Enhance fuzzing for arrays #738 (#755)

Author: volivan239

utbot-framework/src/main/kotlin/org/utbot/engine/UtBotSymbolicEngine.kt

@@ -439,7 +439,7 @@ class UtBotSymbolicEngine(
                 packageName = executableId.classId.packageName
             }
             fuzz(thisMethodDescription, ObjectModelProvider(defaultIdGenerator).apply {
-                limitValuesCreatedByFieldAccessors = 500
+                totalLimit = 500
             })
         }.withMutations(
             TrieBasedFuzzerStatistics(coveredInstructionValues), methodUnderTestDescription, *defaultModelMutators().toTypedArray()

utbot-fuzzers/src/main/kotlin/org/utbot/fuzzer/Fuzzer.kt

@@ -164,22 +164,28 @@ fun defaultModelProviders(idGenerator: IdentityPreservingIdGenerator<Int>): Mode
 }
 
 /**
- * Creates a model provider for [ObjectModelProvider] that generates values for object constructor.
+ * Creates a model provider from a list of providers that we want to use by default in [RecursiveModelProvider]
  */
-fun objectModelProviders(idGenerator: IdentityPreservingIdGenerator<Int>): ModelProvider {
-    return ModelProvider.of(
+internal fun modelProviderForRecursiveCalls(idGenerator: IdentityPreservingIdGenerator<Int>, recursionDepth: Int): ModelProvider {
+    val nonRecursiveProviders = ModelProvider.of(
         CollectionModelProvider(idGenerator),
-        ArrayModelProvider(idGenerator),
         EnumModelProvider(idGenerator),
         StringConstantModelProvider,
-        RegexModelProvider,
         CharToStringModelProvider,
         ConstantsModelProvider,
         PrimitiveDefaultsModelProvider,
         PrimitiveWrapperModelProvider,
     )
+
+    return if (recursionDepth >= 0)
+        nonRecursiveProviders
+            .with(ObjectModelProvider(idGenerator, recursionDepth))
+            .with(ArrayModelProvider(idGenerator, recursionDepth))
+    else
+        nonRecursiveProviders
 }
 
+
 fun defaultModelMutators(): List<ModelMutator> = listOf(
     StringRandomMutator,
     RegexStringModelMutator,

utbot-fuzzers/src/main/kotlin/org/utbot/fuzzer/ModelProvider.kt

@@ -41,6 +41,17 @@ fun interface ModelProvider {
         }
     }
 
+    /**
+     * Applies [transform] for current provider
+     */
+    fun map(transform: (ModelProvider) -> ModelProvider): ModelProvider {
+        return if (this is Combined) {
+            Combined(providers.map(transform))
+        } else {
+            transform(this)
+        }
+    }
+
     /**
      * Creates [ModelProvider] that passes unprocessed classes to `modelProvider`.
      *
@@ -123,7 +134,19 @@ fun interface ModelProvider {
     /**
      * Wrapper class that delegates implementation to the [providers].
      */
-    private class Combined(val providers: List<ModelProvider>): ModelProvider {
+    private class Combined(providers: List<ModelProvider>): ModelProvider {
+        val providers: List<ModelProvider>
+
+        init {
+            // Flattening to avoid Combined inside Combined (for correct work of except, map, etc.)
+            this.providers = providers.flatMap {
+                if (it is Combined)
+                    it.providers
+                else
+                    listOf(it)
+            }
+        }
+
         override fun generate(description: FuzzedMethodDescription): Sequence<FuzzedParameter> = sequence {
             providers.forEach { provider ->
                 provider.generate(description).forEach {

