add test example that is identical to ibek?

examples/README.md

@@ -13,3 +13,17 @@ Issue under investigation
 =========================
 
 The issue is that when an object refers to another object then the error reported is that the offending object's id cannot be found. This masks the underlying schema issue which is what should be reported first. The custom field validator created in make_entity_model seems to be throwing the error before the schema validation issue is reported.
+
+At present for the incorrect schema in entity e1 ibek reports:
+
+```
+KeyError: 'object one not found in []'
+```
+
+And test_refs4.py reports
+
+```
+Extra inputs are not permitted [type=extra_forbidden, input_value='bad argument', input_type=str]
+```
+
+The latter is the useful error that points you at the root cause.

examples/test_refs4.py

@@ -0,0 +1,115 @@
+from __future__ import annotations
+
+from typing import Dict, Literal, Optional, Sequence, Union
+
+from pydantic import (
+    BaseModel,
+    ConfigDict,
+    Field,
+    RootModel,
+    create_model,
+    field_validator,
+    model_validator,
+)
+from pydantic.fields import FieldInfo
+
+id_to_entity: Dict[str, Entity] = {}
+
+
+class Entity(BaseModel):
+    type: str = Field(description="The type of this entity")
+    name: str = Field(..., description="The name of this entity")
+    value: str = Field(..., description="The value of this entity")
+    ref: Optional[str] = Field(
+        default=None, description="Reference another Entity name"
+    )
+    model_config = ConfigDict(extra="forbid")
+
+    @model_validator(mode="after")  # type: ignore
+    def add_ibek_attributes(cls, entity: Entity):
+        id_to_entity[entity.name] = entity
+
+        return entity
+
+
+args = {"type": (Literal["e1"], FieldInfo(description="The type of this entity"))}
+
+
+@field_validator("ref", mode="after")
+def lookup_instance(cls, id):
+    try:
+        return id_to_entity[id]
+    except KeyError:
+        raise KeyError(f"object {id} not found in {list(id_to_entity)}")
+
+
+validators = {"Entity": lookup_instance}
+
+# add validator to the Entity classes using create model
+EntityOne = create_model(
+    "EntityOne",
+    **args,
+    __validators__=validators,
+    __base__=Entity,
+)  # type: ignore
+
+args2 = {"type": (Literal["e2"], FieldInfo(description="The type of this entity"))}
+
+
+@field_validator("ref", mode="after")
+def lookup_instance2(cls, id):
+    try:
+        return id_to_entity[id]
+    except KeyError:
+        raise KeyError(f"object {id} not found in {list(id_to_entity)}")
+
+
+validators2 = {"Entity": lookup_instance2}
+
+EntityTwo = create_model(
+    "EntityTwo",
+    **args2,
+    __validators__=validators2,
+    __base__=Entity,
+)  # type: ignore s
+
+entity_models = (EntityOne, EntityTwo)
+
+
+class EntityModel(RootModel):
+    root: Union[entity_models] = Field(discriminator="type")  # type: ignore
+
+
+class Entities(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+    entities: Sequence[EntityModel] = Field(  # type: ignore
+        description="List of entities classes we want to create"
+    )
+
+
+model1 = Entities(
+    **{
+        "entities": [
+            {"type": "e1", "name": "one", "value": "OneValue"},
+            {"type": "e2", "name": "two", "value": "TwoValue", "ref": "one"},
+        ]
+    }
+)
+
+# demonstrate that entity one has a reference to entity two
+assert model1.entities[1].root.ref.value == "OneValue"
+
+# this should throw an error because entity one has illegal arguments
+model2 = Entities(
+    **{
+        "entities": [
+            {
+                "type": "e1",
+                "name": "one",
+                "value": "OneValue",
+                "illegal": "bad argument",
+            },
+            {"type": "e2", "name": "two", "value": "TwoValue", "ref": "one"},
+        ]
+    }
+)