
+    override fun isApplicableAnnotationUsage(type: AnnotationUsageType): Boolean =
+        type == AnnotationUsageType.DEFINITION
+
+    override fun visitAnnotationUsage(
+        context: JavaContext,
+        element: UElement,
+        annotationInfo: AnnotationInfo,
+        usageInfo: AnnotationUsageInfo
+    ) {
+        if (element !is UAnnotation) {
+            return
+        }
+
+        val parent = element.uastParent ?: return
+
+        if (isInvalidBindingMethod(parent)) {
+            context.report(
+                ISSUE,
+                element,
+                context.getLocation(element),
+                "Do not bind Activities, Services, or BroadcastReceivers as Singleton."
+            )
+        } else if (isInvalidClassDeclaration(parent)) {
+            context.report(
+                ISSUE,
+                element,
+                context.getLocation(element),
+                "Do not mark Activities or Services as Singleton."
+            )
+        }
+    }
+
+    private fun isInvalidBindingMethod(parent: UElement): Boolean {
+        if (parent !is UMethod) {
+            return false
+        }
+
+        if (
+            parent.returnType?.canonicalText !in
+                listOf(
+                    "android.app.Activity",
+                    "android.app.Service",
+                    "android.content.BroadcastReceiver",
+                )
+        ) {
+            return false
+        }
+
+        if (
+            !MULTIBIND_ANNOTATIONS.all { it in parent.annotations.map { it.qualifiedName } } &&
+                !MULTIPROVIDE_ANNOTATIONS.all { it in parent.annotations.map { it.qualifiedName } }
+        ) {
+            return false
+        }
+        return true
+    }
+
+    private fun isInvalidClassDeclaration(parent: UElement): Boolean {
+        if (parent !is UClass) {
+            return false
+        }
+
+        if (
+            parent.javaPsi.superClass?.qualifiedName !in
+                listOf(
+                    "android.app.Activity",
+                    "android.app.Service",
+                    // Fine to mark BroadcastReceiver as singleton in this scenario
+                )
+        ) {
+            return false
+        }
+
+        return true
+    }
+
+    companion object {
+        @JvmField
+        val ISSUE: Issue =
+            Issue.create(
+                id = "SingletonAndroidComponent",
+                briefDescription = "Activity, Service, or BroadcastReceiver marked as Singleton",
+                explanation =
+                    """Activities, Services, and BroadcastReceivers are created and destroyed by
+                        the Android System Server. Marking them with a Dagger scope
+                        results in them being cached and reused by Dagger. Trying to reuse a
+                        component like this will make for a very bad time.""",
+                category = Category.CORRECTNESS,
+                priority = 10,
+                severity = Severity.ERROR,
+                moreInfo =
+                    "https://developer.android.com/guide/components/activities/process-lifecycle",
+                // Note that JAVA_FILE_SCOPE also includes Kotlin source files.
+                implementation =
+                    Implementation(
+                        SingletonAndroidComponentDetector::class.java,
+                        Scope.JAVA_FILE_SCOPE
+                    )
+            )
+
+        private val MULTIBIND_ANNOTATIONS =
+            listOf("dagger.Binds", "dagger.multibindings.IntoMap", "dagger.multibindings.ClassKey")
+
+        val MULTIPROVIDE_ANNOTATIONS =
+            listOf(
+                "dagger.Provides",
+                "dagger.multibindings.IntoMap",
+                "dagger.multibindings.ClassKey"
+            )
+    }
+}
diff --git a/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SystemUIIssueRegistry.kt b/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SystemUIIssueRegistry.kt
index e93264c..cecbc47 100644
--- a/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SystemUIIssueRegistry.kt
+++ b/packages/SystemUI/checks/src/com/android/internal/systemui/lint/SystemUIIssueRegistry.kt
@@ -40,6 +40,7 @@
                 RegisterReceiverViaContextDetector.ISSUE,
                 SoftwareBitmapDetector.ISSUE,
                 NonInjectedServiceDetector.ISSUE,
+                SingletonAndroidComponentDetector.ISSUE,
                 StaticSettingsProviderDetector.ISSUE,
                 DemotingTestWithoutBugDetector.ISSUE,
                 TestFunctionNameViolationDetector.ISSUE,
diff --git a/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/AndroidStubs.kt b/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/AndroidStubs.kt
index e1cca88..8396f3f 100644
--- a/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/AndroidStubs.kt
+++ b/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/AndroidStubs.kt
@@ -21,8 +21,9 @@
 
 internal val libraryNames =
     arrayOf(
-        "framework.jar",
         "androidx.annotation_annotation.jar",
+        "dagger2.jar",
+        "framework.jar",
         "kotlinx-coroutines-core.jar",
     )
 
diff --git a/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/SingletonAndroidComponentDetectorTest.kt b/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/SingletonAndroidComponentDetectorTest.kt
new file mode 100644
index 0000000..0606af8
--- /dev/null
+++ b/packages/SystemUI/checks/tests/com/android/internal/systemui/lint/SingletonAndroidComponentDetectorTest.kt
@@ -0,0 +1,182 @@
+/*
+ * Copyright (C) 2024 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.
