FlowDelegateUsageDetector

@@ -20,194 +20,332 @@ package io.livekit.lint
 
 import com.android.tools.lint.client.api.UElementHandler
 import com.android.tools.lint.detector.api.*
-import com.intellij.psi.CommonClassNames.JAVA_LANG_OBJECT
-import com.intellij.psi.PsiClassType
+import com.intellij.psi.JavaElementVisitor
 import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiJavaCodeReferenceElement
 import com.intellij.psi.PsiMethod
 import org.jetbrains.uast.*
-import org.jetbrains.uast.util.isMethodCall
+import org.jetbrains.uast.kotlin.KotlinUQualifiedReferenceExpression
 
 /** Checks related to DiffUtil computation. */
 class FlowDelegateUsageDetector : Detector(), SourceCodeScanner {
 
+    override fun visitReference(
+        context: JavaContext,
+        visitor: JavaElementVisitor?,
+        reference: PsiJavaCodeReferenceElement,
+        referenced: PsiElement
+    ) {
+        super.visitReference(context, visitor, reference, referenced)
+    }
+
+    override fun visitReference(context: JavaContext, reference: UReferenceExpression, referenced: PsiElement) {
+
+        // Check if we're actually trying to access the flow delegate
+        val referencedMethod = referenced as? PsiMethod ?: return
+        if (referenced.name != "getFlow" || referencedMethod.containingClass?.qualifiedName != "io.livekit.android.util.FlowObservableKt") {
+            return
+        }
+
+        // This should get the property we're trying to receive the flow from.
+        val receiver = ((reference.uastParent as? KotlinUQualifiedReferenceExpression)
+            ?.receiver as? UCallableReferenceExpression)
+            ?: return
+
+        // This should get the original class associated with the property.
+        val className = receiver.qualifierType?.canonicalText
+        val psiClass = if (className != null) context.evaluator.findClass(className) else null
+        val psiField = psiClass?.findFieldByName("${receiver.callableName}\$delegate", true)
+        val isAnnotated = psiField?.hasAnnotation("io.livekit.android.util.FlowObservable") ?: false
+
+        if (!isAnnotated) {
+            val message = DEFAULT_MSG
+            val location = context.getLocation(reference)
+            context.report(ISSUE, reference, location, message)
+        }
+    }
+
+    override fun getApplicableReferenceNames(): List<String>? =
+        listOf("flow")
+
+    override fun visitMethodCall(context: JavaContext, node: UCallExpression, method: PsiMethod) {
+        super.visitMethodCall(context, node, method)
+    }
+
     override fun getApplicableUastTypes() =
-        listOf(UBinaryExpression::class.java, UCallExpression::class.java)
+        listOf(
+            UBinaryExpression::class.java,
+            UCallExpression::class.java,
+            UAnnotation::class.java,
+            UArrayAccessExpression::class.java,
+            UBinaryExpressionWithType::class.java,
+            UBlockExpression::class.java,
+            UBreakExpression::class.java,
+            UCallableReferenceExpression::class.java,
+            UCatchClause::class.java,
+            UClass::class.java,
+            UClassLiteralExpression::class.java,
+            UContinueExpression::class.java,
+            UDeclaration::class.java,
+            UDoWhileExpression::class.java,
+            UElement::class.java,
+            UEnumConstant::class.java,
+            UExpression::class.java,
+            UExpressionList::class.java,
+            UField::class.java,
+            UFile::class.java,
+            UForEachExpression::class.java,
+            UForExpression::class.java,
+            UIfExpression::class.java,
+            UImportStatement::class.java,
+            UClassInitializer::class.java,
+            ULabeledExpression::class.java,
+            ULambdaExpression::class.java,
+            ULiteralExpression::class.java,
+            ULocalVariable::class.java,
+            UMethod::class.java,
+            UObjectLiteralExpression::class.java,
+            UParameter::class.java,
+            UParenthesizedExpression::class.java,
+            UPolyadicExpression::class.java,
+            UPostfixExpression::class.java,
+            UPrefixExpression::class.java,
+            UQualifiedReferenceExpression::class.java,
+            UReturnExpression::class.java,
+            USimpleNameReferenceExpression::class.java,
+            USuperExpression::class.java,
+            USwitchClauseExpression::class.java,
+            USwitchExpression::class.java,
+            UThisExpression::class.java,
+            UThrowExpression::class.java,
+            UTryExpression::class.java,
+            UTypeReferenceExpression::class.java,
+            UUnaryExpression::class.java,
+            UVariable::class.java,
+            UWhileExpression::class.java,
+            UYieldExpression::class.java,
+
+            )
 
