Repository: python-cmd2/cmd2

Issue:
The select() method needs to check for a user response of 0.
The select() method presents a numbered list, starting with "1", for the user to choose from. When a 0 is entered, the last item in the list is automatically selected. Depending on the list size, some negative numbers are also accepted. I would suggest changing the code as follows to flag anything less then 1 as invalid:

```Python3
choice = int(response)
if choice < 1:
     self.poutput("{!r} isn't a valid choice. Pick a number between 1 and {}:\n".format(response, len(fulloptions)))
     continue
result = fulloptions[choice - 1][0]
```

Discussion:

Patch:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index a7383541..22fd5046 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,6 @@
 ## 0.9.7 (TBD, 2018)
+* Bug Fixes
+    * Fixed bug when user chooses a zero or negative index when calling ``Cmd.select()``
 * Enhancements
     * **cmdloop** now only attempts to register a custom signal handler for SIGINT if running in the main thread
     * commands run as a result of ``default_to_shell`` being **True** now run via ``do_shell()`` and are saved
diff --git a/cmd2/cmd2.py b/cmd2/cmd2.py
index a513d0e7..56d74ec8 100644
--- a/cmd2/cmd2.py
+++ b/cmd2/cmd2.py
@@ -2780,6 +2780,8 @@ class Cmd(cmd.Cmd):
 
             try:
                 choice = int(response)
+                if choice < 1:
+                    raise IndexError
                 result = fulloptions[choice - 1][0]
                 break
             except (ValueError, IndexError):


Test patch:
diff --git a/tests/test_cmd2.py b/tests/test_cmd2.py
index 57e1e90f..630a8fa0 100644
--- a/tests/test_cmd2.py
+++ b/tests/test_cmd2.py
@@ -1344,11 +1344,11 @@ def test_select_options(select_app):
     # And verify the expected output to stdout
     assert out == expected
 
-def test_select_invalid_option(select_app):
+def test_select_invalid_option_too_big(select_app):
     # Mock out the input call so we don't actually wait for a user's response on stdin
     m = mock.MagicMock(name='input')
     # If side_effect is an iterable then each call to the mock will return the next value from the iterable.
-    m.side_effect = ['3', '1']  # First pass and invalid selection, then pass a valid one
+    m.side_effect = ['3', '1']  # First pass an invalid selection, then pass a valid one
     builtins.input = m
 
     food = 'fish'
@@ -1368,6 +1368,30 @@ def test_select_invalid_option(select_app):
     # And verify the expected output to stdout
     assert out == expected
 
+def test_select_invalid_option_too_small(select_app):
+    # Mock out the input call so we don't actually wait for a user's response on stdin
+    m = mock.MagicMock(name='input')
+    # If side_effect is an iterable then each call to the mock will return the next value from the iterable.
+    m.side_effect = ['0', '1']  # First pass an invalid selection, then pass a valid one
+    builtins.input = m
+
+    food = 'fish'
+    out = run_cmd(select_app, "eat {}".format(food))
+    expected = normalize("""
+   1. sweet
+   2. salty
+'0' isn't a valid choice. Pick a number between 1 and 2:
+{} with sweet sauce, yum!
+""".format(food))
+
+    # Make sure our mock was called exactly twice with the expected arguments
+    arg = 'Sauce? '
+    calls = [mock.call(arg), mock.call(arg)]
+    m.assert_has_calls(calls)
+
+    # And verify the expected output to stdout
+    assert out == expected
+
 def test_select_list_of_strings(select_app):
     # Mock out the input call so we don't actually wait for a user's response on stdin
     m = mock.MagicMock(name='input', return_value='2')