`uninitialized constant JSON::Fragment` from `require 'json'`

[ntkme]

The root cause is again the famous ruby/rubygems#6490.

$ gem --version
3.3.27

$ gem info json

*** LOCAL GEMS ***

json (2.10.1, 2.6.1)
    Author: Florian Frank
    Homepage: https://github.com/ruby/json
    License: Ruby
    Installed at (2.10.1): /usr/local/bundle
                 (2.6.1, default): /usr/local/lib/ruby/gems/3.1.0

    JSON Implementation for Ruby

$ /usr/local/bin/ruby -I/usr/local/lib/ruby/3.1.0 -r json -e ''
<internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require': uninitialized constant JSON::Fragment (NameError)
	from <internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from /usr/local/lib/ruby/3.1.0/json/ext.rb:8:in `<module:Ext>'
	from /usr/local/lib/ruby/3.1.0/json/ext.rb:6:in `<module:JSON>'
	from /usr/local/lib/ruby/3.1.0/json/ext.rb:3:in `<top (required)>'
	from <internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from <internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from /usr/local/lib/ruby/3.1.0/json.rb:579:in `<module:JSON>'
	from /usr/local/lib/ruby/3.1.0/json.rb:575:in `<top (required)>'
	from <internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
	from <internal:/usr/local/lib/ruby/3.1.0/rubygems/core_ext/kernel_require.rb>:85:in `require'

This happened in my CI job where my gem has a Rakefile based extension, and the Rakefile has require 'json':

https://github.com/sass-contrib/sass-embedded-host-ruby/actions/runs/13320451344/job/37204292341

[ntkme]

I do not expect anything to be done here, because the root cause is really ruby/rubygems#6490

I'm reporting this just incase someone else run into the same issue.

[Fryguy]

I'm also hitting this issue, and I'm not sure how ruby/rubygems#6490 is involved. @ntkme Can you please reopen, as a closed issue is not helpful for those searching and diagnosing this issue?

@byroot, I can reproduce this issue with the following script (Ruby 3.3.7, clean install of Ruby):

#!/usr/bin/env ruby

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "json_pure", "~> 2.6.3"
  gem "json"
end
require "json"

Note this happens specifically with json_pure 2.6.3, but if I upgrade to json_pure 2.7+, then it passes fine.

However in my application I can't control the json_pure version, as it's coming into my application as a transitive dependency. More closely to my situation, this script below is breaking for me, as the latest travis gem has its json_pure dependency as ~> 2.6.3. I don't know how to fix it other than requesting a release of json_pure 2.6.4 with the necessary fixes. 🙏

#!/usr/bin/env ruby

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "travis"
  gem "json"
end
require "json"

[ntkme]

Here is how ruby/rubygems#6490 works:

    Installed at (2.10.1): /usr/local/bundle
                 (2.6.1, default): /usr/local/lib/ruby/gems/3.1.0

In a correct environment, the default $LOAD_PATH looks like (bundle exec ruby -e 'pp $LOAD_PATH'):

["/usr/local/bundle/gems/json-2.10.1/lib"
 "/usr/local/lib/ruby/site_ruby/3.1.0",
 "/usr/local/lib/ruby/site_ruby/3.1.0/aarch64-linux-musl",
 "/usr/local/lib/ruby/site_ruby",
 "/usr/local/lib/ruby/vendor_ruby/3.1.0",
 "/usr/local/lib/ruby/vendor_ruby/3.1.0/aarch64-linux-musl",
 "/usr/local/lib/ruby/vendor_ruby",
 "/usr/local/lib/ruby/3.1.0",
 "/usr/local/lib/ruby/3.1.0/aarch64-linux-musl"]

In this case, both the ruby code and ext are loaded from the same place, as they are the first of $LOAD_PATH

/usr/local/bundle/gems/json-2.10.1/lib/json.rb
/usr/local/bundle/gems/json-2.10.1/lib/json/ext

With an old buggy rubygems, during extconf, -I/usr/local/lib/ruby/3.1.0 is added to the parameter, and $LOAD_PATH becomes:

