feat: add function is blank() to check if a string is blank or not

Author: skayliu

src/main/scala/org/camunda/feel/impl/builtin/BooleanBuiltinFunctions.scala

@@ -25,8 +25,7 @@ object BooleanBuiltinFunctions {
     "not"         -> List(notFunction),
     "is defined"  -> List(isDefinedFunction),
     "get or else" -> List(getOrElse),
-    "assert"      -> List(assertFunction, assertFunction2),
-    "is blank"  -> List(isBlankFunction)
+    "assert"      -> List(assertFunction, assertFunction2)
   )
 
   private def notFunction =
@@ -71,11 +70,4 @@ object BooleanBuiltinFunctions {
     }
   )
 
-  private def isBlankFunction = builtinFunction(
-    params = List("string"),
-    invoke = {case List(ValString(string)) =>
-      ValBoolean(string.isBlank)
-    }
-  )
-
 }

src/main/scala/org/camunda/feel/impl/builtin/StringBuiltinFunctions.scala

@@ -45,7 +45,8 @@ object StringBuiltinFunctions {
     "extract"          -> List(extractFunction),
     "trim"             -> List(trimFunction),
     "uuid"             -> List(uuidFunction),
-    "to base64"        -> List(toBase64Function)
+    "to base64"        -> List(toBase64Function),
+    "is blank"         -> List(isBlankFunction)
   )
 
   private def substringFunction = builtinFunction(
@@ -287,4 +288,11 @@ object StringBuiltinFunctions {
       }
     )
 
+  private def isBlankFunction = builtinFunction(
+    params = List("string"),
+    invoke = {case List(ValString(string)) =>
+      ValBoolean(string.isBlank)
+    }
+  )
+
 }

src/test/scala/org/camunda/feel/impl/builtin/BuiltinFunctionsTest.scala

@@ -243,27 +243,4 @@ class BuiltinFunctionsTest
       "Assertion failure on evaluate the expression 'list contains(assert(my_list, my_list != null, \"The condition is not true\"), 2)': The condition is not true"
     )
   }
-
-  "A is blank() function" should "return Boolean" in {
-    evaluateExpression(
-      expression = """ is blank("") """
-    ) should returnResult(true)
-
-    evaluateExpression(
-      expression = """ is blank(" ") """
-    ) should returnResult(true)
-
-    evaluateExpression(
-      expression = """ is blank("hello world") """
-    ) should returnResult(false)
-
-    evaluateExpression(
-      expression = """ is blank(" hello world ") """
-    ) should returnResult(false)
-
-    evaluateExpression(
-      expression = """ is blank("\t\n\r\f") """
-    ) should returnResult(true)
-  }
-
 }

src/test/scala/org/camunda/feel/impl/builtin/BuiltinStringFunctionsTest.scala

@@ -195,4 +195,32 @@ class BuiltinStringFunctionsTest
 
     evaluateExpression(""" to base64(value: "Camunda") """) should returnResult("Q2FtdW5kYQ==")
   }
+
+  "A is blank() function" should "return true if the string contains only whitespace" in {
+    evaluateExpression(
+      expression = """ is blank("") """
+    ) should returnResult(true)
+
+    evaluateExpression(
+      expression = """ is blank(" ") """
+    ) should returnResult(true)
+
+    evaluateExpression(
+      expression = """ is blank("\t\n\r\f") """
+    ) should returnResult(true)
+
+    evaluateExpression(
+      expression = """ is blank(string: "") """
+    ) should returnResult(true)
+  }
+
+  "A is blank() function" should "return false if the string contains only non-whitespace characters" in {
+    evaluateExpression(
+      expression = """ is blank("hello world") """
+    ) should returnResult(false)
+
+    evaluateExpression(
+      expression = """ is blank(" hello world ") """
+    ) should returnResult(false)
+  }
 }