A few minor tweaks now that we're on Python 3.8

.github/workflows/framework-tests.yaml

@@ -12,7 +12,7 @@ jobs:
         uses: actions/setup-python@v2
 
       - name: Install tox
-        run: pip install tox==4.2.8
+        run: pip install tox
 
       - name: Run linting
         run: tox -e lint
@@ -26,7 +26,7 @@ jobs:
         uses: actions/setup-python@v2
 
       - name: Install tox
-        run: pip install tox==4.2.8
+        run: pip install tox
 
       - name: Run static type checks
         run: tox -e static
@@ -47,7 +47,7 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Install tox
-        run: pip install tox==4.2.8
+        run: pip install tox
 
       - name: Run unit tests
         run: tox -e unit
@@ -73,7 +73,7 @@ jobs:
           go-version: "1.17"
 
       - name: Install tox
-        run: pip install tox==4.2.8
+        run: pip install tox
 
       - name: Install Pebble
         run: go install github.com/canonical/pebble/cmd/pebble@latest

.github/workflows/observability-charm-tests.yaml

@@ -26,7 +26,7 @@ jobs:
           echo -e "\ngit+$GITHUB_SERVER_URL/$GITHUB_REPOSITORY@$GITHUB_SHA#egg=ops" >> requirements.txt
 
       - name: Install dependencies
-        run: pip install tox==4.2.8
+        run: pip install tox
 
       - name: Run the charm tests
         run: tox -vve unit

ops/charm.py

@@ -34,30 +34,31 @@
 from ops.framework import EventBase, EventSource, Framework, Object, ObjectEvents
 
 if TYPE_CHECKING:
-    from typing_extensions import Literal, Required, TypedDict
+    from typing import Literal
+
+    from typing_extensions import Required, TypedDict
 
     from ops.framework import Handle, JsonObject, _SerializedData
     from ops.model import Container, Numerical, Relation, Storage
 
     # CharmMeta also needs these.
     _ActionParam = Dict[str, 'JsonObject']  # <JSON Schema definition>
-    _ActionMetaDict = TypedDict(
-        '_ActionMetaDict', {
-            'title': str,
-            'description': str,
-            'params': Dict[str, _ActionParam],
-            'required': List[str]},
-        total=False)
+
+    class _ActionMetaDict(TypedDict, total=False):
+        title: str
+        description: str
+        params: Dict[str, _ActionParam]
+        required: List[str]
 
     _Scopes = Literal['global', 'container']
-    _RelationMetaDict = TypedDict(
-        '_RelationMetaDict', {
-            'interface': Required[str],
-            'limit': int,
-            'scope': _Scopes},
-        total=False)
-
-    _MultipleRange = TypedDict('_MultipleRange', {'range': str})
+
+    class _RelationMetaDict(TypedDict, total=False):
+        interface: Required[str]
+        limit: int
+        scope: _Scopes
+
+    class _MultipleRange(TypedDict):
+        range: str
     _StorageMetaDict = TypedDict('_StorageMetaDict', {
         'type': Required[str],
         'description': int,
@@ -69,21 +70,20 @@
         'multiple': _MultipleRange
     })
 
-    _ResourceMetaDict = TypedDict(
-        '_ResourceMetaDict', {
-            'type': Required[str],
-            'filename': str,
-            'description': str},
-        total=False)
+    class _ResourceMetaDict(TypedDict, total=False):
+        type: Required[str]
+        filename: str
+        description: str
+
+    class _PayloadMetaDict(TypedDict):
+        type: str
 
-    _PayloadMetaDict = TypedDict('_PayloadMetaDict', {'type': str})
+    class _MountDict(TypedDict, total=False):
+        storage: Required[str]
+        location: str
 
-    _MountDict = TypedDict(
-        '_MountDict', {'storage': Required[str],
-                       'location': str},
-        total=False)
-    _ContainerMetaDict = TypedDict(
-        '_ContainerMetaDict', {'mounts': List[_MountDict]})
+    class _ContainerMetaDict(TypedDict):
+        mounts: List[_MountDict]
 
     _CharmMetaDict = TypedDict(
         '_CharmMetaDict', {  # all are optional
@@ -108,23 +108,20 @@
         }, total=False)
 
     # can't put in *Event because *Event.snapshot needs it.
-    _WorkloadEventSnapshot = TypedDict('_WorkloadEventSnapshot', {
-        'container_name': str
-    }, total=False)
+    class _WorkloadEventSnapshot(TypedDict, total=False):
+        container_name: str
 
