From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2023-06-21T15:44:33+00:00
Subject: [ruby-core:113973] [Ruby master Bug#19726] Script loadde twice when requiring self

Issue #19726 has been updated by jeremyevans0 (Jeremy Evans).


Making this change would not be backwards compatible:

```ruby
# a.rb
if __FILE__ == $0
  # $LOADED_FEATURES << File.expand_path(__FILE__) # would break things
  require './b'
else
  def a
    1
  end
end

# b.rb
require './a'
p a
```

The main script is treated specially compared to required files, in ways beyond this.  I'm not sure that it is worth changing this and introducing backwards compatibility issues.  Especially since this would still be a circular require, which Ruby issues a warning for in verbose warning mode.

----------------------------------------
Bug #19726: Script loadde twice when requiring self
https://bugs.ruby-lang.org/issues/19726#change-103630

* Author: johannes (Johannes Krude)
* Status: Open
* Priority: Normal
* ruby -v:  ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [x86_64-linux]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
The executed program is not added to `$LOADED_FEATURES` unexpectedly resulting in the program possibly being loaded twice:

a.rb:
```
#!/usr/bin/env ruby

require "./b"

C = 42

return unless __FILE__ == $0

puts C
```

b.rb:
```
require "./a"
```

This results in:
```
$ ./a.rb 
./a.rb:5: warning: already initialized constant C
/home/johannes/t/a.rb:5: warning: previous definition of C was here
42
```

Ruby version:
```
$ sudo docker run ruby:3.3.0-preview1 ruby --version
ruby 3.3.0preview1 (2023-05-12 master a1b01e7701) [x86_64-linux]
```

**This could be solved by always adding the executed program to `$LOADED_FEATURES`.**


As a workaround, executed programs can be prepended with:
```
require "pathname"
if __FILE__ == $0
	$LOADED_FEATURES << Pathname.new(__FILE__).expand_path.to_s
end
```



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