fix: Stack overflow on empty $ref value

Signed-off-by: Dmitry Dygalo <dmitry@dygalo.dev>

Author: Stranger6667

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Stack overflow on empty `$ref` value. [#886](https://github.com/Stranger6667/jsonschema/issues/886)
+
 ## [0.37.0] - 2025-11-19
 
 ### Added

crates/jsonschema-py/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Stack overflow on empty `$ref` value. [#886](https://github.com/Stranger6667/jsonschema/issues/886)
+
 ## [0.37.0] - 2025-11-19
 
 ### Added

crates/jsonschema/src/keywords/ref_.rs

@@ -21,8 +21,11 @@ fn compile_reference_validator<'a>(
  Err(error) => return Some(Err(error)),
  };
 
- if alias == current_location {
+ if alias == current_location
+ || (reference.is_empty() && alias.strip_fragment() == current_location.strip_fragment())
+ {
  // Direct self-reference would recurse indefinitely, treat it as an annotation-only schema.
+ // Empty string $ref ("") is a same-document reference per RFC 3986, equivalent to "#"
  return None;
  }
 
@@ -573,4 +576,15 @@ mod tests {
  "Resource './virtualNetwork.json' is not present in a registry and retrieving it failed: No base URI is available"
  );
  }
+
+ #[test]
+ fn test_empty_ref_no_stack_overflow() {
+ // Empty string is a same-document reference per RFC 3986, should behave like $ref: "#"
+ let schema = json!({"$ref": ""});
+ let instance = json!(-1);
+
+ // Should compile without error and validate without stack overflow
+ let validator = crate::validator_for(&schema).expect("Should compile");
+ assert!(validator.is_valid(&instance));
+ }
 }