anyhow instead of error_chain #2721
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rbtcollins
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I have started to review this but I think there's something squiffy about the commit series because the delta github shows me includes things definitely already merged to master. Could you please rebase this and clean up the commit series to just be your changes? |
anyhow provides significantly better error tooling than error_chain, without the derivation support, thiserror fills that gap.
SyncError provides adaption to wrap around error_chain, both where we use it, and if any libraries rustup is using use it. Once introduced we can start incrementally migrating function and error at at time to anyhow without requiring a single big bang commit.
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There are some inconsistencies in use of downcast() vs downcast_ref() in a few places, and a few extra .clone()s which might be avoidable (though they're in test paths)
I've highlighted one or two things, but otherwise I'm up for merging this modulo you having a final pass for happiness and tweaking the few items I mention.
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downcast vs downcast_ref - depends on whether the error is being rethrown or consumed generally: I wouldn't call it inconsistent so much as having different contexts. Of course, spread over a year some inconsistency can always occur |
The main UI impact is that using the anyhow formatters removes some custom code at a slight UI change - rather than repeating the err! macro output around each item in the backtrace, we get it just once (see the comment in common.rs).
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If the light is green, the trap is clean! |
Drop error_chain which is no longer supported, evolving, causes code deprecation warnings, forces everything into one surfaced massive enum and generally is breaking our brains. Use anyhow! for most errors, and ThisError for errors used multiple times or for which we do need to match on.