fix join nil; add Detail(error)

README.md

@@ -1,9 +1,18 @@
 # errors
-[![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fpub-go%2Ferrors.svg?type=shield)](https://app.fossa.com/projects/git%2Bgithub.com%2Fpub-go%2Ferrors?ref=badge_shield)
+
 
 errors with stack, supports multi-cause error format as tree, 
 inspired by [cockroachdb/errors](github.com/cockroachdb/errors)
 
+> 博客：[造一个 Go 语言错误库的轮子](https://youthlin.com/?p=1868)
+
+[![sync-to-gitee](https://github.com/pub-go/errors/actions/workflows/gitee.yaml/badge.svg)](https://github.com/pub-go/errors/actions/workflows/gitee.yaml)
+[![test](https://github.com/pub-go/errors/actions/workflows/test.yaml/badge.svg)](https://github.com/pub-go/errors/actions/workflows/test.yaml)
+[![codecov](https://codecov.io/gh/pub-go/errors/graph/badge.svg?token=OfZF3kQlBS)](https://codecov.io/gh/pub-go/errors)
+[![Go Report Card](https://goreportcard.com/badge/code.gopub.tech/errors)](https://goreportcard.com/report/code.gopub.tech/errors)
+[![Go Reference](https://pkg.go.dev/badge/code.gopub.tech/errors.svg)](https://pkg.go.dev/code.gopub.tech/errors)
+[![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fpub-go%2Ferrors.svg?type=shield)](https://app.fossa.com/projects/git%2Bgithub.com%2Fpub-go%2Ferrors?ref=badge_shield)
+
 Example
 ```go
 package main

errors.go

@@ -176,9 +176,14 @@ func WithStack(err error) error {
 	}
 }
 
+// Join 聚合多个错误
 func Join(errs ...error) error {
+	err := join(errs...)
+	if err == nil {
+		return nil
+	}
 	return &withStack{
-		error: join(errs...),
+		error: err,
 		stack: callers(),
 	}
 }

errors_test.go

@@ -125,6 +125,12 @@ func TestWithStack(t *testing.T) {
 }
 
 func TestJoin(t *testing.T) {
+	if err := errors.Join(); err != nil {
+		t.Errorf("Join() want nil, got: %+v", err)
+	}
+	if err := errors.Join(nil); err != nil {
+		t.Errorf("Join(nil) want nil, got: %+v", err)
+	}
 	print(t, errors.Join(errFmt, errLeafNew))
 }
 

format.go

@@ -27,6 +27,11 @@ func Formattable(err error) FormattableError {
 	return &errorFormatter{err}
 }
 
+// Detail 先将 err 包装为 Formattable 再使用 %+v 格式化为字符串
+func Detail(err error) string {
+	return fmt.Sprintf("%+v", Formattable(err))
+}
+
 // FormatError 能够识别格式化动词智能打印。
 // 当一个错误类型在实现 fmt.Formatter 接口时，可以直接转发给本函数。
 //

format_test.go

@@ -1,6 +1,7 @@
 package errors_test
 
 import (
+	"fmt"
 	"testing"
 
 	"code.gopub.tech/errors"
@@ -16,3 +17,22 @@ func TestFormat(t *testing.T) {
 	err1234 := errors.Join(err12, err34)
 	t.Logf("%+v", err1234)
 }
+
+func TestDetail(t *testing.T) {
+	if s := errors.Detail(nil); s != "<nil>" {
+		t.Errorf("Detail(nil) got %s", s)
+	}
+	t.Logf("%s", errors.Detail(errors.New("error")))
+	e0 := fmt.Errorf("fmtErr")
+	err := errors.F(e0)
+	if e, ok := err.(interface{ Cause() error }); ok {
+		if e.Cause() != e0 {
+			t.Errorf("Cause() failed")
+		}
+	}
+	if e, ok := err.(interface{ Unwrap() error }); ok {
+		if e.Unwrap() != e0 {
+			t.Errorf("Unwrap() failed")
+		}
+	}
+}