Don't return early from target_gids, enable intersection (#198)

## Context

`connection_override` blocks may define a source and target nodeset
which will filter the corresponding cells and associated connections.

However, under some circumstances the filter was not being applied,
which could potentially lead to more connections being instantiated.
When applied the filter it was noticeable it would consider all
populations.
It is unclear whether that actually could happen in current circuits,
but in unit tests that was observable when a nodeset spanned over
multiple populations.

## Scope

 - Apply the intersection of current cell target 
 - Make each ConnectionManager filter the target by its populations.
 
## Testing
 - Unit test reviewed (started failing)
 - blueconfig tests don't seem to get impacted

## Review
* [x] PR description is complete
* [x] Coding style (imports, function length, New functions, classes or
files) are good

neurodamus/connection_manager.py

@@ -559,12 +559,14 @@ def connect_group(self, conn_source, conn_destination, synapse_type_restrict=Non
             mod_override (str): ModOverride given for this connection group
         """
         conn_kwargs = {}
-        pop = self._cur_population
+        conn_pop = self._cur_population
+        dst_pop_name = self._cell_manager.population_name
+        src_pop_name = self._src_cell_manager.population_name
         logging.debug("Connecting group %s -> %s", conn_source, conn_destination)
         src_tspec = TargetSpec(conn_source)
         dst_tspec = TargetSpec(conn_destination)
-        src_target = src_tspec.name and self._target_manager.get_target(src_tspec)
-        dst_target = dst_tspec.name and self._target_manager.get_target(dst_tspec)
+        src_target = src_tspec.name and self._target_manager.get_target(src_tspec, src_pop_name)
+        dst_target = dst_tspec.name and self._target_manager.get_target(dst_tspec, dst_pop_name)
 
         if src_target and src_target.is_void() or dst_target and dst_target.is_void():
             logging.debug("Skip void connectivity for current connectivity: %s - %s",
@@ -573,7 +575,7 @@ def connect_group(self, conn_source, conn_destination, synapse_type_restrict=Non
 
         if SimConfig.dry_run:
             syn_count = self._get_conn_stats(dst_target, src_target)
-            log_all(VERBOSE_LOGLEVEL, "%s -> %s: %d", pop.src_name, conn_destination, syn_count)
+            log_all(VERBOSE_LOGLEVEL, "%s-> %s: %d", conn_pop.src_name, conn_destination, syn_count)
             self._dry_run_stats.synapse_counts[self.CONNECTIONS_TYPE] += syn_count
             return
 
@@ -584,7 +586,7 @@ def connect_group(self, conn_source, conn_destination, synapse_type_restrict=Non
             if self._load_offsets:
                 conn_kwargs["synapses_offset"] = extra_params["synapse_index"][0]
 
-            cur_conn = pop.get_or_create_connection(sgid, tgid, **conn_kwargs)
+            cur_conn = conn_pop.get_or_create_connection(sgid, tgid, **conn_kwargs)
             if cur_conn.locked:
                 continue
             self._add_synapses(cur_conn, syns_params, synapse_type_restrict, offset)
@@ -644,8 +646,9 @@ def _iterate_conn_params(self, src_target, dst_target, gids=None, show_progress=
 
         def target_gids(gids):
             if gids is None:
-                return self._raw_gids
-            gids = numpy.intersect1d(gids, self._raw_gids)
+                gids = self._raw_gids
+            else:
+                gids = numpy.intersect1d(gids, self._raw_gids)
             if dst_target:
                 gids = numpy.intersect1d(gids, dst_target.get_raw_gids())
             return gids

tests/scientific/test_spont_minis.py

@@ -47,11 +47,10 @@ def test_spont_minis(sonata_config_file):
     )
 
     edges_a: SynapseRuleManager = nd.circuits.get_edge_manager("NodeA", "NodeA")
-    assert len(list(edges_a.all_connections())) == 2
+    # Note: Before #198 we would instantiate a projection conn as being internal
+    assert len(list(edges_a.all_connections())) == 1
     conn_2_1 = next(edges_a.get_connections(1, 2))
-    conn_1_2 = next(edges_a.get_connections(2, 1))
     assert conn_2_1._spont_minis.rate == SPONT_RATE
-    assert conn_1_2._spont_minis is None
 
     c1 = edges_a.cell_manager.get_cellref(1)
     voltage_vec = Nd.Vector()