fix(plugin-system): implement register_driver_type and stop discover() aborting on one bad manifest

- driver/registry.py never actually defined register_driver_type, so
  the plugin-system's 'driver plugin registered successfully' scenario
  was unreachable in production (only simulated via test monkeypatch).
  Added a real implementation wired into the existing driver factory
  registry.
- PluginRegistry.discover() only caught PluginValidationError/
  DuplicatePluginError, so a driver-kind manifest that failed wiring
  (DriverRegistryUnavailableError/PluginTargetResolutionError) aborted
  the whole scan, silently skipping co-located tool/skill manifests.
  Now caught and skipped per manifest instead.

openspec: plugin-system capability, archived change cloud-runtime

cloud/plugins.py

@@ -95,6 +95,19 @@ class PluginTargetResolutionError(RuntimeError):
     """Raised when a plugin target cannot be resolved to a callable."""
 
 
+# Exception types `register()` can raise for a single bad manifest (validation
+# failure, name conflict, or driver-wiring failure). `discover()` catches only
+# these so one bad manifest is skipped/logged, per spec's "malformed manifest
+# file is skipped, not fatal" resilience intent -- anything else propagates as
+# a genuine programmer error.
+_PLUGIN_REGISTRATION_FAILURES = (
+    PluginValidationError,
+    DuplicatePluginError,
+    DriverRegistryUnavailableError,
+    PluginTargetResolutionError,
+)
+
+
 class PluginRegistry:
     """Validates, persists, and wires plugins discovered or submitted directly."""
 
@@ -128,7 +141,7 @@ class PluginRegistry:
             try:
                 self.register(manifest)
                 result.registered.append(manifest)
-            except (PluginValidationError, DuplicatePluginError) as exc:
+            except _PLUGIN_REGISTRATION_FAILURES as exc:
                 result.errors.append(
                     f"entry-point plugin {manifest.name!r}: {exc}"
                 )
@@ -137,7 +150,7 @@ class PluginRegistry:
                 try:
                     self.register(manifest)
                     result.registered.append(manifest)
-                except (PluginValidationError, DuplicatePluginError) as exc:
+                except _PLUGIN_REGISTRATION_FAILURES as exc:
                     result.errors.append(
                         f"manifest-file plugin {manifest.name!r}: {exc}"
                     )

driver/registry.py

@@ -42,3 +42,23 @@ def build_driver_factory(
     if not builder:
         raise ValueError(f"unsupported driver_type: {driver_type}")
     return builder(connection_info)
+
+
+def register_driver_type(driver_type: str, factory: DriverFactoryBuilder) -> None:
+    """Register a new ``driver_type`` -> factory-builder mapping.
+
+    This is the extension point external code (e.g. ``cloud.plugins``'
+    driver-kind plugin wiring) uses to add a new driver type without editing
+    this module. ``factory`` must be a callable accepting a
+    ``connection_info`` dict and returning a ``DriverFactory`` (the same
+    shape as :func:`build_wda_driver_factory`); once registered,
+    ``build_driver_factory(driver_type, ...)`` can construct drivers of the
+    new type.
+    """
+    if not driver_type:
+        raise ValueError("driver_type must be a non-empty string")
+    if not callable(factory):
+        raise ValueError(f"factory for driver_type {driver_type!r} must be callable")
+    if driver_type in SUPPORTED_DRIVER_TYPES:
+        raise ValueError(f"driver_type {driver_type!r} is already registered")
+    SUPPORTED_DRIVER_TYPES[driver_type] = factory

tests/test_plugin_registry.py

@@ -15,6 +15,7 @@ from cloud.plugins import (
     DuplicatePluginError,
     PluginManifest,
     PluginRegistry,
+    PluginTargetResolutionError,
     PluginValidationError,
 )
 from cloud.store import CloudStore
@@ -36,6 +37,15 @@ def _manifest(
     )
 
 
+def _fake_driver_factory_builder(connection_info: dict) -> object:
+    """A real ``DriverFactoryBuilder``-shaped function used as a plugin target
+    in tests: takes ``connection_info``, returns a zero-arg factory callable
+    that "constructs" a driver (here, just the connection info itself, so
+    tests can assert on it without needing a real WDA server)."""
+
+    return lambda: dict(connection_info)
+
+
 def test_valid_manifest_registers(tmp_path) -> None:
     registry = PluginRegistry(CloudStore(tmp_path / "cloud.sqlite3"))
 
@@ -67,39 +77,33 @@ def test_duplicate_name_rejected(tmp_path) -> None:
         registry.register(_manifest(entry_point_kind="tool"))
 
 
-def test_driver_kind_wires_into_register_driver_type(
-    tmp_path,
-    monkeypatch,
-) -> None:
-    """A driver-kind manifest calls driver.registry.register_driver_type."""
+def test_driver_kind_wires_into_register_driver_type(tmp_path, monkeypatch) -> None:
+    """A driver-kind manifest is wired end-to-end into the real driver registry:
+    after registration, build_driver_factory() can construct the new type."""
 
