[ruby-core:108560] [Ruby master Bug#15790] Strange interaction between autoload and $LOADED_FEATURES

Issue #15790 has been updated by ioquatix (Samuel Williams).


Another weird edge case we have now:

```
File.write("./empty.rb", "Y = 1")
autoload :X, "./empty.rb"

begin
  pp X
rescue NameError => error
  pp error
  # #<NameError: uninitialized constant Y>
end

pp autoload? :X
# nil

begin
  pp Y
rescue NameError => error
  pp error
  # #<NameError: uninitialized constant Y>
end

pp autoload? :Y
# nil
```

Generates:

```
#<NameError: uninitialized constant X>
nil
1
nil
```

Basically, autoloading can load completely different constants, even if it fails, and then is no longer present. I'm sure there are other odd things that can happen here - i.e. weird edge cases.

----------------------------------------
Bug #15790: Strange interaction between autoload and $LOADED_FEATURES
https://bugs.ruby-lang.org/issues/15790#change-97599

* Author: fxn (Xavier Noria)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 2.6.1p33 (2019-01-30 revision 66950) [x86_64-darwin18]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
If an autoload fails and we remove its associated file from `$LOADED_FEATURES`, the autoload is back:

```
$ cat x.rb
Y = 1 # should be X, emulates a typo

$ cat test.rb
def au
  Object.autoload?(:X).inspect
end

x_rb = File.realpath("x.rb")
autoload :X, x_rb

puts "before failed autoload autoload path is #{au}"

X rescue nil

puts "after failed autoload autoload path is #{au}"

$LOADED_FEATURES.delete(x_rb)

puts "after $LOADED_FEATURES deletion autoload path is #{au}"
```

The output is

```
$ ruby -v test.rb
ruby 2.6.1p33 (2019-01-30 revision 66950) [x86_64-darwin18]
before failed autoload autoload path is "/Users/fxn/tmp/x.rb"
after failed autoload autoload path is nil
after $LOADED_FEATURES deletion autoload path is "/Users/fxn/tmp/x.rb"
```

See? Last line would be expected to print a `nil` autoload path.



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