Add description attribute to SelectorDefinition [#2800]

core/dbt/contracts/selection.py

@@ -8,6 +8,7 @@ from typing import List, Dict, Any, Union
 class SelectorDefinition(JsonSchemaMixin):
     name: str
     definition: Union[str, Dict[str, Any]]
+    description: str = ''
 
 
 @dataclass

test/unit/test_graph_selector_parsing.py

@@ -96,11 +96,13 @@ def test_parse_simple():
     sf = parse_file('''\
         selectors:
           - name: tagged_foo
+            description: Selector for foo-tagged models
             definition:
               tag: foo
     ''')
 
     assert len(sf.selectors) == 1
+    assert sf.selectors[0].description == 'Selector for foo-tagged models'
     parsed = cli.parse_from_selectors_definition(sf)
     assert len(parsed) == 1
     assert 'tagged_foo' in parsed