refactor: rename module 'err' to 'gperr'

internal/gperr/builder.go

@@ -0,0 +1,130 @@
+package gperr
+
+import (
+	"fmt"
+	"sync"
+)
+
+type Builder struct {
+	about string
+	errs  []error
+	sync.Mutex
+}
+
+func NewBuilder(about string) *Builder {
+	return &Builder{about: about}
+}
+
+func (b *Builder) About() string {
+	if !b.HasError() {
+		return ""
+	}
+	return b.about
+}
+
+//go:inline
+func (b *Builder) HasError() bool {
+	return len(b.errs) > 0
+}
+
+func (b *Builder) error() Error {
+	if !b.HasError() {
+		return nil
+	}
+	return &nestedError{Err: New(b.about), Extras: b.errs}
+}
+
+func (b *Builder) Error() Error {
+	if len(b.errs) == 1 {
+		return wrap(b.errs[0])
+	}
+	return b.error()
+}
+
+func (b *Builder) String() string {
+	err := b.error()
+	if err == nil {
+		return ""
+	}
+	return err.Error()
+}
+
+// Add adds an error to the Builder.
+//
+// adding nil is no-op.
+func (b *Builder) Add(err error) *Builder {
+	if err == nil {
+		return b
+	}
+
+	b.Lock()
+	defer b.Unlock()
+
+	switch err := wrap(err).(type) {
+	case *baseError:
+		b.errs = append(b.errs, err.Err)
+	case *nestedError:
+		if err.Err == nil {
+			b.errs = append(b.errs, err.Extras...)
+		} else {
+			b.errs = append(b.errs, err)
+		}
+	default:
+		panic("bug: should not reach here")
+	}
+
+	return b
+}
+
+func (b *Builder) Adds(err string) *Builder {
+	b.Lock()
+	defer b.Unlock()
+	b.errs = append(b.errs, newError(err))
+	return b
+}
+
+func (b *Builder) Addf(format string, args ...any) *Builder {
+	if len(args) > 0 {
+		b.Lock()
+		defer b.Unlock()
+		b.errs = append(b.errs, fmt.Errorf(format, args...))
+	} else {
+		b.Adds(format)
+	}
+
+	return b
+}
+
+func (b *Builder) AddFrom(other *Builder, flatten bool) *Builder {
+	if other == nil || !other.HasError() {
+		return b
+	}
+
+	b.Lock()
+	defer b.Unlock()
+	if flatten {
+		b.errs = append(b.errs, other.errs...)
+	} else {
+		b.errs = append(b.errs, other.error())
+	}
+	return b
+}
+
+func (b *Builder) AddRange(errs ...error) *Builder {
+	b.Lock()
+	defer b.Unlock()
+
+	for _, err := range errs {
+		if err != nil {
+			b.errs = append(b.errs, err)
+		}
+	}
+
+	return b
+}
+
+func (b *Builder) ForEach(fn func(error)) {
+	for _, err := range b.errs {
+		fn(err)
+	}
+}