implement middleware compose

internal/error/builder.go

@@ -2,6 +2,7 @@ package error
 
 import (
 	"fmt"
+	"strings"
 	"sync"
 )
 
@@ -24,7 +25,6 @@ func NewBuilder(format string, args ...any) Builder {
 func (b Builder) Add(err NestedError) Builder {
 	if err != nil {
 		b.Lock()
-		// TODO: if err severity is higher than b.severity, update b.severity
 		b.errors = append(b.errors, err)
 		b.Unlock()
 	}
@@ -49,6 +49,8 @@ func (b Builder) Addf(format string, args ...any) Builder {
 func (b Builder) Build() NestedError {
 	if len(b.errors) == 0 {
 		return nil
+	} else if len(b.errors) == 1 && !strings.ContainsRune(b.message, ' ') {
+		return b.errors[0].Subject(b.message)
 	}
 	return Join(b.message, b.errors...)
 }

internal/error/error.go

@@ -166,6 +166,8 @@ func (ne NestedError) Subject(s any) NestedError {
 	}
 	if ne.subject == "" {
 		ne.subject = subject
+	} else if !strings.ContainsRune(subject, ' ') || strings.ContainsRune(ne.subject, '.') {
+		ne.subject = fmt.Sprintf("%s.%s", subject, ne.subject)
 	} else {
 		ne.subject = fmt.Sprintf("%s > %s", subject, ne.subject)
 	}

internal/error/errors.go

@@ -6,15 +6,16 @@ import (
 )
 
 var (
-	ErrFailure     = stderrors.New("failed")
-	ErrInvalid     = stderrors.New("invalid")
-	ErrUnsupported = stderrors.New("unsupported")
-	ErrUnexpected  = stderrors.New("unexpected")
-	ErrNotExists   = stderrors.New("does not exist")
-	ErrMissing     = stderrors.New("missing")
-	ErrDuplicated  = stderrors.New("duplicated")
-	ErrOutOfRange  = stderrors.New("out of range")
-	ErrTypeError   = stderrors.New("type error")
+	ErrFailure      = stderrors.New("failed")
+	ErrInvalid      = stderrors.New("invalid")
+	ErrUnsupported  = stderrors.New("unsupported")
+	ErrUnexpected   = stderrors.New("unexpected")
+	ErrNotExists    = stderrors.New("does not exist")
+	ErrMissing      = stderrors.New("missing")
+	ErrDuplicated   = stderrors.New("duplicated")
+	ErrOutOfRange   = stderrors.New("out of range")
+	ErrTypeError    = stderrors.New("type error")
+	ErrTypeMismatch = stderrors.New("type mismatch")
 )
 
 const fmtSubjectWhat = "%w %v: %q"
@@ -63,6 +64,14 @@ func OutOfRange(subject any, value any) NestedError {
 	return errorf("%v %w: %v", subject, ErrOutOfRange, value)
 }
 
-func TypeError(subject any, from, to reflect.Value) NestedError {
-	return errorf("%v %w: %T -> %T", subject, ErrTypeError, from.Interface(), to.Interface())
+func TypeError(subject any, from, to reflect.Type) NestedError {
+	return errorf("%v %w: %s -> %s\n", subject, ErrTypeError, from, to)
+}
+
+func TypeError2(subject any, from, to reflect.Value) NestedError {
+	return TypeError(subject, from.Type(), to.Type())
+}
+
+func TypeMismatch[Expect any](value any) NestedError {
+	return errorf("%w: expect %s got %T", ErrTypeMismatch, reflect.TypeFor[Expect](), value)
 }