     override fun createUastHandler(context: JavaContext): UElementHandler? {
         return object : UElementHandler() {
-
+            val context = context
             override fun visitBinaryExpression(node: UBinaryExpression) {
-                checkExpression(context, node)
+                println(0)
             }
 
             override fun visitCallExpression(node: UCallExpression) {
-                checkCall(context, node)
+                node.classReference
+                node.methodName
+                node.methodIdentifier
+                node.receiverType
+                node.receiver
+                node.kind
+                node.valueArguments
+                node.valueArgumentCount
+                node.typeArguments
+                node.typeArgumentCount
+                node.returnType
+                println(1)
             }
-        }
-    }
 
-    private fun defaultEquals(context: JavaContext, node: UElement): Boolean {
-        val resolved: PsiMethod?
+            override fun visitAnnotation(node: UAnnotation) {
+                println(0)
+            }
 
-        when (node) {
-            is UBinaryExpression -> {
-                resolved = node.resolveOperator()
-                if (resolved == null) {
-                    val left = node.leftOperand.getExpressionType() as? PsiClassType
-                    return defaultEquals(context, left)
-                }
+            override fun visitArrayAccessExpression(node: UArrayAccessExpression) {
+                println(0)
             }
-            is UCallExpression -> {
-                resolved = node.takeIf { it.isMethodCall() }
-                    ?.resolve()
+
+            override fun visitBinaryExpressionWithType(node: UBinaryExpressionWithType) {
+                println(0)
             }
-            is UParenthesizedExpression -> {
-                return defaultEquals(context, node.expression)
+
+            override fun visitBlockExpression(node: UBlockExpression) {
+                println(0)
             }
-            else -> {
-                // We don't know any better
-                return false
+
+            override fun visitBreakExpression(node: UBreakExpression) {
+                println(0)
             }
-        }
 
-        return resolved?.containingClass?.qualifiedName == MEDIA_STREAM_TRACK
-    }
+            override fun visitCallableReferenceExpression(node: UCallableReferenceExpression) {
+                println(0)
+            }
 
-    private fun defaultEquals(
-        context: JavaContext,
-        type: PsiClassType?
-    ): Boolean {
-        val cls = type?.resolve() ?: return false
-
-        if (isKotlin(cls) && (context.evaluator.isSealed(cls) || context.evaluator.isData(cls))) {
-            // Sealed class doesn't guarantee that it defines equals/hashCode
-            // but it's likely (we'd need to go look at each inner class)
-            return false
-        }
+            override fun visitCatchClause(node: UCatchClause) {
+                println(0)
+            }
 
-        for (m in cls.findMethodsByName("equals", true)) {
-            if (m is PsiMethod) {
-                val parameters = m.parameterList.parameters
-                if (parameters.size == 1 &&
-                    parameters[0].type.canonicalText == MEDIA_STREAM_TRACK
-                ) {
-                    return m.containingClass?.qualifiedName == MEDIA_STREAM_TRACK
-                }
+            override fun visitClass(node: UClass) {
+                println(0)
             }
-        }
 
-        return false
-    }
+            override fun visitClassLiteralExpression(node: UClassLiteralExpression) {
+                println(0)
+            }
 
