Destroy old pty even if it's no longer running (#249)

For unknown reasons, the pty will occasionally quit running. In these
cases, we still want to remove it so that a fresh one can be created. We
don't actually need this check because error messages from `zle` and
`zpty` are redirected to /dev/null.

One sure way to kill all currently running pty's is to run `exit` in a
subshell. Even without zsh-autosuggestions loaded, the following works:

    % zmodload zsh/zpty
    % zpty -b foo cat
    % zpty -b bar cat
    % zpty
    (31689) bar: cat
    (31666) foo: cat
    % $(exit)
    % zpty
    (finished) bar: cat
    (finished) foo: cat

spec/async_spec.rb

@@ -26,6 +26,16 @@ context 'with asynchronous suggestions enabled' do
       end
     end
   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
 
 

src/async.zsh

@@ -83,13 +83,11 @@ _zsh_autosuggest_async_pty_create() {
 }
 
 _zsh_autosuggest_async_pty_destroy() {
-	if zpty -t $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null; then
-		# Remove the input handler
-		zle -F $_ZSH_AUTOSUGGEST_PTY_FD &>/dev/null
+	# Remove the input handler
+	zle -F $_ZSH_AUTOSUGGEST_PTY_FD &>/dev/null
 
-		# Destroy the zpty
-		zpty -d $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null
-	fi
+	# Destroy the zpty
+	zpty -d $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null
 }
 
 _zsh_autosuggest_async_pty_recreate() {

zsh-autosuggestions.zsh

@@ -661,13 +661,11 @@ _zsh_autosuggest_async_pty_create() {
 }
 
 _zsh_autosuggest_async_pty_destroy() {
-	if zpty -t $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null; then
-		# Remove the input handler
-		zle -F $_ZSH_AUTOSUGGEST_PTY_FD &>/dev/null
+	# Remove the input handler
+	zle -F $_ZSH_AUTOSUGGEST_PTY_FD &>/dev/null
 
-		# Destroy the zpty
-		zpty -d $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null
-	fi
+	# Destroy the zpty
+	zpty -d $ZSH_AUTOSUGGEST_ASYNC_PTY_NAME &>/dev/null
 }
 
 _zsh_autosuggest_async_pty_recreate() {