Change Log

This document contains notes on the major changes for each version of the Rule Engine. In comparison to the git log, this list is curated by the development team for note worthy changes.

Version 5.x.x

Version 5.0.0

Released v5.0.0 on May 17th, 2026

• Breaking: Dropped support for Python versions 3.6, 3.7, 3.8 and 3.9.

• Breaking: Changed the precedence of operators to be more aligned with common programming languages.

• Breaking: The Debug REPL utility now requires development dependencies to be installed.

• Breaking: BYTES literals now throw exceptions for invalid escape sequences

• Breaking: Removed setup.py; project metadata now lives entirely in pyproject.toml (PEP 517/621).

• Breaking: The rule_engine.ast module no longer re-exports names from rule_engine.types (e.g. DataType, coerce_value); import them from rule_engine or rule_engine.types directly.

• Migrated the development workflow and CI from pipenv to uv.

• Added support for raw STRING literals using the r prefix (e.g. r'\w+').

• Vendored the PLY dependency under rule_engine._vendor.ply — the upstream project is unmaintained, so the copy removes an external install requirement and silences third-party vulnerability reports targeting it.

• Added the new OBJECT compound data type for user-defined schemas with named, typed attributes. See the OBJECT section in the Data Types page for details.

  • Use reference() (or the self shorthand sentinel) for self-referential and mutually-recursive schemas.

  • Attribute access is validated at parse time against the declared schema.

  • Item access (obj["name"]) and containment checks ("name" in obj) on OBJECT values are rejected at parse time.

  • SET(OBJECT(...)) is rejected at construction; use ARRAY(OBJECT(...)) instead

  • A custom accessor callable can be specified per OBJECT type (default: getattr()).

  • Added from_dataclass() and type_resolver_from_dataclass() for deriving OBJECT schemas and type_resolvers automatically from Python dataclass() definitions, including nullability for Optional fields and self / mutually-recursive references (closes #55).

  • Added from_sqlalchemy() and type_resolver_from_sqlalchemy() for deriving OBJECT schemas and type_resolvers from SQLAlchemy ORM mapped classes. Columns, relationships, and cycles between mutually-related classes are all expanded automatically. SQLAlchemy is an optional dependency; the import is deferred until these entry points are called.

  • The from_dataclass and from_sqlalchemy entry points (and their type_resolver_from_* companions) accept a strict keyword argument. The default strict=True raises ValueError on any field / column whose type cannot be mapped to a Rule Engine data type; strict=False falls back to UNDEFINED.

• Added ObjectAttributeError, a subclass of AttributeResolutionError, raised when an attribute is not found in an OBJECT schema

• Promoted nullability to a first-class type-system construct via the new NULLABLE one-argument type constructor. See the NULLABLE section in the Data Types page for the full semantics.

  • from_type() maps Python’s Optional[T] / T | None to NULLABLE(from_type(T)).

  • from_dataclass() and from_sqlalchemy() wrap nullable fields, columns, and scalar relationships in NULLABLE(T); type_resolver_from_dataclass() and type_resolver_from_sqlalchemy() preserve the wrappers through to the top-level symbol types.

  • Compound element and value types (ARRAY, SET, MAPPING) store NULLABLE(T) directly when the member may be None.

  • AST operators reject NULLABLE operands at parse time wherever None has no meaningful semantics: arithmetic, ordered comparisons, the regex operators, bitwise and bitwise-shift operators, unary minus, containment, attribute access, item access, slicing, and function arguments all raise EvaluationError (or FunctionCallError for function arguments) with a message pointing at the discharge operators. Equality (==, !=), logical connectives (and, or, not), ternary expressions, and safe-navigation operators remain lenient.

  • A new null-coalesce operator left ?? right discharges NULLABLE(T) to T. Existing safe attribute (&.) and item (&[) accessors still apply to nullable receivers and are the only access forms that do.

• Deprecated: The attributes_nullable kwarg on OBJECT and the value_type_nullable kwarg on ARRAY, SET, and MAPPING now emit DeprecationWarning. Wrap the relevant attribute or element type in NULLABLE instead. The kwargs will be removed in v6.0.

• Deprecated: Accessing MAPPING keys via dot syntax (mapping.key) now emits a MappingAttributeLookupDeprecation warning. Use bracket syntax (mapping["key"]) instead. This fallback will be removed in v6.0. Set Context(mapping_attribute_lookup=False) to opt out now.

