Defer Readline load as long as possible (fix #1081, #1095)0-9-12-defer-readline

Also fixes rweng/pry-rails#50 and rails/spring#244.

8 files changed, 66 insertions, 33 deletions

diff --git a/lib/pry.rb b/lib/pry.rb
index 4b76bcee..2fe87cf6 100644
--- a/lib/pry.rb
+++ b/lib/pry.rb
@@ -196,6 +196,16 @@ class Pry
   # IRB = Pry thing.
   module ExtendCommandBundle
   end
+
+  def self.require_readline
+    return false if @required_readline
+    require 'readline'
+    @required_readline = true
+  rescue LoadError
+    warn "Sorry, you can't use Pry without Readline or a compatible library."
+    warn "Please `gem install rb-readline` or recompile Ruby --with-readline."
+    raise
+  end
 end
 
 if Pry::Helpers::BaseHelpers.mri_18?
@@ -213,19 +223,11 @@ require 'slop'
 require 'rbconfig'
 require 'tempfile'
 
-begin
-  require 'readline'
-rescue LoadError
-  warn "You're running a version of ruby with no Readline support"
-  warn "Please `gem install rb-readline` or recompile ruby --with-readline."
-  exit!
-end
-
 if Pry::Helpers::BaseHelpers.jruby?
   begin
     require 'ffi'
   rescue LoadError
-    warn "Need to `gem install ffi`"
+    warn "For a better Pry experience on JRuby, please `gem install ffi`."
   end
 end
 
@@ -236,7 +238,8 @@ if Pry::Helpers::BaseHelpers.windows? && !Pry::Helpers::BaseHelpers.windows_ansi
   # only fail on jruby (where win32console doesn't work).
   # Instead we'll recommend ansicon, which does.
   rescue LoadError
-    warn "For a better pry experience, please use ansicon: http://adoxa.3eeweb.com/ansicon/"
+    warn "For a better Pry experience on Windows, please use ansicon:"
+    warn "   http://adoxa.3eeweb.com/ansicon/"
   end
 end
 
diff --git a/lib/pry/completion.rb b/lib/pry/completion.rb
index 03ced306..e521aa53 100644
--- a/lib/pry/completion.rb
+++ b/lib/pry/completion.rb
@@ -5,6 +5,14 @@ class Pry
   module BondCompleter
 
     def self.build_completion_proc(target, pry=nil, commands=[""])
+      Pry.require_readline
+
+      # If we're using libedit, don't use Bond.
+      if Readline::VERSION =~ /editline/i
+        Pry.config.completer = InputCompleter
+        return InputCompleter.build_completion_proc(target, pry, commands)
+      end
+
       if !@started
         @started = true
         start
@@ -28,13 +36,6 @@ class Pry
 
   # Implements tab completion for Readline in Pry
   module InputCompleter
-
-    if Readline.respond_to?("basic_word_break_characters=")
-      Readline.basic_word_break_characters = " \t\n\"\\'`><=;|&{("
-    end
-
-    Readline.completion_append_character = nil
-
     ReservedWords = [
       "BEGIN", "END",
       "alias", "and",
@@ -60,10 +61,26 @@ class Pry
       "[]", "[]=", "^", "!", "!=", "!~"
     ]
 
+    # If we haven't configured Readline for completion yet, do it now.
+    # @private
+    def self.initialize_readline
+      Pry.require_readline
+      return if @initialized_readline
+
+      if Readline.respond_to?("basic_word_break_characters=")
+        Readline.basic_word_break_characters = " \t\n\"\\'`><=;|&{("
+      end
+
+      Readline.completion_append_character = nil
+
+      @initialized_readline = true
+    end
+
     # Return a new completion proc for use by Readline.
     # @param [Binding] target The current binding context.
     # @param [Array<String>] commands The array of Pry commands.
     def self.build_completion_proc(target, pry=nil, commands=[""])
+      initialize_readline
 
       proc do |input|
 
diff --git a/lib/pry/config.rb b/lib/pry/config.rb
index 6249e456..21dbdb34 100644
--- a/lib/pry/config.rb
+++ b/lib/pry/config.rb
@@ -5,13 +5,27 @@ class Pry
 
     # Get/Set the object to use for input by default by all Pry instances.
     # Pry.config.input is an option determining the input object - the object from
-    # which Pry retrieves its lines of input. Pry accepts any object that implements the readline method.
-    # This includes IO objects, StringIO, Readline, File and custom objects.
+    # which Pry retrieves its lines of input. Pry accepts any object that
+    # implements the readline method.  This includes IO objects, StringIO,
+    # Readline, File and custom objects. It can also be a Proc which returns an
+    # object implementing the readline method.
     # @return [#readline] The object to use for input by default by all
     #   Pry instances.
     # @example
     #   Pry.config.input = StringIO.new("@x = 10\nexit")
-    attr_accessor :input
+    def input
+      @reified_input ||=
+        if @input.respond_to?(:call)
+          @input.call
+        else
+          @input
+        end
+    end
+
+    def input=(input)
+      @reified_input = nil
+      @input = input
+    end
 
