Narrower handling around unresolved refs

openapi_schema_validator/_keywords.py

@@ -10,6 +10,7 @@
 from jsonschema._utils import find_additional_properties
 from jsonschema.exceptions import FormatError
 from jsonschema.exceptions import ValidationError
+from jsonschema.exceptions import _WrappedReferencingError
 
 
 def handle_discriminator(
@@ -53,7 +54,7 @@ def handle_discriminator(
 
     try:
         validator._validate_reference(ref=ref, instance=instance)
-    except Exception:
+    except _WrappedReferencingError:
         yield ValidationError(
             f"{instance!r} reference {ref!r} could not be resolved",
             context=[],

tests/integration/test_validators.py

@@ -1,9 +1,17 @@
 from base64 import b64encode
+from typing import Any
+from typing import cast
 
 import pytest
 from jsonschema import ValidationError
+from jsonschema.exceptions import (
+    _WrappedReferencingError as WrappedReferencingError,
+)
 from referencing import Registry
 from referencing import Resource
+from referencing.exceptions import InvalidAnchor
+from referencing.exceptions import NoSuchAnchor
+from referencing.exceptions import PointerToNowhere
 from referencing.jsonschema import DRAFT202012
 
 from openapi_schema_validator import OAS30ReadValidator
@@ -353,6 +361,96 @@ def test_oneof_required(self, validator_class):
         result = validator.validate(instance)
         assert result is None
 
+    @pytest.mark.parametrize(
+        "mapping_ref",
+        [
+            "#/components/schemas/Missing",
+            "#missing-anchor",
+            "#bad/frag",
+        ],
+    )
+    def test_discriminator_handles_unresolvable_reference_kinds(
+        self, mapping_ref
+    ):
+        schema = {
+            "oneOf": [{"$ref": "#/components/schemas/MountainHiking"}],
+            "discriminator": {
+                "propertyName": "discipline",
+                "mapping": {"mountain_hiking": mapping_ref},
+            },
+            "components": {
+                "schemas": {
+                    "MountainHiking": {
+                        "type": "object",
+                        "properties": {
+                            "discipline": {"type": "string"},
+                            "length": {"type": "integer"},
+                        },
+                        "required": ["discipline", "length"],
+                    },
+                },
+            },
+        }
+
+        validator = OAS30Validator(
+            schema,
+            format_checker=oas30_format_checker,
+        )
+        with pytest.raises(
+            ValidationError,
+            match=f"reference '{mapping_ref}' could not be resolved",
+        ):
+            validator.validate(
+                {
+                    "discipline": "mountain_hiking",
+                    "length": 10,
+                }
+            )
+
+    @pytest.mark.parametrize(
+        "mapping_ref, expected_cause",
+        [
+            ("#/components/schemas/Missing", PointerToNowhere),
+            ("#missing-anchor", NoSuchAnchor),
+            ("#bad/frag", InvalidAnchor),
+        ],
+    )
+    def test_discriminator_unresolvable_reference_causes(
+        self, mapping_ref, expected_cause
+    ):
+        schema = {
+            "oneOf": [{"$ref": "#/components/schemas/MountainHiking"}],
+            "discriminator": {
+                "propertyName": "discipline",
+                "mapping": {"mountain_hiking": mapping_ref},
+            },
+            "components": {
+                "schemas": {
+                    "MountainHiking": {
+                        "type": "object",
+                        "properties": {
+                            "discipline": {"type": "string"},
+                            "length": {"type": "integer"},
+                        },
+                        "required": ["discipline", "length"],
+                    },
+                },
+            },
+        }
+
+        validator = OAS30Validator(
+            schema,
+            format_checker=oas30_format_checker,
+        )
+
+        with pytest.raises(WrappedReferencingError) as exc_info:
+            cast(Any, validator)._validate_reference(
+                ref=mapping_ref,
+                instance={"discipline": "mountain_hiking", "length": 10},
+            )
+
+        assert isinstance(exc_info.value.__cause__, expected_cause)
+
     @pytest.mark.parametrize(
         "schema_type",
         [