refactor: rename module 'err' to 'gperr'

internal/gperr/base.go

@@ -0,0 +1,64 @@
+package gperr
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+)
+
+// baseError is an immutable wrapper around an error.
+//
+//nolint:recvcheck
+type baseError struct {
+	Err error `json:"err"`
+}
+
+func (err *baseError) Unwrap() error {
+	return err.Err
+}
+
+func (err *baseError) Is(other error) bool {
+	if other, ok := other.(*baseError); ok {
+		return errors.Is(err.Err, other.Err)
+	}
+	return errors.Is(err.Err, other)
+}
+
+func (err baseError) Subject(subject string) Error {
+	err.Err = PrependSubject(subject, err.Err)
+	return &err
+}
+
+func (err *baseError) Subjectf(format string, args ...any) Error {
+	if len(args) > 0 {
+		return err.Subject(fmt.Sprintf(format, args...))
+	}
+	return err.Subject(format)
+}
+
+func (err baseError) With(extra error) Error {
+	return &nestedError{&err, []error{extra}}
+}
+
+func (err baseError) Withf(format string, args ...any) Error {
+	return &nestedError{&err, []error{fmt.Errorf(format, args...)}}
+}
+
+func (err *baseError) Error() string {
+	return err.Err.Error()
+}
+
+// MarshalJSON implements the json.Marshaler interface.
+func (err *baseError) MarshalJSON() ([]byte, error) {
+	//nolint:errorlint
+	switch err := err.Err.(type) {
+	case Error, *withSubject:
+		return json.Marshal(err)
+	case json.Marshaler:
+		return err.MarshalJSON()
+	case interface{ MarshalText() ([]byte, error) }:
+		return err.MarshalText()
+	default:
+		return json.Marshal(err.Error())
+	}
+}