Refactor async mode to no longer use zpty

See technique used in `fast-syntax-highlighting`:
- ca2e18bbc9
- http://www.zsh.org/mla/users/2018/msg00424.html

spec/async_spec.rb

@@ -1,8 +1,4 @@
 context 'with asynchronous suggestions enabled' do
-  before do
-    skip 'Async mode not supported below v5.0.8' if session.zsh_version < Gem::Version.new('5.0.8')
-  end
-
   let(:options) { ["ZSH_AUTOSUGGEST_USE_ASYNC="] }
 
   describe '`up-line-or-beginning-search`' do
@@ -30,55 +26,6 @@ context 'with asynchronous suggestions enabled' do
       end
     end
   end
-
-  it 'should not add extra carriage returns before newlines' do
-    session.
-      send_string('echo "').
-      send_keys('escape').
-      send_keys('enter').
-      send_string('"').
-      send_keys('enter')
-
-    session.clear_screen
-
-    session.send_string('echo')
-    wait_for { session.content }.to eq("echo \"\n\"")
-  end
-
-  it 'should treat carriage returns and newlines as separate characters' do
-    session.
-      send_string('echo "').
-      send_keys('C-v').
-      send_keys('enter').
-      send_string('foo"').
-      send_keys('enter')
-
-    session.
-      send_string('echo "').
-      send_keys('control').
-      send_keys('enter').
-      send_string('bar"').
-      send_keys('enter')
-
-    session.clear_screen
-
-    session.
-      send_string('echo "').
-      send_keys('C-v').
-      send_keys('enter')
-
-    wait_for { session.content }.to eq('echo "^Mfoo"')
-  end
-
-  describe 'exiting a subshell' do
-    it 'should not cause error messages to be printed' do
-      session.run_command('$(exit)')
-
-      sleep 1
-
-      expect(session.content).to eq('$(exit)')
-    end
-  end
 end
 
 

spec/integrations/client_zpty_spec.rb

@@ -1,10 +0,0 @@
-describe 'a running zpty command' do
-  let(:before_sourcing) { -> { session.run_command('zmodload zsh/zpty && zpty -b kitty cat') } }
-
-  it 'is not affected by running zsh-autosuggestions' do
-    sleep 1 # Give a little time for precmd hooks to run
-    session.run_command('zpty -t kitty; echo $?')
-
-    wait_for { session.content }.to end_with("\n0")
-  end
-end

spec/options/async_zpty_name_spec.rb

@@ -1,19 +0,0 @@
-context 'when async suggestions are enabled' do
-  let(:options) { ["ZSH_AUTOSUGGEST_USE_ASYNC="] }
-
-  describe 'the zpty for async suggestions' do
-    it 'is created with the default name' do
-      session.run_command('zpty -t zsh_autosuggest_pty &>/dev/null; echo $?')
-      wait_for { session.content }.to end_with("\n0")
-    end
-
-    context 'when ZSH_AUTOSUGGEST_ASYNC_PTY_NAME is set' do
-      let(:options) { super() + ['ZSH_AUTOSUGGEST_ASYNC_PTY_NAME=foo_pty'] }
-
-      it 'is created with the specified name' do
-        session.run_command('zpty -t foo_pty &>/dev/null; echo $?')
-        wait_for { session.content }.to end_with("\n0")
-      end
-    end
-  end
-end

spec/terminal_session.rb

@@ -18,10 +18,6 @@ class TerminalSession
     tmux_command("new-session -d -x #{opts[:width]} -y #{opts[:height]} '#{cmd}'")
   end
 
-  def zsh_version
-    @zsh_version ||= Gem::Version.new(`#{ZSH_BIN} -c 'echo -n $ZSH_VERSION'`)
-  end
-
   def tmux_socket_name
     @tmux_socket_name ||= SecureRandom.hex(6)
   end