[ruby-core:116270] [Ruby master Bug#20188] `Module#const_source_location` returns wrong information when real constant was defined but autoload is still ongoing

Issue #20188 has been updated by fxn (Xavier Noria).


I tried, the current behavior does not make a lot of sense to me:

```ruby
File.write('/tmp/bar.rb', 'Bar = 1; raise')
autoload :Bar, '/tmp/bar'
Bar rescue nil

p Object.const_source_location(:Bar) # ["foo.rb", 2]
p Object.autoload?(:Bar) # "/tmp/bar"
p Bar # raises
```

In Ruby, an `autoload` is a trigger, you are not even required to define the constant in the receiver. The autoload was triggered, therefore, in my view it should be gone. I would expect:

```ruby
p Object.const_source_location(:Bar) # ["/tmp/bar.rb", 1]
p Object.autoload?(:Bar) # nil
p Bar # 1
```

Regarding the first sentence, here's an autoload that does not define a constant. It is just a trigger:

```ruby
module M
  Bar = 1
end

class Object
  include M
end

File.write('/tmp/bar.rb', '')
autoload :Bar, '/tmp/bar'
Bar

p Object.const_source_location(:Bar) # ["foo.rb", 2]
p Object.autoload?(:Bar) # nil
p Bar # 1
```

Could it be the case that the internal "housekeeping" just does not get a chance because the exeption bubbles up?

----------------------------------------
Bug #20188: `Module#const_source_location` returns wrong information when real constant was defined but autoload is still ongoing
https://bugs.ruby-lang.org/issues/20188#change-106292

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
----------------------------------------
Ref: https://github.com/fxn/zeitwerk/issues/281

`const_source_location` keeps returning the location of the `autoload` call, even after the real constant was defined. It only starts returning the real constant location once the autoload was fully completed.

```ruby
# /tmp/autoload.rb
File.write("/tmp/const.rb", <<~RUBY)
module Const
  LOCATION = Object.const_source_location(:Const)
end
RUBY

autoload :Const, "/tmp/const"

p Const::LOCATION
```

Expected Output:

```ruby
["/tmp/const.rb", 1]
```

Actual Output:

```ruby
["/tmp/autoload.rb", 8]
```

Potential patch: https://github.com/ruby/ruby/pull/9549



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