milarin/adverr
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Merge branch 'master'

Browse Source
This commit is contained in:
Tordarus 2021-12-11 17:23:03 +01:00
commit 401f9bf29b
10 changed files with 596 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

202
README.md
View File

@ -1,3 +1,203 @@
# adverr # adverr
Advanced error handling for Go Package adverr implements errors with call stack traces
as well as error templates for error equality
## Installation
```
go get git.tordarus.net/tordarus/adverr
```
## Usage examples
### Import
```go
import "git.tordarus.net/tordarus/adverr"
```
### Create error templates
```go
var (
ErrDoStuffFailed = adverr.NewErrTmpl("ErrDoStuffFailed", "Could'nt do stuff because of %s")
)
```
### Create independent error (without error template)
```go
func doStuffWithIndependentErr() error {
return adverr.New("Could'nt do stuff")
}
```
### Create error based on template
```go
func doStuff() error {
return ErrDoStuffFailed.New("reasons")
}
```
### Print errors on stderr convieniently
```go
adverr.Print(myErr)
adverr.Println(myErr)
```
### Print errors on stderr and exit with exit code
```go
adverr.Fatal(myErr, 1)
adverr.Fatalln(myErr, 1)
```
### Advantages of error templates
two errors made by the same template will return true when called with `errors.Is()`
```go
func doStuffAndFailWithMsg(msg string) error {
return ErrDoStuffFailed.New(msg)
}
err1 := doStuffAndFailWithMsg("err1")
err2 := doStuffAndFailWithMsg("err2")
fmt.Println(errors.Is(err1, err2)) // true
fmt.Println(err1 == err2) // false
fmt.Println(err1.Error() == err2.Error()) // false
```
### Wrap errors (Causality of errors)
By wrapping errors, you can provide an error that is caused by another error.
A 'Caused by' section will be printed in the stack trace showing the original error.
You can also retrieve the original error by using `errors.Unwrap()`
```go
func doStuffWrapped() error {
err := doStuff()
if err != nil {
return adverr.Wrap("doStuffWrapped failed", err)
}
return nil
}
```
### Chain errors (Errors caused in succession)
By chaining errors, you can provide an error that represents multiple errors caused in succession inside the same function.
For each chained error a 'Previously thrown' section will be printed in the stack trace.
You can programmatically check chained errors using the following methods:
```go
// Get Returns the first error in the chain for which errors.Is(target) returns true
Get(target error) error
// GetByIndex returns the i'th error in the chain
GetByIndex(i int) error
// Chain returns a slice of all chained errors
Chain() []error
// Contains is a shorthand for Get(target) != nil.
// Can be considered as an errors.Is function but for chains instead of causes
Contains(target error) bool
```
Be aware that the standard library calls wrapped errors chains as well! But these chains are something different. Here is an example use case:
You have a list of files from which you only want to read the first one you have read permissions for. This is most likely done in a loop inside the same function.
A chained error can keep all previously failed read errors and show them in a debuggable way. Wrapping by causality would be ambiguous because they might already have been wrapped multiple times and their causes can therefore not be distinguished from previously failed errors (chained errors).
### Retrieve call stack trace (for debugging purposes)
```go
fmt.Println(adverr.Trace())
```
### Example of a printed error
Code:
```go
package main
import (
"adverr"
"errors"
)
var (
ErrDoStuffFailed = adverr.NewErrTmpl("ErrDoStuffFailed", "Could'nt do stuff because of %s")
)
func main() {
err := doStuffInAnotherGoroutine()
if err != nil {
adverr.Fatalln(err, 1)
}
}
func doStuff() error {
err := doGoNativeStuff()
if err != nil {
return ErrDoStuffFailed.Wrap(err, "reasons")
}
return nil
}
func doStuffInAnotherGoroutine() error {
ch := make(chan error, 1)
go func() {
ch <- doStuff()
close(ch)
}()
err := <-ch
if err != nil {
return adverr.Wrap("Goroutine failed because of errors", err)
}
return nil
}
func doGoNativeStuff() error {
return errors.New("some go error")
}
```
Output:
```
adverr.Error: Goroutine failed because of errors
at main.doStuffInAnotherGoroutine (/home/user/go/src/test/main.go:38)
at main.main (/home/user/go/src/test/main.go:13)
at runtime.main (/usr/local/go/src/runtime/proc.go:204)
Caused by ErrDoStuffFailed: Could'nt do stuff because of reasons
at main.doStuff (/home/user/go/src/test/main.go:22)
at main.doStuffInAnotherGoroutine.func1 (/home/user/go/src/test/main.go:32)
Caused by errors.errorString: some go error
(Unknown source)
```
### Globals
You can set the maximum limit of the call stack trace via
```go
adverr.CallStackLength = 50 // default value: 100
```
If you are in a productive environment, consider disabling call traces completely for performance reasons:
```go
adverr.DisableTrace = true // default value: false
```
## Change log
### v0.1.2
Introduced error chaining
### v0.1.1
Improved errors.Is behavior so that ErrTmpl's are considered as targets as well. Example:
```go
err := ErrDoStuffFailed.New("some error")
fmt.Println(errors.Is(err, ErrDoStuffFailed)) // returns true since v0.1.1
```
### v0.1.0
initial release

