Implement Lift for flat errors
#1847
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mhammond
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Nov 14, 2023
| type FfiType = ::uniffi::RustBuffer; | ||
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| fn try_read(buf: &mut &[::std::primitive::u8]) -> ::uniffi::deps::anyhow::Result<Self> { | ||
| panic!("Can't lift flat errors") |
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is it worth opening an issue around getting these errors at buildtime instead of a runtime panic?
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Good point, I made #1850 for this.
Maybe we could test it from Rust, but I'd be worried about trying to exercise the panic through the foreign code. Lowering a flat error from the foreign side is not allowed and implementations can choose to not implement it, segfault, or anything else. I believe all of our implementations fail in a predictable way that could be tested, but I'd be worried that adding the test could break an external bindings generator. |
We noticed a regression in `0.25.x` where dictionaries containing flat errors caused code not to be compiled. We never officially supported compound types that stored errors, but it seems better to allow the code to compile in this case. The reason this isn't supported is that we can't lift flat errors, so therefore we can't lift the dictionary. A better fix for this would be to not implement `Lift` on the dictionary in this case, which would cause a compile error rather than a runtime panic. However, that's actually not so simple as noted in the comment so I went for an easier way. This brings this very close to how they worked in `0.24.x` where we would generate an `FfiConverter` implementation for flat errors, but the lift half of it would just be panics.
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We noticed a regression in
0.25.xwhere dictionaries containing flat errors caused code not to be compiled. We never officially supported compound types that stored errors, but it seems better to allow the code to compile in this case.The reason this isn't supported is that we can't lift flat errors, so therefore we can't lift the dictionary. A better fix for this would be to not implement
Lifton the dictionary in this case, which would cause a compile error rather than a runtime panic. However, that's actually not so simple as noted in the comment so I went for an easier way.This brings this very close to how they worked in
0.24.xwhere we would generate anFfiConverterimplementation for flat errors, but the lift half of it would just be panics.