Treat empty actions.yaml as no actions.yaml. (#459)

* Treat empty actions.yaml as no actions.yaml.

Without this change the operator framework would fall over hard if a
charm had an empty `actions.yaml`.

This was found and reported by @davigar15 (thanks!).

Fixes: #458

* check meta.actions is empty dict when actions is empty

ops/charm.py

@@ -702,6 +702,8 @@ def from_yaml(
         raw_actions = {}
         if actions is not None:
             raw_actions = _loadYaml(actions)
+            if raw_actions is None:
+                raw_actions = {}
         return cls(meta, raw_actions)
 
 

test/charms/test_main/src/charm.py

@@ -73,19 +73,21 @@ def __init__(self, *args):
         self.framework.observe(self.on.mon_relation_departed, self._on_mon_relation_departed)
         self.framework.observe(self.on.ha_relation_broken, self._on_ha_relation_broken)
 
-        self.framework.observe(self.on.start_action, self._on_start_action)
-        self.framework.observe(self.on.foo_bar_action, self._on_foo_bar_action)
-        self.framework.observe(self.on.get_model_name_action, self._on_get_model_name_action)
-        self.framework.observe(self.on.get_status_action, self._on_get_status_action)
+        actions = self.charm_dir / 'actions.yaml'
+        if actions.exists() and actions.read_bytes():
+            self.framework.observe(self.on.start_action, self._on_start_action)
+            self.framework.observe(self.on.foo_bar_action, self._on_foo_bar_action)
+            self.framework.observe(self.on.get_model_name_action, self._on_get_model_name_action)
+            self.framework.observe(self.on.get_status_action, self._on_get_status_action)
+
+            self.framework.observe(self.on.log_critical_action, self._on_log_critical_action)
+            self.framework.observe(self.on.log_error_action, self._on_log_error_action)
+            self.framework.observe(self.on.log_warning_action, self._on_log_warning_action)
+            self.framework.observe(self.on.log_info_action, self._on_log_info_action)
+            self.framework.observe(self.on.log_debug_action, self._on_log_debug_action)
 
         self.framework.observe(self.on.collect_metrics, self._on_collect_metrics)
 
-        self.framework.observe(self.on.log_critical_action, self._on_log_critical_action)
-        self.framework.observe(self.on.log_error_action, self._on_log_error_action)
-        self.framework.observe(self.on.log_warning_action, self._on_log_warning_action)
-        self.framework.observe(self.on.log_info_action, self._on_log_info_action)
-        self.framework.observe(self.on.log_debug_action, self._on_log_debug_action)
-
         if os.getenv('TRY_EXCEPTHOOK', False):
             raise RuntimeError("failing as requested")
 

test/test_charm.py

@@ -94,6 +94,10 @@ def _on_start(self, event):
         with self.assertRaisesRegex(TypeError, "observer methods must now be explicitly provided"):
             framework.observe(charm.on.start, charm)
 
+    def test_empty_action(self):
+        meta = CharmMeta.from_yaml('name: my-charm', '')
+        self.assertEqual(meta.actions, {})
+
     def test_helper_properties(self):
         framework = self.create_framework()
 

test/test_main.py

@@ -326,8 +326,12 @@ def _read_and_clear_state(self):
         if self.CHARM_STATE_FILE.stat().st_size:
             storage = SQLiteStorage(self.CHARM_STATE_FILE)
             with (self.JUJU_CHARM_DIR / 'metadata.yaml').open() as m:
-                with (self.JUJU_CHARM_DIR / 'actions.yaml').open() as a:
-                    meta = CharmMeta.from_yaml(m, a)
+                af = (self.JUJU_CHARM_DIR / 'actions.yaml')
+                if af.exists():
+                    with af.open() as a:
+                        meta = CharmMeta.from_yaml(m, a)
+                else:
+                    meta = CharmMeta.from_yaml(m)
             framework = Framework(storage, self.JUJU_CHARM_DIR, meta, None)
 
             class ThisCharmEvents(CharmEvents):
@@ -557,6 +561,14 @@ def test_event_not_implemented(self):
             self.fail('Event simulation for an unsupported event'
                       ' results in a non-zero exit code returned')
 
+    def test_no_actions(self):
+        (self.JUJU_CHARM_DIR / 'actions.yaml').unlink()
+        self._simulate_event(EventSpec(InstallEvent, 'install'))
+
+    def test_empty_actions(self):
+        (self.JUJU_CHARM_DIR / 'actions.yaml').write_text('')
+        self._simulate_event(EventSpec(InstallEvent, 'install'))
+
     def test_collect_metrics(self):
         fake_script(self, 'add-metric', 'exit 0')
         self._simulate_event(EventSpec(InstallEvent, 'install'))