fix(testing): stop plugin enabled:false schema defaults from silently disabling harness tests (#408)

check_plugin.py, render_plugin.py, and the pytest plugin matrix each built
config as {"enabled": True} then merged in config_schema.json's defaults on
top, letting a plugin's own enabled:false default (a reasonable choice for
a seasonal/opt-in plugin -- 15 of 23 real plugins ship one) silently win.
Every harness/CI render of those plugins was testing "disabled, do
nothing" rather than real behavior.

Extract build_full_config() into testing/loading.py (already the shared
home for plugin-discovery/config-default logic) and use it from all three
call sites: schema defaults, then a forced enabled=True, then harness.json's
config, then the caller's explicit config -- so a test can still
deliberately disable a plugin on purpose, it just can't happen by accident
via the plugin's own shipped schema default anymore.

scripts/check_plugin.py

@@ -37,7 +37,7 @@ os.environ['EMULATOR'] = 'true'
 
 from src.logging_config import get_logger  # noqa: E402
 from src.plugin_system.testing.loading import (  # noqa: E402
-    find_plugin_dir, load_config_defaults, load_harness_spec, load_manifest,
+    build_full_config, find_plugin_dir, load_harness_spec, load_manifest,
 )
 from src.plugin_system.testing.harness import (  # noqa: E402
     RenderResult, render_plugin_matrix, compare_to_goldens, write_goldens,
@@ -97,12 +97,11 @@ def check_one(plugin_id: str, search_dirs: List[str], sizes, mock_data: Dict,
     # matrix path does; explicit CLI flags still override the file.
     spec = load_harness_spec(plugin_dir)
 
-    # config_schema defaults (real-install behavior), then harness.json config,
-    # then CLI --config — most specific wins.
-    full_config = {"enabled": True}
-    full_config.update(load_config_defaults(plugin_dir))
-    full_config.update(spec.get("config", {}))
-    full_config.update(config)
+    # config_schema defaults (real-install behavior, with enabled forced True
+    # so a plugin's own enabled:false default can't accidentally disable
+    # testing), then harness.json config, then CLI --config — most specific
+    # wins.
+    full_config = build_full_config(plugin_dir, spec, config)
 
     # Precedence: CLI flag > LEDMATRIX_TEST_SIZES env > harness.json > default.
     effective_sizes = sizes if sizes else resolve_test_sizes(spec.get("sizes"))

scripts/render_plugin.py

@@ -28,7 +28,7 @@ os.environ['EMULATOR'] = 'true'
 # Import logger after path setup so src.logging_config is importable
 from src.logging_config import get_logger  # noqa: E402
 from src.plugin_system.testing.loading import (  # noqa: E402
-    find_plugin_dir, load_manifest, load_config_defaults,
+    build_full_config, find_plugin_dir, load_manifest,
 )
 logger = get_logger("[Render Plugin]")
 
@@ -83,16 +83,13 @@ def main() -> int:
     manifest = load_manifest(Path(plugin_dir))
 
     # Parse config: start with schema defaults, then apply overrides
-    config_defaults = load_config_defaults(Path(plugin_dir))
     try:
         user_config = json.loads(args.config)
     except json.JSONDecodeError as e:
         logger.error("Invalid JSON config: %s", e)
         return 1
 
-    config = {'enabled': True}
-    config.update(config_defaults)
-    config.update(user_config)
+    config = build_full_config(Path(plugin_dir), cli_config=user_config)
 
     # Load mock data if provided
     mock_data = {}

src/plugin_system/testing/loading.py

@@ -88,3 +88,27 @@ def load_harness_spec(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
         with open(mock_path, 'r') as mf:
             spec['mock_data_contents'] = json.load(mf)
     return spec
+
+
+def build_full_config(
+    plugin_dir: Union[str, Path],
+    spec: Optional[Dict[str, Any]] = None,
+    cli_config: Optional[Dict[str, Any]] = None,
+) -> Dict[str, Any]:
+    """Build the config a plugin sees under test.
+
+    Merge order: config_schema.json defaults, then a forced ``enabled: True``,
+    then harness.json's config overlay, then the caller's explicit config --
+    most specific wins. `enabled` is re-asserted *after* the schema defaults
+    so a plugin that reasonably ships `enabled: false` (e.g. a seasonal or
+    opt-in plugin) can't silently make every harness run test "disabled, do
+    nothing" by accident -- callers that genuinely want to test the disabled
+    path can still do so via `cli_config={"enabled": False}`.
+    """
+    spec = spec or {}
+    config: Dict[str, Any] = {}
+    config.update(load_config_defaults(plugin_dir))
+    config["enabled"] = True
+    config.update(spec.get("config", {}))
+    config.update(cli_config or {})
+    return config

