feat: add support for controlling readline history features

You can disable loading or saving the history file and disable loading
the readline rc file. This is controlled by pragma history_features
which is a bit string. Setting a bit disables the feature.

Also cleaned up a python traceback if an invalid pragma was specified
on the command line. Just displays an error message and drops into
interactive mode.

I had a hand when running regression tests with
tet-admin.py::testBasicInteractive. It was loading the history file
and saving the commands making the file huge. So disable all
history_features by default when testing by setting pragma to 7.

Author: rouilj

roundup/admin.py

@@ -114,6 +114,7 @@ def __init__(self):
             'display_header': False,
             'display_protected': False,
             'indexer_backend': "as set in config.ini",
+            'history_features': 0,
             'history_length': -1,
             '_reopen_tracker': False,
             'savepoint_limit': self._default_savepoint_setting,
@@ -132,6 +133,15 @@ def __init__(self):
             _("Have 'display designator' and 'specification class' show\n"
               "      protected fields: creator, id etc.\n"),
 
+            'history_features':
+            _("Controls history options. It is a bitstring where setting\n"
+              "      the bit disables the feature. A value of 0 (default)\n"
+              "      enables all features. Value 1 disables loading of\n"
+              "      history.  Value 2 disables saving history. Value 4\n"
+              "      disables loading init file. Since it is a bitstring a\n"
+              "      value of 6 disables both loading init file and saving\n"
+              "      history.\n"),
+
             'history_length':
             _("Set the number of lines of history to keep for this session.\n"
               "      -1 is infinite.\n"),
@@ -2263,6 +2273,21 @@ def run_command(self, args):
             ret = 1
         return ret
 
+    def history_features(self, feature):
+        """ self.settings['history_features'] = 0: load rc, load/save history
+         self.settings['history_features'] = 1: do not load history
+         self.settings['history_features'] = 2: do not save history
+         self.settings['history_features'] = 4: don't load rc
+        """
+
+        features = {  # bit bashing
+            'load_history': 1,
+            'save_history': 2,
+            'load_rc': 4}
+
+        # setting the bit disables the feature, so use not.
+        return not self.settings['history_features'] & features[feature]
+
     def interactive(self):
         """Run in an interactive mode
         """
@@ -2277,13 +2302,15 @@ def interactive(self):
         try:
             import readline
             try:
-                readline.read_init_file(initfile)
+                if self.history_features('load_rc'):
+                    readline.read_init_file(initfile)
             except IOError: # FileNotFoundError under python3
                 # file is optional
                 pass
 
             try:
-                readline.read_history_file(histfile)
+                if self.history_features('load_history'):
+                    readline.read_history_file(histfile)
             except IOError:  # FileNotFoundError under python3
                 # no history file yet
                 pass
@@ -2322,7 +2349,8 @@ def interactive(self):
 
         # looks like histfile is saved with mode 600
         if readline:
-            readline.write_history_file(histfile)
+            if self.history_features('save_history'):
+                readline.write_history_file(histfile)
         return 0
 
     def main(self):  # noqa: PLR0912, PLR0911
@@ -2374,7 +2402,10 @@ def main(self):  # noqa: PLR0912, PLR0911
             elif opt == '-d':
                 self.print_designator = 1
             elif opt == '-P':
-                self.do_pragma([arg])
+                try:
+                    self.do_pragma([arg])
+                except UsageError as e:
+                    print('\n%s\n' %  e)
             elif opt == '-u':
                 login_opt = arg.split(':')
                 self.name = login_opt[0]

test/test_admin.py

@@ -134,7 +134,10 @@ def testBasicInteractive(self):
 
         self.install_init()
         self.admin=AdminTool()
-        sys.argv=['main', '-i', self.dirname]
+        # set history_features to disable loading/saving history
+        # and loading rc file. Otherwise file gets large and
+        # breaks testing or overwrites the users history file.
+        sys.argv=['main', '-i', self.dirname, '-P', 'history_features=7']
 
         with captured_output() as (out, err):
             ret = self.admin.main()