Add tests cases for Composable functions returning null value (#3953)

Co-authored-by: Oleksandr Karpovich <oleksandr.karpovich@jetbrains.com>

compose/integrations/composable-test-cases/gradle.properties

@@ -1,12 +1,13 @@
 org.gradle.jvmargs=-Xmx2048M -XX:MaxMetaspaceSize=512m
 kotlin.code.style=official
 android.useAndroidX=true
-kotlin.version=1.9.20-RC
+kotlin.version=1.9.20
 agp.version=7.3.0
-compose.version=1.5.10-rc01
+compose.version=1.5.10
 
 #empty by default - a default version will be used
-compose.kotlinCompilerPluginVersion=1.5.2.1-rc01
+#compose.kotlinCompilerPluginVersion=23.11.20
+compose.kotlinCompilerPluginVersion=1.5.3
 
 # default|failingJs - see enum class CasesToRun
 tests.casesToRun=default

compose/integrations/composable-test-cases/testcases/lambdas/lib/src/commonMain/kotlin/Dependencies.kt

@@ -1,4 +1,5 @@
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.ReadOnlyComposable
 import androidx.compose.runtime.cache
 import androidx.compose.runtime.currentComposer
 import com.example.common.TextLeafNode
@@ -12,3 +13,20 @@ fun ComposableSomeText(someText : () -> String) {
 val composableInt: Int
     @Composable
     get() = currentComposer.cache(false) { 100 }
+
+
+@Composable
+fun ComposableAlwaysReturnsNull(): String? {
+    return null
+}
+
+@Composable
+fun ComposableAlwaysReturnsNullUnit(): Unit? {
+    val u: Unit? = null
+    return u
+}
+
+@Composable
+fun ComposableAlwaysReturnsUnit(): Unit? {
+    return Unit
+}

compose/integrations/composable-test-cases/testcases/lambdas/main/src/commonTest/kotlin/Tests.kt

@@ -113,6 +113,35 @@ class Tests {
         }
         assertEquals("root:{Value = 100}", root.dump())
     }
+
+    @Test
+    fun testComposableAlwaysReturnsNull() {
+        val root = composeText {
+            val v = ComposableAlwaysReturnsNull()
+            TextLeafNode("Value = ${v ?: "null"}")
+        }
+        assertEquals("root:{Value = null}", root.dump())
+    }
+
+    @Test
+    fun testComposableAlwaysReturnsNullUnit() {
+        val root = composeText {
+            val v = ComposableAlwaysReturnsNullUnit()
+            TextLeafNode("Value = ${v ?: "null"}")
+        }
+        assertEquals("root:{Value = null}", root.dump())
+    }
+
+    @Test
+    fun testComposableAlwaysReturnsUnit() {
+        val root = composeText {
+            val v = ComposableAlwaysReturnsUnit().let {
+                if (it == Unit) "Unit" else it.toString()
+            }
+            TextLeafNode("Value = $v")
+        }
+        assertEquals("root:{Value = Unit}", root.dump())
+    }
 }
 
 private fun someText(): String {