Skip autocompletion for non-interactive interpreter

Sadly I forget where it was pointed out, but invoking the control port via
shell is a *lot* faster than stem...

  #!/bin/bash -e

  cmd="$@"
  pass="ControlPortPassword"

  function test_tor() {
      echo "$1" >&3
      sed "/^250 OK\r$/q" <&3
      echo QUIT >&3
      exec 3<&-
  }

  exec 3<>/dev/tcp/127.0.0.1/9051
  echo AUTHENTICATE \"$pass\" >&3
  read -u 3
  test_tor "$cmd"

  ====================

  atagar@morrigan:~$ time ./bench.sh 'GETINFO version' 1>/dev/null

  real	0m0.007s
  user	0m0.004s
  sys	0m0.003s

  ====================

  atagar@morrigan:~$ time tor-prompt --run 'GETINFO version' 1>/dev/null

  real	0m0.186s
  user	0m0.072s
  sys	0m0.030s

Generally speaking this is expected. Spinning up an interpreter takes time. But
in doing a quick investigation realized this is quite a bit slower than it
needs to be...

  total tor-prompt runtime          0.186 seconds
  --------------------------------------------------------
  python interpreter startup        0.016 seconds (9%)
  import statements                 0.079 seconds (42%)
  check if tor is running           0.014 seconds (8%)
  connect to tor                    0.009 seconds (5%)
  autocompete setup                 0.065 seconds (34%)
  invoke tor controller command     0.003 seconds (2%)

Autocompletion is only relevant when the user is presented with an interactive
interpreter. If we're merely invoking a command it's pointless.

So TL;DR: tor-prompt is now ~34% faster when used to invoke controller commands.

2 files changed, 9 insertions, 5 deletions

diff --git a/docs/change_log.rst b/docs/change_log.rst
index edf574c3..21b6c85e 100644
--- a/docs/change_log.rst
+++ b/docs/change_log.rst
@@ -77,6 +77,10 @@ The following are only available within Stem's `git repository
 
   * Added NetBSD to our `download page <download.html>`_
 
+ * **Interpreter**
+
+  * tor-prompt is now ~34% faster when used to non-interactively invoke commands
+
 .. _version_1.7:
 
 Version 1.7 (October 7th, 2018)
diff --git a/stem/interpreter/__init__.py b/stem/interpreter/__init__.py
index b10109e8..a4911a65 100644
--- a/stem/interpreter/__init__.py
+++ b/stem/interpreter/__init__.py
@@ -118,11 +118,6 @@ def main():
     sys.exit(1)
 
   with controller:
-    autocompleter = stem.interpreter.autocomplete.Autocompleter(controller)
-    readline.parse_and_bind('tab: complete')
-    readline.set_completer(autocompleter.complete)
-    readline.set_completer_delims('\n')
-
     interpreter = stem.interpreter.commands.ControlInterpreter(controller)
     showed_close_confirmation = False
 
@@ -158,6 +153,11 @@ def main():
         sys.exit(1)
 
     else:
+      autocompleter = stem.interpreter.autocomplete.Autocompleter(controller)
+      readline.parse_and_bind('tab: complete')
+      readline.set_completer(autocompleter.complete)
+      readline.set_completer_delims('\n')
+
       for line in msg('msg.startup_banner').splitlines():
         line_format = HEADER_BOLD_OUTPUT if line.startswith('  ') else HEADER_OUTPUT
         print(format(line, *line_format))