51
calltrace.go Normal file
View File

@ -0,0 +1,51 @@
package adverr
import (
"runtime"
"strconv"
"strings"
)
// CallTrace represents a call stack trace similar to Java's stack trace
type CallTrace struct {
frames *runtime.Frames
more bool
}
// Trace returns a new CallTrace starting from this call
// Use skip to skip the first entries in the trace
func Trace(skip int) *CallTrace {
if DisableTrace {
return nil
}
pc := make([]uintptr, CallStackLength+1)
n := runtime.Callers(skip+1, pc)
pc = pc[:n]
return &CallTrace{runtime.CallersFrames(pc), n == CallStackLength+1}
}
func (ct *CallTrace) String() string {
if ct == nil {
return ""
}
b := new(strings.Builder)
for frame, ok := ct.frames.Next(); ok; frame, ok = ct.frames.Next() {
b.WriteString("\tat ")
b.WriteString(frame.Function)
b.WriteString(" (")
b.WriteString(frame.File)
b.WriteString(":")
b.WriteString(strconv.Itoa(frame.Line))
b.WriteString(")")
b.WriteString("\n")
}
if ct.more {
b.WriteString("\t ...\n")
}
return b.String()
}

34
doc.go Normal file
View File

@ -0,0 +1,34 @@
/*
Package adverr implements errors with call stack traces
as well as error templates for error equality
Usage examples
Creating templates:
var (
ErrDoStuffFailed = adverr.NewErrTmpl("ErrDoStuffFailed", "Could'nt do stuff because of %s")
)
Creating independent error (without error template):
func doStuffWithIndependentErr() error {
return adverr.New("Could'nt do stuff")
}
Creating error based on template:
func doStuff() error {
return ErrDoStuffFailed.New("reasons")
}
Printing errors on stderr convieniently:
Print(myErr)
Println(myErr)
Printing errors on stderr and exit with exitcode:
Fatal(myErr, 1)
Fatalln(myErr, 1)
Advantages of error templates
two errors made by the same template will return true when called with errors.Is()
*/
package adverr

157
error.go Normal file
View File

@ -0,0 +1,157 @@
package adverr
import (
"errors"
"reflect"
"strings"
)
// Error is a wrapper for error with stack trace
type Error struct {
msg string
callTrace *CallTrace
tmpl *ErrTmpl
cause error
prev []error
}
// New returns a new Error with the given message
func New(msg string) *Error {
return &Error{
msg: msg,
callTrace: Trace(2),
}
}
// Wrap returns a new Error with the given message which is caused by cause
func Wrap(msg string, cause error) *Error {
return &Error{
msg: msg,
cause: cause,
callTrace: Trace(2),
}
}
// Chain returns a new Error with the given message and a slice of errors
// which were caused in the same function in succession
func Chain(msg string, errors []error) *Error {
return &Error{
msg: msg,
callTrace: Trace(2),
prev: errors,
}
}
func errtype(err error) string {
if e, ok := err.(*Error); ok && e.tmpl != nil {
return errtype(e.tmpl)
} else if tmpl, ok := err.(*ErrTmpl); ok {
return tmpl.name
}
t := reflect.TypeOf(err)
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t.PkgPath() + "." + t.Name()
}
func (e *Error) Unwrap() error {
return e.cause
}
func (e *Error) Error() string {
b := new(strings.Builder)
printErr(e, b)
return b.String()
}
// Is implements the error equality function used by errors.Is()
// It returns true if the error is the same instance or is created using the same ErrTmpl
func (e *Error) Is(target error) bool {
// same error instance
if target == e {
return true
}
// no template used, therefore no equality possible
if e.tmpl == nil {
return false
}
// same template, therefore errors are equal to another
if tErr, ok := target.(*Error); ok {
return tErr.tmpl == e.tmpl
}
// target is the template itself, therefore they are considered equal to another
if tTmpl, ok := target.(*ErrTmpl); ok {
return tTmpl == e.tmpl
}
return false
}
// Get Returns the first error in the chain for which errors.Is(target) returns true
func (e *Error) Get(target error) error {
if e.prev == nil {
return nil
}
for _, prevErr := range e.prev {
if errors.Is(prevErr, target) {
return prevErr
}
}
return nil
}
// GetByIndex returns the i'th error in the chain
func (e *Error) GetByIndex(i int) error {
if e.prev == nil {
return nil
}
return e.prev[i]
}
// Contains is a shorthand for Get(target) != nil.
// Can be considered as an errors.Is function but for chains instead of causes
func (e *Error) Contains(target error) bool {
return e.Get(target) != nil
}
// Chain returns a slice of all chained errors
func (e *Error) Chain() []error {
return e.prev[:]
}
func printErr(err error, b *strings.Builder) {
e, ok := err.(*Error)
if ok {
b.WriteString(errtype(e))
b.WriteString(": ")
b.WriteString(e.msg)
b.WriteString("\n")
b.WriteString(e.callTrace.String())
} else {
b.WriteString(errtype(err))
b.WriteString(": ")
b.WriteString(err.Error())
b.WriteString("\n")
b.WriteString("\t(Unknown source)\n")
}
cause := errors.Unwrap(err)
if cause != nil {
b.WriteString("Caused by ")
printErr(cause, b)
}
if ok {
for _, prevErr := range e.prev {
b.WriteString("Previously thrown ")
printErr(prevErr, b)
}
}
}

