From 6f573feaeb120c6115d75ee5cdbb7401946277c3 Mon Sep 17 00:00:00 2001
From: Steve Howell <steve@zulip.com>
Date: Wed, 18 Dec 2013 11:59:02 -0500
Subject: [PATCH] Add "length" option to check_list validator.

(imported from commit 4f8e203f964d1c936fe548b2f77a2e4aae745ae9)
---
 zerver/lib/validator.py | 4 +++-
 zerver/tests.py         | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/zerver/lib/validator.py b/zerver/lib/validator.py
index 7013649dbb..8312ee2738 100644
--- a/zerver/lib/validator.py
+++ b/zerver/lib/validator.py
@@ -41,11 +41,13 @@ def check_bool(var_name, val):
         return '%s is not a boolean' % (var_name,)
     return None
 
-def check_list(sub_validator):
+def check_list(sub_validator, length=None):
     def f(var_name, val):
         if not isinstance(val, list):
             return '%s is not a list' % (var_name,)
 
+        if length is not None and length != len(val):
+            return '%s should have exactly %d items' % (var_name, length)
         for i, item in enumerate(val):
             vname = '%s[%d]' % (var_name, i)
             error = sub_validator(vname, item)
diff --git a/zerver/tests.py b/zerver/tests.py
index d88448f8af..7fad4d9646 100644
--- a/zerver/tests.py
+++ b/zerver/tests.py
@@ -290,6 +290,10 @@ class ValidatorTestCase(TestCase):
         error = check_list(check_list(check_string))('x', x)
         self.assertEqual(error, 'x[1][2] is not a string')
 
+        x = ["hello", "goodbye", "hello again"]
+        error = check_list(check_string, length=2)('x', x)
+        self.assertEqual(error, 'x should have exactly 2 items')
+
     def test_check_dict(self):
         keys = [
             ('names', check_list(check_string)),