[ruby-core:83008] [Ruby trunk Bug#13939] Ruby 2.4.2 has issue supporting Seattle.rb style for define_method

Issue #13939 has been updated by danielpclark (Daniel P. Clark).


> Perhaps the error message could be more indicative of the error or what the exact
problem is or how to solve it. I understand that the () provide additional information
that is in some way useful to the parser, or whatever is responsible, so perhaps the
message above could be changed somewhat.

> I guess ruby core prefers short messages when possible (aka "syntax error, unexpected '}'")
but this is indeed not always extremely helpful. With more recent changes such as the
did-you-mean-gem, but also some other discussions about better and more fine-tuned 
control over warnings/error messages, that may be more helpful to the average ruby 
hacker.

I apologize I wrote that earlier with a different error message.  Here's what importing 'read_source' does in Ruby 2.4.2 (but will work for any other version of Ruby).

~~~
/usr/share/rvm/rubies/ruby-2.3.5/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- read_source (LoadError)
	from /usr/share/rvm/rubies/ruby-2.3.5/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /home/danielpclark/dev/faster_path/test/monkeypatches/faster_path_test.rb:3:in `<top (required)>'
	from /usr/share/rvm/rubies/ruby-2.3.5/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /usr/share/rvm/rubies/ruby-2.3.5/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /home/danielpclark/.rvm/gems/ruby-2.3.5/gems/rake-12.0.0/lib/rake/rake_test_loader.rb:15:in `block in <main>'
	from /home/danielpclark/.rvm/gems/ruby-2.3.5/gems/rake-12.0.0/lib/rake/rake_test_loader.rb:4:in `select'
	from /home/danielpclark/.rvm/gems/ruby-2.3.5/gems/rake-12.0.0/lib/rake/rake_test_loader.rb:4:in `<main>'
rake aborted!
Command failed with status (1)
/home/danielpclark/.rvm/gems/ruby-2.3.5/gems/rake-12.0.0/exe/rake:27:in `<top (required)>'
/home/danielpclark/.rvm/gems/ruby-2.3.5/bin/ruby_executable_hooks:15:in `eval'
/home/danielpclark/.rvm/gems/ruby-2.3.5/bin/ruby_executable_hooks:15:in `<main>'
~~~

I wasn't going to include it here because I think that problem should be a different bug report.  The same error will occur for gem 'method_source' and only for Ruby 2.4.2.  I'm not sure this require issue is a Ruby bug yet.

The error shown in this report is not from being required but from running the test suite in the gem.

> By the way your last example does not work as-is :D

Ah, for that last example there should be a method defined within a class.

~~~ruby
class Example
  def apple
    "Johny Apple Seed was here"
  end

  define_method :johny, instance_method(:apple)
end
~~~

----------------------------------------
Bug #13939: Ruby 2.4.2 has issue supporting Seattle.rb style for define_method
https://bugs.ruby-lang.org/issues/13939#change-66917

* Author: danielpclark (Daniel P. Clark)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-linux]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
In Ruby 2.3 & 2.4.0 you can do this

~~~ruby
define_method :some_method_name { "asdf" }
~~~

As of my trying 2.4.2 this is no longer supported.  Anyone who tries to load my 'read_source' gem will get a failure message in require without explaining the specific area of code.

~~~
SyntaxError: /home/danielpclark/dev/read_source/test/support/example.rb:18: syntax error, unexpected '{', expecting keyword_end
ethod :also_attr_method_name { "asdf" }
                              ^
/home/danielpclark/dev/read_source/test/support/example.rb:18: syntax error, unexpected '}', expecting keyword_end
so_attr_method_name { "asdf" }
                              ^
	from (irb):2:in `require_relative'
	from (irb):2
	from /usr/share/rvm/rubies/ruby-2.4.2/bin/irb:11:in `<main>'
~~~

To fix my gem for Ruby 2.4.2 I now have to wrap the method name in parenthesis `()`

~~~ruby
define_method(:some_method_name) { "asdf" }
~~~

And that will work.  But I find this odd as the following will still work in 2.4.2:

~~~ruby
define_method :johny, instance_method(:apple)
~~~

Which is still Seattle.rb style.



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