Change subclass determiner to assignability determiner

components-api/src/main/scala/pl/touk/nussknacker/engine/api/typed/AssignabilityDeterminer.scala

@@ -0,0 +1,251 @@
+package pl.touk.nussknacker.engine.api.typed
+
+import cats.data.Validated._
+import cats.data.{NonEmptyList, Validated, ValidatedNel}
+import cats.implicits.{catsSyntaxValidatedId, _}
+import org.apache.commons.lang3.ClassUtils
+import pl.touk.nussknacker.engine.api.typed.typing._
+
+/**
+  * This class determine whether we can assign one type to another type - that is if its the same class, a subclass or can be converted to another type. We provide two modes of conversion -
+ * 1. Loose conversion is based on the fact that TypingResults are
+ * sets of possible supertypes with some additional restrictions (like TypedObjectTypingResult). It is basically how SpEL
+ * can convert things. Like CommonSupertypeFinder it's in the spirit of "Be type safe as much as possible, but also provide some helpful
+ * conversion for types not in the same jvm class hierarchy like boxed Integer to boxed Long and so on".
+ * 2. Strict conversion checks whether we can convert to a wider type. Eg only widening numerical types
+ * are allowed ( Int -> Long). For other types it should work the same as a loose conversion.
+ *
+  */
+object AssignabilityDeterminer {
+
+  private val javaMapClass       = classOf[java.util.Map[_, _]]
+  private val javaListClass      = classOf[java.util.List[_]]
+  private val arrayOfAnyRefClass = classOf[Array[AnyRef]]
+
+  /**
+   * This method checks if `givenType` can by subclass of `superclassCandidate`
+   * It will return true if `givenType` is equals to `superclassCandidate` or `givenType` "extends" `superclassCandidate`
+   */
+  def isAssignableLoose(from: TypingResult, to: TypingResult): ValidatedNel[String, Unit] =
+    isAssignable(from, to, LooseConversionChecker)
+
+  def isAssignableStrict(from: TypingResult, to: TypingResult): ValidatedNel[String, Unit] =
+    isAssignable(from, to, StrictConversionChecker)
+
+  private def isAssignable(from: TypingResult, to: TypingResult, conversionChecker: ConversionChecker) = {
+    (from, to) match {
+      case (_, Unknown)       => ().validNel
+      case (Unknown, _)       => ().validNel
+      case (TypedNull, other) => isNullAsignableTo(other)
+      case (_, TypedNull)     => s"No type can be subclass of ${TypedNull.display}".invalidNel
+      case (given: SingleTypingResult, superclass: TypedUnion) =>
+        isAnyOfAssignableToAnyOf(NonEmptyList.one(given), superclass.possibleTypes, conversionChecker)
+      case (given: TypedUnion, superclass: SingleTypingResult) =>
+        isAnyOfAssignableToAnyOf(given.possibleTypes, NonEmptyList.one(superclass), conversionChecker)
+      case (given: SingleTypingResult, superclass: SingleTypingResult) =>
+        isSingleAssignableToSingle(given, superclass, conversionChecker)
+      case (given: TypedUnion, superclass: TypedUnion) =>
+        isAnyOfAssignableToAnyOf(given.possibleTypes, superclass.possibleTypes, conversionChecker)
+    }
+  }
+
+  private def isNullAsignableTo(to: TypingResult): ValidatedNel[String, Unit] = to match {
+    // TODO: Null should not be subclass of typed map that has all values assigned.
