Deregister partially replaced multi-output plugins (#775)

* Deregister partially replaced multi-output plugins

strax/context.py

@@ -328,9 +328,24 @@ def register(self, plugin_class):
         if isinstance(plugin_class.provides, str):
             plugin_class.provides = tuple([plugin_class.provides])
 
+        # Register the plugin for all datatypes it provides,
+        # tracking which plugins we booted out.
+        deregistered = []
         for p in plugin_class.provides:
+            old_plugin_class = self._plugin_class_registry.get(p, None)
+            if old_plugin_class and old_plugin_class != plugin_class:
+                deregistered.append(old_plugin_class)
             self._plugin_class_registry[p] = plugin_class
 
+        # If we booted a plugin from a datatype, we must boot it from other
+        # datatypes it makes too, to preserve a one-to-one mapping between
+        # datatypes and registered plugins.
+        for old_plugin in deregistered:
+            for d in old_plugin.provides:
+                currently_registered = self._plugin_class_registry.get(d)
+                if old_plugin == currently_registered:
+                    del self._plugin_class_registry[d]
+
         already_seen = []
         for plugin in self._plugin_class_registry.values():
             if plugin in already_seen:

tests/test_context.py

@@ -9,6 +9,7 @@
 import unittest
 import shutil
 import uuid
+import pytest
 
 
 def _apply_function_to_data(function) -> ty.Tuple[np.ndarray, np.ndarray]:
@@ -224,6 +225,28 @@ def test_get_plugins_with_cache(self):
             not_cached_plugins.keys() == cached_plugins.keys()
         ), f"_get_plugins returns different plugins if cached!"
 
+    def test_multioutput_deregistration(self):
+        """Test that a multi-output plugin is deregistered once one of its outputs is provided by
+        another plugin."""
+
+        class RecordsPlus(strax.Plugin):
+            depends_on = tuple()
+            data_kind = dict(records="records", plus="plus")
+            dtype = dict(records=strax.record_dtype(), plus=strax.record_dtype())
+            provides = ("records", "plus")
+
+        st = self.get_context(False)
+        st.register(RecordsPlus)
+        st.register(Records)
+
+        # Records will make the records, not RecordsPlus
+        plugins = st._get_plugins(("records",), run_id)
+        assert isinstance(plugins["records"], Records)
+
+        # Plus is no longer available.
+        with pytest.raises(KeyError):
+            plugins = st.key_for("plus", run_id)
+
     def test_register_no_defaults(self, runs_default_allowed=False):
         """Test if we only register a plugin with no run-defaults."""
         st = self.get_context(runs_default_allowed)