fix: 🐛 sort and deduplicate issues before raising error

src/check_datapackage/check.py

@@ -89,11 +89,12 @@ class for more details, especially about the default values.
     issues = _check_object_against_json_schema(properties, schema)
     issues += apply_extensions(properties, config.extensions)
     issues = exclude(issues, config.exclusions, properties)
+    issues = sorted(set(issues))
 
     if error and issues:
         raise DataPackageError(issues)
 
-    return sorted(set(issues))
+    return issues
 
 
 def _set_should_fields_to_required(schema: dict[str, Any]) -> dict[str, Any]:

tests/test_check.py

@@ -10,7 +10,7 @@
     example_resource_properties,
 )
 from check_datapackage.exclusion import Exclusion
-from check_datapackage.extensions import Extensions
+from check_datapackage.extensions import Extensions, RequiredCheck
 from check_datapackage.internals import _map
 from tests.test_extensions import lowercase_check
 
@@ -636,3 +636,19 @@ def test_error_as_true():
 
     with raises(DataPackageError):
         check(properties, error=True)
+
+
+def test_error_true_no_duplicate_issues():
+    resources_required = RequiredCheck(
+        jsonpath="$.resources",
+        message="'resources' is a required property",
+    )
+
+    with raises(DataPackageError) as error:
+        check(
+            {},
+            error=True,
+            config=Config(extensions=Extensions(required_checks=[resources_required])),
+        )
+
+    assert str(error).count(resources_required.message) == 1