[NU-1701] Introduce canCastTo, castTo and castToOrNull extension meth…

…ods in SpeL.

designer/server/src/test/scala/pl/touk/nussknacker/ui/api/ExpressionSuggesterSpec.scala

@@ -114,6 +114,11 @@ class ExpressionSuggesterSpec
         Map("empty" -> List(StaticMethodDefinition(MethodTypeInfo(Nil, None, Typed[Boolean]), "empty", None))),
         Map.empty
       ),
+      ClassDefinition(
+        Unknown,
+        Map("canCastTo" -> List(StaticMethodDefinition(MethodTypeInfo(Nil, None, Typed[Boolean]), "canCastTo", None))),
+        Map.empty
+      ),
     )
   )
 
@@ -149,6 +154,7 @@ class ExpressionSuggesterSpec
     "listOfUnions" -> Typed.genericTypeClass[java.util.List[A]](List(Typed(Typed[A], Typed[B]))),
     "dictFoo"      -> DictInstance("dictFoo", EmbeddedDictDefinition(Map.empty[String, String])).typingResult,
     "dictBar"      -> DictInstance("dictBar", EmbeddedDictDefinition(Map.empty[String, String])).typingResult,
+    "unknown"      -> Unknown
   )
 
   private def spelSuggestionsFor(input: String, row: Int = 0, column: Int = -1): List[ExpressionSuggestion] = {
@@ -202,6 +208,7 @@ class ExpressionSuggesterSpec
       "#other",
       "#union",
       "#unionOfLists",
+      "#unknown",
       "#util"
     )
   }
@@ -219,6 +226,7 @@ class ExpressionSuggesterSpec
       "#other",
       "#union",
       "#unionOfLists",
+      "#unknown",
       "#util"
     )
   }
@@ -765,6 +773,12 @@ class ExpressionSuggesterSpec
     )
   }
 
+  test("should suggest methods for unknown") {
+    spelSuggestionsFor("#unknown.") shouldBe List(
+      suggestion("canCastTo", Typed[Boolean]),
+    )
+  }
+
 }
 
 object ExpressionSuggesterTestData {

docs/Changelog.md

@@ -62,6 +62,7 @@
 * [#6925](https://github.com/TouK/nussknacker/pull/6925) Fix situation when preset labels were presented as `null` when node didn't pass the validation.
 * [#6935](https://github.com/TouK/nussknacker/pull/6935) Spel: Scenario labels added to meta variable - `#meta.scenarioLabels`
 * [#6952](https://github.com/TouK/nussknacker/pull/6952) Improvement: TypeInformation support for scala.Option
+* [#6840](https://github.com/TouK/nussknacker/pull/6840) Introduce canCastTo, castTo and castToOrNull extension methods in SpeL.
 
 ## 1.17
 

docs/scenarios_authoring/Spel.md

@@ -376,3 +376,16 @@ On the other hand, formatter created using `#DATE_FORMAT.formatter()` method wil
 - `#DATE_FORMAT.lenientFormatter('yyyy-MM-dd EEEE', 'PL')` - creates lenient version `DateTimeFormatter` using given pattern and locale
 
 For full list of available format options take a look at [DateTimeFormatter api docs](https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/format/DateTimeFormatter.html).
+
+## Casting.
+
+When a type cannot be determined by parser, the type is presented as `Unknown`. When we know what the type will be on
+runtime, we can cast a given type, and then we can operate on the cast type.
+
+E.g. having a variable `obj` of a type: `List[Unknown]` and we know the elements are strings then we can cast elements
+to String: `#obj.![#this.castToOrNull('java.lang.String')]`.
+
+Available methods:
+- `canCastTo` - checks if a type can be cast to a given class.
+- `castTo` - casts a type to a given class or throws exception if type cannot be cast.
+- `castToOrNull` - casts a type to a given class or return null if type cannot be cast.