We can see it also in rh-ruby27 collection.

+++ This bug was initially created as a clone of Bug #1835836 +++

Description of problem:

When rubygem-psych RPM is installed, run the following test.rb script. Then the following error happens.

```
$ gem info psych

*** LOCAL GEMS ***

psych (3.1.0)
    Authors: Aaron Patterson, SHIBATA Hiroshi, Charles Oliver Nutter
    Homepage: https://github.com/ruby/psych
    License: MIT
    Installed at: /usr/share/gems

    Psych is a YAML parser and emitter
```

```
$ cat test.rb 
require 'psych'
Gem.load_yaml
```

```
$ ruby test.rb
/usr/lib64/gems/ruby/psych-3.1.0/psych.so: warning: already initialized constant Psych::Parser::ANY
...

/usr/share/gems/gems/psych-3.1.0/lib/psych/parser.rb:34:in `<class:Parser>': superclass mismatch for class Mark (TypeError)
```


Version-Release number of selected component (if applicable):
ruby-2.7.1-130.fc33.x86_64
rubygem-psych-3.1.0-130.fc33.x86_64

How reproducible:


Steps to Reproduce:
1. Create this Ruby script.

```
$ cat test.rb 
require 'psych'
Gem.load_yaml
```

2. Run the script.

$ ruby test.rb 

Actual results:

```
$ ruby test.rb 
/usr/lib64/gems/ruby/psych-3.1.0/psych.so: warning: already initialized constant Psych::Parser::ANY
/usr/lib64/gems/ruby/psych-3.1.0/psych.so: warning: already initialized constant Psych::Parser::UTF8
/usr/lib64/gems/ruby/psych-3.1.0/psych.so: warning: already initialized constant Psych::Parser::UTF16LE
/usr/lib64/gems/ruby/psych-3.1.0/psych.so: warning: already initialized constant Psych::Parser::UTF16BE
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:7: warning: already initialized constant Psych::ClassLoader::BIG_DECIMAL
/usr/share/ruby/psych/class_loader.rb:7: warning: previous definition of BIG_DECIMAL was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:8: warning: already initialized constant Psych::ClassLoader::COMPLEX
/usr/share/ruby/psych/class_loader.rb:8: warning: previous definition of COMPLEX was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:9: warning: already initialized constant Psych::ClassLoader::DATE
/usr/share/ruby/psych/class_loader.rb:9: warning: previous definition of DATE was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:10: warning: already initialized constant Psych::ClassLoader::DATE_TIME
/usr/share/ruby/psych/class_loader.rb:10: warning: previous definition of DATE_TIME was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:11: warning: already initialized constant Psych::ClassLoader::EXCEPTION
/usr/share/ruby/psych/class_loader.rb:11: warning: previous definition of EXCEPTION was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:12: warning: already initialized constant Psych::ClassLoader::OBJECT
/usr/share/ruby/psych/class_loader.rb:12: warning: previous definition of OBJECT was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:13: warning: already initialized constant Psych::ClassLoader::PSYCH_OMAP
/usr/share/ruby/psych/class_loader.rb:13: warning: previous definition of PSYCH_OMAP was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:14: warning: already initialized constant Psych::ClassLoader::PSYCH_SET
/usr/share/ruby/psych/class_loader.rb:14: warning: previous definition of PSYCH_SET was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:15: warning: already initialized constant Psych::ClassLoader::RANGE
/usr/share/ruby/psych/class_loader.rb:15: warning: previous definition of RANGE was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:16: warning: already initialized constant Psych::ClassLoader::RATIONAL
/usr/share/ruby/psych/class_loader.rb:16: warning: previous definition of RATIONAL was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:17: warning: already initialized constant Psych::ClassLoader::REGEXP
/usr/share/ruby/psych/class_loader.rb:17: warning: previous definition of REGEXP was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:18: warning: already initialized constant Psych::ClassLoader::STRUCT
/usr/share/ruby/psych/class_loader.rb:18: warning: previous definition of STRUCT was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:19: warning: already initialized constant Psych::ClassLoader::SYMBOL
/usr/share/ruby/psych/class_loader.rb:19: warning: previous definition of SYMBOL was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/class_loader.rb:65: warning: already initialized constant Psych::ClassLoader::CACHE
/usr/share/ruby/psych/class_loader.rb:65: warning: previous definition of CACHE was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/scalar_scanner.rb:9: warning: already initialized constant Psych::ScalarScanner::TIME
/usr/share/ruby/psych/scalar_scanner.rb:9: warning: previous definition of TIME was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/scalar_scanner.rb:12: warning: already initialized constant Psych::ScalarScanner::FLOAT
/usr/share/ruby/psych/scalar_scanner.rb:12: warning: previous definition of FLOAT was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/scalar_scanner.rb:17: warning: already initialized constant Psych::ScalarScanner::INTEGER
/usr/share/ruby/psych/scalar_scanner.rb:17: warning: previous definition of INTEGER was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/stream.rb:13: warning: already initialized constant Psych::Nodes::Stream::ANY
/usr/share/ruby/psych/nodes/stream.rb:13: warning: previous definition of ANY was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/stream.rb:16: warning: already initialized constant Psych::Nodes::Stream::UTF8
