Which libraries are loaded by default in pry? - ruby

Question

When I use Tempfile class in pry, I don't use require it.
% pry -f
pry(main)> Tempfile
Tempfile < #<Class:0x00007fb5121149b8>
But when in irb I must to require tempfile first.
% irb
irb(main):001:0> Tempfile
NameError: uninitialized constant Tempfile
from (irb):1
from /Users/ironsand/.rbenv/versions/2.4.3/bin/irb:11:in `<main>'
irb(main):002:0> require 'tempfile'
=> true
So it seems pry load some libraries by default.
Which libraries are actually loaded?
This is my environment
% ruby -v
ruby 2.4.3p205 (2017-12-14 revision 61247) [x86_64-darwin17]
% irb --version
pirb 0.9.6(09/06/30)
% pry --version
Pry version 0.11.3 on Ruby 2.4.3

Answer 1

You can compare $LOADED_FEATURES to see everything that's loaded in a default pry session vs an irb session (or a plain ruby script).
The short answer is that Pry loads whichever libraries it needs to provide its own behaviour. The long answer is too long (and too likely to get out of date, or differ between versions) to list here -- better to ask your current environment.
It's good practice not to rely on other libraries to load their dependencies for you, because those dependencies can change. (Though in cases like this, it can be hard to notice you're missing a require, because everything still works.)

Answer 2

As an alternative to $LOADED_FEATURES, which can be a bit excessive, consider:
Gem.loaded_specs.values.each {|s| puts s.name}
which only lists gems with specs
[20] pry(main)> Gem.loaded_specs.values.each {|s| puts s.name};nil
did_you_mean
coderay
method_source
pry
io-console
vls
=> nil
BTW, in this example, I had loaded the vls gem manually.