28
error_test.go Normal file
View File

@ -0,0 +1,28 @@
package adverr
import (
"errors"
"fmt"
"testing"
)
func TestErr(t *testing.T) {
DisableTrace = false
err := doStuff()
Println(err)
}
func doStuff() error {
return Wrap("wrapped error", Wrap("test error", fmt.Errorf("asd: %w", errors.New("test"))))
}
func TestErrorChain(t *testing.T) {
errors := make([]error, 0)
errors = append(errors, doStuff())
errors = append(errors, doStuff())
errors = append(errors, doStuff())
Println(Chain("Neither of that stuff worked", errors))
}

56
error_tmpl.go Normal file
View File

@ -0,0 +1,56 @@
package adverr
import "fmt"
var (
// ErrTmplUsedAsErr is returned from ErrTmpl.Error() because an error template should never be used as an actual error value
ErrTmplUsedAsErr = NewErrTmpl("ErrTmplUsedAsErr", "Error template used as error value: %s")
)
// ErrTmpl is an error template to define equalities between different errors
type ErrTmpl struct {
name string
format string
}
// NewErrTmpl returns a new error template with the given format string as a predefined error message
func NewErrTmpl(name, format string) *ErrTmpl {
return &ErrTmpl{name, format}
}
// Error implementation just for satisfying the error interface
// Please dont use ErrTmpls as actual errors
func (t *ErrTmpl) Error() string {
return ErrTmplUsedAsErr.New(errtype(t)).Error()
}
// New returns a new Error in which the given values are being formatted into the format string of its template
func (t *ErrTmpl) New(args ...interface{}) *Error {
return &Error{
msg: fmt.Sprintf(t.format, args...),
cause: nil,
tmpl: t,
callTrace: Trace(2),
}
}
// Wrap returns a new Error with a given cause in which args are being formatted into the format string of its template
func (t *ErrTmpl) Wrap(cause error, args ...interface{}) *Error {
return &Error{
msg: fmt.Sprintf(t.format, args...),
cause: cause,
tmpl: t,
callTrace: Trace(2),
}
}
// Chain returns a new Error with the given message and a slice of errors
// which were caused in the same function in succession
func (t *ErrTmpl) Chain(msg string, errors []error) *Error {
return &Error{
msg: msg,
callTrace: Trace(2),
tmpl: t,
prev: errors,
}
}

28
error_tmpl_test.go Normal file
View File

@ -0,0 +1,28 @@
package adverr
import (
"testing"
)
var (
ErrDoStuffFailed = NewErrTmpl("ErrDoStuffFailed", "test error: %s")
)
func TestErrTmpl(t *testing.T) {
err := doTemplateStuff()
Println(err)
}
func doTemplateStuff() error {
return ErrDoStuffFailed.New("because of reasons")
}
func TestErrTmplChain(t *testing.T) {
errors := make([]error, 0)
errors = append(errors, doTemplateStuff())
errors = append(errors, doTemplateStuff())
errors = append(errors, doTemplateStuff())
Println(ErrDoStuffFailed.Chain("Neither of that stuff worked", errors))
}

10
globals.go Normal file
View File

@ -0,0 +1,10 @@
package adverr
// DisableTrace decides if any call stack traces will be gathered when creating Errors
// If your application is doing performance-heavy tasks with lots of Error creations, you may consider setting this to true
// If set to true, all CallTraces in Error will be nil
var DisableTrace bool = false
// CallStackLength decides how many calls from the call stack should be gathered at most
// Changing this value has no effect if DisableTrace is true
var CallStackLength int = 100

3
go.mod Normal file
View File

@ -0,0 +1,3 @@
module git.tordarus.net/tordarus/adverr
go 1.15

28
utils.go Normal file
View File

@ -0,0 +1,28 @@
package adverr
import (
"fmt"
"os"
)
// Println prints the given err to stderr followed by a newline
func Println(err error) {
fmt.Fprintln(os.Stderr, err)
}
// Print prints the given err to stderr
func Print(err error) {
fmt.Fprint(os.Stderr, err)
}
// Fatalln prints the given err to stderr followed by a newline and exits immediately with the given exit code
func Fatalln(err error, exitcode int) {
fmt.Fprintln(os.Stderr, err)
os.Exit(exitcode)
}
// Fatal prints the given err to stderr and exits immediately with the given exit code
func Fatal(err error, exitcode int) {
fmt.Fprint(os.Stderr, err)
os.Exit(exitcode)
}