chore: add compatibility with the next ops release (#178)

The next release of ops has some backwards-incompatible changes to
private methods. This PR does the minimum to keep Scenario working with
the current version of ops and the next release.

I'll open a ticket for doing a nicer version of this where the new
`_JujuContext` class is used (which would presumably mean requiring the
new version of ops). But this will let people continue upgrading their
ops as long as they're using the latest 6.x of Scenario.

The relevant ops PR is: canonical/operator#1313

pyproject.toml

@@ -8,7 +8,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ops-scenario"
 
-version = "6.1.5"
+version = "6.1.6"
 
 authors = [
     { name = "Pietro Pasotti", email = "[email protected]" }

scenario/ops_main_mock.py

@@ -3,6 +3,7 @@
 # See LICENSE file for licensing details.
 import inspect
 import os
+import pathlib
 import sys
 from typing import TYPE_CHECKING, Any, Optional, Sequence, cast
 
@@ -15,7 +16,7 @@
 from ops.log import setup_root_logging
 
 # use logger from ops.main so that juju_log will be triggered
-from ops.main import CHARM_STATE_FILE, _Dispatcher, _get_charm_dir, _get_event_args
+from ops.main import CHARM_STATE_FILE, _Dispatcher, _get_event_args
 from ops.main import logger as ops_logger
 
 if TYPE_CHECKING:  # pragma: no cover
@@ -33,6 +34,17 @@ class BadOwnerPath(RuntimeError):
     """Error raised when the owner path does not lead to a valid ObjectEvents instance."""
 
 
+# TODO: Use ops.jujucontext's _JujuContext.charm_dir.
+def _get_charm_dir():
+    charm_dir = os.environ.get("JUJU_CHARM_DIR")
+    if charm_dir is None:
+        # Assume $JUJU_CHARM_DIR/lib/op/main.py structure.
+        charm_dir = pathlib.Path(f"{__file__}/../../..").resolve()
+    else:
+        charm_dir = pathlib.Path(charm_dir).resolve()
+    return charm_dir
+
+
 def _get_owner(root: Any, path: Sequence[str]) -> ops.ObjectEvents:
     """Walk path on root to an ObjectEvents instance."""
     obj = root
@@ -75,7 +87,17 @@ def _emit_charm_event(
             f"Use Context.run_custom instead.",
         )
 
-    args, kwargs = _get_event_args(charm, event_to_emit)
+    try:
+        args, kwargs = _get_event_args(charm, event_to_emit)
+    except TypeError:
+        # ops 2.16+
+        import ops.jujucontext  # type: ignore
+
+        args, kwargs = _get_event_args(
+            charm,
+            event_to_emit,
+            ops.jujucontext._JujuContext.from_dict(os.environ),  # type: ignore
+        )
     ops_logger.debug("Emitting Juju event %s.", event_name)
     event_to_emit.emit(*args, **kwargs)
 
@@ -159,7 +181,16 @@ def setup(state: "State", event: "Event", context: "Context", charm_spec: "_Char
     charm_class = charm_spec.charm_type
     charm_dir = _get_charm_dir()
 
-    dispatcher = _Dispatcher(charm_dir)
+    try:
+        dispatcher = _Dispatcher(charm_dir)
+    except TypeError:
+        # ops 2.16+
+        import ops.jujucontext  # type: ignore
+
+        dispatcher = _Dispatcher(
+            charm_dir,
+            ops.jujucontext._JujuContext.from_dict(os.environ),  # type: ignore
+        )
     dispatcher.run_any_legacy_hook()
 
     framework = setup_framework(charm_dir, state, event, context, charm_spec)