Allow reusing anchors in YAML

src/check_jsonschema/loaders/instance/yaml.py

@@ -1,8 +1,12 @@
 import typing as t
+import warnings
 
 import ruamel.yaml
+from ruamel.yaml.error import ReusedAnchorWarning
 
-_yaml = ruamel.yaml.YAML(typ="safe")
+warnings.simplefilter("ignore", ReusedAnchorWarning)
+
+_yaml = ruamel.yaml.YAML(typ="safe", pure=True)
 
 # ruamel.yaml parses timestamp values into datetime.datetime values which differs from
 # JSON which parses timestamps as strings. Turn off this feature.

src/check_jsonschema/loaders/schema/readers.py

@@ -2,16 +2,20 @@
 
 import json
 import typing as t
+import warnings
 
 import identify
 import ruamel.yaml
+from ruamel.yaml.error import ReusedAnchorWarning
 
 from check_jsonschema import utils
 
 from ...cachedownloader import CacheDownloader
 from ..errors import SchemaParseError
 
-yaml = ruamel.yaml.YAML(typ="safe")
+warnings.simplefilter("ignore", ReusedAnchorWarning)
+
+yaml = ruamel.yaml.YAML(typ="safe", pure=True)
 
 
 def _json_load_schema(schema_location: str, fp: t.IO) -> dict:

tests/unit/test_loaders.py

@@ -2,6 +2,7 @@
 import pathlib
 
 import pytest
+import ruamel.yaml.composer
 
 from check_jsonschema.loaders import BadFileTypeError, InstanceLoader, SchemaLoader
 from check_jsonschema.loaders.instance.json5 import ENABLED as JSON5_ENABLED
@@ -80,6 +81,38 @@ def test_schemaloader_local_yaml_data(tmp_path, filename):
     }
 
 
+@pytest.mark.parametrize(
+    "filename",
+    [
+        "schema.yaml",
+    ],
+)
+@pytest.mark.filterwarnings("ignore:ReusedAnchorWarning")
+def test_schemaloader_local_yaml_dup_anchor(tmp_path, filename):
+    f = tmp_path / filename
+    f.write_text(
+        """
+---
+"$schema": https://json-schema.org/draft/2020-12/schema
+type: object
+properties:
+  a:
+    type: object
+    properties:
+      b: &anchor
+        type: array
+        items:
+          type: integer
+      c: &anchor
+        type: string
+"""
+    )
+    try:
+        SchemaLoader(str(f))
+    except ruamel.yaml.composer.ComposerError as e:
+        raise AssertionError(f"YAML loader does not support duplicate anchors {e}")
+
+
 @pytest.mark.parametrize(
     "schemafile",
     [
@@ -141,6 +174,31 @@ def test_instanceloader_yaml_data(tmp_path, filename, default_ft):
     assert data == [(str(f), {"a": {"b": [1, 2], "c": "d"}})]
 
 
+@pytest.mark.parametrize(
+    "filename",
+    [
+        "foo.yaml",
+    ],
+)
+@pytest.mark.filterwarnings("ignore:ReusedAnchorWarning")
+def test_instanceloader_yaml_dup_anchor(tmp_path, filename):
+    f = tmp_path / filename
+    f.write_text(
+        """\
+a:
+  b: &anchor
+   - 1
+   - 2
+  c: &anchor d
+"""
+    )
+    loader = InstanceLoader([str(f)])
+    try:
+        list(loader.iter_files())
+    except ruamel.yaml.composer.ComposerError as e:
+        raise AssertionError(f"YAML loader does not support duplicate anchors {e}")
+
+
 def test_instanceloader_unknown_type(tmp_path):
     f = tmp_path / "foo"  # no extension here
     f.write_text("{}")  # json data (could be detected as either)