/usr/share/ruby/psych/nodes/stream.rb:16: warning: previous definition of UTF8 was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/stream.rb:19: warning: already initialized constant Psych::Nodes::Stream::UTF16LE
/usr/share/ruby/psych/nodes/stream.rb:19: warning: previous definition of UTF16LE was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/stream.rb:22: warning: already initialized constant Psych::Nodes::Stream::UTF16BE
/usr/share/ruby/psych/nodes/stream.rb:22: warning: previous definition of UTF16BE was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/sequence.rb:43: warning: already initialized constant Psych::Nodes::Sequence::ANY
/usr/share/ruby/psych/nodes/sequence.rb:43: warning: previous definition of ANY was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/sequence.rb:46: warning: already initialized constant Psych::Nodes::Sequence::BLOCK
/usr/share/ruby/psych/nodes/sequence.rb:46: warning: previous definition of BLOCK was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/sequence.rb:49: warning: already initialized constant Psych::Nodes::Sequence::FLOW
/usr/share/ruby/psych/nodes/sequence.rb:49: warning: previous definition of FLOW was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:10: warning: already initialized constant Psych::Nodes::Scalar::ANY
/usr/share/ruby/psych/nodes/scalar.rb:10: warning: previous definition of ANY was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:13: warning: already initialized constant Psych::Nodes::Scalar::PLAIN
/usr/share/ruby/psych/nodes/scalar.rb:13: warning: previous definition of PLAIN was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:16: warning: already initialized constant Psych::Nodes::Scalar::SINGLE_QUOTED
/usr/share/ruby/psych/nodes/scalar.rb:16: warning: previous definition of SINGLE_QUOTED was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:19: warning: already initialized constant Psych::Nodes::Scalar::DOUBLE_QUOTED
/usr/share/ruby/psych/nodes/scalar.rb:19: warning: previous definition of DOUBLE_QUOTED was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:22: warning: already initialized constant Psych::Nodes::Scalar::LITERAL
/usr/share/ruby/psych/nodes/scalar.rb:22: warning: previous definition of LITERAL was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/scalar.rb:25: warning: already initialized constant Psych::Nodes::Scalar::FOLDED
/usr/share/ruby/psych/nodes/scalar.rb:25: warning: previous definition of FOLDED was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/mapping.rb:17: warning: already initialized constant Psych::Nodes::Mapping::ANY
/usr/share/ruby/psych/nodes/mapping.rb:17: warning: previous definition of ANY was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/mapping.rb:20: warning: already initialized constant Psych::Nodes::Mapping::BLOCK
/usr/share/ruby/psych/nodes/mapping.rb:20: warning: previous definition of BLOCK was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/nodes/mapping.rb:23: warning: already initialized constant Psych::Nodes::Mapping::FLOW
/usr/share/ruby/psych/nodes/mapping.rb:23: warning: previous definition of FLOW was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/visitors/visitor.rb:11: warning: already initialized constant Psych::Visitors::Visitor::DISPATCH
/usr/share/ruby/psych/visitors/visitor.rb:11: warning: previous definition of DISPATCH was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/visitors/to_ruby.rb:336: warning: already initialized constant Psych::Visitors::ToRuby::SHOVEL
/usr/share/ruby/psych/visitors/to_ruby.rb:336: warning: previous definition of SHOVEL was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/handler.rb:27: warning: already initialized constant Psych::Handler::OPTIONS
/usr/share/ruby/psych/handler.rb:27: warning: previous definition of OPTIONS was here
/usr/share/gems/gems/psych-3.1.0/lib/psych/handler.rb:30: warning: already initialized constant Psych::Handler::EVENTS
/usr/share/ruby/psych/handler.rb:30: warning: previous definition of EVENTS was here
Traceback (most recent call last):
	9: from test.rb:2:in `<main>'
	8: from /usr/share/rubygems/rubygems.rb:696:in `load_yaml'
	7: from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:72:in `require'
	6: from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:72:in `require'
	5: from /usr/share/gems/gems/psych-3.1.0/lib/psych.rb:20:in `<top (required)>'
	4: from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:72:in `require'
	3: from /usr/share/rubygems/rubygems/core_ext/kernel_require.rb:72:in `require'
	2: from /usr/share/gems/gems/psych-3.1.0/lib/psych/parser.rb:2:in `<top (required)>'
	1: from /usr/share/gems/gems/psych-3.1.0/lib/psych/parser.rb:33:in `<module:Psych>'
/usr/share/gems/gems/psych-3.1.0/lib/psych/parser.rb:34:in `<class:Parser>': superclass mismatch for class Mark (TypeError)
```


Expected results:

The error does not happens. This issue does not happen on the upstream Ruby.

```
$ ruby test.rb 
$ echo $?
0
```

Additional info:

I think this issue is related to this upstream issue.
https://github.com/ruby/psych/issues/386

--- Additional comment from Jun Aruga on 2020-05-14 17:37:07 UTC ---

This issue also happen on f31 with:
  ruby-2.7.1-130.fc32.x86_64
  rubygems-3.1.2-130.fc32.noarch
  rubygem-psych-3.1.0-130.fc32.x86_64.
But it does not happen on f30 with:
  ruby-2.6.5-124.fc31.x86_64
  rubygems-3.0.3-124.fc31.noarch
  rubygem-psych-3.1.0-124.fc31.x86_64.

