serde: serialize dyn Error Values using collect_str#89
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lgtm. As for the CI (codegen) failure, I implemented a way to automatically fix that (rust-lang/futures-rs#2562), but forgot to port it to this repository. I will open a PR later. |
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@taiki-e great, happy to rebase this once CI is sorted out! |
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Currently, `valuable-serde` handles `Value::Error` variants incorrectly. When `valuable-serde` encounters a `Value::Error`, it returns the error immediately as a serialization error: https://github.com/tokio-rs/valuable/blob/1fc2ad50fcae7fc0da81dc40a385c235636ba525/valuable-serde/src/lib.rs#L267 This is _not_ correct. If a `serde` serializer returns an error, this means something has gone wrong while serializing a value. Returning an error makes the serialization fail. However, this is *not* what `valuable`'s `Value::Error` means. `Value::Error` represents that we are _recording a value which happens to be an `Error`_, not that something went wrong _while_ recording the value. This means that `valuable-serde` will currently return an `Error` (indicating that serialization failed) any time it attempts to record an `Error` value, and serialization will fail. This commit changes `valuable-serde` to record the error using its `Display` implementation, using `serde`'s `collect_str` method. Now, `Error`s will be serialized by recording their messages as a string, rather than causing the serialization to fail. Using `collect_str` allows the serializer to write the display representation to its own internal buffer, rather than having to format the error to a temporary `String` beforehand. Fixes #88
taiki-e
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Mar 8, 2022
hawkw
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Mar 8, 2022
Depends on #89 This PR changes `valuable-serde`'s recording of `dyn Error` values to record the error as a `serde` struct with `message` and `source` fields. This way, we can serialize errors with source chains more nicely. When the backtrace support for `std::error::Error` is stable, we could also record backtraces as a field. We could even consider adding a build script to detect the nightly compiler and conditionally enable a `cfg` for backtrace support, but that seems better left to a follow-up.
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Currently,
valuable-serdehandlesValue::Errorvariants incorrectly.When
valuable-serdeencounters aValue::Error, it returns the errorimmediately as a serialization error:
valuable/valuable-serde/src/lib.rs
Line 267 in 1fc2ad5
This is not correct. If a
serdeserializer returns an error, thismeans something has gone wrong while serializing a value. Returning an
error makes the serialization fail. However, this is not what
valuable'sValue::Errormeans.Value::Errorrepresents that we arerecording a value which happens to be an
Error, not that somethingwent wrong while recording the value. This means that
valuable-serdewill currently return an
Error(indicating that serialization failed)any time it attempts to record an
Errorvalue, and serialization willfail.
This commit changes
valuable-serdeto record the error using itsDisplayimplementation, usingserde'scollect_strmethod. Now,Errors will be serialized by recording their messages as a string,rather than causing the serialization to fail.
Using
collect_strallows the serializer to write the displayrepresentation to its own internal buffer, rather than having to format
the error to a temporary
Stringbeforehand.Fixes #88