Can't activate gem: how do I figure out which gem has a dependency on this one?

I'm getting the following error:

Gem::Exception: can't activate hpricot (= 0.6.161, runtime), 
already activated hpricot-0.8.3

0.6 is installed locally, 0.8.3 is frozen in my app.

This is my "stacktrace":

Loading production environment (Rails 2.3.10)
/software/ruby-ror-gem-1.3.1/lib/rubygems.rb:149:in `activate':Gem::Exception: can't activate hpricot (= 0.6.161, runtime), already activated hpricot-0.8.3
/e/app/www.example.com/rails/releases/20101117142713/vendor/rails/railties/lib/console_with_helpers.rb:5:NameError: uninitialized constant ApplicationController

How do I figure out which gem or library has a dependency on hpricot 0.6?

I've added the output of user438962's command below:

{"daemons-1.0.9"=>[],
 "scgi_dp_rails-0.0.5"=>["preforkdp", "daemons"],
 "rails-2.3.10"=>[],
 "rwfd-0.1.0"=>[],
 "nokogiri-1.3.2"=>["racc", "rexical", "rake-compiler", "hoe"],
 "activesupport-2.3.10"=>[],
 "rack-1.0.1"=>
  ["test-spec",
   "camping",
   "fcgi",
   "memcache-client",
   "mongrel",
   "ruby-openid",
   "thin"],
 "rack-1.1.0"=>
  ["test-spec", "camping", "fcgi", "memcache-client", "mongrel", "thin"],
 "preforkdp-0.1.2"=>["rwfd"],
 "activerecord-2.3.10"=>[],
 "hpricot-0.6.161"=>[],
 "cgi_multipart_eof_fix-开发者_如何学编程2.5.0"=>[],
 "fastthread-1.0.1"=>[],
 "gem_plugin-0.2.3"=>[],
 "activeresource-2.3.10"=>[],
 "ferret-0.11.6"=>["rake"],
 "mysql-2.7"=>[],
 "actionmailer-2.3.10"=>[],
 "actionpack-2.3.10"=>[],
 "hpricot-0.8.3"=>[],
 "mongrel_upload_progress-0.2.2"=>["mongrel", "gem_plugin"],
 "mongrel-1.1.3"=>
  ["gem_plugin", "daemons", "fastthread", "cgi_multipart_eof_fix"],
 "mongrel_cluster-1.0.5"=>["gem_plugin", "mongrel"],
 "rake-0.8.4"=>[],
 "haml-2.0.9"=>[],
 "remvee-mini_magick-1.2.3.4.0"=>[]}

If you use Bundler, you avoid this problem and you have the really great command : bundle viz

This Command generate a graph with all dependencies.

require 'rubygems'
require 'pp'
h = {}
Gem.source_index.each{|g, spec| h[g] = spec.dependencies.map{|d| d.name} }
pp h

I found that rfeedparser is the gem that uses hpricot 0.6.

The problem is that this version (0.6) works with rfeedparser, but emits the warning "Passing no parameters to XML::SaxParser.new is deprecated."

Well, with newer versions of hpricot (at least 0.8.2), this warning seems to have taken effect, because now having that version of hpricot or newer causes "ArgumentError: wrong number of arguments (1 for 0)" when calling FeedParser.parse(url).

Unfortunately, I've found that the only way to make this work with legacy Rails (we have a 2.2.2 app) is to uninstall any hpricot version that's not 0.6.

The issue will be that one of the gems you use depends on hpricot version 0.6.161 and so tries to load it, but that you already have hpricot-0.8.3 loaded. The more recent version might be loaded if you're using hpricot yourself, and have required hpricot for use without specifying a version. If that's the case, you can change your own require to be the same version as the other gem uses (0.6.161).

The other reason the more recent version of hpricot is being loaded, could be that another gem you use depends on that version of hpricot, meaning you can't use the specific versions of those two gems you have because they have clashing requirements for their hpricot version.

Use the methods other users have posted to help you track down the dependencies of the gems you are using.

You could try grepping your load path:

$:.each do |dir|
  cmd = %(grep -r hpricot #{dir})
  puts cmd
  puts `#{cmd}`
end