Add context feature

README.md

@@ -215,7 +215,32 @@ Output:
 }
 ```
 
+### Context
 
+`goerr` provides `WithContext` method to add values from context to the error. Values can be added to context.Context by `goerr.InjectValue`.
+
+```go
+func someAction(id requestID) error {
+	ctx := context.Background()
+	ctx = goerr.InjectValue(ctx, "request_id", id)
+
+	// ... some action
+
+	return goerr.New("failed").WithContext(ctx)
+}
+
+func main() {
+	id := requestID("req-123")
+	if err := someAction(id); err != nil {
+		slog.Default().Error("aborted", slog.Any("error", err))
+	}
+}
+```
+
+Output:
+```
+2024/10/19 09:51:04 ERROR aborted error.message=failed error.values.request_id=req-123 (snip)
+```
 
 ## License
 

context.go

@@ -0,0 +1,24 @@
+package goerr
+
+import "context"
+
+type errContext struct {
+	values map[string]any
+}
+
+type errContextKey struct{}
+
+func InjectValue(ctx context.Context, key string, value any) context.Context {
+	newCtx := errContext{
+		values: make(map[string]any),
+	}
+	oldCtx, ok := ctx.Value(errContextKey{}).(*errContext)
+	if ok {
+		for k, v := range oldCtx.values {
+			newCtx.values[k] = v
+		}
+	}
+
+	newCtx.values[key] = value
+	return context.WithValue(ctx, errContextKey{}, &newCtx)
+}

context_test.go

@@ -0,0 +1,41 @@
+package goerr_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/m-mizutani/goerr"
+)
+
+func funcWithContext(ctx context.Context, color string) error {
+	if color != "red" {
+		return goerr.New("color is not red").With("color", color).WithContext(ctx)
+	}
+	return nil
+}
+
+func TestContext(t *testing.T) {
+	reqID := "req-123"
+
+	ctx := context.Background()
+	ctx = goerr.InjectValue(ctx, "request_id", reqID)
+
+	err := funcWithContext(ctx, "blue")
+
+	if err == nil {
+		t.Error("Expected error, got nil")
+	}
+
+	goErr := goerr.Unwrap(err)
+	if goErr == nil {
+		t.Error("Expected goerr.Error, got other type")
+	}
+
+	if goErr.Values()["color"] != "blue" {
+		t.Errorf("Expected color value to be 'blue', got '%v'", goErr.Values()["color"])
+	}
+
+	if goErr.Values()["request_id"] != reqID {
+		t.Errorf("Expected request_id value to be '%s', got '%v'", reqID, goErr.Values()["request_id"])
+	}
+}

errors.go

@@ -1,6 +1,7 @@
 package goerr
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -21,20 +22,24 @@ func New(format string, args ...any) *Error {
 // Wrap creates a new Error and add message.
 func Wrap(cause error, msg ...any) *Error {
 	err := newError()
-
-	if len(msg) > 0 {
-		var newMsgs []string
-		for _, m := range msg {
-			newMsgs = append(newMsgs, fmt.Sprintf("%v", m))
-		}
-		err.msg = strings.Join(newMsgs, " ")
-	}
-
+	err.msg = toWrapMessage(msg...)
 	err.cause = cause
 
 	return err
 }
 
+func toWrapMessage(msg ...any) string {
+	if len(msg) == 0 {
+		return ""
+	}
+
+	var newMsgs []string
+	for _, m := range msg {
+		newMsgs = append(newMsgs, fmt.Sprintf("%v", m))
+	}
+	return strings.Join(newMsgs, " ")
+}
+
 // Wrapf creates a new Error and add message. The error message is formatted by fmt.Sprintf.
 func Wrapf(cause error, format string, args ...any) *Error {
 	err := newError()
@@ -158,6 +163,21 @@ func (x *Error) With(key string, value any) *Error {
 	return x
 }
 
+// WithContext adds key and value related to the error event from context.Context
+func (x *Error) WithContext(ctx context.Context) *Error {
+	if ctx == nil {
+		return x
+	}
+
+	if errCtx, ok := ctx.Value(errContextKey{}).(*errContext); ok {
+		for k, v := range errCtx.values {
+			x.values[k] = v
+		}
+	}
+
+	return x
+}
+
 // Unstack trims stack trace by 1. It can be used for internal helper or utility functions.
 func (x *Error) Unstack() *Error {
 	x.st = unstack(x.st, 1)

examples/context/main.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"context"
+	"log/slog"
+
+	"github.com/m-mizutani/goerr"
+)
+
+type requestID string
+
+func someAction(id requestID) error {
+	ctx := context.Background()
+	ctx = goerr.InjectValue(ctx, "request_id", id)
+
+	// ... some action
+
+	return goerr.New("failed").WithContext(ctx)
+}
+
+func main() {
+	id := requestID("req-123")
+	if err := someAction(id); err != nil {
+		slog.Default().Error("aborted", slog.Any("error", err))
+	}
+}