+    case TypedObjectWithValue(_, _) => s"${TypedNull.display} cannot be subclass of type with value".invalidNel
+    case _                          => ().validNel
+  }
+
+  private def isSingleAssignableToSingle(
+      from: SingleTypingResult,
+      to: SingleTypingResult,
+      conversionChecker: ConversionChecker
+  ): ValidatedNel[String, Unit] = {
+    val objTypeRestriction = isSingleAssignableToTypedClass(from, to.runtimeObjType, conversionChecker)
+    val typedObjectRestrictions = (_: Unit) =>
+      to match {
+        case superclass: TypedObjectTypingResult =>
+          val givenTypeFields = from match {
+            case given: TypedObjectTypingResult => given.fields
+            case _                              => Map.empty[String, TypingResult]
+          }
+
+          superclass.fields.toList
+            .map { case (name, typ) =>
+              givenTypeFields.get(name) match {
+                case None =>
+                  s"Field '$name' is lacking".invalidNel
+                case Some(givenFieldType) =>
+                  condNel(
+                    isAssignable(givenFieldType, typ, conversionChecker).isValid,
+                    (),
+                    s"Field '$name' is of the wrong type. Expected: ${givenFieldType.display}, actual: ${typ.display}"
+                  )
+              }
+            }
+            .foldLeft(().validNel[String])(_.combine(_))
+        case _ =>
+          ().validNel
+      }
+    val dictRestriction = (_: Unit) => {
+      (from, to) match {
+        case (given: TypedDict, superclass: TypedDict) =>
+          condNel(
+            given.dictId == superclass.dictId,
+            (),
+            "The type and the superclass candidate are Dicts with unequal IDs"
+          )
+        case (_: TypedDict, _) =>
+          "The type is a Dict but the superclass candidate not".invalidNel
+        case (_, _: TypedDict) =>
+          "The superclass candidate is a Dict but the type not".invalidNel
+        case _ =>
+          ().validNel
+      }
+    }
+    val taggedValueRestriction = (_: Unit) => {
+      (from, to) match {
+        case (givenTaggedValue: TypedTaggedValue, superclassTaggedValue: TypedTaggedValue) =>
+          condNel(
+            givenTaggedValue.tag == superclassTaggedValue.tag,
+            (),
+            s"Tagged values have unequal tags: ${givenTaggedValue.tag} and ${superclassTaggedValue.tag}"
+          )
+        case (_: TypedTaggedValue, _) => ().validNel
+        case (_, _: TypedTaggedValue) =>
+          s"The type is not a tagged value".invalidNel
+        case _ => ().validNel
+      }
+    }
+    // Type like Integer can be subclass of Integer{5}, because Integer could
+    // possibly have value of 5, that would make it subclass of Integer{5}.
+    // This allows us to supply unknown Integer to function that requires
+    // Integer{5}.
+    val dataValueRestriction = (_: Unit) => {
+      (from, to) match {
+        case (TypedObjectWithValue(_, givenValue), TypedObjectWithValue(_, candidateValue))
+            if givenValue == candidateValue =>
+          ().validNel
+        case (TypedObjectWithValue(_, givenValue), TypedObjectWithValue(_, candidateValue)) =>
+          s"Types with value have different values: $givenValue and $candidateValue".invalidNel
+        case _ => ().validNel
+      }
+    }
+    objTypeRestriction andThen
+      (typedObjectRestrictions combine dictRestriction combine taggedValueRestriction combine dataValueRestriction)
+  }
+
+  private def isSingleAssignableToTypedClass(
+      from: SingleTypingResult,
+      to: TypedClass,
+      conversionChecker: ConversionChecker
+  ): ValidatedNel[String, Unit] = {
+    def typeParametersMatches(givenClass: TypedClass, superclassCandidate: TypedClass) = {
+      def canBeSubOrSuperclass(givenClassParam: TypingResult, superclassParam: TypingResult) =
+        condNel(
+          isAssignable(givenClassParam, superclassParam, conversionChecker).isValid ||
+            isAssignable(superclassParam, givenClassParam, conversionChecker).isValid,
+          (),
+          f"None of ${givenClassParam.display} and ${superclassParam.display} is a subclass of another"
+        )
+
+      (givenClass, superclassCandidate) match {
+        case (TypedClass(_, givenElementParam :: Nil), TypedClass(superclass, superclassParam :: Nil))
+            // Array are invariant but we have built-in conversion between array types - this check should be moved outside this class when we move away canBeConvertedTo as well
