Not running command if redirection fails

1 files changed, 56 insertions, 48 deletions

diff --git a/cmd2/cmd2.py b/cmd2/cmd2.py
index c2affe79..67cd62f3 100644
--- a/cmd2/cmd2.py
+++ b/cmd2/cmd2.py
@@ -1723,43 +1723,45 @@ class Cmd(cmd.Cmd):
             already_redirecting = self.redirecting
 
             # Handle any redirection for this command
-            saved_state = self._redirect_output(statement)
+            redir_error, saved_state = self._redirect_output(statement)
 
-            # See if we need to update self.redirecting
-            if not already_redirecting:
-                self.redirecting = saved_state.redirecting
-
-            try:
-                timestart = datetime.datetime.now()
-                if self._in_py:
-                    self._last_result = None
-
-                # precommand hooks
-                data = plugin.PrecommandData(statement)
-                for func in self._precmd_hooks:
-                    data = func(data)
-                statement = data.statement
-                # call precmd() for compatibility with cmd.Cmd
-                statement = self.precmd(statement)
-
-                # go run the command function
-                stop = self.onecmd(statement)
-
-                # postcommand hooks
-                data = plugin.PostcommandData(stop, statement)
-                for func in self._postcmd_hooks:
-                    data = func(data)
-                # retrieve the final value of stop, ignoring any statement modification from the hooks
-                stop = data.stop
-                # call postcmd() for compatibility with cmd.Cmd
-                stop = self.postcmd(stop, statement)
-
-                if self.timing:
-                    self.pfeedback('Elapsed: %s' % str(datetime.datetime.now() - timestart))
-            finally:
-                self._restore_output(statement, saved_state)
+            # Do not continue if an error occurred while trying to redirect
+            if not redir_error:
+                # See if we need to update self.redirecting
                 if not already_redirecting:
-                    self.redirecting = False
+                    self.redirecting = saved_state.redirecting
+
+                try:
+                    timestart = datetime.datetime.now()
+                    if self._in_py:
+                        self._last_result = None
+
+                    # precommand hooks
+                    data = plugin.PrecommandData(statement)
+                    for func in self._precmd_hooks:
+                        data = func(data)
+                    statement = data.statement
+                    # call precmd() for compatibility with cmd.Cmd
+                    statement = self.precmd(statement)
+
+                    # go run the command function
+                    stop = self.onecmd(statement)
+
+                    # postcommand hooks
+                    data = plugin.PostcommandData(stop, statement)
+                    for func in self._postcmd_hooks:
+                        data = func(data)
+                    # retrieve the final value of stop, ignoring any statement modification from the hooks
+                    stop = data.stop
+                    # call postcmd() for compatibility with cmd.Cmd
+                    stop = self.postcmd(stop, statement)
+
+                    if self.timing:
+                        self.pfeedback('Elapsed: %s' % str(datetime.datetime.now() - timestart))
+                finally:
+                    self._restore_output(statement, saved_state)
+                    if not already_redirecting:
+                        self.redirecting = False
 
         except EmptyStatement:
             # don't do anything, but do allow command finalization hooks to run
@@ -1885,19 +1887,20 @@ class Cmd(cmd.Cmd):
             raise EmptyStatement()
         return statement
 
-    def _redirect_output(self, statement: Statement) -> RedirectionSavedState:
+    def _redirect_output(self, statement: Statement) -> Tuple[bool, RedirectionSavedState]:
         """Handles output redirection for >, >>, and |.
 
         :param statement: a parsed statement from the user
-        :return: A RedirectionSavedState object
+        :return: A bool telling if an error occurred and a RedirectionSavedState object
         """
         import io
         import subprocess
 
-        ret_val = RedirectionSavedState(redirecting=False, piping=False)
+        redir_error = False
+        saved_state = RedirectionSavedState(redirecting=False, piping=False)
 
         if not self.allow_redirection:
-            return ret_val
+            return redir_error, saved_state
 
         if statement.pipe_to:
             # Create a pipe with read and write sides
@@ -1928,22 +1931,25 @@ class Cmd(cmd.Cmd):
                                      creationflags=creationflags,
                                      start_new_session=start_new_session)
 
-                ret_val = RedirectionSavedState(redirecting=True, self_stdout=self.stdout,
-                                                piping=True, pipe_proc_reader=self.pipe_proc_reader)
+                saved_state = RedirectionSavedState(redirecting=True, self_stdout=self.stdout,
+                                                    piping=True, pipe_proc_reader=self.pipe_proc_reader)
 
                 self.pipe_proc_reader = utils.ProcReader(proc, self.stdout, sys.stderr)
                 self.stdout = pipe_write
             except Exception as ex:
-                self.perror('Not piping because - {}'.format(ex), traceback_war=False)
+                self.perror('Failed to open pipe because - {}'.format(ex), traceback_war=False)
                 pipe_read.close()
                 pipe_write.close()
+                redir_error = True
 
         elif statement.output:
             import tempfile
             if (not statement.output_to) and (not self.can_clip):
-                raise EnvironmentError("Cannot redirect to paste buffer; install 'pyperclip' and re-run to enable")
+                self.perror("Cannot redirect to paste buffer; install 'pyperclip' and re-run to enable",
+                            traceback_war=False)
+                redir_error = True
 
-            if statement.output_to:
+            elif statement.output_to:
                 # going to a file
                 mode = 'w'
                 # statement.output can only contain
@@ -1952,19 +1958,21 @@ class Cmd(cmd.Cmd):
                     mode = 'a'
                 try:
                     new_stdout = open(statement.output_to, mode)
-                    ret_val = RedirectionSavedState(redirecting=True, self_stdout=self.stdout, sys_stdout=sys.stdout)
+                    saved_state = RedirectionSavedState(redirecting=True,
+                                                        self_stdout=self.stdout, sys_stdout=sys.stdout)
                     sys.stdout = self.stdout = new_stdout
                 except OSError as ex:
-                    self.perror('Not redirecting because - {}'.format(ex), traceback_war=False)
+                    self.perror('Failed to redirect because - {}'.format(ex), traceback_war=False)
+                    redir_error = True
             else:
                 # going to a paste buffer
                 new_stdout = tempfile.TemporaryFile(mode="w+")
-                ret_val = RedirectionSavedState(redirecting=True, self_stdout=self.stdout, sys_stdout=sys.stdout)
+                saved_state = RedirectionSavedState(redirecting=True, self_stdout=self.stdout, sys_stdout=sys.stdout)
                 sys.stdout = self.stdout = new_stdout
                 if statement.output == constants.REDIRECTION_APPEND:
                     self.poutput(get_paste_buffer())
 
-        return ret_val
+        return redir_error, saved_state
 
     def _restore_output(self, statement: Statement, saved_state: RedirectionSavedState) -> None:
         """Handles restoring state after output redirection as well as