Add Python Black format check and apply format changes (#3)

* Add Python Black format check and apply format changes

Bring this repo in line with our standards to use Python Black
formatting conventions, and enforce it in the lint checks.

* Split lint from tests and only run on 3.9 (black requires 3.6+)

* Ignore spurious E203 from flake8 (see PyCQA/pycodestyle#914)

.github/workflows/tests.yaml

@@ -4,8 +4,22 @@ on:
   - pull_request
 
 jobs:
-  lint-unit-and-func-tests:
-    name: Lint, Unit, & Functional Tests
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v2
+    - name: Setup Python
+      uses: actions/setup-python@v2
+      with:
+        python-version: 3.9
+    - name: Install Tox
+      run: pip install tox
+    - name: Run lint
+      run: tox -e lint
+  unit-and-func-tests:
+    name: Unit, & Functional Tests
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -19,8 +33,8 @@ jobs:
         python-version: ${{ matrix.python }}
     - name: Install Tox
       run: pip install tox
-    - name: Run lint, unit, and functional tests
-      run: tox
+    - name: Run unit & functional tests
+      run: tox -e unit,functional
 
   # TODO
   #integration-test:

loadbalancer_interface/base.py

@@ -19,36 +19,40 @@ def __init__(self, charm, relation_name):
         # Future-proof against the need to evolve the relation protocol
         # by ensuring that we agree on a version number before starting.
         # This may or may not be made moot by a future feature in Juju.
-        for event in (charm.on[relation_name].relation_created,
-                      charm.on.leader_elected,
-                      charm.on.upgrade_charm):
+        for event in (
+            charm.on[relation_name].relation_created,
+            charm.on.leader_elected,
+            charm.on.upgrade_charm,
+        ):
             self.framework.observe(event, self._set_version)
 
     def _set_version(self, event):
         if self.unit.is_leader():
-            if hasattr(event, 'relation'):
+            if hasattr(event, "relation"):
                 relations = [event.relation]
             else:
                 relations = self.model.relations.get(self.relation_name, [])
             for relation in relations:
-                relation.data[self.app]['version'] = str(schemas.max_version)
+                relation.data[self.app]["version"] = str(schemas.max_version)
 
     @cached_property
     def relations(self):
         relations = self.model.relations.get(self.relation_name, [])
-        return [relation
-                for relation in sorted(relations, key=attrgetter('id'))
-                if self._schema(relation)]
+        return [
+            relation
+            for relation in sorted(relations, key=attrgetter("id"))
+            if self._schema(relation)
+        ]
 
     def _schema(self, relation=None):
         if relation is None:
             return schemas.versions[schemas.max_version]
         if relation.app not in relation.data:
             return None
         data = relation.data[relation.app]
-        if 'version' not in data:
+        if "version" not in data:
             return None
-        remote_version = int(data['version'])
+        remote_version = int(data["version"])
         return schemas.versions[min((schemas.max_version, remote_version))]
 
     @property

loadbalancer_interface/consumer.py

@@ -21,8 +21,8 @@ class LBConsumersEvents(ObjectEvents):
 
 
 class LBConsumers(VersionedInterface):
-    """ API used to interact with consumers of a loadbalancer provider.
-    """
+    """API used to interact with consumers of a loadbalancer provider."""
+
     state = StoredState()
     on = LBConsumersEvents()
 
@@ -31,9 +31,11 @@ def __init__(self, charm, relation_name):
         self.relation_name = relation_name
         self.state.set_default(known_requests={})
 
-        for event in (charm.on[relation_name].relation_created,
-                      charm.on[relation_name].relation_joined,
-                      charm.on[relation_name].relation_changed):
+        for event in (
+            charm.on[relation_name].relation_created,
+            charm.on[relation_name].relation_joined,
+            charm.on[relation_name].relation_changed,
+        ):
             self.framework.observe(event, self._check_consumers)
 
     def _check_consumers(self, event):
@@ -42,8 +44,7 @@ def _check_consumers(self, event):
 
