Make fuzzer use generic field types #2430 (#2431)

Author: IlyaMuravjov

utbot-java-fuzzing/src/main/kotlin/org/utbot/fuzzing/providers/Objects.kt

@@ -206,7 +206,7 @@ internal fun findAccessibleModifiableFields(description: FuzzedDescription?, cla
             FieldDescription(
                 name = field.name,
                 type = if (description != null) toFuzzerType(
-                    field.type,
+                    field.genericType,
                     description.typeCache
                 ) else FuzzedType(field.type.id),
                 canBeSetDirectly = isAccessible(

utbot-java-fuzzing/src/test/java/org/utbot/fuzzing/samples/StringListHolder.java

@@ -0,0 +1,20 @@
+package org.utbot.fuzzing.samples;
+
+import java.util.List;
+
+public class StringListHolder {
+    private List<String> strings;
+
+
+    public List<String> getStrings() {
+        return strings;
+    }
+
+
+    public void setStrings(List<String> strings) {
+        this.strings = strings;
+    }
+
+
+    public void methodUnderTest() {}
+}

utbot-java-fuzzing/src/test/kotlin/org/utbot/fuzzing/JavaFuzzingTest.kt

@@ -9,6 +9,7 @@ import org.utbot.framework.plugin.api.UtAssembleModel
 import org.utbot.framework.plugin.api.UtNullModel
 import org.utbot.framework.plugin.api.UtPrimitiveModel
 import org.utbot.framework.plugin.api.util.*
+import org.utbot.framework.plugin.api.util.constructor.ValueConstructor
 import org.utbot.fuzzer.FuzzedConcreteValue
 import org.utbot.fuzzing.samples.DeepNested
 import org.utbot.fuzzer.FuzzedType
@@ -17,13 +18,15 @@ import org.utbot.fuzzer.IdentityPreservingIdGenerator
 import org.utbot.fuzzing.providers.NullValueProvider
 import org.utbot.fuzzing.samples.AccessibleObjects
 import org.utbot.fuzzing.samples.FailToGenerateListGeneric
+import org.utbot.fuzzing.samples.StringListHolder
 import org.utbot.fuzzing.samples.Stubs
 import org.utbot.fuzzing.utils.Trie
 import java.lang.reflect.GenericArrayType
 import java.lang.reflect.ParameterizedType
 import java.lang.reflect.Type
 import java.util.IdentityHashMap
 import java.util.concurrent.atomic.AtomicInteger
+import kotlin.reflect.jvm.javaMethod
 
 internal object TestIdentityPreservingIdGenerator : IdentityPreservingIdGenerator<Int> {
     private val cache = mutableMapOf<Any, Int>()
@@ -273,6 +276,31 @@ class JavaFuzzingTest {
         }
     }
 
+    @Test
+    fun `fuzzer correctly works with settable field that has a parameterized type`() {
+        val seenStringListHolders = mutableListOf<StringListHolder>()
+        var remainingRuns = 100
+        runBlockingWithContext {
+            runJavaFuzzing(
+                TestIdentityPreservingIdGenerator,
+                methodUnderTest = StringListHolder::methodUnderTest.javaMethod!!.executableId,
+                constants = emptyList(),
+                names = emptyList(),
+            ) { thisInstance, _, _ ->
+                thisInstance?.let {
+                    seenStringListHolders.add(
+                        ValueConstructor().construct(listOf(it.model)).single().value as StringListHolder
+                    )
+                }
+                remainingRuns--
+                BaseFeedback(Trie.emptyNode(), if (remainingRuns > 0) Control.CONTINUE else Control.STOP)
+            }
+        }
+        val seenStrings = seenStringListHolders.flatMap { it.strings.orEmpty().filterNotNull() }
+        assertNotEquals(emptyList<String>(), seenStrings)
+        seenStrings.forEach { assertInstanceOf(String::class.java, it) }
+    }
+
     @Test
     fun `value providers override every function of fuzzing in simple case`() {
         val provided = MarkerValueProvider<FuzzedType, FuzzedValue, FuzzedDescription>("p")