Support for Python3.9 type hint syntax#2795
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- Rename the new python-version level to 3.10: PEP 604 unions (X | None)
require Python 3.10, not 3.9. Split the feature flag into
builtinGenerics (PEP 585, 3.9+) and unionOperators (PEP 604, 3.10+),
which also yields a 3.9 level with builtin generics but typing
Optional/Union. Make 3.10 the default python-version.
- Emit " = None" defaults outside the quoted annotation: the annotation
'Foo | None = None' is invalid syntax.
- Only quote PEP 604 unions when a member actually needs a forward
reference, and never quote inside an already-quoted annotation.
- Restore withTyping("Dict") registration in the dict converter so the
typing import is emitted for pre-3.9 versions, and revert typeObject's
map branch to the runtime type "dict".
- Cover the legacy typing.* code paths in QUICKTEST via
quickTestRendererOptions for 3.5/3.6/3.7/3.9.
- Run python fixtures under Python 3.12 in CI and the fixture driver.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
With dataclasses (3.7+), optional properties become nullable unions and get a " = None" default — except when the property type is Any (null is absorbed into it) or plain null (the union collapses), which got no default yet could sort after defaulted fields, making the generated dataclass raise "TypeError: non-default argument follows default argument" at import. This was latent on master because CI only ever exercised 3.5/3.6, which don't use dataclasses; with 3.10 as the new default it breaks e.g. vega-lite.schema and the combinations samples. Emit " = None" for root-level Any/None fields too, and make the property sort order compute exactly "will this field render with a default" via followTargetType — the old kind-based predicate saw pre-transformation types (transformed unions have kind "any" at sort time) and could order a non-defaulted field after defaulted ones. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Description
In python 3.9 and onwards, some generics are type hinted differently (Dict, List should be lowercase dict, list instead) as well as some syntax changes (Optional[Type] syntax replaced with Type | None syntax, along with Union[Type1, Type2] replaced with Type1 | Type2)
I added a new option to pythonOptions.features, a boolean "builtinGenerics". In python 3.9 it's enabled, and disabled for the previous versions. I use pretty simple logic to do it, just a couple of if statements and ternary operators to account for the new syntax.
Some ways quotes are handled around types was changed to support wrapping around unions. (see _suppressQuotes in PythonRenderer's
namedTypemethod)Motivation and Context
To keep up with newer Python syntax.
How Has This Been Tested?
Tested with python 3.7 and python 3.9 using the scripted tests that use mypy (confirms that the syntax is valid, and that with python 3.7, it's not trying to use any of the new syntax) along with looking at the outputs manually and confirming that 3.9 uses the newer syntax.