write to history incrementally

This makes it less essential for drivers to finalize the pry instance.

lib/pry/commands/exit_program.rb

@@ -5,7 +5,6 @@ class Pry
     description 'End the current program. Aliases: quit-program, !!!'
 
     def process
-      Pry.save_history if Pry.config.history.should_save
       Kernel.exit target.eval(arg_string).to_i
     end
   end

lib/pry/history.rb

@@ -7,17 +7,16 @@ class Pry
     # @return [Fixnum] Number of lines in history when Pry first loaded.
     attr_reader :original_lines
 
-    def initialize
+    def initialize(options={})
       @history = []
-      @saved_lines = 0
       @original_lines = 0
+      @file_path = options[:file_path]
       restore_default_behavior
     end
 
     # Assign the default methods for loading, saving, pushing, and clearing.
     def restore_default_behavior
       @loader  = method(:read_from_file)
-      @saver   = method(:write_to_file)
       @pusher  = method(:push_to_readline)
       @clearer = method(:clear_readline)
     end
@@ -26,19 +25,9 @@ class Pry
     # @return [Integer] The number of lines loaded
     def load
       @loader.call do |line|
-        @pusher.call(line.chomp)
+        Readline::HISTORY << line.chomp
         @history << line.chomp
       end
-      @saved_lines = @original_lines = @history.length
-    end
-
-    # Write this session's history using `History.saver`.
-    # @return [Integer] The number of lines saved
-    def save
-      history_to_save = @history[@saved_lines..-1]
-      @saver.call(history_to_save)
-      @saved_lines = @history.length
-      history_to_save.length
     end
 
     # Add a line to the input history, ignoring blank and duplicate lines.
@@ -48,6 +37,7 @@ class Pry
       unless line.empty? || (@history.last && line == @history.last)
         @pusher.call(line)
         @history << line
+        @history_file.puts line if save_history?
       end
       line
     end
@@ -59,7 +49,6 @@ class Pry
     def clear
       @clearer.call
       @history = []
-      @saved_lines = 0
     end
 
     # @return [Fixnum] The number of lines in history.
@@ -96,15 +85,9 @@ class Pry
     # The default saver. Appends the given lines to `Pry.history.config.file`.
     # @param [Array<String>] lines
     def write_to_file(lines)
-      history_file = File.expand_path(Pry.config.history.file)
-
-      begin
-        File.open(history_file, 'a') do |f|
-          lines.each { |ln| f.puts ln }
-        end
-      rescue Errno::EACCES
-        # We should probably create an option Pry.show_warnings?!?!?!
-        warn 'Unable to write to your history file, history not saved'
+      if write_to_history?
+        history_file.close
+        @history_file = nil
       end
     end
 
@@ -118,5 +101,28 @@ class Pry
     def clear_readline
       Readline::HISTORY.shift until Readline::HISTORY.empty?
     end
+
+    # The history file for appending
+    def history_file
+      if @history_file.nil?
+        begin
+          @history_file ||= File.open(file_path, 'a')
+          @history_file.sync = true
+        rescue Errno::EACCES
+          # We should probably create an option Pry.show_warnings?!?!?!
+          warn 'Unable to write to your history file, history not saved'
+          @history_file = false
+        end
+      end
+      @history_file
+    end
+
+    def save_history?
+      Pry.config.history.should_save && history_file
+    end
+
+    def file_path
+      @file_path || Pry.config.history.file
+    end
   end
 end

lib/pry/pry_class.rb

@@ -191,11 +191,6 @@ class Pry
     Pry.history.load
   end
 
-  # Save new lines of Readline history if required.
-  def self.save_history
-    Pry.history.save
-  end
-
   # @return [Boolean] Whether this is the first time a Pry session has
   #   been started since loading the Pry class.
   def self.initial_session?

lib/pry/repl.rb

@@ -76,8 +76,6 @@ class Pry
     # Clean-up after the repl session.
     def epilogue
       pry.exec_hook :after_session, pry.output, pry.current_binding, pry
-
-      Pry.save_history if Pry.config.history.should_save
     end
 
     # Read a line of input from the user, special handling for:

spec/pry_history_spec.rb

@@ -11,10 +11,6 @@ describe Pry do
       @saved_history.lines.each { |l| blk.call(l) }
     end
 
-    Pry.history.saver = proc do |lines|
-      @saved_history << lines.map { |l| "#{l}\n" }.join
-    end
-
     Pry.load_history
   end
 
@@ -44,56 +40,30 @@ describe Pry do
     end
   end
 
-  describe ".save_history" do
-    it "should include a trailing newline" do
-      Pry.history << "4"
-      Pry.save_history
-      @saved_history.should =~ /4\n\z/
+  describe "saving to a file" do
+    before do
+      @histfile = Tempfile.new(["pryhistory", "txt"])
+      @history = Pry::History.new(:file_path => @histfile.path)
+      Pry.config.history.should_save = true
+      @history.pusher = proc{ }
     end
 
-    it "should not change anything if history is not changed" do
-      @saved_history = "4\n5\n6\n"
-      Pry.save_history
-      @saved_history.should == "4\n5\n6\n"
+    after do
+      @histfile.close(true)
+      Pry.config.history.should_save = false
     end
 
-    it "should append new lines to the file" do
-      Pry.history << "4"
-      Pry.save_history
-      @saved_history.should == "1\n2\n3\n4\n"
+    it "should save lines to a file as they are written" do
+      @history.push "5"
+      File.read(@histfile.path).should == "5\n"
     end
 
-    it "should not clobber lines written by other Pry's in the meantime" do
-      Pry.history << "5"
-      @saved_history << "4\n"
-      Pry.save_history
+    it "should interleave lines from many places" do
+      @history.push "5"
+      File.open(@histfile.path, 'a'){ |f| f.puts "6" }
+      @history.push "7"
 
-      Pry.history.to_a[-3..-1].should == ["2", "3", "5"]
-      @saved_history.should == "1\n2\n3\n4\n5\n"
-    end
-
-    it "should not delete lines from the file if this session's history was cleared" do
-      Pry.history.clear
-      Pry.save_history
-      @saved_history.should == "1\n2\n3\n"
-    end
-
-    it "should save new lines that are added after the history was cleared" do
-      Pry.history.clear
-      Pry.history << "4"
-      Pry.save_history
-      @saved_history.should =~ /1\n2\n3\n4\n/
-    end
-
-    it "should only append new lines the second time it is saved" do
-      Pry.history << "4"
-      Pry.save_history
-      @saved_history << "5\n"
-      Pry.history << "6"
-      Pry.save_history
-
-      Pry.history.to_a[-4..-1].should == ["2", "3", "4", "6"]
-      @saved_history.should == "1\n2\n3\n4\n5\n6\n"
+      File.read(@histfile.path).should == "5\n6\n7\n"
     end
   end
 end