Skip none overrides on localdns profile

src/aks-preview/HISTORY.rst

@@ -11,6 +11,7 @@ To release a new version, please select a new version number (usually plus 1 to
 
 Pending
 +++++++
+* Fix `--localdns-config` parameter to handle null values in JSON configuration files gracefully, preventing crashes when DNS override sections are null.
 
 18.0.0b40
 +++++++

src/aks-preview/azext_aks_preview/_helpers.py

@@ -448,3 +448,19 @@ def get_extension_in_allow_list(result):
     if _check_if_extension_type_is_in_allow_list(result.extension_type.lower()):
         return result
     return None
+
+
+def process_dns_overrides(overrides_dict, target_dict, build_override_func):
+    """Helper function to safely process DNS overrides with null checks.
+
+    Processes DNS override dictionaries from LocalDNS configuration,
+    filtering out null values and applying the build function to valid entries.
+
+    :param overrides_dict: Dictionary containing DNS overrides (can be None)
+    :param target_dict: Target dictionary to populate with processed overrides
+    :param build_override_func: Function to build override objects from dict values
+    """
+    if overrides_dict is not None:
+        for key, value in overrides_dict.items():
+            if value is not None:
+                target_dict[key] = build_override_func(value)

src/aks-preview/azext_aks_preview/agentpool_decorator.py

@@ -50,6 +50,7 @@
 from azext_aks_preview._helpers import (
     get_nodepool_snapshot_by_snapshot_id,
     filter_hard_taints,
+    process_dns_overrides,
 )
 
 logger = get_logger(__name__)
@@ -1477,13 +1478,16 @@ def build_override(override_dict):
                 return self.models.LocalDNSOverride(**filtered)
 
             # Build kubeDNSOverrides and vnetDNSOverrides from the localdns_profile
-            kube_overrides = localdns_profile.get("kubeDNSOverrides")
-            for key, value in kube_overrides.items():
-                kube_dns_overrides[key] = build_override(value)
-
-            vnet_overrides = localdns_profile.get("vnetDNSOverrides")
-            for key, value in vnet_overrides.items():
-                vnet_dns_overrides[key] = build_override(value)
+            process_dns_overrides(
+                localdns_profile.get("kubeDNSOverrides"),
+                kube_dns_overrides,
+                build_override
+            )
+            process_dns_overrides(
+                localdns_profile.get("vnetDNSOverrides"),
+                vnet_dns_overrides,
+                build_override
+            )
 
             agentpool.local_dns_profile = self.models.LocalDNSProfile(
                 mode=localdns_profile.get("mode"),
@@ -1816,13 +1820,16 @@ def build_override(override_dict):
                 return self.models.LocalDNSOverride(**filtered)
 
             # Build kubeDNSOverrides and vnetDNSOverrides from the localdns_profile
-            kube_overrides = localdns_profile.get("kubeDNSOverrides")
-            for key, value in kube_overrides.items():
-                kube_dns_overrides[key] = build_override(value)
-
-            vnet_overrides = localdns_profile.get("vnetDNSOverrides")
-            for key, value in vnet_overrides.items():
-                vnet_dns_overrides[key] = build_override(value)
+            process_dns_overrides(
+                localdns_profile.get("kubeDNSOverrides"),
+                kube_dns_overrides,
+                build_override
+            )
+            process_dns_overrides(
+                localdns_profile.get("vnetDNSOverrides"),
+                vnet_dns_overrides,
+                build_override
+            )
 
             agentpool.local_dns_profile = self.models.LocalDNSProfile(
                 mode=localdns_profile.get("mode"),

src/aks-preview/azext_aks_preview/tests/latest/test_agentpool_decorator.py

@@ -2684,6 +2684,151 @@ def common_update_blue_green_upgrade_settings(self):
         )
         self.assertEqual(dec_agentpool_3, ground_truth_agentpool_3)
 
