Support ErrorRef in # error formatter
#328
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This is brilliant!! I'm not the greatest with traditional macros, so I'm not 100% sure about compatibility either. I will rebase this to be compatible with the last PR. |
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The weird borrowing magic is part of the point (PR slog-rs#328)
This commit adds support for error references for the `#` error formatter from the `kv` macro. If the passed error is an owned error value it uses `ErrorValue`; otherwise if it can be dereferenced into an error then it uses `ErrorRef`. The way to detect if the value implements `Error` directly or if it's an error reference is based on auto-deref coercion as described in the following articles: - <https://lukaskalbertodt.github.io/2019/12/05/generalized-autoref-based-specialization.html> - <https://github.com/dtolnay/case-studies/tree/master/autoref-specialization> I believe it to be fully backwards compatible with existing uses of `#`. This provides a short-hand for the `ErrorRef` wrapper in most common cases. However, it does not support temporary lifetime extension. This means that the following example needs to introduce a temporary binding to use the shorthand syntax: ```rust // explicit ref with lifetime extension info!(logger, "not found"; "error" => ErrorRef(&std::io::Error::from(std::io::ErrorKind::NotFound))); // `#` shorthand with temporary binding let error = std::io::Error::from(std::io::ErrorKind::NotFound); info!(logger, "not found"; "error" => #&error); ``` In practice, this use case is not an issue. Such a temporary can instead be passed by value (the reference is useless) through `ErrorValue`. There are [discussions in Zulip](https://rust-lang.zulipchat.com/#narrow/stream/403629-t-lang.2Ftemporary-lifetimes-2024) to support explicit lifetime extensions and support this use case in the future.
Avoids duplicating multiple times across multiple macros. Explicitly suppress unused_import warning (needed with clippy deny warnings)
Clippy gives a warning here
The weird borrowing magic is part of the point (PR slog-rs#328)
Requires `impl Error for Arc<T>`, which only exists on recent versions. Uses rustversion to conditionally disable.
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The weird borrowing magic is part of the point (PR #328)
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This commit adds support for error references for the
#error formatter from thekvmacro. If the passed error is an owned error value it usesErrorValue; otherwise if it can be dereferenced into an error then it usesErrorRef.The way to detect if the value implements
Errordirectly or if it's an error reference is based on auto-deref coercion as described in the following articles:I believe it to be fully backwards compatible with existing uses of
#. This provides a short-hand for theErrorRefwrapper in most common cases. However, it does not support temporary lifetime extension.This means that the following example needs to introduce a temporary binding to use the shorthand syntax:
In practice, this use case is not an issue. Such a temporary can instead be passed by value (the reference is useless) through
ErrorValue. There are discussions in Zulip to support explicit lifetime extensions and support this use case in the future.Make sure to:
This is a follow up to #327 to add support for the macro shorthand
#. I sent it in its own PR as the logic is more complex and I don't want to block the simple error reference wrapper because of the macro logic. Commit with macro support