+ */
+
+package com.android.internal.systemui.lint
+
+import com.android.tools.lint.checks.infrastructure.TestFile
+import com.android.tools.lint.checks.infrastructure.TestFiles
+import com.android.tools.lint.detector.api.Detector
+import com.android.tools.lint.detector.api.Issue
+import org.junit.Test
+
+class SingletonAndroidComponentDetectorTest : SystemUILintDetectorTest() {
+    override fun getDetector(): Detector = SingletonAndroidComponentDetector()
+
+    override fun getIssues(): List<Issue> = listOf(SingletonAndroidComponentDetector.ISSUE)
+
+    @Test
+    fun testBindsServiceAsSingleton() {
+        lint()
+            .files(
+                TestFiles.kotlin(
+                    """
+                    package test.pkg
+
+                    import android.app.Service
+                    import com.android.systemui.dagger.SysUISingleton
+                    import dagger.Binds
+                    import dagger.Module
+                    import dagger.multibindings.ClassKey
+                    import dagger.multibindings.IntoMap
+
+                    @Module
+                    interface BadModule {
+                       @SysUISingleton
+                       @Binds
+                       @IntoMap
+                       @ClassKey(SingletonService::class)
+                       fun bindSingletonService(service: SingletonService): Service
+                    }
+                """
+                        .trimIndent()
+                ),
+                *stubs
+            )
+            .issues(SingletonAndroidComponentDetector.ISSUE)
+            .run()
+            .expect(
+                """
+                src/test/pkg/BadModule.kt:12: Error: Do not bind Activities, Services, or BroadcastReceivers as Singleton. [SingletonAndroidComponent]
+                   @SysUISingleton
+                   ~~~~~~~~~~~~~~~
+                1 errors, 0 warnings
+                """
+                    .trimIndent()
+            )
+    }
+
+    @Test
+    fun testProvidesBroadcastReceiverAsSingleton() {
+        lint()
+            .files(
+                TestFiles.kotlin(
+                    """
+                    package test.pkg
+
+                    import android.content.BroadcastReceiver
+                    import com.android.systemui.dagger.SysUISingleton
+                    import dagger.Provides
+                    import dagger.Module
+                    import dagger.multibindings.ClassKey
+                    import dagger.multibindings.IntoMap
+
+                    @Module
+                    abstract class BadModule {
+                       @SysUISingleton
+                       @Provides
+                       @IntoMap
+                       @ClassKey(SingletonBroadcastReceiver::class)
+                       fun providesSingletonBroadcastReceiver(br: SingletonBroadcastReceiver): BroadcastReceiver {
+                          return br
+                       }
+                    }
+                """
+                        .trimIndent()
+                ),
+                *stubs
+            )
+            .issues(SingletonAndroidComponentDetector.ISSUE)
+            .run()
+            .expect(
+                """
+                src/test/pkg/BadModule.kt:12: Error: Do not bind Activities, Services, or BroadcastReceivers as Singleton. [SingletonAndroidComponent]
+                   @SysUISingleton
+                   ~~~~~~~~~~~~~~~
+                1 errors, 0 warnings
+                """
+                    .trimIndent()
+            )
+    }
+    @Test
+    fun testMarksActivityAsSingleton() {
+        lint()
+            .files(
+                TestFiles.kotlin(
+                    """
+                    package test.pkg
+
+                    import android.app.Activity
+                    import com.android.systemui.dagger.SysUISingleton
+
+                    @SysUISingleton
+                    class BadActivity : Activity() {
+                    }
+                """
+                        .trimIndent()
+                ),
+                *stubs
+            )
+            .issues(SingletonAndroidComponentDetector.ISSUE)
+            .run()
+            .expect(
+                """
+                src/test/pkg/BadActivity.kt:6: Error: Do not mark Activities or Services as Singleton. [SingletonAndroidComponent]
+                @SysUISingleton
+                ~~~~~~~~~~~~~~~
+                1 errors, 0 warnings
+                """
+                    .trimIndent()
+            )
+    }
+    @Test
+    fun testMarksBroadcastReceiverAsSingleton() {
+        lint()
+            .files(
+                TestFiles.kotlin(
+                    """
+                    package test.pkg
+
+                    import android.content.BroadcastReceiver
+                    import com.android.systemui.dagger.SysUISingleton
+
+                    @SysUISingleton
+                    class SingletonReceveiver : BroadcastReceiver() {
+                    }
+                """
+                        .trimIndent()
+                ),
+                *stubs
+            )
+            .issues(SingletonAndroidComponentDetector.ISSUE)
+            .run()
+            .expectClean()
+    }
+
+    // Define stubs for Android imports. The tests don't run on Android so
+    // they don't "see" any of Android specific classes. We need to define
+    // the method parameters for proper resolution.
+    private val singletonStub: TestFile =
+        java(
+            """
+        package com.android.systemui.dagger;
+
+        public @interface SysUISingleton {
+        }
+        """
+        )
+
+    private val stubs = arrayOf(singletonStub) + androidStubs
+}