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89 lines
3.4 KiB
Markdown
89 lines
3.4 KiB
Markdown
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merry [](https://github.com/ansel1/merry/actions?query=branch%3Amaster+workflow%3ABuild+) [](https://godoc.org/github.com/ansel1/merry/v2) [](https://goreportcard.com/report/github.com/ansel1/merry/v2)
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=====
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Add context to errors, including automatic stack capture, cause chains, HTTP status code, user
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messages, and arbitrary values.
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The package is largely based on http://github.com/go-errors/errors, with additional
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inspiration from https://github.com/go-errgo/errgo and https://github.com/amattn/deeperror.
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Installation
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------------
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go get github.com/ansel1/merry/v2
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Features
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--------
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Wrapped errors work a lot like google's golang.org/x/net/context package:
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each wrapper error contains the inner error, a key, and a value.
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Like contexts, errors are immutable: adding a key/value to an error
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always creates a new error which wraps the original.
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This package comes with built-in support for adding information to errors:
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* stacktraces
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* changing the error message
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* HTTP status codes
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* End user error messages
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* causes
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You can also add your own additional information.
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The stack capturing feature can be turned off for better performance, though it's pretty fast. Benchmarks
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on an 2017 MacBook Pro, with go 1.10:
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BenchmarkNew_withStackCapture-8 2000000 749 ns/op
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BenchmarkNew_withoutStackCapture-8 20000000 64.1 ns/op
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Merry errors are fully compatible with errors.Is, As, and Unwrap.
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Example
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-------
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To add a stacktrace, a user message, and an HTTP code to an error:
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err = merry.Wrap(err, WithUserMessagef("Username %s not found.", username), WithHTTPCode(404))
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To fetch context information from error:
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userMsg := UserMessage(err)
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statusCode := HTTPCode(err)
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stacktrace := Stacktrace(err)
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To print full details of the error:
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log.Printf("%v+", err) // or log.Println(merry.Details(err))
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v1 -> v2
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--------
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v1 used a fluent API style which proved awkward in some cases. In general, fluent APIs
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don't work that well in go, because they interfere with how interfaces are typically used to
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compose with other packages. v2 uses a functional options API style which more easily
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allows other packages to augment this one.
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This also fixed bad smell with v1's APIs: they mostly returned a big, ugly `merry.Error` interface,
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instead of plain `error` instances. v2 has a smaller, simpler API, which exclusively uses plain
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errors.
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v2 also implements a simpler and more robust integration with errors.Is/As/Unwrap. v2's functions will
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work with error wrapper chains even if those chains contain errors not created with this package, so
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long as those errors conform to the Unwrap() convention.
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v2 allows more granular control over stacktraces: stack capture can be turned on or off on individual errors,
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overriding the global setting. External stacktraces can be used as well.
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v1 has been reimplemented in terms of v2, and the versions are completely compatible, and can be mixed.
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Plugs
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-----
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- Check out my HTTP client library: [github.com/gemalto/requester](https://github.com/gemalto/requester)
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- Check out my log library: [github.com/gemalto/flume](https://github.com/gemalto/flume)
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License
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-------
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This package is licensed under the MIT license, see LICENSE.MIT for details.
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