errcontext

Documentation

Overview

Package errcontext attaches structured logging context to errors. It wraps errors with a Context map using xerrors.Extend, enabling downstream callers to extract slog.Attr key-value pairs for logging.

Index

• func Add(err error, context ...slog.Attr) error
• type Context
  • func Get(err error) Context
  • func (c Context) Flatten() []slog.Attr
  • func (c Context) LogValue() slog.Value

Examples

• Add

Functions

func Add

func Add(err error, context ...slog.Attr) error

Add attaches the given slog.Attr key-value pairs to err as logging context. If err already has a Context, the existing map is mutated in place (last-entry-wins). Returns nil if err is nil, or err unchanged if no attrs are provided.

Example

package main

import (
	"errors"
	"log/slog"
	"os"

	"github.com/wood-jp/xerrors"
	"github.com/wood-jp/xerrors/errcontext"
)

func newLogger() *slog.Logger {
	return slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
			if a.Key == slog.TimeKey && len(groups) == 0 {
				return slog.Attr{}
			}
			return a
		},
	}))
}

func main() {
	err := errors.New("request failed")
	err = errcontext.Add(err,
		slog.String("user_id", "u123"),
		slog.Int("status", 503),
	)
	newLogger().Error("handler error", xerrors.Log(err))
}

Output:
{"level":"ERROR","msg":"handler error","error":{"error":"request failed","error_detail":{"context":{"status":503,"user_id":"u123"}}}}

Types

type Context

type Context map[string]slog.Value

Context is a map of key-value pairs attached to an error for structured logging.

func Get

func Get(err error) Context

Get extracts the Context attached to err, or nil if none is present.

func (Context) Flatten

func (c Context) Flatten() []slog.Attr

Flatten returns the context as a slice of slog.Attr sorted by key.

func (Context) LogValue

func (c Context) LogValue() slog.Value

LogValue implements slog.LogValuer. An empty context returns an empty group. A non-empty context returns a group containing a single "context" attr whose value is a group of the key-value pairs in sorted key order.