82 lines
3.4 KiB
Markdown
82 lines
3.4 KiB
Markdown
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# [slog](https://pkg.go.dev/log/slog) shim
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[](https://github.com/sagikazarmark/slog-shim/actions/workflows/ci.yaml)
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[](https://pkg.go.dev/mod/github.com/sagikazarmark/slog-shim)
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[](https://builtwithnix.org)
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Go 1.21 introduced a [new structured logging package](https://golang.org/doc/go1.21#slog), `log/slog`, to the standard library.
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Although it's been eagerly anticipated by many, widespread adoption isn't expected to occur immediately,
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especially since updating to Go 1.21 is a decision that most libraries won't make overnight.
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Before this package was added to the standard library, there was an _experimental_ version available at [golang.org/x/exp/slog](https://pkg.go.dev/golang.org/x/exp/slog).
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While it's generally advised against using experimental packages in production,
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this one served as a sort of backport package for the last few years,
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incorporating new features before they were added to the standard library (like `slices`, `maps` or `errors`).
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This package serves as a bridge, helping libraries integrate slog in a backward-compatible way without having to immediately update their Go version requirement to 1.21. On Go 1.21 (and above), it acts as a drop-in replacement for `log/slog`, while below 1.21 it falls back to `golang.org/x/exp/slog`.
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**How does it achieve backwards compatibility?**
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Although there's no consensus on whether dropping support for older Go versions is considered backward compatible, a majority seems to believe it is.
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(I don't have scientific proof for this, but it's based on conversations with various individuals across different channels.)
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This package adheres to that interpretation of backward compatibility. On Go 1.21, the shim uses type aliases to offer the same API as `slog/log`.
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Once a library upgrades its version requirement to Go 1.21, it should be able to discard this shim and use `log/slog` directly.
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For older Go versions, the library might become unstable after removing the shim.
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However, since those older versions are no longer supported, the promise of backward compatibility remains intact.
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## Installation
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```shell
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go get github.com/sagikazarmark/slog-shim
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```
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## Usage
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Import this package into your library and use it in your public API:
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```go
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package mylib
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import slog "github.com/sagikazarmark/slog-shim"
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func New(logger *slog.Logger) MyLib {
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// ...
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}
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```
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When using the library, clients can either use `log/slog` (when on Go 1.21) or `golang.org/x/exp/slog` (below Go 1.21):
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```go
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package main
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import "log/slog"
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// OR
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import "golang.org/x/exp/slog"
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mylib.New(slog.Default())
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```
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**Make sure consumers are aware that your API behaves differently on different Go versions.**
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Once you bump your Go version requirement to Go 1.21, you can drop the shim entirely from your code:
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```diff
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package mylib
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- import slog "github.com/sagikazarmark/slog-shim"
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+ import "log/slog"
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func New(logger *slog.Logger) MyLib {
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// ...
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}
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```
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## License
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The project is licensed under a [BSD-style license](LICENSE).
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