Issue python#28563: Make plural form selection more lenient and accepting

non-integer numbers.  Django tests depend on this.

Author: serhiy-storchaka

Lib/gettext.py

@@ -156,6 +156,14 @@ def _parse(tokens, priority=-1):
 
     return result, nexttok
 
+def _as_int(n):
+    try:
+        i = round(n)
+    except TypeError:
+        raise TypeError('Plural value must be an integer, got %s' %
+                        (n.__class__.__name__,)) from None
+    return n
+
 def c2py(plural):
     """Gets a C expression as used in PO files for plural forms and returns a
     Python function that implements an equivalent expression.
@@ -179,11 +187,11 @@ def c2py(plural):
             elif c == ')':
                 depth -= 1
 
-        ns = {}
+        ns = {'_as_int': _as_int}
         exec('''if True:
             def func(n):
                 if not isinstance(n, int):
-                    raise ValueError('Plural value must be an integer.')
+                    n = _as_int(n)
                 return int(%s)
             ''' % result, ns)
         return ns['func']

Lib/test/test_gettext.py

@@ -365,12 +365,16 @@ def test_division(self):
         self.assertRaises(ZeroDivisionError, f, 0)
 
     def test_plural_number(self):
-        f = gettext.c2py('1')
-        self.assertEqual(f(1), 1)
-        self.assertRaises(ValueError, f, 1.0)
-        self.assertRaises(ValueError, f, '1')
-        self.assertRaises(ValueError, f, [])
-        self.assertRaises(ValueError, f, object())
+        f = gettext.c2py('n != 1')
+        self.assertEqual(f(1), 0)
+        self.assertEqual(f(2), 1)
+        self.assertEqual(f(1.0), 0)
+        self.assertEqual(f(2.0), 1)
+        self.assertEqual(f(1.1), 1)
+        self.assertRaises(TypeError, f, '2')
+        self.assertRaises(TypeError, f, b'2')
+        self.assertRaises(TypeError, f, [])
+        self.assertRaises(TypeError, f, object())