handle 500 error with empty string

src/registrar/models/domain.py

@@ -13,6 +13,7 @@ from typing import Any
 from registrar.models.host import Host
 from registrar.models.host_ip import HostIP
 from registrar.utility.enums import DefaultEmail
+from registrar.utility import errors
 
 from registrar.utility.errors import (
     ActionNotAllowed,
@@ -192,9 +193,17 @@ class Domain(TimeStampedModel, DomainHelper):
 
     @classmethod
     def available(cls, domain: str) -> bool:
-        """Check if a domain is available."""
+        """Check if a domain is available.
+        This is called by the availablility api and
+        is called in the validate function on the request/domain page
+
+        throws- RegistryError or InvalidDomainError"""
         if not cls.string_could_be_domain(domain):
-            raise ValueError("Not a valid domain: %s" % str(domain))
+            logger.warning("Not a valid domain: %s" % str(domain))
+            # throw invalid domain error so that it can be caught in
+            # validate_and_handle_errors in domain_helper
+            raise errors.InvalidDomainError()
+
         domain_name = domain.lower()
         req = commands.CheckDomain([domain_name])
         return registry.send(req, cleaned=True).res_data[0].avail

src/registrar/models/utility/domain_helper.py

@@ -33,6 +33,7 @@ class DomainHelper:
         # Split into pieces for the linter
         domain = cls._validate_domain_string(domain, blank_ok)
 
+        if domain != "":
             try:
                 if not check_domain_available(domain):
                     raise errors.DomainUnavailableError()

src/registrar/tests/test_models_domain.py

@@ -20,7 +20,7 @@ from registrar.models.user import User
 from registrar.utility.errors import ActionNotAllowed, NameserverError
 
 from registrar.models.utility.contact_error import ContactError, ContactErrorCodes
-
+from registrar.utility import errors
 
 from django_fsm import TransitionNotAllowed  # type: ignore
 from epplibwrapper import (
@@ -502,16 +502,26 @@ class TestDomainAvailable(MockEppLib):
         self.assertFalse(available)
         patcher.stop()
 
-    def test_domain_available_with_value_error(self):
+    def test_domain_available_with_invalid_error(self):
         """
         Scenario: Testing whether an invalid domain is available
-            Should throw ValueError
+            Should throw InvalidDomainError
 
-            Validate ValueError is raised
+            Validate InvalidDomainError is raised
         """
-        with self.assertRaises(ValueError):
+        with self.assertRaises(errors.InvalidDomainError()):
             Domain.available("invalid-string")
 
+    def test_domain_available_with_empty_string(self):
+        """
+        Scenario: Testing whether an empty string domain name is available
+            Should throw InvalidDomainError
+
+            Validate InvalidDomainError is raised
+        """
+        with self.assertRaises(errors.InvalidDomainError()):
+            Domain.available("")
+
     def test_domain_available_unsuccessful(self):
         """
         Scenario: Testing behavior when registry raises a RegistryError