utbot-fuzzers/src/main/kotlin/org/utbot/fuzzer/providers/ArrayModelProvider.kt

@@ -1,34 +1,65 @@
 package org.utbot.fuzzer.providers
 
+import org.utbot.framework.plugin.api.ClassId
 import org.utbot.framework.plugin.api.UtArrayModel
+import org.utbot.framework.plugin.api.UtModel
+import org.utbot.framework.plugin.api.UtPrimitiveModel
 import org.utbot.framework.plugin.api.util.defaultValueModel
+import org.utbot.framework.plugin.api.util.intClassId
 import org.utbot.framework.plugin.api.util.isArray
 import org.utbot.fuzzer.FuzzedMethodDescription
-import org.utbot.fuzzer.FuzzedParameter
-import org.utbot.fuzzer.IdGenerator
-import org.utbot.fuzzer.ModelProvider
-import org.utbot.fuzzer.ModelProvider.Companion.yieldAllValues
-import java.util.function.IntSupplier
+import org.utbot.fuzzer.IdentityPreservingIdGenerator
 
 class ArrayModelProvider(
-    private val idGenerator: IdGenerator<Int>
-) : ModelProvider {
-    override fun generate(description: FuzzedMethodDescription): Sequence<FuzzedParameter> = sequence {
-        description.parametersMap
-            .asSequence()
-            .filter { (classId, _) -> classId.isArray }
-            .forEach { (arrayClassId, indices) ->
-                yieldAllValues(indices, listOf(0, 10).map { arraySize ->
-                    UtArrayModel(
-                        id = idGenerator.createId(),
-                        arrayClassId,
-                        length = arraySize,
-                        arrayClassId.elementClassId!!.defaultValueModel(),
-                        mutableMapOf()
-                    ).fuzzed {
-                        this.summary = "%var% = ${arrayClassId.elementClassId!!.simpleName}[$arraySize]"
-                    }
-                })
+    idGenerator: IdentityPreservingIdGenerator<Int>,
+    recursionDepthLeft: Int = 1
+) : RecursiveModelProvider(idGenerator, recursionDepthLeft) {
+    override fun createNewInstance(parentProvider: RecursiveModelProvider, newTotalLimit: Int): RecursiveModelProvider =
+        ArrayModelProvider(parentProvider.idGenerator, parentProvider.recursionDepthLeft - 1)
+            .copySettingsFrom(parentProvider)
+            .apply {
+                totalLimit = newTotalLimit
+                if (parentProvider is ArrayModelProvider)
+                    branchingLimit = 1      // This improves performance but also forbids generating "jagged" arrays
             }
+
+    override fun generateModelConstructors(
+        description: FuzzedMethodDescription,
+        classId: ClassId
+    ): List<ModelConstructor> {
+        if (!classId.isArray)
+            return listOf()
+        val lengths = generateArrayLengths(description)
+        return lengths.map { length ->
+            ModelConstructor(List(length) { classId.elementClassId!! }) { values ->
+                createFuzzedArrayModel(classId, length, values.map { it.model } )
+            }
+        }
+    }
+
+    private fun generateArrayLengths(description: FuzzedMethodDescription): List<Int> {
+        val fuzzedLengths = fuzzValuesRecursively(
+            types = listOf(intClassId),
+            baseMethodDescription = description,
+            modelProvider = ConstantsModelProvider
+        )
+
+        // Firstly we will use most "interesting" default sizes, then we will use small sizes obtained from src
+        return listOf(3, 0) + fuzzedLengths
+            .map { (it.single().model as UtPrimitiveModel).value as Int }
+            .filter { it in 1..10 && it != 3 }
+            .toSortedSet()
+            .toList()
     }
+
+    private fun createFuzzedArrayModel(arrayClassId: ClassId, length: Int, values: List<UtModel>?) =
+        UtArrayModel(
+            idGenerator.createId(),
+            arrayClassId,
+            length,
+            arrayClassId.elementClassId!!.defaultValueModel(),
+            values?.withIndex()?.associate { it.index to it.value }?.toMutableMap() ?: mutableMapOf()
+        ).fuzzed {
+            this.summary = "%var% = ${arrayClassId.elementClassId!!.simpleName}[$length]"
+        }
 }