A quick and dirty exception handler for the Go programming language

except.go

/*
MIT license:

Copyright (c) 2012 Harley Laue <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

*/
/*
--------------------------------------
*/
/*
As a general note, I do not recommend using this. If you do choose to use it, please make sure everything is properly handled and only use it internally.
*/
package except

// Return true if exception was handled and false to continue panicing
type Catchable func(e error) bool

// f is the function to try, and c lets us know if the exception was properly handled
func Try(f func(), c Catchable) {
	func() {
		defer catch(c)
		f()
	}()
}

// Throw an exception
func Throw(e error) {
	panic(e)
}

func catch(c Catchable) {
	if err := recover(); err != nil {
		if e, ok := err.(error); ok {
			if r := c(e); r == false {
				// Error not handled. Panicing anyway
				panic(e)
			}
		} else {
			// Panicing anyway
			panic(e)
		}
	}
}

main.go

// an example using the except library
package main

import (
	"errors"
	"except"
	"fmt"
	"time"
)

var (
	failError  = errors.New("Fail!")
	fubarError = errors.New("Fubar!")
)

func a() {
	fmt.Println("a()")
}

func b() {
	fmt.Println("b()")
	except.Throw(failError)
}

func c() {
	fmt.Println("c()")
}

func main() {
	fmt.Println("This try will be caught and continue")
	except.Try(func() {
		a()
		b()
		c()
	}, func(e error) bool {
		if e == failError {
			return true
		}
		return false
	})

	time.Sleep(1 * time.Second)

	fmt.Println("This try is going to fail")
	except.Try(func() {
		a()
		b()
		c()
	}, func(e error) bool {
		if e == fubarError {
			return true
		}
		return false
	})

	time.Sleep(1 * time.Second)
}