-    private fun checkCall(context: JavaContext, node: UCallExpression) {
-        if (defaultEquals(context, node)) {
-            // Within cast or instanceof check which implies a more specific type
-            // which provides an equals implementation?
-            if (withinCastWithEquals(context, node)) {
-                return
+            override fun visitContinueExpression(node: UContinueExpression) {
+                println(0)
             }
 
-            val message = DEFAULT_MSG
-            val location = context.getCallLocation(
-                node,
-                includeReceiver = false,
-                includeArguments = true
-            )
-            context.report(ISSUE, node, location, message)
-        }
-    }
+            override fun visitDeclaration(node: UDeclaration) {
+                println(0)
+            }
 
-    /**
-     * Is this .equals() call within another if check which checks
-     * instanceof on a more specific type than we're calling equals on?
-     * If so, does that more specific type define its own equals?
-     *
-     * Also handle an implicit check via short circuit evaluation; e.g.
-     * something like "return a is A && b is B && a.equals(b)".
-     */
-    private fun withinCastWithEquals(context: JavaContext, node: UExpression): Boolean {
-        var parent = skipParenthesizedExprUp(node.uastParent)
-        if (parent is UQualifiedReferenceExpression) {
-            parent = skipParenthesizedExprUp(parent.uastParent)
-        }
-        val target: PsiElement? = when (node) {
-            is UCallExpression -> node.receiver?.tryResolve()
-            is UBinaryExpression -> node.leftOperand.tryResolve()
-            else -> null
-        }
+            override fun visitDeclarationsExpression(node: UDeclarationsExpression) {
+                println(0)
+            }
 
-        if (parent is UPolyadicExpression && parent.operator == UastBinaryOperator.LOGICAL_AND) {
-            val operands = parent.operands
-            for (operand in operands) {
-                if (operand === node) {
-                    break
-                }
-                if (isCastWithEquals(context, operand, target)) {
-                    return true
-                }
+            override fun visitDoWhileExpression(node: UDoWhileExpression) {
+                println(0)
             }
-        }
-        val ifStatement = node.getParentOfType<UElement>(UIfExpression::class.java, false, UMethod::class.java)
-                as? UIfExpression ?: return false
-        val condition = ifStatement.condition
-        return isCastWithEquals(context, condition, target)
-    }
 
