How Does Bundler Work, Anyway? (RubyConf 2015)

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how does bundler work, anyway?

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how does bundler work, anyway?

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a brief (?) history of dependency management

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André Arko @indirect

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therubyway.io

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let’s share ruby code

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Gemﬁle gem “foo”

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Terminal $ bundle install

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Terminal $ bundle exec foo

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done! pretty cool, right?

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but… what just happened?

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iiiiit’s History ⚔ Time

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1994 2000 2003 2009 dependency timeline require setup.rb RubyGems Bundler

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require it loads the codes

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def require(filename) eval File.read(filename) end

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i’m sure it’s ﬁne run code twice?

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$LOADED_FEATURES = [] def require(filename) if $LOADED_FEATURES.include?(filename) return true end eval File.read(filename) $LOADED_FEATURES << filename end

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probably ﬁne too only absolute paths?

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$LOAD_PATH = [] def require(filename) full_path = $LOAD_PATH.first do |path| File.exist?(File.join(path, filename)) end eval File.read(full_path) end

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load paths are ⛄ pretty ❄ cool

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but now we need… setup.rb

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how do setup.rb? ruby setup.rb setup ruby setup.rb conﬁg ruby setup.rb install

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use ruby libraries 1. Find a cool library 2. Download the library 3. Untar the library 4. Run `ruby setup.rb all`

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no versions no uninstall but it’s ﬁne, I’m sure

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maybe a little bit incredibly tedious

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what if you could… gem install gem uninstall gem list rails

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bonus round! gem install rails -v 4.1 gem install rails -v 4.2 gem install rails -v 5.0

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gem "rack", "1.0" require "rack"

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$ rackup _1.2.2_ -p 3000

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so many gems! 100,000 gems 1,000,000 versions

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but gem apps don’t play well with others

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welcome to the team here’s your machine we expect setting up to take a week

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# config/application.rb […] config.gem “rack” config.gem “rails” config.gem “what?” […]

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“why is this broken in production?” “dunno, it works on every developer machine” 3 days of debugging later… “oh, look, one production server has frobnitz 1.1.3, but the others have 1.1.4” “welp. that explains those exceptions ”

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version conﬂicts gem install rails rails s cd ../other-project rails s

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activation errors how common can they be, really?

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$ rails s Gem::LoadError: can't activate rack (~> 1.0.0., runtime) for ["actionpack-2.3.5"], already activated rack-1.1.0 for ["thin-1.2.7"] activation errors

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the moral runtime resolution install-time resolution

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wait… how do we resolve at install-time?

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addressable (2.3.7) arel (6.0.0) bcrypt (3.1.10) binding_of_caller (0.7.2) debug_inspector (>= 0.0.1) builder (3.2.2) byebug (3.5.1) columnize (~> 0.8) debugger-linecache (~> 1.2) slop (~> 3.6) celluloid (0.16.0) Gemﬁle.lock

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bundle install my old friend 1. Read the Gemﬁle (and lock, if it's there) 2. Ask RubyGems.org for a list of every gem we need 2. Find gems allowed by the Gemﬁle that work together 3. Write down those versions in the lock for future installs 4. Install gems until every locked gem is installed

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bundle exec everyone’s nemesis 1. Read the Gemﬁle (and lock, if it's there) 2a. Use locked gems if possible OR 2b. Find versions that work to put in the lock 3. Remove any existing gems the $LOAD_PATH 4. Add each gem in the lock to the $LOAD_PATH

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pro tip no more bundle exec! $ bundle binstubs rspec-core $ bin/rspec repeat as needed for other gems