How to deal with multiple versions of time when using macros

[paolobarbolini]

In launchbadge/sqlx#1455 I'm trying to upgrade sqlx to time 0.3, but it was decided to keep support for time 0.2. Time 0.3 is imported as time_03 and time 0.2 is imported as time_02.

Macros though seem to expect time not to have been renamed

time/time-macros/src/datetime.rs

Line 47 in d700977

const DATE_TIME: ::time::#(type_name) = ::time::PrimitiveDateTime::new(

How can we fix this?

[jhpratt]

Yeah, this isn't currently possible. There is no equivalent of $crate for proc macros, and this would need the name for a different crate.

[paolobarbolini]

What do you think if macros had a flag that simplify removed the :: at the beginning of time imports? That way at the beginning of the file I could simply write use time_03 as time; and it would work. It would basically be an opt-in to the behavior currently present in all tokio macros:

If you rename the Tokio crate in your dependencies this macro will not work. If you must rename the current version of Tokio because you’re also using an older version of Tokio, you must make the current version of Tokio available as tokio in the module where this macro is expanded.

https://docs.rs/tokio/1.12.0/tokio/attr.main.html#note

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Another option could be to be able to have the option to specify under what name the macro can find time.

[jhpratt]

While that may work for something like tokio, "time" is something that could reasonably appear as a module name locally, which would naturally cause ambiguities. As to accepting something that could specify where time is found after renaming, yes, it's possible, but I've no idea what such syntax would be. It would necessarily have to be passed at every call site, mind you.