Add -r/--randomsource option.

The new option is not active yet.

diceware/__init__.py

@@ -86,6 +86,7 @@ def get_random_sources():
 def handle_options(args):
     """Handle commandline options.
     """
+    random_sources = get_random_sources().keys()
     parser = argparse.ArgumentParser(description="Create a passphrase")
     parser.add_argument(
         '-n', '--num', default=6, type=int,
@@ -103,6 +104,12 @@ def handle_options(args):
     parser.add_argument(
         '-d', '--delimiter', default='',
         help="Separate words by DELIMITER. Empty string by default.")
+    parser.add_argument(
+        '-r', '--randomsource', default='system', choices=random_sources,
+        metavar="SOURCE",
+        help=(
+            "Get randomness from this source. Possible values: `%s'. "
+            "Default: system" % "', `".join(random_sources)))
     parser.add_argument(
         'infile', nargs='?', metavar='INFILE', default=None,
         type=argparse.FileType('r'),

tests/exp_help_output.txt

 usage: diceware [-h] [-n NUM] [-c | --no-caps] [-s NUM] [-d DELIMITER]
-                [--version]
+                [-r SOURCE] [--version]
                 [INFILE]
 
 Create a passphrase
@@ -16,4 +16,7 @@ optional arguments:
                         Insert NUM special chars into generated word.
   -d DELIMITER, --delimiter DELIMITER
                         Separate words by DELIMITER. Empty string by default.
+  -r SOURCE, --randomsource SOURCE
+                        Get randomness from this source. Possible values:
+                        `system'. Default: system
   --version             output version information and exit.

tests/test_diceware.py

@@ -211,6 +211,7 @@ class TestDicewareModule(object):
         assert options.infile is None
         assert options.version is False
         assert options.delimiter == ""
+        assert options.randomsource == "system"
 
     def test_handle_options_infile(self, tmpdir):
         # we can give an infile
@@ -235,6 +236,23 @@ class TestDicewareModule(object):
         options = handle_options(['-d', 'WOW'])
         assert options.delimiter == 'WOW'
 
+    def test_handle_options_randomsource(self):
+        # we can choose the source of randomness
+        source_names = get_random_sources().keys()
+        for name in source_names:
+            options = handle_options(['-r', name])
+            assert options.randomsource == name
+            options = handle_options(['--randomsource', name])
+            assert options.randomsource == name
+
+    def test_handle_options_randomsource_rejects_invalid(self, capsys):
+        # we can not choose illegal values for source of randomness
+        with pytest.raises(SystemExit):
+            handle_options(['-r', 'not-a-valid-source-name'])
+        out, err = capsys.readouterr()
+        assert out == ''
+        assert "invalid choice" in err
+
     def test_main(self, capsys):
         # we can get a passphrase
         main([])  # call with default options in place