-    private fun isCastWithEquals(context: JavaContext, node: UExpression, target: PsiElement?): Boolean {
-        when {
-            node is UBinaryExpressionWithType -> {
-                if (target != null) {
-                    val resolved = node.operand.tryResolve()
-                    // Unfortunately in some scenarios isEquivalentTo returns false for equal instances
-                    //noinspection LintImplPsiEquals
-                    if (resolved != null && !(target == resolved || target.isEquivalentTo(resolved))) {
-                        return false
-                    }
-                }
-                return !defaultEquals(context, node.type as? PsiClassType)
-            }
-            node is UPolyadicExpression && node.operator == UastBinaryOperator.LOGICAL_AND -> {
-                for (operand in node.operands) {
-                    if (isCastWithEquals(context, operand, target)) {
-                        return true
-                    }
-                }
-            }
-            node is UParenthesizedExpression -> {
-                return isCastWithEquals(context, node.expression, target)
+            override fun visitElement(node: UElement) {
+                println(0)
+            }
+
+            override fun visitEnumConstant(node: UEnumConstant) {
+                println(0)
+            }
+
+            override fun visitExpression(node: UExpression) {
+                println(0)
+            }
+
+            override fun visitExpressionList(node: UExpressionList) {
+                println(0)
+            }
+
+            override fun visitField(node: UField) {
+                println(0)
+            }
+
+            override fun visitFile(node: UFile) {
+                println(0)
+            }
+
+            override fun visitForEachExpression(node: UForEachExpression) {
+                println(0)
+            }
+
+            override fun visitForExpression(node: UForExpression) {
+                println(0)
+            }
+
+            override fun visitIfExpression(node: UIfExpression) {
+                println(0)
+            }
+
+            override fun visitImportStatement(node: UImportStatement) {
+                println(0)
+            }
+
+            override fun visitInitializer(node: UClassInitializer) {
+                println(0)
+            }
+
+            override fun visitLabeledExpression(node: ULabeledExpression) {
+                println(0)
+            }
+
+            override fun visitLambdaExpression(node: ULambdaExpression) {
+                println(0)
+            }
+
+            override fun visitLiteralExpression(node: ULiteralExpression) {
+                println(0)
+            }
+
+            override fun visitLocalVariable(node: ULocalVariable) {
+                println(0)
+            }
+
+            override fun visitMethod(node: UMethod) {
+                println(0)
+            }
+
+
+            override fun visitObjectLiteralExpression(node: UObjectLiteralExpression) {
+                println(0)
+            }
+
+            override fun visitParameter(node: UParameter) {
+                println(0)
+            }
+
+            override fun visitParenthesizedExpression(node: UParenthesizedExpression) {
+                println(0)
+            }
+
+            override fun visitPolyadicExpression(node: UPolyadicExpression) {
+                println(0)
+            }
+
+            override fun visitPostfixExpression(node: UPostfixExpression) {
+                println(0)
+            }
+
+            override fun visitPrefixExpression(node: UPrefixExpression) {
+                println(0)
+            }
+
+            override fun visitQualifiedReferenceExpression(node: UQualifiedReferenceExpression) {
+                println(0)
+            }
+
+            override fun visitReturnExpression(node: UReturnExpression) {
+                println(0)
+            }
+
+            override fun visitSimpleNameReferenceExpression(node: USimpleNameReferenceExpression) {
+                println(0)
+
+                //(((node as KotlinUSimpleReferenceExpression).uastParent as KotlinUQualifiedReferenceExpression).receiver as KotlinUCallableReferenceExpression).qualifierType?.canonicalText
+            }
+
+            override fun visitSuperExpression(node: USuperExpression) {
+                println(0)
+            }
+
+            override fun visitSwitchClauseExpression(node: USwitchClauseExpression) {
+                println(0)
+            }
+
+            override fun visitSwitchExpression(node: USwitchExpression) {
+                println(0)
+            }
+
+            override fun visitThisExpression(node: UThisExpression) {
+                println(0)
+            }
+
+            override fun visitThrowExpression(node: UThrowExpression) {
+                println(0)
+            }
+
+            override fun visitTryExpression(node: UTryExpression) {
+                println(0)
+            }
+
+            override fun visitTypeReferenceExpression(node: UTypeReferenceExpression) {
+                println(0)
+            }
+
+            override fun visitUnaryExpression(node: UUnaryExpression) {
+                println(0)
+            }
+
+            override fun visitVariable(node: UVariable) {
+                println(0)
+            }
+
+            override fun visitWhileExpression(node: UWhileExpression) {
+                println(0)
             }
-        }
-        return false
-    }
 
-    private fun checkExpression(context: JavaContext, node: UBinaryExpression) {
-        if (node.operator == UastBinaryOperator.IDENTITY_EQUALS ||
-            node.operator == UastBinaryOperator.EQUALS
-        ) {
-            val left = node.leftOperand.getExpressionType() ?: return
-            val right = node.rightOperand.getExpressionType() ?: return
-            if (left is PsiClassType && right is PsiClassType
-                && (left.className == "MediaStreamTrack" || right.className == "MediaStreamTrack")
-            ) {
-                if (node.operator == UastBinaryOperator.EQUALS) {
-                    if (defaultEquals(context, node)) {
-                        if (withinCastWithEquals(context, node)) {
-                            return
-                        }
-
-                        val message = DEFAULT_MSG
-                        val location = node.operatorIdentifier?.let {
-                            context.getLocation(it)
-                        } ?: context.getLocation(node)
-                        context.report(ISSUE, node, location, message)
-                    }
-                } else {
-                    val message = DEFAULT_MSG
-                    val location = node.operatorIdentifier?.let {
-                        context.getLocation(it)
-                    } ?: context.getLocation(node)
-                    context.report(ISSUE, node, location, message)
-                }
+            override fun visitYieldExpression(node: UYieldExpression) {
+                println(0)
             }
         }
     }
@@ -216,20 +354,18 @@ class FlowDelegateUsageDetector : Detector(), SourceCodeScanner {
         private const val MEDIA_STREAM_TRACK = "org.webrtc.MediaStreamTrack"
 