Version 4.x.x

Version 4.5.0

Released v4.5.0 on June 19th, 2024

• StringSyntaxError is now raised for invalid string literals

• FunctionCallError is now raised when a typed function returns an incompatible value

• Added the new BYTES data type

• Added some new data attributes

  • Added starts_with and ends_with to ARRAY, and STRING

Version 4.4.0

Released v4.4.0 on April 5th, 2024

• Added the $range builtin function

• Added the rule_engine.parser.utilities module with a few functions and documentation

Version 4.3.0

Released v4.3.0 on January 15th, 2024

• Added the is_nan attribute for FLOAT values

Version 4.2.0

Released v4.2.0 on December 11th, 2023

• Added attributes for coercion of types to themselves, e.g. to_str for STRING values

Version 4.1.0

Released v4.1.0 on August 3rd, 2023

• Added the $abs builtin function

• Added support to from_type to handle Python’s type hints

Version 4.0.0

Released v4.0.0 on July 15th, 2023

• Breaking: Changed STRING.to_ary to return an array of characters instead of splitting the string

  • Use the new builtin $split function to split a string on whitespace into an array of words

• Breaking: Changed Context to use keyword-only arguments

• Breaking: Dropped support for Python versions 3.4 and 3.5

• Breaking: Invalid floating point literals now raise FloatSyntaxError instead of RuleSyntaxError

• Breaking: Moved rule_engine.engine.Builtins to rule_engine.builtins.Builtins

• Added the new FUNCTION data type

Version 3.x.x

Version 3.6.0

Released v3.6.0 on June 16th, 2023

• Removed testing for Python versions 3.4 and 3.5 on GitHub Actions

• Add regex error details to the Debug REPL utility

• Add support for Python-style comments

Version 3.5.0

Released v3.5.0 on July 16th, 2022

• Added the new TIMEDELTA data type

Version 3.4.0

Released v3.4.0 on March 19th, 2022

• Add support for string concatenation via the + operator

Version 3.3.0

Released v3.3.0 on July 20th, 2021

• Added to_epoch to DATETIME

Version 3.2.0

Released v3.2.0 on April 3rd, 2021

• Refactored the ast module to move the DataType class into a new, dedicated types module.

• Added the new ComprehensionExpression

• Added suggestions to AttributeResolutionError and SymbolResolutionError

Version 3.1.0

Released v3.1.0 on March 15th, 2021

• Added the new SET data type

Version 3.0.0

Released v3.0.0 on March 1st, 2021

• Switched the FLOAT datatype to use Python’s Decimal from float internally

• Reserved the if, elif, else, for and while keywords for future use, they can no longer be used as symbol names

• Added some new data attributes

  • Added ceiling, floor and to_str to FLOAT

Version 2.x.x

Version 2.4.0

Released v2.4.0 on November 7th, 2020

• Added the Debug REPL utility

• Added the safe navigation version of the attribute, item and slice operators

• Added the new MAPPING data type

• Switched from Travis-CI to GitHub Actions for continuous integration

• Added support for iterables to have multiple member types

Version 2.3.0

Released v2.3.0 on October 11th, 2020

• Added support for arithmetic comparisons for all currently supported data types

• Added support for proper type hinting of builtin symbols

• Added the $re_groups builtin symbol for extracting groups from a regular expression match

• Added some new data attributes

  • Added to_ary to STRING

  • Added to_int and to_flt to STRING

Version 2.2.0

Released v2.2.0 on September 9th, 2020

• Added script entries to the Pipfile for development

• Added support for slices on sequence data types

Version 2.1.0

Released v2.1.0 on August 3rd, 2020

• Added coverage reporting to Travis-CI

• Changed DataType. from an enum to a custom class

• Improvements for the ARRAY data type

  • Added get[item] support for arrays, allowing items to be retrieved by index

  • Added ability for specifying the member type and optionally null

Version 2.0.0

Released v2.0.0 on October 2nd, 2019

• Added proper support for attributes

• Added a change log

• Added additional information to the Graphviz output

• Added the new ARRAY data type

• Started using Travis-CI

  • Added automatic unit testing using Travis-CI

  • Added automatic deployment of documentation using Travis-CI

• Removed the resolver conversion functions

  • Removed to_recursive_resolver in favor of attributes

  • Removed to_default_resolver in favor of the default_value kwarg to __init__()

Version 1.x.x

Version 1.1.0

Released v1.1.0 on March 27th, 2019

• Added the to_default_dict() function

• Added the to_recursive_resolver() function

Version 1.0.0

Released v1.0.0 on December 15th, 2018

• First major release