Fix min length in cli

Fixes https://github.com/lesspass/lesspass/issues/408

cli/lesspass/actions.py

@@ -0,0 +1,19 @@
+import argparse
+
+
+class Range(argparse.Action):
+    def __init__(self, min=None, max=None, *args, **kwargs):
+        self.min = min
+        self.max = max
+        kwargs["metavar"] = "[%d-%d]" % (self.min, self.max)
+        super(Range, self).__init__(*args, **kwargs)
+
+    def __call__(self, parser, namespace, value, option_string=None):
+        if not (self.min <= value <= self.max):
+            msg = "invalid choice: %r (choose from %d to %d)" % (
+                value,
+                self.min,
+                self.max,
+            )
+            raise argparse.ArgumentError(self, msg)
+        setattr(namespace, self.dest, value)

cli/lesspass/cli.py

@@ -1,6 +1,7 @@
 import argparse
 import os
 
+from lesspass import actions
 from lesspass import version
 from lesspass import name
 from lesspass import description
@@ -38,9 +39,7 @@ def parse_args(args):
         "-v", "--version", action="version", version=version.__version__
     )
     parser.add_argument(
-        "site",
-        nargs="?",
-        help="site used in the password generation (required)"
+        "site", nargs="?", help="site used in the password generation (required)"
     )
     parser.add_argument(
         "login", nargs="?", help="login used in the password generation. Default to ''."
@@ -55,8 +54,11 @@ def parse_args(args):
         "-L",
         "--length",
         default=16,
+        action=actions.Range,
+        min=5,
+        max=35,
         type=int,
-        help="password length (default: 16, max: 35)",
+        help="password length (default: 16, min:5, max: 35)",
     )
     parser.add_argument(
         "-C", "--counter", default=1, type=int, help="password counter (default: 1)"

cli/tests/test_functional.py

@@ -0,0 +1,16 @@
+import unittest
+import pexpect
+import signal
+import time
+
+import sys
+
+
+class TestFunctional(unittest.TestCase):
+    def test_length_below_the_minimum(self):
+        p = pexpect.spawn(
+            "python3 lesspass/core.py  site login masterpassword --lowercase --digits --length 2"
+        )
+        self.assertTrue(
+            "error: argument -L/--length: invalid choice: 2" in str(p.read())
+        )