         private const val DEFAULT_MSG =
-            "Suspicious equality check: MediaStreamTracks should not be checked for equality. Check id() instead."
+            "Incorrect flow property usage: Only properties marked with the @FlowObservable annotation can be observed using `io.livekit.android.util.flow`."
 
         private val IMPLEMENTATION =
             Implementation(FlowDelegateUsageDetector::class.java, Scope.JAVA_FILE_SCOPE)
 
         @JvmField
         val ISSUE = Issue.create(
-            id = "MediaTrackEqualsDetector",
-            briefDescription = "Suspicious DiffUtil Equality",
+            id = "FlowDelegateUsageDetector",
+            briefDescription = "flow on a non-@FlowObservable property",
             explanation = """
-                `areContentsTheSame` is used by `DiffUtil` to produce diffs. If the \
-                method is implemented incorrectly, such as using identity equals \
-                instead of equals, or calling equals on a class that has not implemented \
-                it, weird visual artifacts can occur.
+                Only properties marked with the @FlowObservable annotation can be observed using
+                `io.livekit.android.util.flow`.
                 """,
             category = Category.CORRECTNESS,
             priority = 4,

@@ -2,135 +2,114 @@
 
 package io.livekit.lint
 
-import com.android.tools.lint.checks.infrastructure.LintDetectorTest.bytes
 import com.android.tools.lint.checks.infrastructure.TestFile
-import com.android.tools.lint.checks.infrastructure.TestFiles.java
-import com.android.tools.lint.checks.infrastructure.TestLintTask
+import com.android.tools.lint.checks.infrastructure.TestFiles.kotlin
 import com.android.tools.lint.checks.infrastructure.TestLintTask.lint
 import org.junit.Test
 
 class FlowDelegateUsageDetectorTest {
     @Test
-    fun objectEquals() {
+    fun normalFlowAccess() {
         lint()
             .allowMissingSdk()
             .files(
-                java(
+                flowAccess(),
+                kotlin(
                     """
-          package foo;
-
-          class Example {
-            public boolean foo() {
-              Object a = new Object();
-              Object b = new Object();
-              return a.equals(b);
-            }
-          }"""
+                    package foo
+                    import io.livekit.android.util.FlowObservable
+                    import io.livekit.android.util.flow
+                    import io.livekit.android.util.flowDelegate
+                    class Example {
+                        @field:FlowObservable
+                        val value: Int by flowDelegate(0)
+                        fun foo() {
+                            ::value.flow
+                            return
+                        }
+                    }"""
                 ).indented()
             )
-            .issues(MediaTrackEqualsDetector.ISSUE)
+            .issues(FlowDelegateUsageDetector.ISSUE)
             .run()
             .expectClean()
     }
 
