fix(core): return a list from load_entity and pair iris by title

- LoadEntityResult.entities is now List[OswBaseModel]; pydantic v1 tried
  the Union's first member, so an empty result became a truthy
  OswBaseModel that is neither subscriptable nor sized
- resolve() keys the loaded entities by full page title instead of
  zipping them against request.iris; load_entity skips pages it cannot
  build, which shifted every later iri onto the wrong entity
- an iri with no matching entity is logged and left out of nodes
- export_entity_jsonld drops the now dead isinstance branch that hid the
  empty result from its NotFound check

Closes #198

Author: LukasGold

src/osw/core.py

@@ -268,10 +268,19 @@ def resolve(self, request: ResolveParam):
                 entities = osw_obj.load_entity(
                     OSW.LoadEntityParam(titles=request.iris)
                 ).entities
-                # create a dict with request.iris as keys and the loaded entities as values
-                # by iterating over both lists
+                # load_entity() skips pages it cannot build, so the returned
+                # list can be shorter than request.iris. Pair by full title
+                # instead of by position, so a skipped page does not shift
+                # every following entity onto the wrong iri.
+                entities_by_title = {
+                    get_full_title(entity): entity for entity in entities
+                }
                 nodes = {}
-                for iri, entity in zip(request.iris, entities):
+                for iri in request.iris:
+                    entity = entities_by_title.get(iri)
+                    if entity is None:
+                        _logger.warning(f"Could not resolve iri '{iri}'")
+                        continue
                     nodes[iri] = entity
                 return ResolveResult(nodes=nodes)
 
@@ -1280,8 +1289,8 @@ def __init__(self, **data):
     class LoadEntityResult(BaseModel):
         """Result of load_entity()"""
 
-        entities: Union[model.OswBaseModel, List[model.OswBaseModel]]
-        """The dataclass instance(s)"""
+        entities: List[model.OswBaseModel]
+        """The list of dataclass instances"""
 
     # fmt: off
     @overload

src/osw/service/ops/entities.py

@@ -92,8 +92,6 @@ def export_entity_jsonld(
         OSW.LoadEntityParam(titles=[title], autofetch_schema=True)
     )
     entities = result.entities
-    if not isinstance(entities, list):
-        entities = [entities]
     if not entities:
         raise errors.NotFound(f"Entity '{title}' not found.")
     export = ctx.osw.export_jsonld(

tests/test_load_entity_result_shape.py

@@ -0,0 +1,100 @@
+"""Unit tests for load_entity()'s result shape and resolve()'s iri pairing.
+
+Regression guard for #198: https://github.com/OpenSemanticLab/osw-python/issues/198
+LoadEntityResult.entities was declared as Union[OswBaseModel, List[OswBaseModel]],
+so pydantic v1 tried the bare OswBaseModel variant first and an empty list
+validated as OswBaseModel() instead of staying an empty list. Separately,
+OswDefaultBackend.resolve() zipped request.iris against load_entity()'s result
+positionally, so a page load_entity() skipped shifted every later iri onto the
+wrong entity.
+
+These run fully offline: no site touches the network.
+"""
+
+from unittest.mock import MagicMock
+
+from oold.backend.interface import ResolveParam
+
+import osw.core
+import osw.model.entity as model
+from osw.core import OSW
+from osw.wtsite import WtSite
+
+
+def _make_entity(namespace: str, title: str) -> model.Item:
+    entity = model.Item(label=[model.Label(text=title)])
+    entity.meta = model.Meta(wiki_page=model.WikiPage(namespace=namespace, title=title))
+    return entity
+
+
+def _build_backend(monkeypatch):
+    """Constructs an OSW instance and returns its OswDefaultBackend.
+
+    set_resolver/set_backend are replaced so construction does not touch the
+    real global oold registry; set_backend is used to capture the backend
+    instance it would otherwise register.
+    """
+    captured = {}
+
+    def _capture_set_backend(param):
+        captured["backend"] = param.backend
+
+    monkeypatch.setattr(osw.core, "set_resolver", lambda param: None)
+    monkeypatch.setattr(osw.core, "set_backend", _capture_set_backend)
+
+    site = MagicMock(spec=WtSite)
+    OSW(site=site)
+
+    return captured["backend"]
+
+
+def test_load_entity_result_keeps_empty_list_as_list():
+    result = OSW.LoadEntityResult(entities=[])
+
+    assert result.entities == []
+    assert bool(result.entities) is False
+    assert len(result.entities) == 0
+
+
+def test_load_entity_result_keeps_non_empty_list_and_subclass():
+    item = model.Item(label=[model.Label(text="x")])
+
+    result = OSW.LoadEntityResult(entities=[item])
+
+    assert isinstance(result.entities, list)
+    assert len(result.entities) == 1
+    assert isinstance(result.entities[0], model.Item)
+
+
+def test_resolve_pairs_iris_by_title_not_position(monkeypatch):
+    backend = _build_backend(monkeypatch)
+    good = _make_entity("Item", "OSWAlignGood")
+
+    def _stub_load_entity(self, param):
+        # "Item:OSWAlignBad" could not be built and load_entity() silently
+        # skips it, so the returned list is shorter than request.iris.
+        return OSW.LoadEntityResult(entities=[good])
+
+    monkeypatch.setattr(OSW, "load_entity", _stub_load_entity)
+
+    result = backend.resolve(
+        ResolveParam(iris=["Item:OSWAlignBad", "Item:OSWAlignGood"])
+    )
+
+    assert result.nodes == {"Item:OSWAlignGood": good}
+    assert "Item:OSWAlignBad" not in result.nodes
+
+
+def test_resolve_returns_all_entities_when_every_iri_resolves(monkeypatch):
+    backend = _build_backend(monkeypatch)
+    first = _make_entity("Item", "OSWFirst")
+    second = _make_entity("Item", "OSWSecond")
+
+    def _stub_load_entity(self, param):
+        return OSW.LoadEntityResult(entities=[first, second])
+
+    monkeypatch.setattr(OSW, "load_entity", _stub_load_entity)
+
+    result = backend.resolve(ResolveParam(iris=["Item:OSWFirst", "Item:OSWSecond"]))
+
+    assert result.nodes == {"Item:OSWFirst": first, "Item:OSWSecond": second}