On f31, the result of `ruby test.rb` is like this.

```
$ ruby test.rb 
/usr/share/gems/gems/psych-3.1.0/lib/psych.rb:237: warning: already initialized constant Psych::LIBYAML_VERSION
/usr/share/ruby/psych.rb:237: warning: previous definition of LIBYAML_VERSION was here
/usr/share/gems/gems/psych-3.1.0/lib/psych.rb:239: warning: already initialized constant Psych::NOT_GIVEN
/usr/share/ruby/psych.rb:239: warning: previous definition of NOT_GIVEN was here

$ echo $?
0
```

--- Additional comment from Jun Aruga on 2020-05-14 18:21:48 UTC ---

Sorry for the 2 typos.

> This issue also happen on f31 with:

Correction
This issue also happen on f32 with:

> But it does not happen on f30 with:

Correction
But it does not happen on f31 with:

--- Additional comment from Vít Ondruch on 2020-05-14 20:52:39 UTC ---

> On f31, the result of `ruby test.rb` is like this.
> 
> ```
> $ ruby test.rb 
> /usr/share/gems/gems/psych-3.1.0/lib/psych.rb:237: warning: already
> initialized constant Psych::LIBYAML_VERSION
> /usr/share/ruby/psych.rb:237: warning: previous definition of
> LIBYAML_VERSION was here
> /usr/share/gems/gems/psych-3.1.0/lib/psych.rb:239: warning: already
> initialized constant Psych::NOT_GIVEN
> /usr/share/ruby/psych.rb:239: warning: previous definition of NOT_GIVEN was
> here
> 
> $ echo $?
> 0
> ```

IOW the issues is still the same, only the magnitude is different.

https://github.com/rubygems/rubygems/issues/3131

--- Additional comment from Mamoru TASAKA on 2020-05-14 23:51:14 UTC ---

This is the same as https://src.fedoraproject.org/rpms/rubygem-racc/pull-request/1#comment-37003

i.e.
```
require "psych"
gem "psych"
require "psych"
```

causes this error.

--- Additional comment from Jun Aruga on 2020-05-15 08:53:49 UTC ---

Thanks for the information. It's very helpful.

I found a temporary workflow to avoid this issue.

```
<mock-chroot> sh-5.0# diff -u /usr/share/rubygems/rubygems.rb{.orig,}
--- /usr/share/rubygems/rubygems.rb.orig	2020-03-31 12:44:55.000000000 +0200
+++ /usr/share/rubygems/rubygems.rb	2020-05-15 10:48:33.008250387 +0200
@@ -685,7 +685,7 @@
     return unless defined?(gem)
 
     begin
-      gem 'psych', '>= 2.0.0'
+      # gem 'psych', '>= 2.0.0'
     rescue Gem::LoadError
       # It's OK if the user does not have the psych gem installed.  We will
       # attempt to require the stdlib version
```

Then the above test.rb works.

```
$ ruby test.rb 

$ echo $?
0
```

As a long term solution in Fedora, I think that it's better to change rubygem-psych to the default bundled gem like rubygem-racc did.

--- Additional comment from Vít Ondruch on 2020-05-15 08:58:48 UTC ---

As a long term, RubyGems should not call `gem` command. There used to be the Syck/Psych switch, which was partly removed, but not entirely. I was looking into this a bit, but it is unfortunately rabbit hole.

--- Additional comment from Jun Aruga on 2020-05-15 09:47:04 UTC ---

> I found a temporary workflow to avoid this issue.

Or like this in safer manner.

```
<mock-chroot> sh-5.0# diff -u /usr/share/rubygems/rubygems.rb{.orig,}
--- /usr/share/rubygems/rubygems.rb.orig	2020-03-31 12:44:55.000000000 +0200
+++ /usr/share/rubygems/rubygems.rb	2020-05-15 11:43:34.851595500 +0200
@@ -685,7 +685,11 @@
     return unless defined?(gem)
 
     begin
-      gem 'psych', '>= 2.0.0'
+      begin
+        require 'psych'
+      rescue ::LoadError
+        gem 'psych', '>= 2.0.0'
+      end
     rescue Gem::LoadError
       # It's OK if the user does not have the psych gem installed.  We will
       # attempt to require the stdlib version
```

--- Additional comment from Jun Aruga on 2020-05-15 10:53:55 UTC ---

Here is a list of the rubygem packages depending on psych.
When loading the rubygem package and calling Gem.load_yaml, this issue happen.
https://rubygems.org/gems/psych/reverse_dependencies

Rubocop had had the issue. But the project dropped the psych dependency later to avoid the issue.
https://github.com/rubocop-hq/rubocop/commit/95d2110e49e160ffb785a74b22727593f17d552b