ego

ego means Error can be handled implicitly in GO.

It's an experimental toy Go preprocessor/transpiler that introduces the ? operator for more concise error handling. It aims to reduce boilerplate code by replacing verbose error checks with a single character.

For example, ego transforms this:

s := hello()?

Into this:

s, err := hello()
if err != nil {
    return err
}

Installation

$ go install github.com/aisk/ego@latest

Usage

Create a file named hello.ego with the following content:

package main

import (
	"io"
	"os"
)

func hello() error {
	f := os.Open("hello.ego")?
	defer f.Close()
	s := io.ReadAll(f)?
	println(string(s))
	return nil
}

func main() {
	hello()
}

Run the ego transpiler and save the output to a .go file:

$ cat hello.ego | ego > hello.go

The transpiled hello.go will contain:

package main

import (
	"io"
	"os"
)

func hello() error {
	f, err := os.Open("hello.ego")
	if err != nil {
		return err
	}
	defer f.Close()
	s, err := io.ReadAll(f)
	if err != nil {
		return err
	}
	println(string(s))
	return nil
}

func main() {
	hello()
}

Design Principles

The goal of this project is to design a Go language extension with more syntactic sugar, implemented as a preprocessor. The precompiled result is completely standard Go code, indistinguishable from hand-written Go code.

Core Design Philosophy: Zero Lock-in

• If you decide this project isn't suitable, you can simply delete all .ego files and continue development with the original Go code
• If your team doesn't want to introduce ego, you can edit .ego files locally and commit the generated standard Go code to your version control server
• The precompiled Go code has no runtime dependencies or special libraries

Design Constraints

To achieve zero lock-in, there are some intentional limitations:

1. The ? operator does not support method chaining - For example, a()?.b()? is not supported because it would require introducing intermediate variables, and it's difficult to provide reasonable names for these variables
2. Currently does not support the ? operator in for loop initialization statements - For example, for item := range getItems()? is not yet supported. This limitation may be removed in the future
3. When discarding return values, functions must have only an error return - When you don't accept any return values from a function (i.e., when using f()?), the function must have exactly one return value of type error. If a function returns multiple values (e.g., func f() (int, error)), you need to use _ to discard the non-error return values: _ = f()?

These constraints ensure the generated Go code remains clean, readable, and identical to hand-written code.

TODO

• Implement a Go-compatible command-line tool that supports all Go flags and commands, with the only difference being that it preprocesses all .ego files to .go files before running compile or test operations