     @Test
-    fun objectEqualityOperator() {
+    fun nonAnnotatedFlowAccess() {
         lint()
             .allowMissingSdk()
             .files(
-                java(
+                flowAccess(),
+                kotlin(
                     """
-          package foo;
-          
-          class Example {
-            public boolean foo() {
-              Object a = new Object();
-              Object b = new Object();
-              return a == b;
-            }
-          }"""
+                    package foo
+                    import io.livekit.android.util.FlowObservable
+                    import io.livekit.android.util.flow
+                    import io.livekit.android.util.flowDelegate
+                    class Example {
+                        val value: Int by flowDelegate(0)
+                        fun foo() {
+                            this::value.flow
+                            return
+                        }
+                    }"""
                 ).indented()
             )
-            .issues(MediaTrackEqualsDetector.ISSUE)
-            .run()
-            .expectClean()
-    }
-
-    @Test
-    fun mediaTrackEquals() {
-        lint()
-            .allowMissingSdk()
-            .files(
-                mediaStreamTrack(),
-                java(
-                    """
-          package foo;
-          import org.webrtc.MediaStreamTrack;
-          
-          class Example {
-            public boolean foo() {
-              MediaStreamTrack a = new MediaStreamTrack();
-              MediaStreamTrack b = new MediaStreamTrack();
-              return a.equals(b);
-            }
-          }"""
-                ).indented()
-            )
-            .issues(MediaTrackEqualsDetector.ISSUE)
+            .issues(FlowDelegateUsageDetector.ISSUE)
             .run()
             .expectErrorCount(1)
     }
+}
 
-    @Test
-    fun mediaTrackEqualityOperator() {
-        lint()
-            .allowMissingSdk()
-            .files(
-                mediaStreamTrack(),
-                java(
-                    """
-          package foo;
-          import org.webrtc.MediaStreamTrack;
-          
-          class Example {
-            public boolean foo() {
-              ABC a = new ABC();
-              MediaStreamTrack b = new MediaStreamTrack();
-              a.equals(b);
-              return a == b;
+fun flowAccess(): TestFile {
+    return kotlin(
+        """
+        package io.livekit.android.util
+        
+        import kotlin.reflect.KProperty
+        import kotlin.reflect.KProperty0
+        
+        internal val <T> KProperty0<T>.delegate: Any?
+            get() { getDelegate() }
+        
+        @Suppress("UNCHECKED_CAST")
+        val <T> KProperty0<T>.flow: StateFlow<T>
+            get() = delegate as StateFlow<T>
+        
+        @Target(AnnotationTarget.PROPERTY)
+        @Retention(AnnotationRetention.SOURCE)
+        @MustBeDocumented
+        annotation class FlowObservable
+        
+        class MutableStateFlowDelegate<T>
+        internal constructor(
+            private val flow: MutableStateFlow<T>,
+            private val onSetValue: ((newValue: T, oldValue: T) -> Unit)? = null
+        ) : MutableStateFlow<T> by flow {
+        
+            operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
+                return flow.value
             }
-            public boolean equals(Object o){
-            return false;
+        
+            operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
+                val oldValue = flow.value
+                flow.value = value
+                onSetValue?.invoke(value, oldValue)
             }
-          }"""
-                ).indented()
-            )
-            .issues(MediaTrackEqualsDetector.ISSUE)
-            .run()
-            .expectErrorCount(1)
-    }
-
-    @Test
-    fun properMediaTrackEquality() {
-        lint()
-            .allowMissingSdk()
-            .files(
-                mediaStreamTrack(),
-                java(
-                    """
-          package foo;
+        }
+        
+        public fun <T> flowDelegate(
+            initialValue: T,
+            onSetValue: ((newValue: T, oldValue: T) -> Unit)? = null
+        ): MutableStateFlowDelegate<T> {
+            return MutableStateFlowDelegate(MutableStateFlow(initialValue), onSetValue)
+        }
 
-          class Example {
-            public boolean foo() {
-              MediaStreamTrack a = new MediaStreamTrack();
-              MediaStreamTrack b = new MediaStreamTrack();
-              return a.getId() == b.getId();
-            }
-          }"""
-                ).indented()
-            )
-            .issues(MediaTrackEqualsDetector.ISSUE)
-            .run()
-            .expectClean()
-    }
+        interface StateFlow<out T> {
+            val value: T
+        }
+        class MutableStateFlow<T>(override var value: T) : StateFlow<T>
+    """
+    ).indented()
 }
\ No newline at end of file