-    _RelationDepartedEventSnapshot = TypedDict('_RelationDepartedEventSnapshot', {
-        'relation_name': str,
-        'relation_id': int,
-        'app_name': Optional[str],
-        'unit_name': Optional[str],
-        'departing_unit': Optional[str]
-    }, total=False)
+    class _RelationDepartedEventSnapshot(TypedDict, total=False):
+        relation_name: str
+        relation_id: int
+        app_name: Optional[str]
+        unit_name: Optional[str]
+        departing_unit: Optional[str]
 
-    _StorageEventSnapshot = TypedDict('_StorageEventSnapshot', {
-        'storage_name': str,
-        'storage_index': int,
-        'storage_location': str,
-    }, total=False)
+    class _StorageEventSnapshot(TypedDict, total=False):
+        storage_name: str
+        storage_index: int
+        storage_location: str
 
 
 class HookEvent(EventBase):
@@ -425,12 +422,11 @@ class RelationEvent(HookEvent):
 
     """
     if TYPE_CHECKING:
-        _RelationEventSnapshot = TypedDict('_RelationEventSnapshot', {
-            'relation_name': Required[str],
-            'relation_id': Required[int],
-            'app_name': Optional[str],
-            'unit_name': Optional[str]
-        }, total=False)
+        class _RelationEventSnapshot(TypedDict, total=False):
+            relation_name: Required[str]
+            relation_id: Required[int]
+            app_name: Optional[str]
+            unit_name: Optional[str]
 
     def __init__(self, handle: 'Handle', relation: 'Relation',
                  app: Optional[model.Application] = None,
@@ -1195,7 +1191,7 @@ def __init__(self, role: RelationRole, relation_name: str, raw: '_RelationMetaDi
         self.scope = raw.get('scope') or self._default_scope
         if self.scope not in self.VALID_SCOPES:
             raise TypeError("scope should be one of {}; not '{}'".format(
-                ', '.join("'{}'".format(s) for s in self.VALID_SCOPES), self.scope))
+                ', '.join(f"'{s}'" for s in self.VALID_SCOPES), self.scope))
 
 
 class StorageMeta:

ops/framework.py

@@ -50,8 +50,7 @@
 
 if TYPE_CHECKING:
     from pathlib import Path
-
-    from typing_extensions import Literal, Protocol, Type
+    from typing import Literal, Protocol, Type
 
     from ops.charm import CharmMeta
     from ops.model import JsonObject, Model, _ModelBackend
@@ -613,7 +612,7 @@ def __init__(self, storage: Union[SQLiteStorage, JujuStorage],
 
         # Parse the env var once, which may be used multiple times later
         debug_at = os.environ.get('JUJU_DEBUG_AT')
-        self._juju_debug_at = (set(x.strip() for x in debug_at.split(','))
+        self._juju_debug_at = ({x.strip() for x in debug_at.split(',')}
                                if debug_at else set())  # type: Set[str]
 
     def set_breakpointhook(self):

ops/lib/__init__.py

@@ -185,7 +185,7 @@ def _parse_lib(spec):
     logger.debug("    Parsing %r", spec.name)
 
     try:
-        with open(spec.origin, 'rt', encoding='utf-8') as f:
+        with open(spec.origin, encoding='utf-8') as f:
             libinfo = {}
             for n, line in enumerate(f):
                 if len(libinfo) == len(_NEEDED_KEYS):

ops/model.py

@@ -64,9 +64,9 @@
         Client,
         ExecProcess,
         FileInfo,
-        LayerDict,
         Plan,
         ServiceInfo,
+        _LayerDict,
     )
     from typing_extensions import TypedDict
 
@@ -87,10 +87,12 @@
     # public since it is used in ops.testing
     K8sSpec = Mapping[str, JsonObject]
 
-    _StatusDict = TypedDict('_StatusDict', {'status': str, 'message': str})
+    class _StatusDict(TypedDict):
+        status: str
+        message: str
 
     # the data structure we can use to initialize pebble layers with.
-    _Layer = Union[str, LayerDict, pebble.Layer]
+    _Layer = Union[str, _LayerDict, pebble.Layer]
 
     # mapping from relation name to a list of relation objects
     _RelationMapping_Raw = Dict[str, Optional[List['Relation']]]
@@ -109,11 +111,10 @@
     UnitOrApplication = Union['Unit', 'Application']
     UnitOrApplicationType = Union[Type['Unit'], Type['Application']]
 
-    _AddressDict = TypedDict('_AddressDict', {
-        'address': str,  # Juju < 2.9
-        'value': str,  # Juju >= 2.9
-        'cidr': str
-    })
+    class _AddressDict(TypedDict):
+        address: str  # Juju < 2.9
+        value: str  # Juju >= 2.9
+        cidr: str
     _BindAddressDict = TypedDict('_BindAddressDict', {
         'interface-name': str,
         'addresses': List[_AddressDict]