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98 lines
4.3 KiB
Go
98 lines
4.3 KiB
Go
// Package merry adds 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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//
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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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//
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// This package comes with built-in support for adding information to errors:
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//
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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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//
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// You can also add your own additional information.
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//
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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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//
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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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//
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// Usage
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//
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// This package contains functions for creating errors, or wrapping existing errors. To create:
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//
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// err := New("boom!")
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// err := Errorf("error fetching %s", filename)
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//
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// Additional context information can be attached to errors using functional options, called Wrappers:
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//
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// err := New("record not found", WithHTTPCode(404))
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//
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// Errorf() also accepts wrappers, mixed in with the format args:
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//
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// err := Errorf("user %s not found", username, WithHTTPCode(404))
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//
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// Wrappers can be applied to existing errors with Wrap():
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//
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// err = Wrap(err, WithHTTPCode(404))
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//
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// Wrap() will add a stacktrace to any error which doesn't already have one attached. WrapSkipping()
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// can be used to control where the stacktrace starts.
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//
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// This package contains wrappers for adding specific context information to errors, such as an
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// HTTPCode. You can create your own wrappers using the primitive Value(), WithValue(), and Set()
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// functions.
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//
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// Errors produced by this package implement fmt.Formatter, to print additional information about the
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// error:
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//
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// fmt.Printf("%v", err) // print error message and causes
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// fmt.Printf("%s", err) // same as %s
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// fmt.Printf("%q", err) // same as fmt.Printf("%q", err.Error())
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// fmt.Printf("%v+", err) // print Details(err)
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//
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// Details() prints the error message, all causes, the stacktrace, and additional error
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// values configured with RegisterDetailFunc(). By default, it will show the HTTP status
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// code and user message.
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//
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// Stacktraces
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//
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// By default, any error created by or wrapped by this package will automatically have
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// a stacktrace captured and attached to the error. This capture only happens if the
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// error doesn't already have a stack attached to it, so wrapping the error with additional
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// context won't capture additional stacks.
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//
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// When and how stacks are captured can be customized. SetMaxStackDepth() can globally configure
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// how many frames to capture. SetStackCaptureEnabled() can globally configure whether
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// stacks are captured by default.
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//
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// Wrap(err, NoStackCapture()) can be used to selectively suppress stack capture for a particular
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// error.
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//
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// Wrap(err, CaptureStack(false)) will capture a new stack at the Wrap call site, even if the err
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// already had an earlier stack attached. The new stack overrides the older stack.
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//
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// Wrap(err, CaptureStack(true)) will force a stack capture at the call site even if stack
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// capture is disabled globally.
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//
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// Finally, Wrappers are passed a depth argument so they know how deep they are in the call stack
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// from the call site where this package's API was called. This allows Wrappers to implement their
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// own stack capturing logic.
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//
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// The package contains functions for creating new errors with stacks, or adding a stack to `error`
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// instances. Functions with add context (e.g. `WithValue()`) work on any `error`, and will
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// automatically convert them to merry errors (with a stack) if necessary.
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//
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// Hooks
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//
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// AddHooks() can install wrappers which are applied to all errors processed by this package. Hooks
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// are applied before any other wrappers or processing takes place. They can be used to integrate
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// with errors from other packages, normalizing errors (such as applying standard status codes to
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// application errors), localizing user messages, or replacing the stack capturing mechanism.
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package merry
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