Fix some issues for Python 3.8

dbt_common/clients/agate_helper.py

@@ -1,6 +1,6 @@
 from codecs import BOM_UTF8
 
-import agate  # type: ignore
+import agate
 import datetime
 import isodate
 import json

dbt_common/clients/jinja.py

@@ -124,6 +124,7 @@ def new_context(
                 "shared or locals parameters."
             )
 
+        vars = {} if vars is None else vars
         parent = ChainMap(vars, self.globals) if self.globals else vars
 
         return self.environment.context_class(self.environment, parent, self.name, self.blocks)
@@ -544,6 +545,7 @@ def render_template(template, ctx: Dict[str, Any], node=None) -> str:
 
 def _get_blocks_hash(text: str, allowed_blocks: Optional[Set[str]], collect_raw_data: bool) -> int:
     """Provides a hash function over the arguments to extract_toplevel_blocks, in order to support caching."""
+    allowed_blocks = allowed_blocks or set()
     allowed_tuple = tuple(sorted(allowed_blocks) or [])
     return text.__hash__() + allowed_tuple.__hash__() + collect_raw_data.__hash__()
 

dbt_common/contracts/config/metadata.py

@@ -9,7 +9,7 @@
 
 class Metadata(Enum):
     @classmethod
-    def from_field(cls: Type[M], fld: Field[Any]) -> M:
+    def from_field(cls: Type[M], fld: Field) -> M:
         default = cls.default_field()
         key = cls.metadata_key()
 
@@ -28,7 +28,7 @@ def metadata_key(cls) -> str:
         raise NotImplementedError("Not implemented")
 
 
-def _get_meta_value(cls: Type[M], fld: Field[Any], key: str, default: Any) -> M:
+def _get_meta_value(cls: Type[M], fld: Field, key: str, default: Any) -> M:
     # a metadata field might exist. If it does, it might have a matching key.
     # If it has both, make sure the value is valid and return it. If it
     # doesn't, return the default.
@@ -65,5 +65,5 @@ def metadata_key(cls) -> str:
         return "show_hide"
 
     @classmethod
-    def should_show(cls, fld: Field[Any]) -> bool:
+    def should_show(cls, fld: Field) -> bool:
         return cls.from_field(fld) == cls.Show

dbt_common/dataclass_schema.py

@@ -62,7 +62,7 @@ class dbtClassMixin(DataClassMessagePackMixin):
     against the schema
     """
 
-    _mapped_fields: ClassVar[Optional[Dict[Any, List[Tuple[Field[Any], str]]]]] = None
+    _mapped_fields: ClassVar[Optional[Dict[Any, List[Tuple[Field, str]]]]] = None
 
     # Config class used by Mashumaro
     class Config(dbtMashConfig):