validator: Add generic check_or.

Added generic check_or function and tests.
Fixes part of #17914.

Co-authored-by: Gaurav Pandey <gauravguitarrocks@gmail.com>

zerver/lib/validator.py

@@ -582,3 +582,15 @@ def check_string_or_int(var_name: str, val: object) -> Union[str, int]:
         return val
 
     raise ValidationError(_("{var_name} is not a string or integer").format(var_name=var_name))
+
+
+def check_or(sub_validator1: Validator[Any], sub_validator2: Validator[Any]) -> Validator[Any]:
+    def f(var_name: str, val: object) -> Validator[Any]:
+        try:
+            return sub_validator1(var_name, val)
+        except ValidationError:
+            pass
+
+        return sub_validator2(var_name, val)
+
+    return f

zerver/tests/test_decorators.py

@@ -70,6 +70,7 @@ from zerver.lib.validator import (
     check_int_in,
     check_list,
     check_none_or,
+    check_or,
     check_short_string,
     check_string,
     check_string_fixed_length,
@@ -991,6 +992,25 @@ class ValidatorTestCase(ZulipTestCase):
         with self.assertRaisesRegex(ValidationError, r"x is not a string or integer"):
             check_string_or_int("x", x)
 
+    def test_check_or(self) -> None:
+        x: Any = "valid"
+        check_or(check_string_in(["valid"]), check_url)("x", x)
+
+        x = "http://zulip-bots.example.com/"
+        check_or(check_string_in(["valid"]), check_url)("x", x)
+
+        x = "invalid"
+        with self.assertRaisesRegex(ValidationError, r"x is not a URL"):
+            check_or(check_string_in(["valid"]), check_url)("x", x)
+
+        x = "http://127.0.0"
+        with self.assertRaisesRegex(ValidationError, r"x is not a URL"):
+            check_or(check_string_in(["valid"]), check_url)("x", x)
+
+        x = 1
+        with self.assertRaisesRegex(ValidationError, r"x is not a string"):
+            check_or(check_string_in(["valid"]), check_url)("x", x)
+
 
 class DeactivatedRealmTest(ZulipTestCase):
     def test_send_deactivated_realm(self) -> None: