errors

package
v0.0.11 Latest Latest
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 Go to latest Published: Jul 14, 2020 License: Apache-2.0 Imports: 6 Imported by: 9

Documentation

Overview

Package errors is heavily inspired by "github.com/pkg/errors"

Example (StackTrace) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func fn() error {
	e1 := errors.New("error")
	e2 := errors.Wrapf(e1, "inner")
	e3 := errors.Wrapf(e2, "middle")
	return errors.Wrapf(e3, "outer")
}

func main() {
	err, ok := errors.Cause(fn()).(errors.WithStackTrace)
	if !ok {
		panic("oops, err does not implement stackTracer")
	}

	st := err.StackTrace()
	fmt.Printf("%+v", st[0:2]) // top two frames

	// Example output:
	// github.com/VirtusLab/go-extended/pkg/errors_test.fn
	//	/home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:47
	// github.com/VirtusLab/go-extended/pkg/errors_test.Example_stackTrace
	//	/home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:127
}

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func Cause 

func Cause(err error) error

Cause returns the underlying cause of the error, if possible. An error value has a cause if it implements the following interface: 

type causer interface {
       Cause() error
}

If the error does not implement Cause, the original error will be returned. If the error is nil, nil will be returned without further investigation.

Example 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func fn() error {
	e1 := errors.New("error")
	e2 := errors.Wrapf(e1, "inner")
	e3 := errors.Wrapf(e2, "middle")
	return errors.Wrapf(e3, "outer")
}

func main() {
	err := fn()
	fmt.Println(err)
	fmt.Println(errors.Cause(err))

}

Output:

outer: middle: inner: error
error
Example (Printf) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	err := errors.Wrapf(func() error {
		return func() error {
			//lint:ignore S1039 the test introduces it on purpose
			return errors.Errorf("hello %s", fmt.Sprintf("world"))
		}()
	}(), "failed")

	fmt.Printf("%v", err)

}

Output:

failed: hello world

func Errorf 

func Errorf(format string, args ...interface{}) error

Errorf returns a new error with the supplied formatted message and stack trace. It records the stack trace at the point it was called.

Example (Extended) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	err := errors.Errorf("whoops: %s", "foo")
	fmt.Printf("%+v", err)

	// Example output:
	// whoops: foo
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleErrorf
	//         /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:101
	// testing.runExample
	//         /home/dfc/go/src/testing/example.go:114
	// testing.RunExamples
	//         /home/dfc/go/src/testing/example.go:38
	// testing.(*M).Run
	//         /home/dfc/go/src/testing/testing.go:744
	// main.main
	//         /github.com/VirtusLab/go-extended/pkg/errors/_test/_testmain.go:102
	// runtime.main
	//         /home/dfc/go/src/runtime/proc.go:183
	// runtime.goexit
	//         /home/dfc/go/src/runtime/asm_amd64.s:2059
}

func FormatCauseAndStack 

func FormatCauseAndStack(err error, f *Stack, s fmt.State, verb rune)

FormatCauseAndStack helps to implement fmt.Formatter used by Sprint(f) or Fprint(f) etc. Use for custom error implementations with Cause and StackFormatter

Example 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

type ErrCustom struct {
	stack *errors.Stack
	s     string
}

func (e *ErrCustom) Error() string {
	return e.s
}

func (e *ErrCustom) Format(s fmt.State, verb rune) {
	errors.FormatCauseAndStack(e, e.stack, s, verb)
}

func (e *ErrCustom) StackTrace() errors.StackTrace {
	return e.stack.StackTrace()
}

func NewErrCustom(s string) *ErrCustom {
	return &ErrCustom{
		stack: errors.Callers(),
		s:     s,
	}
}

func main() {
	err := NewErrCustom("whoops")

	fmt.Println(err)

}

Output:

whoops
Example (Printf) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

type ErrCustom struct {
	stack *errors.Stack
	s     string
}

func (e *ErrCustom) Error() string {
	return e.s
}

func (e *ErrCustom) Format(s fmt.State, verb rune) {
	errors.FormatCauseAndStack(e, e.stack, s, verb)
}

func (e *ErrCustom) StackTrace() errors.StackTrace {
	return e.stack.StackTrace()
}

func NewErrCustom(s string) *ErrCustom {
	return &ErrCustom{
		stack: errors.Callers(),
		s:     s,
	}
}

func main() {
	err := NewErrCustom("whoops")

	fmt.Printf("%+v", err)

	// Example output:
	// whoops
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleFormatCauseAndStack_prints
	//         /home/dfc/go/src/github.com/VirtusLab/go-extended/pkg/errors/custom_test.go:41
	// testing.runExample
	//         /home/dfc/go/src/testing/example.go:121
	// testing.runExamples
	//         /home/dfc/go/src/testing/example.go:45
	// testing.(*M).Run
	//         /home/dfc/go/src/testing/testing.go:1073
	// main.main
	//        _testmain.go:108
	// runtime.main
	//         /home/dfc/go/src/runtime/proc.go:200
	// runtime.goexit
	//         /home/dfc/go/src/runtime/asm_amd64.s:1337
}

func New 

func New(message string) error

New returns a new error with the supplied message and a stack trace. It records the stack trace at the point it was called.

Example 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	err := errors.New("whoops")
	fmt.Println(err)

}

Output:

whoops
Example (Printf) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	err := errors.New("whoops")
	fmt.Printf("%+v", err)

	// Example output:
	// whoops
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleNew_printf
	//         /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:17
	// testing.runExample
	//         /home/dfc/go/src/testing/example.go:114
	// testing.RunExamples
	//         /home/dfc/go/src/testing/example.go:38
	// testing.(*M).Run
	//         /home/dfc/go/src/testing/testing.go:744
	// main.main
	//         /github.com/VirtusLab/go-extended/pkg/errors/_test/_testmain.go:106
	// runtime.main
	//         /home/dfc/go/src/runtime/proc.go:183
	// runtime.goexit
	//         /home/dfc/go/src/runtime/asm_amd64.s:2059
}

func Wrap 

func Wrap(e error) error

Wrap wraps a given error with a stack trace. Please note the error type will change when wrapped. It records the stack trace at the point it was called.

Example 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	cause := errors.New("whoops")
	err := errors.Wrap(cause)
	fmt.Println(err)

}

Output:

whoops
Example (Extended) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func fn() error {
	e1 := errors.New("error")
	e2 := errors.Wrapf(e1, "inner")
	e3 := errors.Wrapf(e2, "middle")
	return errors.Wrapf(e3, "outer")
}

func main() {
	err := fn()
	fmt.Printf("%+v\n", err)

	// Example output:
	// error
	// github.com/VirtusLab/go-extended/pkg/errors_test.fn
	//         /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:47
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleCause_printf
	//         /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:63
	// testing.runExample
	//         /home/dfc/go/src/testing/example.go:114
	// testing.RunExamples
	//         /home/dfc/go/src/testing/example.go:38
	// testing.(*M).Run
	//         /home/dfc/go/src/testing/testing.go:744
	// main.main
	//         /github.com/VirtusLab/go-extended/pkg/errors/_test/_testmain.go:104
	// runtime.main
	//         /home/dfc/go/src/runtime/proc.go:183
	// runtime.goexit
	//         /home/dfc/go/src/runtime/asm_amd64.s:2059
	// github.com/VirtusLab/go-extended/pkg/errors_test.fn
	// 	  /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:48: inner
	// github.com/VirtusLab/go-extended/pkg/errors_test.fn
	//        /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:49: middle
	// github.com/VirtusLab/go-extended/pkg/errors_test.fn
	//      /home/dfc/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:50: outer
}
Example (Printf) 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	cause := errors.New("whoops")
	err := errors.Wrap(cause)
	fmt.Printf("%+v", err)

	// Example Output:
	// whoops
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleWithStack_printf
	//         /home/fabstu/go/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:55
	// testing.runExample
	//         /usr/lib/go/src/testing/example.go:114
	// testing.RunExamples
	//         /usr/lib/go/src/testing/example.go:38
	// testing.(*M).Run
	//         /usr/lib/go/src/testing/testing.go:744
	// main.main
	//         github.com/VirtusLab/go-extended/pkg/errors/_test/_testmain.go:106
	// runtime.main
	//         /usr/lib/go/src/runtime/proc.go:183
	// runtime.goexit
	//         /usr/lib/go/src/runtime/asm_amd64.s:2086
	// github.com/VirtusLab/go-extended/pkg/errors_test.ExampleWithStack_printf
	//         /home/fabstu/go/src/github.com/VirtusLab/go-extended/pkg/errors/example_test.go:56
	// testing.runExample
	//         /usr/lib/go/src/testing/example.go:114
	// testing.RunExamples
	//         /usr/lib/go/src/testing/example.go:38
	// testing.(*M).Run
	//         /usr/lib/go/src/testing/testing.go:744
	// main.main
	//         github.com/VirtusLab/go-extended/pkg/errors/_test/_testmain.go:106
	// runtime.main
	//         /usr/lib/go/src/runtime/proc.go:183
	// runtime.goexit
	//         /usr/lib/go/src/runtime/asm_amd64.s:2086
}

func Wrapf 

func Wrapf(e error, format string, args ...interface{}) error

Wrapf wraps a given error with a formatted message and a stack trace. Please note the error type will change when wrapped. It records the stack trace at the point it was called.

Example 
package main

import (
	"fmt"

	"github.com/VirtusLab/go-extended/pkg/errors"
)

func main() {
	cause := errors.New("whoops")
	err := errors.Wrapf(cause, "oh noes")
	fmt.Println(err)

	cause = errors.New("whoops")
	err = errors.Wrapf(cause, "oh noes #%d", 2)
	fmt.Println(err)

	// Example output:
	// oh noes: whoops
	// oh noes #2: whoops
}

Types

type Frame 

type Frame uintptr

Frame represents a program counter inside a stack frame. For historical reasons if Frame is interpreted as a uintptr its value represents the program counter + 1.

func (Frame) Format 

func (f Frame) Format(s fmt.State, verb rune)

Format formats the frame according to the fmt.Formatter interface. 

%s    source file
%d    source line
%n    function name
%v    equivalent to %s:%d

Format accepts flags that alter the printing of some verbs, as follows: 

%+s   function name and path of source file relative to the compile time
      GOPATH separated by \n\t (<funcName>\n\t<path>)
%+v   equivalent to %+s:%d

func (Frame) MarshalText 

func (f Frame) MarshalText() ([]byte, error)

MarshalText formats a stacktrace Frame as a text string. The output is the same as that of fmt.Sprintf("%+v", f), but without newlines or tabs.

type Stack 

type Stack []uintptr

Stack represents a stack of program counters.

func Callers 

func Callers() *Stack

Callers gets a stack dump using runtime.Callers

func (*Stack) Format 

func (s *Stack) Format(st fmt.State, verb rune)

Format implements fmt.Formatter used by Sprint(f) or Fprint(f) etc.

func (*Stack) StackTrace 

func (s *Stack) StackTrace() StackTrace

StackTrace creates a StackTrace for this Stack

type StackTrace 

type StackTrace []Frame

StackTrace is stack of Frames from innermost (newest) to outermost (oldest).

func (StackTrace) Format 

func (st StackTrace) Format(s fmt.State, verb rune)

Format formats the stack of Frames according to the fmt.Formatter interface. 

%s	lists source files for each Frame in the stack
%v	lists the source file and line number for each Frame in the stack

Format accepts flags that alter the printing of some verbs, as follows: 

%+v   Prints filename, function, and line number for each Frame in the stack.

type WithCause 

type WithCause interface {
	// Cause returns the error that caused this error
	Cause() error
}

WithCause represents an error that was caused by another error

type WithStackTrace 

type WithStackTrace interface {
	// StackTrace returns a stack trace for this error
	StackTrace() StackTrace
}

WithStackTrace represents an error with a stack trace

Source Files

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