Error types

.pre-commit-config.yaml

@@ -29,11 +29,15 @@ repos:
     rev: 5.12.0
     hooks:
       - id: isort
-  - repo: https://github.com/psf/black
-    rev: 23.3.0
+  # Run the Ruff linter.
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    # Ruff version.
+    rev: v0.1.2
     hooks:
-      - id: black
-        args: [--safe]
+      # Run the Ruff linter.
+      - id: ruff
+      # Run the Ruff formatter.
+      - id: ruff-format
   - repo: https://github.com/asottile/blacken-docs
     rev: 1.13.0
     hooks:
@@ -48,19 +52,6 @@ repos:
     hooks:
       - id: tox-ini-fmt
         args: ["-p", "fix"]
-  - repo: https://github.com/PyCQA/flake8
-    rev: 6.0.0
-    hooks:
-      - id: flake8
-        additional_dependencies:
-          - flake8-bugbear==23.3.23
-          - flake8-comprehensions==3.12
-          - flake8-pytest-style==1.7.2
-          - flake8-spellcheck==0.28
-          - flake8-unused-arguments==0.0.13
-          - flake8-noqa==1.3.1
-          - pep8-naming==0.13.3
-          - flake8-pyproject==1.2.3
   - repo: https://github.com/pre-commit/mirrors-prettier
     rev: "v2.7.1"
     hooks:

README.md

@@ -82,7 +82,7 @@ available. The charm has no config, no relations, no networks, no leadership, an
 With that, we can write the simplest possible scenario test:
 
 ```python
-from scenario import State, Context
+from scenario import State, Context, Event
 from ops.charm import CharmBase
 from ops.model import UnknownStatus
 
@@ -93,7 +93,7 @@ class MyCharm(CharmBase):
 
 def test_scenario_base():
     ctx = Context(MyCharm, meta={"name": "foo"})
-    out = ctx.run('start', State())
+    out = ctx.run(Event("start"), State())
     assert out.unit_status == UnknownStatus()
 ```
 
@@ -1045,6 +1045,23 @@ state = State(stored_state=[
 And the charm's runtime will see `self.stored_State.foo` and `.baz` as expected. Also, you can run assertions on it on
 the output side the same as any other bit of state.
 
+# Resources
+
+If your charm requires access to resources, you can make them available to it through `State.resources`.
+From the perspective of a 'real' deployed charm, if your charm _has_ resources defined in `metadata.yaml`, they _must_ be made available to the charm. That is a Juju-enforced constraint: you can't deploy a charm without attaching all resources it needs to it.
+However, when testing, this constraint is unnecessarily strict (and it would also mean the great majority of all existing tests would break) since a charm will only notice that a resource is not available when it explicitly asks for it, which not many charms do.
+
+So, the only consistency-level check we enforce in Scenario when it comes to resource is that if a resource is provided in State, it needs to have been declared in metadata.
+
+```python
+from scenario import State, Context
+ctx = Context(MyCharm, meta={'name': 'juliette', "resources": {"foo": {"type": "oci-image"}}})
+with ctx.manager("start", State(resources={'foo': '/path/to/resource.tar'})) as mgr:
+    # if the charm, at runtime, were to call self.model.resources.fetch("foo"), it would get '/path/to/resource.tar' back.
+    path = mgr.charm.model.resources.fetch('foo')
+    assert path == '/path/to/resource.tar' 
+```
+
 # Emitting custom events
 
 While the main use case of Scenario is to emit juju events, i.e. the built-in `start`, `install`, `*-relation-changed`,

pyproject.toml

@@ -8,7 +8,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ops-scenario"
 
-version = "5.4.1"
+version = "5.5"
 
 authors = [
     { name = "Pietro Pasotti", email = "[email protected]" }
@@ -50,10 +50,38 @@ scenario = "scenario"
 include = '\.pyi?$'
 
 
-[tool.flake8]
-dictionaries = ["en_US","python","technical","django"]
-max-line-length = 100
-ignore = ["SC100", "SC200", "B008"]
+[tool.ruff]
+# Same as Black.
+line-length = 88
+indent-width = 4
+
+# Assume Python 3.11
+target-version = "py311"
+
+[tool.ruff.lint]
+# Enable Pyflakes (`F`) and a subset of the pycodestyle (`E`)  codes by default.
+select = ["E4", "E7", "E9", "F"]
+ignore = []
+
+# Allow fix for all enabled rules (when `--fix`) is provided.
+fixable = ["ALL"]
+unfixable = []
+
+# Allow unused variables when underscore-prefixed.
+dummy-variable-rgx = "^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?))$"
+
+[tool.ruff.format]
+# Like Black, use double quotes for strings.
+quote-style = "double"
+
+# Like Black, indent with spaces, rather than tabs.
+indent-style = "space"
+
+# Like Black, respect magic trailing commas.
+skip-magic-trailing-comma = false
+
+# Like Black, automatically detect the appropriate line ending.
+line-ending = "auto"
 
 [tool.isort]
 profile = "black"

scenario/consistency_checker.py

@@ -64,6 +64,7 @@ def check_consistency(
     for check in (
         check_containers_consistency,
         check_config_consistency,
+        check_resource_consistency,
         check_event_consistency,
         check_secrets_consistency,
         check_storages_consistency,
@@ -92,6 +93,27 @@ def check_consistency(
         )
 
 
+def check_resource_consistency(
+    *,
+    state: "State",
+    charm_spec: "_CharmSpec",
+    **_kwargs,  # noqa: U101
+) -> Results:
+    """Check the internal consistency of the resources from metadata and in State."""
+    errors = []
+    warnings = []
+
+    resources_from_meta = set(charm_spec.meta.get("resources", {}))
+    resources_from_state = set(state.resources)
+    if not resources_from_meta.issuperset(resources_from_state):
+        errors.append(
+            f"any and all resources passed to State.resources need to have been defined in "
+            f"metadata.yaml. Metadata resources: {resources_from_meta}; "
+            f"State.resources: {resources_from_state}.",
+        )
+    return Results(errors, warnings)
+
+
 def check_event_consistency(
     *,
     event: "Event",
@@ -396,7 +418,7 @@ def _get_relations(r):
 
     known_endpoints = [a[0] for a in all_relations_meta]
     for relation in state.relations:
-        if not (ep := relation.endpoint) in known_endpoints:
+        if (ep := relation.endpoint) not in known_endpoints:
             errors.append(f"relation endpoint {ep} is not declared in metadata.")
 
     seen_ids = set()