["/usr/local/lib/ruby/3.1.0",
 "/usr/local/bundle/gems/json-2.10.1/lib"
 "/usr/local/lib/ruby/site_ruby/3.1.0",
 "/usr/local/lib/ruby/site_ruby/3.1.0/aarch64-linux-musl",
 "/usr/local/lib/ruby/site_ruby",
 "/usr/local/lib/ruby/vendor_ruby/3.1.0",
 "/usr/local/lib/ruby/vendor_ruby/3.1.0/aarch64-linux-musl",
 "/usr/local/lib/ruby/vendor_ruby",
 "/usr/local/lib/ruby/3.1.0",
 "/usr/local/lib/ruby/3.1.0/aarch64-linux-musl"]

And now it loads the ruby code of 2.6.1 and the ext of 2.10.1, thus causing the incompatibility:

• /usr/local/lib/ruby/3.1.0/json.rb -> loaded from "/usr/local/lib/ruby/3.1.0"
• /usr/local/bundle/gems/json-2.10.1/lib/json/ext -> loaded from "/usr/local/bundle/gems/json-2.10.1/lib"

The reason it won't load the ext from 2.6.1 is because it's under a different load path, which is at the very end of the load path:

• /usr/local/lib/ruby/3.1.0/aarch64-linux-musl/json/ext -> comes from "/usr/local/lib/ruby/3.1.0/aarch64-linux-musl"

[Fryguy]

Ah ok, I think I understand. I'm not sure my situation is the exactly the same, but the underlying problem sounds similar.

In my case both json_pure and json have a json/ext.rb file. json_pure 2.6.3 calls require 'json/ext/parser', but that json/ext/parser is in the json library. So there is some seemingly intentional cross-gem requires going on, which might be related.

I've created an updated script:

#!/usr/bin/env ruby

puts "Before:"
pp $LOAD_PATH

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "json_pure", "~> 2.6.3"
  gem "json", :require => false
end

puts "After:"
pp $LOAD_PATH

require "json"

ruby test.rb
Before:
["/Users/jfrey/.gem/ruby/3.3.7/gems/io-console-0.8.0/lib",
 "/Users/jfrey/.gem/ruby/3.3.7/extensions/arm64-darwin-23/3.3.0/io-console-0.8.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby/3.3.0/arm64-darwin23",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby/3.3.0/arm64-darwin23",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/arm64-darwin23"]
After:
["/Users/jfrey/.gem/ruby/3.3.7/gems/io-console-0.8.0/lib",
 "/Users/jfrey/.gem/ruby/3.3.7/gems/bundler-2.6.3/lib",
 "/Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib",
 "/Users/jfrey/.gem/ruby/3.3.7/gems/json-2.10.1/lib",
 "/Users/jfrey/.gem/ruby/3.3.7/extensions/arm64-darwin-23/3.3.0/json-2.10.1",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby/3.3.0/arm64-darwin23",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/site_ruby",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby/3.3.0/arm64-darwin23",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/vendor_ruby",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0",
 "/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/arm64-darwin23"]
/Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `require': uninitialized constant JSON::Fragment (NameError)

        kernel_class.send(:no_warning_require, name)
                    ^^^^^
	from /Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `block (2 levels) in replace_require'
	from /Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib/json/ext.rb:8:in `<module:Ext>'
	from /Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib/json/ext.rb:6:in `<module:JSON>'
	from /Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib/json/ext.rb:3:in `<top (required)>'
	from /Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `require'
	from /Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `block (2 levels) in replace_require'
	from /Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib/json.rb:579:in `<module:JSON>'
	from /Users/jfrey/.gem/ruby/3.3.7/gems/json_pure-2.6.3/lib/json.rb:575:in `<top (required)>'
	from /Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `require'
	from /Users/jfrey/.rubies/ruby-3.3.7/lib/ruby/3.3.0/bundled_gems.rb:69:in `block (2 levels) in replace_require'
	from test.rb:16:in `<main>'

[ntkme]

@Fryguy Right, in your case it's more of a user error that you're mixing different versions of json_pure and json.

Preferably, you should get json_pure removed. As you said you cannot do that, then a workaround is to change the $LOAD_PATH order before require 'json' is called:

#!/usr/bin/env ruby

require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "json_pure", "~> 2.6.3"
  gem "json", :require => false
end

$LOAD_PATH.unshift(*Gem::Dependency.new("json").to_spec.full_require_paths)

require "json"