Restore compatibility with Python >= 3.8

v5.7.4

[release] bum up version number for development

Fixes to walkers

• Fix walker cache logic in NodeWalker (@by-Exist)

Bug fixes, improvements, optimizations

• Fix pickling of AST. The change also affects parsing within multiprocessing (@fizbin)
• Fall back to repr() for types not handled by json(@dnicolodi)
• Ensure there is exactly one method cache per Walker class
• Bug fixes, upgrades, and improvements by (@dnicolodi)

Resolve feature backlog

• Make sure that the generated parser is the same as the bootstrap
  parser.
• Honor grouping in pattern expressions with the semantics of
  re.findall(pattern, text)[0]. Now groups that should not be
  returned when parsing should use the (?:) syntax. Now patterns
  align with Python re independently of the
  @@ignorecase setting for the grammar.
• Allow {} interpolation in `constant[ expressions with the
  semantics of ]{.title-ref}[str.format()]{.title-ref}`
• Add [constant]{.title-ref} as a multiline version of
  `constant`.
• Add ^[constant]{.title-ref} and ^`constant[ as syntax
  for an `alert]{.title-ref} expression. Alerts produce no tokens bug
  get registed in [parseinfo]{.title-ref} records.
• BUG: make the -> skip expression always stop at EOF.
• Make the -> skip expression go over comments, and not log while
  skipping.
• Patch problem with pickling FailedCut while running parsing in
  parallel.
• Optimize model pickling and parallel processing to reduce runtime
  and memory use with parproc
• Add a representation of ~ cut expressions to parse traces

bugfix release

• Fix that settings passed to Context.parse() were ignored. Add Context.active_config for the configuration active during a parse
• Define Node._parent as part of the @dataclass

fix regressions

• Make AST and Node hashable. Necessary for caching Node.children()
• Implement Node.__eq__() in terms of identity or Node.ast.__eq__()__
• Fix regression in which rule order is lost in generated parsers (@dtrckd)
• Restore Node.ast (was removed because of problems with __eq__())
• Get Node.children() from Node.ast when there are no attributes defined for the Node. This restores the desired behavior while developing a parse model.

Reloaded

• Now config: ParserConfig is used in __init__() and parse() methods of contexts.ParseContext, grammars.Grammar, and elsewhere to avoid the very long parameter lists that abounded. ParseContext also provides clean and clear ways of overridinga group of settings with another
• All names defined in the successful choice in a rule are now defined in the resulting AST_. Names within optionals that did not match will have their values set to None, and closures that did not match will be set to ``[]`
• Moved build configuration from setup.py in favor of setup.cfg and pyproject.toml (@KOLANICH_)
• Node.children() is now computed only when required, and cached
• Classes in generated object models are now @dataclass
• Optimize and get rid of bugs and annoyances while keeping backwards compatibility
• Drop support for Python < 3.10

Bug fix release

• Fix bug in which rule fields were forced on empty AST (@Victorious3)

Long awaited update

• Several important refactorings in contexts.ParseContext
• Make ignorecase settings apply to defined @@keywords
• Move checking of keywords used as names into ParseContext
• Output of generated parsers again matches that of model parsers
• Improve "expecting one of:" messages so elements are in declaration order
• Stop code generation if there are closures over possibly empty expressions
• Preserve name declaration order in returned AST
• Update the bootstrap parser (tatsu/bootstrap.py) to the generated parser
• Now generated parser's main() only outputs the JSON for the parse AST
• Minor version bumped in case the many fixes break backwards-compatibility
• Minor documentation issues fixed
• All tests run with Python 3.8, 3.9, 3.10

Maintenance release

• #156 Clarify limitations of left-recursion in PEG (@apalala).
• #159 Clean up examples and tutorial, upgrade them to Python 3 (@okomarov).
• Test with Python 3.9 (@apalala)
• Update CircleCI build (@apalala)