Generically compute dynamic defaults for Fields (Cherry-pick of #16206)
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As discussed on pantsbuild#16175, we don't currently consume the "dynamic" defaults of field values for the purposes of `parametrize`. That is at least partially because there is no generic way to do so: a `Field` has no way to declare a dynamic default currently, because `Field`s cannot declare a dependency `@rule_helper` to compute their value (...yet? see pantsbuild#12934 (comment)). This change adds a mechanism for generically declaring the default value of a `Field`. This is definitely not the most ergonomic API: over the next few versions, many dynamic `Field` defaults will hopefully move to `__defaults__`. And pantsbuild#12934 (comment) will hopefully allow for significantly cleaning up those that remain. Fixes pantsbuild#16175. [ci skip-rust] [ci skip-build-wheels]
Eric-Arellano
approved these changes
Jul 19, 2022
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As discussed on #16175, we don't currently consume the "dynamic" defaults of field values for the purposes of
parametrize. That is at least partially because there is no generic way to do so: aFieldhas no way to declare a dynamic default currently, becauseFields cannot declare a dependency@rule_helperto compute their value (...yet? see #12934 (comment)).This change adds a mechanism for generically declaring the default value of a
Field. This is definitely not the most ergonomic API: over the next few versions, many dynamicFielddefaults will hopefully move to__defaults__. And #12934 (comment) will hopefully allow for significantly cleaning up those that remain.Fixes #16175.