Make Server.has_session() use returncode

has_session() would erroneously return true if tmux returned an unexpected
string, such as "no current session".

Instead of adding yet another string to the list to check against, use the
return code of the 'tmux has-session' command, which is documented to return 0
(Shell true) if targeted session exists, and return 1 (Shell false) in any
other case.

Author: John de Largentaye

libtmux/common.py

@@ -189,6 +189,7 @@ def __init__(self, *args, **kwargs):
             self.process.stdout.close()
             stderr = self.process.stderr.read()
             self.process.stderr.close()
+            returncode = self.process.returncode
         except Exception as e:
             logger.error(
                 'Exception for %s: \n%s' % (
@@ -197,6 +198,8 @@ def __init__(self, *args, **kwargs):
                 )
             )
 
+        self.returncode = returncode
+
         self.stdout = console_to_str(stdout)
         self.stdout = self.stdout.split('\n')
         self.stdout = list(filter(None, self.stdout))  # filter empty values

libtmux/server.py

@@ -334,24 +334,11 @@ def has_session(self, target_session, exact=True):
 
         proc = self.cmd('has-session', '-t%s' % target_session)
 
-        if not proc.stdout:
-            return True
-        if any(
-            x in proc.stdout for x in
-            ['failed to connect to server', 'error connecting to']
-        ):
-            return False
-        elif 'no server running' in proc.stdout:  # tmux 2.0
-            return False
-        elif 'can\'t find session' in proc.stdout:  # tmux 2.1
-            return False
-        elif 'bad session name' in proc.stdout:  # tmux >= 1.9
-            return False
-        elif 'session not found' in proc.stdout:
-            return False
-        else:
+        if not proc.returncode:
             return True
 
+        return False
+
     def kill_server(self):
         """``$ tmux kill-server``."""
         self.cmd('kill-server')