+    def common_update_localdns_profile(self):
+        import tempfile
+        import json
+        import os
+
+        # Test case 1: LocalDNS config provided - verify method is called
+        localdns_config = {
+            "mode": "Required",
+            "kubeDNSOverrides": {
+                ".": {
+                    "cacheDurationInSeconds": 3600,
+                    "protocol": "PreferUDP"
+                }
+            }
+        }
+
+        with tempfile.NamedTemporaryFile(mode="w+", delete=False, suffix=".json") as f:
+            json.dump(localdns_config, f)
+            f.flush()
+            config_file_path = f.name
+
+        try:
+            dec_1 = AKSPreviewAgentPoolUpdateDecorator(
+                self.cmd,
+                self.client,
+                {"localdns_config": config_file_path},
+                self.resource_type,
+                self.agentpool_decorator_mode,
+            )
+
+            agentpool_1 = self.create_initialized_agentpool_instance()
+            dec_1.context.attach_agentpool(agentpool_1)
+            dec_agentpool_1 = dec_1.update_localdns_profile(agentpool_1)
+
+            # Verify that LocalDNS profile was created and assigned
+            self.assertIsNotNone(dec_agentpool_1.local_dns_profile)
+            self.assertEqual(dec_agentpool_1.local_dns_profile.mode, "Required")
+
+        finally:
+            os.unlink(config_file_path)
+
+        # Test case 2: No LocalDNS config provided - no change
+        dec_2 = AKSPreviewAgentPoolUpdateDecorator(
+            self.cmd,
+            self.client,
+            {},
+            self.resource_type,
+            self.agentpool_decorator_mode,
+        )
+
+        agentpool_2 = self.create_initialized_agentpool_instance()
+        original_local_dns_profile = agentpool_2.local_dns_profile
+        dec_2.context.attach_agentpool(agentpool_2)
+        dec_agentpool_2 = dec_2.update_localdns_profile(agentpool_2)
+
+        # Verify LocalDNS profile wasn't changed
+        self.assertEqual(dec_agentpool_2.local_dns_profile, original_local_dns_profile)
+
+        # Test case 3: LocalDNS config with null values
+        localdns_config_with_nulls = {
+            "mode": "Required",
+            "kubeDNSOverrides": None,
+            "vnetDNSOverrides": {
+                ".": {
+                    "cacheDurationInSeconds": 1800,
+                    "protocol": "ForceTCP"
+                }
+            }
+        }
+
+        with tempfile.NamedTemporaryFile(mode="w+", delete=False, suffix=".json") as f:
+            json.dump(localdns_config_with_nulls, f)
+            f.flush()
+            config_file_path = f.name
+
+        try:
+            dec_3 = AKSPreviewAgentPoolUpdateDecorator(
+                self.cmd,
+                self.client,
+                {"localdns_config": config_file_path},
+                self.resource_type,
+                self.agentpool_decorator_mode,
+            )
+
+            agentpool_3 = self.create_initialized_agentpool_instance()
+            dec_3.context.attach_agentpool(agentpool_3)
+            dec_agentpool_3 = dec_3.update_localdns_profile(agentpool_3)
+
+            # Verify that LocalDNS profile was created with null handling
+            self.assertIsNotNone(dec_agentpool_3.local_dns_profile)
+            self.assertEqual(dec_agentpool_3.local_dns_profile.mode, "Required")
+            # kubeDNSOverrides should be empty dict due to null input
+            self.assertEqual(len(dec_agentpool_3.local_dns_profile.kube_dns_overrides), 0)
+            # vnetDNSOverrides should have one entry
+            self.assertEqual(len(dec_agentpool_3.local_dns_profile.vnet_dns_overrides), 1)
+
+        finally:
+            os.unlink(config_file_path)
+
+    def common_test_process_dns_overrides_helper(self):
+        from azext_aks_preview._helpers import process_dns_overrides
+
+        # Test the process_dns_overrides utility function functionality
+
+        # Test case 1: Valid DNS overrides without nulls
+        dns_overrides = {
+            ".": {
+                "cacheDurationInSeconds": 3600,
+                "protocol": "PreferUDP"
+            }
+        }
+        target_dict = {}
+
+        def mock_build_override(override_dict):
+            return self.models.LocalDNSOverride(
+                cache_duration_in_seconds=override_dict.get("cacheDurationInSeconds"),
+                protocol=override_dict.get("protocol")
+            )
+
+        process_dns_overrides(dns_overrides, target_dict, mock_build_override)
+        self.assertEqual(len(target_dict), 1)
+        self.assertIn(".", target_dict)
+
+        # Test case 2: DNS overrides with null values (should handle gracefully)
+        dns_overrides_with_nulls = {
+            ".": {
+                "cacheDurationInSeconds": 1800,
+                "protocol": None
+            }
+        }
+        target_dict_2 = {}
+
+        process_dns_overrides(dns_overrides_with_nulls, target_dict_2, mock_build_override)
+        self.assertEqual(len(target_dict_2), 1)
+
+        # Test case 3: None input (should handle gracefully)
+        target_dict_3 = {}
+        process_dns_overrides(None, target_dict_3, mock_build_override)
+        self.assertEqual(len(target_dict_3), 0)
+
+        # Test case 4: Empty input (should handle gracefully)
+        target_dict_4 = {}
+        process_dns_overrides({}, target_dict_4, mock_build_override)
+        self.assertEqual(len(target_dict_4), 0)
+
 
 class AKSPreviewAgentPoolUpdateDecoratorStandaloneModeTestCase(
     AKSPreviewAgentPoolUpdateDecoratorCommonTestCase
@@ -2721,6 +2866,12 @@ def test_update_upgrade_strategy(self):
     def test_update_blue_green_upgrade_settings(self):
         self.common_update_blue_green_upgrade_settings()
 
+    def test_update_localdns_profile(self):
+        self.common_update_localdns_profile()
+
+    def test_process_dns_overrides_helper(self):
+        self.common_test_process_dns_overrides_helper()
+
     def test_update_agentpool_profile_preview(self):
         import inspect
 
@@ -2808,6 +2959,12 @@ def test_update_upgrade_strategy(self):
     def test_update_blue_green_upgrade_settings(self):
         self.common_update_blue_green_upgrade_settings()
 
+    def test_update_localdns_profile(self):
+        self.common_update_localdns_profile()
+
+    def test_process_dns_overrides_helper(self):
+        self.common_test_process_dns_overrides_helper()
+
     def test_update_agentpool_profile_preview(self):
         import inspect