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214 lines
4.9 KiB
214 lines
4.9 KiB
package common
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import (
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"fmt"
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"runtime"
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)
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//----------------------------------------
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// Convenience method.
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func ErrorWrap(cause interface{}, format string, args ...interface{}) Error {
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if causeCmnError, ok := cause.(*cmnError); ok { //nolint:gocritic
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msg := fmt.Sprintf(format, args...)
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return causeCmnError.Stacktrace().Trace(1, msg)
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} else if cause == nil {
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return newCmnError(FmtError{format, args}).Stacktrace()
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} else {
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// NOTE: causeCmnError is a typed nil here.
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msg := fmt.Sprintf(format, args...)
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return newCmnError(cause).Stacktrace().Trace(1, msg)
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}
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}
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//----------------------------------------
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// Error & cmnError
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/*
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Usage with arbitrary error data:
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```go
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// Error construction
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type MyError struct{}
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var err1 error = NewErrorWithData(MyError{}, "my message")
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...
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// Wrapping
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var err2 error = ErrorWrap(err1, "another message")
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if (err1 != err2) { panic("should be the same")
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...
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// Error handling
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switch err2.Data().(type){
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case MyError: ...
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default: ...
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}
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```
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*/
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type Error interface {
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Error() string
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Stacktrace() Error
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Trace(offset int, format string, args ...interface{}) Error
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Data() interface{}
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}
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// New Error with formatted message.
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// The Error's Data will be a FmtError type.
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func NewError(format string, args ...interface{}) Error {
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err := FmtError{format, args}
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return newCmnError(err)
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}
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// New Error with specified data.
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func NewErrorWithData(data interface{}) Error {
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return newCmnError(data)
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}
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type cmnError struct {
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data interface{} // associated data
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msgtraces []msgtraceItem // all messages traced
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stacktrace []uintptr // first stack trace
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}
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var _ Error = &cmnError{}
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// NOTE: do not expose.
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func newCmnError(data interface{}) *cmnError {
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return &cmnError{
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data: data,
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msgtraces: nil,
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stacktrace: nil,
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}
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}
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// Implements error.
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func (err *cmnError) Error() string {
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return fmt.Sprintf("%v", err)
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}
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// Captures a stacktrace if one was not already captured.
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func (err *cmnError) Stacktrace() Error {
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if err.stacktrace == nil {
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var offset = 3
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var depth = 32
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err.stacktrace = captureStacktrace(offset, depth)
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}
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return err
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}
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// Add tracing information with msg.
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// Set n=0 unless wrapped with some function, then n > 0.
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func (err *cmnError) Trace(offset int, format string, args ...interface{}) Error {
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msg := fmt.Sprintf(format, args...)
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return err.doTrace(msg, offset)
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}
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// Return the "data" of this error.
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// Data could be used for error handling/switching,
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// or for holding general error/debug information.
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func (err *cmnError) Data() interface{} {
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return err.data
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}
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func (err *cmnError) doTrace(msg string, n int) Error {
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pc, _, _, _ := runtime.Caller(n + 2) // +1 for doTrace(). +1 for the caller.
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// Include file & line number & msg.
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// Do not include the whole stack trace.
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err.msgtraces = append(err.msgtraces, msgtraceItem{
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pc: pc,
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msg: msg,
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})
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return err
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}
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func (err *cmnError) Format(s fmt.State, verb rune) {
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switch verb {
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case 'p':
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s.Write([]byte(fmt.Sprintf("%p", &err)))
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default:
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if s.Flag('#') {
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s.Write([]byte("--= Error =--\n"))
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// Write data.
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s.Write([]byte(fmt.Sprintf("Data: %#v\n", err.data)))
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// Write msg trace items.
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s.Write([]byte(fmt.Sprintf("Msg Traces:\n")))
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for i, msgtrace := range err.msgtraces {
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s.Write([]byte(fmt.Sprintf(" %4d %s\n", i, msgtrace.String())))
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}
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// Write stack trace.
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if err.stacktrace != nil {
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s.Write([]byte(fmt.Sprintf("Stack Trace:\n")))
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for i, pc := range err.stacktrace {
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fnc := runtime.FuncForPC(pc)
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file, line := fnc.FileLine(pc)
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s.Write([]byte(fmt.Sprintf(" %4d %s:%d\n", i, file, line)))
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}
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}
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s.Write([]byte("--= /Error =--\n"))
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} else {
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// Write msg.
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s.Write([]byte(fmt.Sprintf("%v", err.data)))
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}
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}
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}
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//----------------------------------------
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// stacktrace & msgtraceItem
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func captureStacktrace(offset int, depth int) []uintptr {
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var pcs = make([]uintptr, depth)
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n := runtime.Callers(offset, pcs)
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return pcs[0:n]
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}
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type msgtraceItem struct {
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pc uintptr
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msg string
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}
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func (mti msgtraceItem) String() string {
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fnc := runtime.FuncForPC(mti.pc)
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file, line := fnc.FileLine(mti.pc)
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return fmt.Sprintf("%s:%d - %s",
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file, line,
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mti.msg,
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)
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}
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//----------------------------------------
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// fmt error
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/*
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FmtError is the data type for NewError() (e.g. NewError().Data().(FmtError))
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Theoretically it could be used to switch on the format string.
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```go
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// Error construction
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var err1 error = NewError("invalid username %v", "BOB")
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var err2 error = NewError("another kind of error")
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...
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// Error handling
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switch err1.Data().(cmn.FmtError).Format() {
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case "invalid username %v": ...
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case "another kind of error": ...
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default: ...
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}
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```
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*/
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type FmtError struct {
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format string
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args []interface{}
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}
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func (fe FmtError) Error() string {
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return fmt.Sprintf(fe.format, fe.args...)
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}
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func (fe FmtError) String() string {
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return fmt.Sprintf("FmtError{format:%v,args:%v}",
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fe.format, fe.args)
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}
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func (fe FmtError) Format() string {
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return fe.format
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}
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