feat: improve error printing#517
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Pull request overview
Updates cot-core::Error’s Debug formatting so that {:?} produces a human-friendly error message plus its source chain (similar to anyhow), while {:#?} retains the original structured debug output. This improves the default panic output from Result::unwrap() / expect() in cot::main.
Changes:
- Implement non-alternate
Debugformatting to print the error viaDisplayplus a “caused by” source chain. - Preserve the prior
Debugoutput behind alternate formatting ({:#?}).
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Bencher Report| Branch | improve-errors |
| Testbed | github-ubuntu-latest |
Click to view all benchmark results
| Benchmark | Latency | Benchmark Result microseconds (µs) (Result Δ%) | Upper Boundary microseconds (µs) (Limit %) |
|---|---|---|---|
| empty_router/empty_router | 📈 view plot 🚷 view threshold | 6,774.80 µs(+11.19%)Baseline: 6,093.20 µs | 7,677.76 µs (88.24%) |
| json_api/json_api | 📈 view plot 🚷 view threshold | 1,054.60 µs(-1.84%)Baseline: 1,074.37 µs | 1,323.65 µs (79.67%) |
| nested_routers/nested_routers | 📈 view plot 🚷 view threshold | 1,016.20 µs(+2.40%)Baseline: 992.35 µs | 1,204.08 µs (84.40%) |
| single_root_route/single_root_route | 📈 view plot 🚷 view threshold | 959.17 µs(+0.46%)Baseline: 954.82 µs | 1,167.50 µs (82.16%) |
| single_root_route_burst/single_root_route_burst | 📈 view plot 🚷 view threshold | 18,737.00 µs(+5.71%)Baseline: 17,724.56 µs | 21,190.21 µs (88.42%) |
seqre
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seqre
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Please make cargo insta test for this functionality
When using `Result::expect()`, (e.g. in the default `cot::main`) errors are printed using `Debug` printer. This causes very ugly errors to be produced. Instead, when the alternate mode is not being used, just format the error nicely, along with the error source chain. This roughly duplicates the `anyhow::Error` error printing logic: https://docs.rs/anyhow/latest/anyhow/struct.Error.html#method.chain
Comment on lines
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| let error = self.inner(); | ||
| Display::fmt(error, f)?; | ||
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| if let Some(source) = error.source() { |
seqre
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May 21, 2026
seqre
approved these changes
May 21, 2026
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When using
Result::expect(), (e.g. in the defaultcot::main) errors are printed usingDebugprinter. This causes very ugly errors to be produced. Instead, when the alternate mode is not being used, just format the error nicely, along with the error source chain.This roughly duplicates the
anyhow::Errorerror printing logic: https://docs.rs/anyhow/latest/anyhow/struct.Error.html#method.chainThe change turns this:
into this:
