Kiura Magomadov "Addition to Go2 draft error handling" September 2018

addition_to_Go2_draft_error_handling.md

This is just another way to deal with errors following Go2 draft structure.

If I understood correctly handle is used as defer in many proposals, which, could be a drawback in case we want the function to fail as soon as error occurs. So, a better scenario could be as follows:

1. Unhandled error occurs - it is thrown and parent function should handle it
2. Handled error occurs - handle function catches it and performs some operations before exiting the function (in the handle function one can decide to throw an error again if he/she needs to add additional info to the err)

func CopyFile(src, dst string) throws error {
	r := os.Open(src) // option 1
	defer r.Close()

	w := os.Create(dst)
	err := io.Copy(w, r) // option 2
	err2 := w.Close() // option 2
	handle err || err2 { // handle function is executed if `err` or `err2` is not equal to `nil`
		w.Close()
		os.Remove(dst)
		// optionally throw error here
		// return errors.New("could not copy.")
	}
}

Actually I am not sure why try catch is not considered, it seems it could be the best solution (familiar syntax)

func CopyFile(src, dst string) throws error {
	r := os.Open(src) // thrown so parent function can catch it or pass to its parent
	defer r.Close()

	w := os.Create(dst)
	try { // handle special case
		io.Copy(w, r)
		w.Close()
	} catch err {
		w.Close()
		os.Remove(dst)
		// optionally throw error here
		// return errors.New("could not copy.")
		// or to make it consistent with other languages throw it
		// throw errors.New("could not copy.")
	}
}

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Methods without comments:

func CopyFile(src, dst string) throws error {
	r := os.Open(src)
	defer r.Close()

	w := os.Create(dst)
	err := io.Copy(w, r)
	err2 := w.Close()
	handle err || err2 {
		w.Close()
		os.Remove(dst)
	}
}

func CopyFile(src, dst string) throws error {
	r := os.Open(src)
	defer r.Close()

	w := os.Create(dst)
	try {
		io.Copy(w, r)
		w.Close()
	} catch err {
		w.Close()
		os.Remove(dst)
	}
}