Support id

src/azure-cli/azure/cli/command_modules/role/_help.py

@@ -861,6 +861,8 @@
 examples:
   - name: Show the 'Reader' role definition.
     text: az role definition show --scope /subscriptions/00000000-0000-0000-0000-000000000000 --name acdd72a7-3385-48ef-bd42-f606fba81ae7
+  - name: Show the 'Reader' role definition with its resource ID.
+    text: az role definition show --id /subscriptions/00000000-0000-0000-0000-000000000000/providers/Microsoft.Authorization/roleDefinitions/acdd72a7-3385-48ef-bd42-f606fba81ae7
 """
 
 helps['role definition update'] = """

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

@@ -359,6 +359,12 @@ class PrincipalType(str, Enum):
 
     with self.argument_context('role definition') as c:
         c.argument('role_definition_id', options_list=['--name', '-n'], help='the role definition name')
+        c.argument('role_id', options_list=['--id'],
+                   help='The fully qualified role definition ID. Use the format, '
+                        '/subscriptions/{guid}/providers/Microsoft.Authorization/roleDefinitions/{roleDefinitionId} '
+                        'for subscription level role definitions, or '
+                        '/providers/Microsoft.Authorization/roleDefinitions/{roleDefinitionId} '
+                        'for tenant level role definitions.')
         c.argument('custom_role_only', arg_type=get_three_state_flag(), help='custom roles only(vs. build-in ones)')
         c.argument('role_definition', help="json formatted content which defines the new role.")
         c.argument('name', arg_type=name_arg_type, completer=get_role_definition_name_completion_list, help="the role's name")

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

@@ -69,8 +69,17 @@ def list_role_definitions(cmd, name=None, resource_group_name=None, scope=None,
     return _search_role_definitions(cmd.cli_ctx, definitions_client, name, [scope], custom_role_only)
 
 
-def show_role_definition(cmd, scope, name):
+def show_role_definition(cmd, scope=None, name=None, role_id=None):
+    if not any((scope, name, role_id)):
+        raise CLIError('Usage error: Provide --scope and --name, or --id')
+    if not role_id and not (name and scope):
+        raise CLIError('Usage error: Provide both --scope and --name')
+
     definitions_client = _auth_client_factory(cmd.cli_ctx, scope).role_definitions
+    # https://learn.microsoft.com/en-us/rest/api/authorization/role-definitions/get-by-id?view=rest-authorization-2022-04-01&tabs=HTTP
+    if role_id:
+        return definitions_client.get_by_id(role_id)
+    # https://learn.microsoft.com/en-us/rest/api/authorization/role-definitions/get?view=rest-authorization-2022-04-01&tabs=HTTP
     return definitions_client.get(scope, name)