Feature #19849: Requiring file with autoload results in confusing error if file doesn't exist

• Status: Open
• Assignee: -
• Target version: -

[p8 (Petrik de Heus)]

Given the following file that calls the Example constant:

# example.rb
require_relative 'autoload_example.rb'

Example.new

and an autoload to define the Example constant, with an unknown path:

# autoload_example.rb
autoload "Example", "path_unknown"

Running ruby example.rb results in the following error:

<internal:~/.rubies/ruby-3.2.2/lib/ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- path_unknown (LoadError)
	from <internal:~/.rubies/ruby-3.2.2/lib/ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from example.rb:4:in `<main>'

The error is somewhat confusing as it doesn't show the location of the autoload which caused the error.
This can be especially confusing if the autoload is called somewhere deep in a gem.

[p8 (Petrik de Heus)]

• Description updated (diff)

[p8 (Petrik de Heus)]

• Tracker changed from Bug to Feature
• Backport deleted (3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN)

[Eregon (Benoit Daloze)]

It cannot be part of the backtrace, because that line is executed way before and not when autoloading the constant.

It could maybe be part of the error message, but that might be weird and also quite difficult, because autoloading calls require and that might be overridden, so it's hard to pass that state from autoloading to require and know to which require call it should apply.

[mame (Yusuke Endoh)]

• Description updated (diff)

[mame (Yusuke Endoh)]

Briefly discussed at the dev meeting.

We understand the problem, but doesn't find a good solution. Since the call line of autoload does not exist in the call stack when the exception occurs, it cannot be displayed as a backtrace.
It may be possible to include it in an error message or Exception#cause. If there are specific suggestions on how to actually implement it and how to display it, it could be considered.