     @cached_property
     def all_requests(self):
-        """ A list of all current consumer requests.
-        """
+        """A list of all current consumer requests."""
         if not self.unit.is_leader():
             # Only the leader can process requests, so avoid mistakes
             # by not even reading the requests if not the leader.
@@ -54,17 +55,15 @@ def all_requests(self):
             local_data = relation.data[self.app]
             remote_data = relation.data[relation.app]
             for key, request_sdata in sorted(remote_data.items()):
-                if not key.startswith('request_'):
+                if not key.startswith("request_"):
                     continue
-                name = key[len('request_'):]
-                response_sdata = local_data.get('response_' + name)
-                request = schema.Request.loads(name,
-                                               request_sdata,
-                                               response_sdata)
+                name = key[len("request_") :]
+                response_sdata = local_data.get("response_" + name)
+                request = schema.Request.loads(name, request_sdata, response_sdata)
                 request.relation = relation
                 if not request.backends:
-                    for unit in sorted(relation.units, key=attrgetter('name')):
-                        addr = relation.data[unit].get('ingress-address')
+                    for unit in sorted(relation.units, key=attrgetter("name")):
+                        addr = relation.data[unit].get("ingress-address")
                         if addr:
                             request.backends.append(addr)
                 requests.append(request)
@@ -73,53 +72,56 @@ def all_requests(self):
 
     @property
     def new_requests(self):
-        """ A list of requests with changes or no response.
-        """
-        return [request for request in self.all_requests
-                if request.hash != self.state.known_requests[request.id]]
+        """A list of requests with changes or no response."""
+        return [
+            request
+            for request in self.all_requests
+            if request.hash != self.state.known_requests[request.id]
+        ]
 
     @property
     def removed_requests(self):
-        """ A list of requests which have been removed, either explicitly or
+        """A list of requests which have been removed, either explicitly or
         because the relation was removed.
         """
         current_ids = {request.id for request in self.all_requests}
         unknown_ids = self.state.known_requests.keys() - current_ids
         schema = self._schema()
-        return [schema.Request._from_id(req_id, self.relations)
-                for req_id in sorted(unknown_ids)]
+        return [
+            schema.Request._from_id(req_id, self.relations)
+            for req_id in sorted(unknown_ids)
+        ]
 
     def send_response(self, request):
-        """ Send a specific request's response.
-        """
+        """Send a specific request's response."""
         request.response.received_hash = request.sent_hash
-        key = 'response_' + request.name
+        key = "response_" + request.name
         request.relation.data[self.app][key] = request.response.dumps()
         self.state.known_requests[request.id] = request.hash
         if not self.new_requests:
             try:
                 from charms.reactive import clear_flag
-                prefix = 'endpoint.' + self.relation_name
-                clear_flag(prefix + '.requests_changed')
+
+                prefix = "endpoint." + self.relation_name
+                clear_flag(prefix + ".requests_changed")
             except ImportError:
                 pass  # not being used in a reactive charm
 
     def revoke_response(self, request):
-        """ Revoke / remove the response for a given request.
-        """
+        """Revoke / remove the response for a given request."""
         if request.id:
             self.state.known_requests.pop(request.id, None)
         if request.relation:
-            key = 'response_' + request.name
+            key = "response_" + request.name
             request.relation.data.get(self.app, {}).pop(key, None)
 
     @property
     def is_changed(self):
         return bool(self.new_requests or self.removed_requests)
 
     def manage_flags(self):
-        """ Used to interact with charms.reactive-base charms.
-        """
+        """Used to interact with charms.reactive-base charms."""
         from charms.reactive import toggle_flag
-        prefix = 'endpoint.' + self.relation_name
-        toggle_flag(prefix + '.requests_changed', self.is_changed)
+
+        prefix = "endpoint." + self.relation_name
+        toggle_flag(prefix + ".requests_changed", self.is_changed)