-    calls: list[tuple[str, object]] = []
-
-    def fake_register(name: str, builder) -> None:
-        calls.append((name, builder))
-
-    # driver/registry.py does not yet expose register_driver_type in the real
-    # codebase, so injecting it via monkeypatch simulates the future state
-    # where it does (per design.md D6 / Open Questions).
-    monkeypatch.setattr(
-        driver_registry_module,
-        "register_driver_type",
-        fake_register,
-        raising=False,
+    monkeypatch.delitem(
+        driver_registry_module.SUPPORTED_DRIVER_TYPES, "custom-driver", raising=False
     )
 
     registry = PluginRegistry(CloudStore(tmp_path / "cloud.sqlite3"))
-    registry.register(_manifest(entry_point_kind="driver", name="custom-driver"))
-
-    assert len(calls) == 1
-    registered_name, registered_builder = calls[0]
-    assert registered_name == "custom-driver"
-    assert callable(registered_builder)
+    registry.register(
+        _manifest(
+            entry_point_kind="driver",
+            name="custom-driver",
+            target="tests.test_plugin_registry:_fake_driver_factory_builder",
+        )
+    )
 
     stored = registry.store.get_plugin("custom-driver")
     assert stored is not None
     assert stored[1] is True  # wired
 
+    factory = driver_registry_module.build_driver_factory(
+        "custom-driver", {"server_url": "http://example"}
+    )
+    driver = factory()
+    assert driver == {"server_url": "http://example"}
+
 
 def test_driver_kind_raises_when_extension_point_missing(
     tmp_path,
@@ -255,3 +259,108 @@ def test_discover_combines_entry_points_and_manifest_files(
     names = {m.name for m in result.registered}
     assert names == {"via-entry-point", "via-file"}
     assert result.errors == []
+
+
+def test_discover_does_not_abort_when_driver_wiring_fails(
+    tmp_path,
+    monkeypatch,
+) -> None:
+    """A driver-kind manifest that fails wiring must not abort the whole
+    discover() scan: a co-located tool manifest should still get registered,
+    and the failure should surface as a discovery error, not an exception."""
+
+    # Force the driver-registry extension point to look unavailable so the
+    # driver-kind manifest below fails wiring with DriverRegistryUnavailableError.
+    monkeypatch.delattr(
+        driver_registry_module,
+        "register_driver_type",
+        raising=False,
+    )
+
+    plugins_dir = tmp_path / "plugins"
+    (plugins_dir / "a-broken-driver").mkdir(parents=True)
+    (plugins_dir / "a-broken-driver" / "plugin.json").write_text(
+        json.dumps(
+            {
+                "name": "broken-driver",
+                "version": "1.0.0",
+                "entry_point_kind": "driver",
+                "target": "cloud.store:CloudStore",
+            }
+        ),
+        encoding="utf-8",
+    )
+    (plugins_dir / "b-ok-tool").mkdir(parents=True)
+    (plugins_dir / "b-ok-tool" / "plugin.json").write_text(
+        json.dumps(
+            {
+                "name": "ok-tool",
+                "version": "1.0.0",
+                "entry_point_kind": "tool",
+                "target": "cloud.store:CloudStore",
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    registry = PluginRegistry(CloudStore(tmp_path / "cloud.sqlite3"))
+    result = registry.discover(scan_path=plugins_dir)
+
+    # The broken driver manifest is recorded as a discovery error, not raised.
+    assert any("broken-driver" in err for err in result.errors)
+    # The co-located tool manifest still registered despite the driver failure.
+    assert any(m.name == "ok-tool" for m in result.registered)
+    assert registry.store.get_plugin("ok-tool") is not None
+    assert registry.store.get_plugin("broken-driver") is None
+
+
+def test_discover_reports_target_resolution_failure_without_aborting(
+    tmp_path,
+) -> None:
+    """A driver-kind manifest whose target can't resolve to a callable
+    (PluginTargetResolutionError) is likewise skipped/logged, not fatal."""
+
+    plugins_dir = tmp_path / "plugins"
+    (plugins_dir / "bad-target-driver").mkdir(parents=True)
+    (plugins_dir / "bad-target-driver" / "plugin.json").write_text(
+        json.dumps(
+            {
+                "name": "bad-target-driver",
+                "version": "1.0.0",
+                "entry_point_kind": "driver",
+                # os.path.sep exists but is not callable -> PluginTargetResolutionError
+                "target": "os.path:sep",
+            }
+        ),
+        encoding="utf-8",
+    )
+    (plugins_dir / "ok-tool-2").mkdir(parents=True)
+    (plugins_dir / "ok-tool-2" / "plugin.json").write_text(
+        json.dumps(
+            {
+                "name": "ok-tool-2",
+                "version": "1.0.0",
+                "entry_point_kind": "tool",
+                "target": "cloud.store:CloudStore",
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    registry = PluginRegistry(CloudStore(tmp_path / "cloud.sqlite3"))
+
+    with pytest.raises(PluginTargetResolutionError):
+        # Direct register() call still raises loudly for a single manifest...
+        registry._wire_driver(
+            _manifest(
+                name="direct-check",
+                entry_point_kind="driver",
+                target="os.path:sep",
+            )
+        )
+
+    result = registry.discover(scan_path=plugins_dir)
+
+    assert any("bad-target-driver" in err for err in result.errors)
+    assert any(m.name == "ok-tool-2" for m in result.registered)
+    assert registry.store.get_plugin("ok-tool-2") is not None