[dataclass_transform] support implicit default for "init" parameter in field specifiers #15010
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…n field specifiers
…py into wesleywright-field-specifier-defaults
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jhance
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…n field specifiers (#15010) (Basic functionality was implemented by @wesleywright in #14870. I added overload resolution.) This note from PEP 681 was missed in the initial implementation of field specifiers: > If unspecified, init defaults to True. Field specifier functions can use overloads that implicitly specify the value of init using a literal bool value type (Literal[False] or Literal[True]). This commit adds support for reading a default from the declared type of the `init` parameter if possible. Otherwise, it continues to use the typical default of `True`. The implementation was non-trivial, since regular overload resolution can't be used in the dataclass plugin, which is applied before type checking. As a workaround, I added a simple overload resolution helper that should be enough to support typical use cases. It doesn't do full overload resolution using types, but it knows about `None`, `Literal[True]` and `Literal[False]` and a few other things. --------- Co-authored-by: Wesley Collin Wright <wesleyw@dropbox.com>
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(Basic functionality was implemented by @wesleywright in #14870. I added overload resolution.)
This note from PEP 681 was missed in the initial implementation of field specifiers:
This commit adds support for reading a default from the declared type of the
initparameter if possible. Otherwise, it continues to use the typical default ofTrue.The implementation was non-trivial, since regular overload resolution can't be used in the dataclass plugin, which is applied before type checking. As a workaround, I added a simple overload resolution helper that should be enough to support typical use cases. It doesn't do full overload resolution using types, but it knows about
None,Literal[True]andLiteral[False]and a few other things.