pry起動時に「Sorry, you can't use Pry without Readline or a compatible library.」と言われる場合あるいはirbで矢印キーが動かない場合

irbで矢印キーを入力するとエスケープ文字が出力されてしまったり、pryを移動させるとエラーになってしまう場合の対処。

OSのバージョンをSierraにしたからか、irbやpryがうまく動かなくなってしまった。

# bundle exec pry
Sorry, you can't use Pry without Readline or a compatible library.
Possible solutions:
 * Rebuild Ruby with Readline support using `--with-readline`
 * Use the rb-readline gem, which is a pure-Ruby port of Readline
 * Use the pry-coolline gem, a pure-ruby alternative to Readline
bundler: failed to load command: pry (/private/tmp/hoge/vendor/bundle/bin/pry)
LoadError: dlopen(/Users/sugamasao/.rbenv/versions/2.3.1/lib/ruby/2.3.0/x86_64-darwin15/readline.bundle, 9): Library not loaded: /usr/local/opt/readline/lib/libreadline.6.dylib
  Referenced from: /Users/sugamasao/.rbenv/versions/2.3.1/lib/ruby/2.3.0/x86_64-darwin15/readline.bundle
  Reason: image not found - /Users/sugamasao/.rbenv/versions/2.3.1/lib/ruby/2.3.0/x86_64-darwin15/readline.bundle
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/default.rb:151:in `require'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/default.rb:151:in `lazy_readline'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/default.rb:6:in `block in <class:Default>'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/default.rb:125:in `instance_eval'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/default.rb:125:in `block (2 levels) in <class:Default>'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/behavior.rb:54:in `public_send'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/config/behavior.rb:54:in `method_missing'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/history.rb:19:in `restore_default_behavior'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/history.rb:14:in `initialize'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/pry_class.rb:33:in `new'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/pry_class.rb:33:in `history'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/pry_class.rb:222:in `load_history'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/pry_class.rb:129:in `initial_session_setup'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/cli.rb:206:in `block in <top (required)>'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/cli.rb:83:in `block in parse_options'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/cli.rb:83:in `each'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/lib/pry/cli.rb:83:in `parse_options'
  /private/tmp/hoge/vendor/bundle/gems/pry-0.10.4/bin/pry:16:in `<top (required)>'
  /private/tmp/hoge/vendor/bundle/bin/pry:23:in `load'
  /private/tmp/hoge/vendor/bundle/bin/pry:23:in `<top (required)>'

調べてみると、どうも readline がおかしいらしい。

readlineを入れ直す

複数バージョン入っていたので一度全て消してインストール

$ brew uninstall readline
Uninstalling /usr/local/Cellar/readline/7.0... (45 files, 2M)
readline 6.3.5, 6.3.8 are still installed.
Remove all versions with `brew uninstall --force readline`.
$ brew uninstall --force readline
Uninstalling readline... (92 files, 4M)
$ brew install readline
==> Auto-updated Homebrew!
Updated 2 taps (homebrew/core, homebrew/science).

Rubyを入れ直す

rbenvなのでrbenvでuninstallしてinstallする

$ rbenv uninstall 2.3.1
rbenv: remove /Users/sugamasao/.rbenv/versions/2.3.1? y
$ rbenv install 2.3.1

これでpryを起動したりするとうまく動くようになった。やったー