+            if javaListClass.isAssignableFrom(superclass) || arrayOfAnyRefClass.isAssignableFrom(superclass) =>
+          isAssignable(givenElementParam, superclassParam, conversionChecker)
+        case (
+              TypedClass(_, givenKeyParam :: givenValueParam :: Nil),
+              TypedClass(superclass, superclassKeyParam :: superclassValueParam :: Nil)
+            ) if javaMapClass.isAssignableFrom(superclass) =>
+          // Map's key generic param is invariant. We can't just check givenKeyParam == superclassKeyParam because of Unknown type which is a kind of wildcard
+          condNel(
+            isAssignable(givenKeyParam, superclassKeyParam, conversionChecker).isValid &&
+              isAssignable(superclassKeyParam, givenKeyParam, conversionChecker).isValid,
+            (),
+            s"Key types of Maps ${givenKeyParam.display} and ${superclassKeyParam.display} are not equals"
+          ) andThen (_ => isAssignable(givenValueParam, superclassValueParam, conversionChecker))
+        case _ =>
+          // for unknown types we are lax - the generic type may be co- contra- or in-variant - and we don't want to
+          // return validation errors in this case. It's better to accept to much than too little
+          condNel(
+            superclassCandidate.params.zip(givenClass.params).forall { case (superclassParam, givenClassParam) =>
+              canBeSubOrSuperclass(givenClassParam, superclassParam).isValid
+            },
+            (),
+            s"Wrong type parameters"
+          )
+      }
+    }
+    val givenClass = from.runtimeObjType
+
+    val equalClassesOrCanAssign =
+      condNel(
+        givenClass == to,
+        (),
+        f"${givenClass.display} and ${to.display} are not the same"
+      ) orElse
+        isAssignable(givenClass.klass, to.klass)
+
+    val canBeSubclass = equalClassesOrCanAssign andThen (_ => typeParametersMatches(givenClass, to))
+    canBeSubclass orElse conversionChecker.isConvertable(from, to)
+  }
+
+  private def isAnyOfAssignableToAnyOf(
+      from: NonEmptyList[SingleTypingResult],
+      to: NonEmptyList[SingleTypingResult],
+      conversionChecker: ConversionChecker
+  ): ValidatedNel[String, Unit] = {
+    // Would be more safety to do givenTypes.forAll(... superclassCandidates.exists ...) - we wil protect against
+    // e.g. (String | Int).isAnyOfAssignableToAnyOf(String) which can fail in runtime for Int, but on the other hand we can't block user's intended action.
+    // He/she could be sure that in this type, only String will appear. He/she also can't easily downcast (String | Int) to String so leaving here
+    // "double exists" looks like a good tradeoff
+    condNel(
+      from.exists(given => to.exists(isSingleAssignableToSingle(given, _, conversionChecker).isValid)),
+      (),
+      s"""None of the following types:
+         |${from.map(" - " + _.display).toList.mkString(",\n")}
+         |can be a subclass of any of:
+         |${to.map(" - " + _.display).toList.mkString(",\n")}""".stripMargin
+    )
+  }
+
+  // we use explicit autoboxing = true flag, as ClassUtils in commons-lang3:3.3 (used in Flink) cannot handle JDK 11...
+  private def isAssignable(from: Class[_], to: Class[_]): ValidatedNel[String, Unit] =
+    condNel(ClassUtils.isAssignable(from, to, true), (), s"$to is not assignable from $from")
+
+  // TODO: Conversions should be checked during typing, not during generic usage of TypingResult.canBeSubclassOf(...)
+  private sealed trait ConversionChecker {
+
+    def isConvertable(
+        from: SingleTypingResult,
+        to: TypedClass
+    ): ValidatedNel[String, Unit]
+
+  }
+
+  private object StrictConversionChecker extends ConversionChecker {
+
+    override def isConvertable(
+        from: SingleTypingResult,
+        to: TypedClass
+    ): ValidatedNel[String, Unit] = {
+      val errMsgPrefix =
+        s"${from.runtimeObjType.display} cannot be strictly converted to ${to.display}"
+      condNel(TypeConversionHandler.canBeStrictlyConvertedTo(from, to), (), errMsgPrefix)
+    }
+
+  }
+
+  private object LooseConversionChecker extends ConversionChecker {
+
+    override def isConvertable(
+        from: SingleTypingResult,
+        to: TypedClass
+    ): ValidatedNel[String, Unit] = {
+      val errMsgPrefix = s"${from.runtimeObjType.display} cannot be converted to ${to.display}"
+      condNel(TypeConversionHandler.canBeLooselyConvertedTo(from, to), (), errMsgPrefix)
+    }
+
+  }
+
+}