error functions

src/ytdl_sub/script/functions/__init__.py

@@ -1,17 +1,19 @@
 from ytdl_sub.script.functions.array_functions import ArrayFunctions
 from ytdl_sub.script.functions.boolean_functions import BooleanFunctions
+from ytdl_sub.script.functions.conditional_functions import ConditionalFunctions
+from ytdl_sub.script.functions.error_functions import ErrorFunctions
 from ytdl_sub.script.functions.map_functions import MapFunctions
 from ytdl_sub.script.functions.numeric_functions import NumericFunctions
-from ytdl_sub.script.functions.special_functions import SpecialFunctions
 from ytdl_sub.script.functions.string_functions import StringFunctions
 
 
 class Functions(
     StringFunctions,
     NumericFunctions,
-    SpecialFunctions,
+    ConditionalFunctions,
     ArrayFunctions,
     MapFunctions,
     BooleanFunctions,
+    ErrorFunctions,
 ):
     pass

src/ytdl_sub/script/functions/conditional_functions.py

@@ -5,7 +5,7 @@ from ytdl_sub.script.types.resolvable import AnyTypeReturnableB
 from ytdl_sub.script.types.resolvable import Boolean
 
 
-class SpecialFunctions:
+class ConditionalFunctions:
     @staticmethod
     def if_(
         condition: Boolean, true: AnyTypeReturnableA, false: AnyTypeReturnableB

src/ytdl_sub/script/functions/error_functions.py

@@ -0,0 +1,16 @@
+from ytdl_sub.script.types.resolvable import AnyType
+from ytdl_sub.script.types.resolvable import Boolean
+from ytdl_sub.script.types.resolvable import String
+from ytdl_sub.script.utils.exceptions import UserThrownRuntimeError
+
+
+class ErrorFunctions:
+    @staticmethod
+    def throw(error_message: String) -> AnyType:
+        raise UserThrownRuntimeError(error_message)
+
+    @staticmethod
+    def assert_(condition: Boolean, assert_message: String) -> Boolean:
+        if not condition.value:
+            raise UserThrownRuntimeError(assert_message)
+        return condition

src/ytdl_sub/script/types/function.py

@@ -23,6 +23,8 @@ from ytdl_sub.script.types.variable import FunctionArgument
 from ytdl_sub.script.types.variable import Variable
 from ytdl_sub.script.types.variable_dependency import VariableDependency
 from ytdl_sub.script.utils.exception_formatters import FunctionArgumentsExceptionFormatter
+from ytdl_sub.script.utils.exceptions import FunctionRuntimeException
+from ytdl_sub.script.utils.exceptions import UserThrownRuntimeError
 from ytdl_sub.script.utils.type_checking import FunctionInputSpec
 from ytdl_sub.script.utils.type_checking import is_union
 from ytdl_sub.utils.exceptions import StringFormattingException
@@ -167,4 +169,11 @@ class BuiltInFunction(Function, TypeHintedFunctionType):
             for arg in self.args
         ]
 
-        return self.callable(*resolved_args)
+        try:
+            return self.callable(*resolved_args)
+        except UserThrownRuntimeError:
+            raise
+        except Exception as exc:
+            raise FunctionRuntimeException(
+                f"Runtime error occurred when executing the function %{self.name}: {str(exc)}"
+            ) from exc

src/ytdl_sub/script/utils/exceptions.py

@@ -15,11 +15,19 @@ class IncompatibleFunctionArguments(UserException):
     """Function has invalid arguments"""
 
 
-class UnreachableSyntaxException(InvalidSyntaxException):
+class FunctionRuntimeException(ValueError):
+    """Exception thrown when a ytdl-sub function has an error occur at runtime"""
+
+
+class UserThrownRuntimeError(ValidationException):
+    """An error explicitly thrown by the user via a function"""
+
+
+class _UnreachableSyntaxException(InvalidSyntaxException):
     """For use in places where code _should_ never reach, but might from bugs"""
 
 
-UNREACHABLE = UnreachableSyntaxException(
+UNREACHABLE = _UnreachableSyntaxException(
     "If you see this error, you have discovered a bug in the script parser!\n"
     "Please upload your config/subscription file(s) to and make a GitHub issue at "
     "https://github.com/jmbannon/ytdl-sub/issues"

tests/unit/script/types/test_function.py

@@ -5,7 +5,9 @@ import pytest
 from ytdl_sub.script.script import Script
 from ytdl_sub.script.types.resolvable import Boolean
 from ytdl_sub.script.types.resolvable import String
+from ytdl_sub.script.utils.exceptions import FunctionRuntimeException
 from ytdl_sub.script.utils.exceptions import IncompatibleFunctionArguments
+from ytdl_sub.script.utils.exceptions import UserThrownRuntimeError
 
 
 def _incompatible_arguments_match(expected: str, recieved: str) -> str:
@@ -78,3 +80,20 @@ class TestFunction:
             match=_incompatible_arguments_match(expected="Array, Integer", recieved="Map, Integer"),
         ):
             Script({"func": function_str}).resolve()
+
+    def test_runtime_error(self):
+        with pytest.raises(
+            FunctionRuntimeException,
+            match=re.escape(
+                "Runtime error occurred when executing the function %div: division by zero"
+            ),
+        ):
+            Script({"divide_by_zero": "{%div(8820, 0)}"}).resolve()
+
+    def test_user_throw(self):
+        with pytest.raises(UserThrownRuntimeError, match=re.escape("test this error message")):
+            Script({"throw_error": "{%throw('test this error message')}"}).resolve()
+
+    def test_user_assert(self):
+        with pytest.raises(UserThrownRuntimeError, match=re.escape("test this error message")):
+            Script({"throw_error": "{%assert(False, 'test this error message')}"}).resolve()