[Scons-dev] Why are Builders excluded from env.Clone()?

[Dirk Bächle]

Hi Jonathon,

On 09.12.2016 18:03, Jonathon Reinhart wrote:
>
> [...]
>
> This behavior does appear to be intentional, however:
>
>     builders = self._dict.get('BUILDERS', {})
>
>     clone = copy.copy(self)
>     # BUILDERS is not safe to do a simple copy
>     clone._dict = semi_deepcopy_dict(self._dict, ['BUILDERS'])
>     clone._dict['BUILDERS'] = BuilderDict(builders, clone)
>

please check issue #2821 (http://scons.tigris.org/issues/show_bug.cgi?id=2821) where the latest changes have been made in this area.

> BUILDERS is explicitly excluded in the semi_deepcopy_dict() call.
>
> My questions:
>  - Why are Builders explicitly excluded from the env.Clone()?

Because it's possible that during the deep-copy, the original is altered too (see comment in BuilderDict::__semi_deepcopy__).

>  - Would it be reasonable to add an optional argument to Clone()
>    (e.g. really_deep) which causes Builders to not be excluded?
>

As the bug description reveals, no real cure has been found yet. If you have a solution that successfully deep-copies the BUILDERs 
dict, and is guaranteed to leave the original environment intact...we'd definitely be happy to hear about it.

Best regards,

Dirk