zerr: update implementation

core/zerr/err.go

@@ -12,6 +12,8 @@ import (
 	"gitlab.bareksa.com/backend/zen/core/zoptions"
 )
 
+var _ Error = (*Err)(nil)
+
 type Err struct {
 	message       string
 	publicMessage string
@@ -210,3 +212,8 @@ func (mu *Err) Sequence() *Sequence {
 func (mu *Err) Unwrap() []error {
 	return mu.errs
 }
+
+// IsMulti implements Error.
+func (mu *Err) IsMulti() bool {
+	return len(mu.errs) > 1
+}

core/zerr/err_write_to.go

@@ -0,0 +1,74 @@
+package zerr
+
+import (
+	"io"
+	"strconv"
+	"strings"
+
+	"github.com/pborman/indent"
+)
+
+// WriteBuilder writes the error to the builder.
+//
+// w is guaranteed to never return error because
+// the underlying most writer is a strings.Builder.
+func (er *Err) WriteBuilder(w io.Writer) {
+	if len(er.errs) == 0 {
+		_, _ = io.WriteString(w, "[nil]")
+		return
+	}
+	var previous string
+	if err := er.sequence.Outer(); err != nil && !err.IsMulti() {
+		previous = err.GetMessage()
+	}
+	current, _ := strings.CutPrefix(er.message, previous)
+	if current != "" {
+		if previous != "" {
+			_, _ = io.WriteString(w, ": ")
+		}
+		_, _ = io.WriteString(w, current)
+	}
+
+	if len(er.errs) == 1 {
+		err := er.errs[0]
+		if wb, ok := err.(interface{ WriteBuilder(io.Writer) }); ok {
+			wb.WriteBuilder(w)
+			return
+		}
+		_, _ = io.WriteString(w, ": ")
+		_, _ = io.WriteString(w, err.Error())
+		return
+	}
+
+	_, _ = io.WriteString(w, ":\n")
+	w = indent.NewWriter(w, "  ")
+
+	for i, e := range er.errs {
+		if i > 0 {
+			_, _ = io.WriteString(w, "\n")
+		}
+		_, _ = io.WriteString(w, strconv.Itoa(i+1))
+		_, _ = io.WriteString(w, ". ")
+		if wb, ok := e.(interface{ WriteBuilder(io.Writer) }); ok {
+			wb.WriteBuilder(w)
+			continue
+		}
+		_, _ = io.WriteString(w, e.Error())
+		_, _ = io.WriteString(w, "\n")
+	}
+}
+
+func writeString(w io.Writer, s string) (n int64, err error) {
+	n64, err := io.WriteString(w, s)
+	return int64(n64), err
+}
+
+func writeByte(w io.Writer, b byte) (n int64, err error) {
+	n64, err := w.Write([]byte{b})
+	return int64(n64), err
+}
+
+func writeBytes(w io.Writer, b []byte) (n int64, err error) {
+	n64, err := w.Write(b)
+	return int64(n64), err
+}

core/zerr/error.go

@@ -61,4 +61,11 @@ type Error interface {
 
 	// Sequence returns the state of the error sequence.
 	Sequence() *Sequence
+
+	// IsMulti returns true if the error is a multiple error.
+	IsMulti() bool
+
+	// Resolve returns error (self) if all the errors
+	// are valid.
+	Resolve() error
 }

go.mod

@@ -14,6 +14,7 @@ require (
 require (
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/pborman/indent v1.2.1 // indirect
 	golang.org/x/sys v0.18.0 // indirect
 	golang.org/x/text v0.14.0 // indirect
 )

go.sum

@@ -11,6 +11,8 @@ github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovk
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
 github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/pborman/indent v1.2.1 h1:lFiviAbISHv3Rf0jcuh489bi06hj98JsVMtIDZQb9yM=
+github.com/pborman/indent v1.2.1/go.mod h1:FitS+t35kIYtB5xWTZAPhnmrxcciEEOdbyrrpz5K6Vw=
 github.com/tidwall/pretty v1.2.1 h1:qjsOFOWWQl+N3RsoF5/ssm1pHmJJwhjlSbZ51I6wMl4=
 github.com/tidwall/pretty v1.2.1/go.mod h1:ITEVvHYasfjBbM0u2Pg8T2nJnzm8xPwvNhhsoaGGjNU=
 golang.org/x/net v0.23.0 h1:7EYJ93RZ9vYSZAIb2x3lnuvqO5zneoD6IvWjuhfxjTs=