     # Get/Set the object to use for output by default by all Pry instances.
     # Pry.config.output is an option determining the output object - the object to which
diff --git a/lib/pry/history.rb b/lib/pry/history.rb
index df50df21..4f63838f 100644
--- a/lib/pry/history.rb
+++ b/lib/pry/history.rb
@@ -1,6 +1,6 @@
 class Pry
-  # The History class is responsible for maintaining the user's input history, both
-  # internally and within Readline.
+  # The History class is responsible for maintaining the user's input history,
+  # both internally and within Readline.
   class History
     attr_accessor :loader, :saver, :pusher, :clearer
 
@@ -111,11 +111,13 @@ class Pry
     # The default pusher. Appends the given line to Readline::HISTORY.
     # @param [String] line
     def push_to_readline(line)
+      Pry.require_readline
       Readline::HISTORY << line
     end
 
     # The default clearer. Clears Readline::HISTORY.
     def clear_readline
+      Pry.require_readline
       Readline::HISTORY.shift until Readline::HISTORY.empty?
     end
   end
diff --git a/lib/pry/pry_class.rb b/lib/pry/pry_class.rb
index c030b82e..0de17b95 100644
--- a/lib/pry/pry_class.rb
+++ b/lib/pry/pry_class.rb
@@ -107,8 +107,7 @@ class Pry
   # Including: loading .pryrc, loading plugins, loading requires, and
   # loading history.
   def self.initial_session_setup
-
-    return if !initial_session?
+    return unless initial_session?
 
     # note these have to be loaded here rather than in pry_instance as
     # we only want them loaded once per entire Pry lifetime.
@@ -262,6 +261,7 @@ class Pry
   end
 
   def self.auto_resize!
+    Pry.require_readline
     ver = Readline::VERSION
     if ver[/edit/i]
       warn <<-EOT
@@ -286,7 +286,7 @@ Readline version #{ver} detected - will not auto_resize! correctly.
   end
 
   def self.set_config_defaults
-    config.input = Readline
+    config.input = proc { Pry.require_readline; Readline }
     config.output = $stdout
     config.commands = Pry::Commands
     config.prompt_name = DEFAULT_PROMPT_NAME
@@ -310,12 +310,7 @@ Readline version #{ver} detected - will not auto_resize! correctly.
     config.correct_indent = true
     config.collision_warning = false
     config.output_prefix = "=> "
-
-    if defined?(Bond) && Readline::VERSION !~ /editline/i
-      config.completer = Pry::BondCompleter
-    else
-      config.completer = Pry::InputCompleter
-    end
+    config.completer = Pry::BondCompleter
 
     config.gist ||= OpenStruct.new
     config.gist.inspecter = proc(&:pretty_inspect)
diff --git a/lib/pry/pry_instance.rb b/lib/pry/pry_instance.rb
index a3f67206..51cc48a0 100644
--- a/lib/pry/pry_instance.rb
+++ b/lib/pry/pry_instance.rb
@@ -619,7 +619,7 @@ class Pry
         input.completion_proc = completion_proc
       end
 
-      if input == Readline
+      if defined?(Readline) && input == Readline
         if !$stdout.tty? && $stdin.tty? && !Pry::Helpers::BaseHelpers.windows?
           Readline.output = File.open('/dev/tty', 'w')
         end
diff --git a/lib/pry/terminal.rb b/lib/pry/terminal.rb
index 10cbcf85..6116de6a 100644
--- a/lib/pry/terminal.rb
+++ b/lib/pry/terminal.rb
@@ -53,7 +53,7 @@ class Pry::Terminal
     end
 
     def screen_size_according_to_readline
-      if Readline.respond_to?(:get_screen_size)
+      if defined?(Readline) && Readline.respond_to?(:get_screen_size)
         size = Readline.get_screen_size
         size if nonzero_column?(size)
       end
diff --git a/spec/completion_spec.rb b/spec/completion_spec.rb
index f6dd60cc..6dff5bf1 100644
--- a/spec/completion_spec.rb
+++ b/spec/completion_spec.rb
@@ -10,6 +10,8 @@ def completer_test(bind, pry=nil, assert_flag=true)
   return proc {|*symbols| symbols.each(&test) }
 end
 
+Pry.require_readline
+
 if defined?(Bond) && Readline::VERSION !~ /editline/i
   describe 'bond-based completion' do
     it 'should pull in Bond by default' do