test/plugins/test_harness.py

@@ -253,3 +253,61 @@ class TestCheckPluginHonorsHarnessJson:
         )
         assert captured["freeze_time"] == "2030-01-01 00:00:00"
         assert captured["config"]["timezone"] == "America/New_York"
+
+
+class TestBuildFullConfigForcesEnabled:
+    """Regression: a plugin's own config_schema.json may reasonably default
+    enabled to False (e.g. a seasonal or opt-in plugin) -- march-madness and
+    14 other real plugins do. The harness must still test it as enabled
+    unless a caller explicitly asks otherwise, or every render silently
+    becomes a same-shaped "disabled, do nothing" no-op."""
+
+    def _make_plugin_with_disabled_default(self, tmp_path):
+        pdir = tmp_path / "plugins" / "demo-seasonal"
+        pdir.mkdir(parents=True)
+        (pdir / "manifest.json").write_text(json.dumps({
+            "id": "demo-seasonal", "name": "Demo Seasonal", "version": "1.0.0",
+            "author": "test", "entry_point": "manager.py",
+            "class_name": "DemoSeasonal", "display_modes": ["demo-seasonal"],
+            "compatible_versions": ["*"],
+        }))
+        (pdir / "config_schema.json").write_text(json.dumps({
+            "type": "object",
+            "properties": {"enabled": {"type": "boolean", "default": False}},
+        }))
+        return pdir
+
+    def test_schema_disabled_default_does_not_win(self, tmp_path):
+        from src.plugin_system.testing.loading import build_full_config
+        plugin_dir = self._make_plugin_with_disabled_default(tmp_path)
+        config = build_full_config(plugin_dir)
+        assert config["enabled"] is True
+
+    def test_harness_json_config_can_still_disable(self, tmp_path):
+        from src.plugin_system.testing.loading import build_full_config
+        plugin_dir = self._make_plugin_with_disabled_default(tmp_path)
+        config = build_full_config(plugin_dir, spec={"config": {"enabled": False}})
+        assert config["enabled"] is False
+
+    def test_explicit_cli_config_can_still_disable(self, tmp_path):
+        from src.plugin_system.testing.loading import build_full_config
+        plugin_dir = self._make_plugin_with_disabled_default(tmp_path)
+        config = build_full_config(plugin_dir, cli_config={"enabled": False})
+        assert config["enabled"] is False
+
+    def test_check_one_renders_a_schema_disabled_plugin_as_enabled(self, tmp_path, monkeypatch):
+        """End-to-end: check_plugin.py's check_one() must not blank-render a
+        plugin just because its own schema defaults enabled to False."""
+        mod = _load_check_plugin_cli()
+        plugin_dir = self._make_plugin_with_disabled_default(tmp_path)
+        captured = {}
+        monkeypatch.setattr(mod, "render_plugin_matrix",
+                            lambda **kw: captured.update(kw) or [])
+        monkeypatch.setattr(mod, "compare_to_goldens", lambda *a, **k: [])
+        mod.check_one(
+            plugin_id="demo-seasonal", search_dirs=[str(tmp_path / "plugins")],
+            sizes=None, mock_data={}, config={}, run_update=True,
+            out_dir=None, update_golden=False, golden_dir_override=None,
+            freeze_time=None,
+        )
+        assert captured["config"]["enabled"] is True

test/plugins/test_plugin_matrix.py

@@ -22,7 +22,7 @@ import pytest
 from src.plugin_system.testing.harness import (
     render_plugin_matrix, compare_to_goldens,
 )
-from src.plugin_system.testing.loading import load_config_defaults, load_harness_spec
+from src.plugin_system.testing.loading import build_full_config, load_harness_spec
 from src.plugin_system.testing.sizes import resolve_test_sizes
 
 PROJECT_ROOT = Path(__file__).resolve().parents[2]
@@ -81,9 +81,7 @@ def test_plugin_renders_across_sizes_and_screens(plugin_id: str) -> None:
     plugin_dir = _PLUGINS[plugin_id]
     spec = load_harness_spec(plugin_dir)
 
-    config = {"enabled": True}
-    config.update(load_config_defaults(plugin_dir))
-    config.update(spec.get("config", {}))
+    config = build_full_config(plugin_dir, spec)
 
     # Sizes: LEDMATRIX_TEST_SIZES env (test on real hardware) wins, then the
     # plugin's own harness.json "sizes", else the default representative sample.