Preludes?

[killercup]

In general, it seems that the usage of glob imports (use foo::*;) is generally discouraged in Rust [1], while at the same time the std lib and some other crates offer "prelude" modules [2] that users are supposed to glob import for convenience.

Should there be a guideline describing when/whether a prelude is good to have?

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Sorry if this is not something that is considered "API" enough for the API guidelines.

Context: assert-rs/assert_cli#75 (comment) made me look up what the API guidelines say, and I couldn't find anything on the topic.

[emk]

There are definitely some APIs—especially for things like testing libraries or diesel—where I'm going to have to import the same 6 symbols every time I use the library. Usually this is a mix of traits and a few essential functions or types.

Personally, I'm rather fond of glob imports for cases like these, because otherwise I have to spend a lot more time digging around in the docs and figuring out errors just to get things done. Yes, I understand that in some sense it's not "ideal", because a new export might someday be added to the glob and conflict with some other import. But that's absolutely a risk I'm willing to pay in the name of convenience for certain carefully-chosen APIs.

I do have a rule of "no glob imports for things which aren't preludes", though. That seems pretty sensible.