Fixed a couple potential crashes on opening files

Fixed crashes that occur when attempting to open a file in a non-existent directory or a when the filename is too long.

Specifically fixed this when redirecting output to a file and when saving a transcript based on the history.

Also added a couple unit tests related to the fixes.

Author: tleonhardt

cmd2/cmd2.py

@@ -1696,7 +1696,7 @@ def onecmd_plus_hooks(self, line):
                 if self.timing:
                     self.pfeedback('Elapsed: %s' % str(datetime.datetime.now() - timestart))
             finally:
-                if self.allow_redirection:
+                if self.allow_redirection and self.redirecting:
                     self._restore_output(statement)
         except EmptyStatement:
             pass
@@ -1840,7 +1840,11 @@ def _redirect_output(self, statement):
                 # REDIRECTION_APPEND or REDIRECTION_OUTPUT
                 if statement.output == constants.REDIRECTION_APPEND:
                     mode = 'a'
-                sys.stdout = self.stdout = open(os.path.expanduser(statement.output_to), mode)
+                try:
+                    sys.stdout = self.stdout = open(os.path.expanduser(statement.output_to), mode)
+                except (FileNotFoundError, OSError) as ex:
+                    self.perror('Not Redirecting because - {}'.format(ex), traceback_war=False)
+                    self.redirecting = False
             else:
                 # going to a paste buffer
                 sys.stdout = self.stdout = tempfile.TemporaryFile(mode="w+")
@@ -2878,16 +2882,19 @@ def _generate_transcript(self, history, transcript_file):
         self.echo = saved_echo
 
         # finally, we can write the transcript out to the file
-        with open(transcript_file, 'w') as fout:
-            fout.write(transcript)
-
-        # and let the user know what we did
-        if len(history) > 1:
-            plural = 'commands and their outputs'
+        try:
+            with open(transcript_file, 'w') as fout:
+                fout.write(transcript)
+        except (FileNotFoundError, OSError) as ex:
+            self.perror('Failed to save transcript: {}'.format(ex), traceback_war=False)
         else:
-            plural = 'command and its output'
-        msg = '{} {} saved to transcript file {!r}'
-        self.pfeedback(msg.format(len(history), plural, transcript_file))
+            # and let the user know what we did
+            if len(history) > 1:
+                plural = 'commands and their outputs'
+            else:
+                plural = 'command and its output'
+            msg = '{} {} saved to transcript file {!r}'
+            self.pfeedback(msg.format(len(history), plural, transcript_file))
 
     @with_argument_list
     def do_edit(self, arglist):

tests/test_cmd2.py

@@ -615,6 +615,44 @@ def test_output_redirection(base_app):
     finally:
         os.remove(filename)
 
+def test_output_redirection_to_nonexistent_directory(base_app):
+    filename = '~/fakedir/this_does_not_exist.txt'
+
+    # Verify that writing to a file in a non-existent directory doesn't work
+    run_cmd(base_app, 'help > {}'.format(filename))
+    expected = normalize(BASE_HELP)
+    with pytest.raises(FileNotFoundError):
+        with open(filename) as f:
+            content = normalize(f.read())
+        assert content == expected
+
+    # Verify that appending to a file also works
+    run_cmd(base_app, 'help history >> {}'.format(filename))
+    expected = normalize(BASE_HELP + '\n' + HELP_HISTORY)
+    with pytest.raises(FileNotFoundError):
+        with open(filename) as f:
+            content = normalize(f.read())
+        assert content == expected
+
+def test_output_redirection_to_too_long_filename(base_app):
+    filename = '~/sdkfhksdjfhkjdshfkjsdhfkjsdhfkjdshfkjdshfkjshdfkhdsfkjhewfuihewiufhweiufhiweufhiuewhiuewhfiuwehfiuewhfiuewhfiuewhfiuewhiuewhfiuewhfiuewfhiuwehewiufhewiuhfiweuhfiuwehfiuewfhiuwehiuewfhiuewhiewuhfiuewhfiuwefhewiuhewiufhewiufhewiufhewiufhewiufhewiufhewiufhewiuhewiufhewiufhewiuheiufhiuewheiwufhewiufheiufheiufhieuwhfewiuhfeiufhiuewfhiuewheiwuhfiuewhfiuewhfeiuwfhewiufhiuewhiuewhfeiuwhfiuwehfuiwehfiuehiuewhfieuwfhieufhiuewhfeiuwfhiuefhueiwhfw'
+
+    # Verify that writing to a file in a non-existent directory doesn't work
+    run_cmd(base_app, 'help > {}'.format(filename))
+    expected = normalize(BASE_HELP)
+    with pytest.raises(OSError):
+        with open(filename) as f:
+            content = normalize(f.read())
+        assert content == expected
+
+    # Verify that appending to a file also works
+    run_cmd(base_app, 'help history >> {}'.format(filename))
+    expected = normalize(BASE_HELP + '\n' + HELP_HISTORY)
+    with pytest.raises(OSError):
+        with open(filename) as f:
+            content = normalize(f.read())
+        assert content == expected
+
 
 def test_feedback_to_output_true(base_app):
     base_app.feedback_to_output = True

tests/test_transcript.py

@@ -154,6 +154,32 @@ def test_history_transcript(request, capsys):
 
     assert transcript == expected
 
+def test_history_transcript_bad_filename(request, capsys):
+    app = CmdLineApp()
+    app.stdout = StdOut()
+    run_cmd(app, 'orate this is\na /multiline/\ncommand;\n')
+    run_cmd(app, 'speak /tmp/file.txt is not a regex')
+
+    expected = r"""(Cmd) orate this is
+> a /multiline/
+> command;
+this is a \/multiline\/ command
+(Cmd) speak /tmp/file.txt is not a regex
+\/tmp\/file.txt is not a regex
+"""
+
+    # make a tmp file
+    history_fname = '~/fakedir/this_does_not_exist.txt'
+
+    # tell the history command to create a transcript
+    run_cmd(app, 'history -t "{}"'.format(history_fname))
+
+    # read in the transcript created by the history command
+    with pytest.raises(FileNotFoundError):
+        with open(history_fname) as f:
+            transcript = f.read()
+        assert transcript == expected
+
 @pytest.mark.parametrize('expected, transformed', [
     # strings with zero or one slash or with escaped slashes means no regular
     # expression present, so the result should just be what re.escape returns.