[App Service]az appservice plan create: Add default OS as Linux

src/azure-cli/azure/cli/command_modules/appservice/_params.py

@@ -126,7 +126,9 @@ def load_arguments(self, _):
 subscription than the app service environment, please use the resource ID for --app-service-environment parameter. ",
                    local_context_attribute=LocalContextAttribute(name='ase_name', actions=[LocalContextAction.GET]))
         c.argument('sku', arg_type=sku_arg_type)
-        c.argument('is_linux', action='store_true', required=False, help='host web app on Linux worker')
+        c.argument('is_linux', arg_type=get_three_state_flag(), default=None, required=False,
+                   help='Host web app on Linux worker. Defaults to true unless --hyper-v is specified. '
+                        'Use "--is-linux false" to create a Windows plan.')
         c.argument('hyper_v', action='store_true', required=False, help='Host Windows Container Web App on Hyper-V worker.')
         c.argument('per_site_scaling', action='store_true', required=False, help='Enable per-app scaling at the '
                                                                                  'App Service plan level to allow for '

src/azure-cli/azure/cli/command_modules/appservice/_validators.py

@@ -109,6 +109,12 @@ def _validate_asp_sku(sku, app_service_environment, zone_redundant):
 
 def validate_asp_create(namespace):
     validate_tags(namespace)
+    # is_linux is None when not explicitly provided by the user (default).
+    # Resolve the default: Linux unless --hyper-v is specified.
+    if namespace.is_linux is None:
+        namespace.is_linux = not namespace.hyper_v
+    elif namespace.is_linux and namespace.hyper_v:
+        raise MutuallyExclusiveArgumentError('Usage error: --is-linux true and --hyper-v cannot be used together.')
     if namespace.sku is None:
         if namespace.is_linux:
             namespace.sku = 'P0V3'
@@ -120,8 +126,6 @@ def validate_asp_create(namespace):
             namespace.sku = 'B1'
     sku = _normalize_sku(namespace.sku)
     _validate_asp_sku(sku, namespace.app_service_environment, namespace.zone_redundant)
-    if namespace.is_linux and namespace.hyper_v:
-        raise MutuallyExclusiveArgumentError('Usage error: --is-linux and --hyper-v cannot be used together.')
 
 
 def validate_functionapp_asp_create(namespace):

src/azure-cli/azure/cli/command_modules/appservice/custom.py

@@ -66,7 +66,6 @@
                     retryable_method,
                     raise_missing_token_suggestion,
                     _get_location_from_resource_group,
-                    _list_app,
                     is_functionapp,
                     is_linux_webapp,
                     _rename_server_farm_props,
@@ -4921,6 +4920,13 @@ def create_app_service_plan(cmd, resource_group_name, name, is_linux, hyper_v, p
                             is_managed_instance=None, mi_system_assigned=None, mi_user_assigned=None,
                             default_identity=None, rdp_enabled=None, vnet=None, subnet=None,
                             registry_adapters=None, install_scripts=None, storage_mounts=None):
+    if is_linux is None:
+        is_linux = not hyper_v
+    elif is_linux and hyper_v:
+        raise MutuallyExclusiveArgumentError('--hyper-v creates a Windows container plan and cannot be combined '
+                                             'with --is-linux. Use "--is-linux false --hyper-v" to create a '
+                                             'Windows container plan.')
+
     if sku is None:
         sku = 'P0V3' if is_linux else 'B1'