Gracefully handle (ignore) null bytes in history lines

Fixes #1789.

Readline is unable to add lines to its history that contain a null byte;
we should therefore avoid saving such lines to the history file, and
ignore any such lines that are already present in the file.

lib/pry/history.rb

@@ -34,6 +34,8 @@ class Pry
     # @return [Integer] The number of lines loaded
     def load
       @loader.call do |line|
+        next if invalid_readline_line?(line)
+
         @pusher.call(line.chomp)
         @history << line.chomp
         @original_lines += 1
@@ -44,7 +46,9 @@ class Pry
     # @param [String] line
     # @return [String] The same line that was passed in
     def push(line)
-      unless line.empty? || (@history.last && line == @history.last)
+      empty_or_invalid_line = line.empty? || invalid_readline_line?(line)
+
+      unless empty_or_invalid_line || (@history.last && line == @history.last)
         @pusher.call(line)
         @history << line
         if !should_ignore?(line) && Pry.config.history.should_save
@@ -144,5 +148,11 @@ class Pry
     def history_file_path
       File.expand_path(@file_path || Pry.config.history.file)
     end
+
+    def invalid_readline_line?(line)
+      # `Readline::HISTORY << line` raises an `ArgumentError` if `line`
+      # includes a null byte
+      line.include?("\0")
+    end
   end
 end

spec/history_spec.rb

@@ -5,7 +5,7 @@ describe Pry do
   before do
     Pry.history.clear
 
-    @saved_history = "1\n2\n3\n"
+    @saved_history = "1\n2\n3\ninvalid\0 line\n"
 
     Pry.history.loader = proc do |&blk|
       @saved_history.lines.each { |l| blk.call(l) }
@@ -28,6 +28,12 @@ describe Pry do
       expect(Pry.history.to_a.grep('_ += 1').count).to eq 1
     end
 
+    it "does not record lines that contain a NULL byte" do
+      c = Pry.history.to_a.count
+      Pry.history << "a\0b"
+      expect(Pry.history.to_a.count).to eq c
+    end
+
     it "does not record empty lines" do
       c = Pry.history.to_a.count
       Pry.history << ''