Feature #7376

Proposal for new syntax construct to define errors

Added by Kenn Ejima over 2 years ago. Updated over 2 years ago.

[ruby-core:49465]
Status:Rejected
Priority:Normal
Assignee:-

Description

=begin
As discussed here - https://gist.github.com/4091803

When we define an error class in a module, we do one of the following two ways.

module App
class Error < StandardError; end
class ServerError < Error; end
class ClientError < Error; end
end

module App
Error = Class.new(StandardError)
ServerError = Class.new(Error)
ClientError = Class.new(Error)
end

IMO, the ugliness of the syntax is partly responsible that not many libraries have custom errors of their own, even when it makes sense.

It would be great if we could write this way instead:

module App
define_error Error # inherits StandardError by default
define_error ServerError, ClientError < Error # inherits App::Error
end

Which would encourage define errors.

I realized that the same could apply to empty class inheritance in general, but errors are much more likely to inherit without adding any features - thus naming specifically (({define_error})) here.

Or, as Matz suggested in the comment:

module App
define_error :Error
define_error :ServerError, :ClientError, super: Error
end

this one looks good too.
=end

History

#1 Updated by Yukihiro Matsumoto over 2 years ago

  • Status changed from Open to Rejected

Put the following code to your program:

class Module
def define_error(*errors, superclass: StandardError)
errors.each do |e|
self.const_set(e, Class.new(superclass))
end
end
end

def define_error(errors, **k)
Object.define_error(
errors, **k)
end

Matz.

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