Fixed #3890 -- Added USSocialSecurityNumberField. Thanks James Bennet.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4910 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/localflavor/usa/forms.py

@@ -9,6 +9,7 @@ from django.utils.translation import gettext
 import re
 
 phone_digits_re = re.compile(r'^(?:1-?)?(\d{3})[-\.]?(\d{3})[-\.]?(\d{4})$')
+ssn_re = re.compile(r"^(?P<area>\d{3})[-\ ]?(?P<group>\d{2})[-\ ]?(?P<serial>\d{4})$")
 
 class USZipCodeField(RegexField):
     def __init__(self, *args, **kwargs):
@@ -28,6 +29,47 @@ class USPhoneNumberField(Field):
             return u'%s-%s-%s' % (m.group(1), m.group(2), m.group(3))
         raise ValidationError(u'Phone numbers must be in XXX-XXX-XXXX format.')
 
+class USSocialSecurityNumberField(Field):
+    """
+    A United States Social Security number.
+    
+    Checks the following rules to determine whether the number is valid:
+    
+        * Conforms to the XXX-XX-XXXX format.
+        * No group consists entirely of zeroes.
+        * The leading group is not "666" (block "666" will never be allocated).
+        * The number is not in the promotional block 987-65-4320 through 987-65-4329,
+          which are permanently invalid.
+        * The number is not one known to be invalid due to otherwise widespread
+          promotional use or distribution (e.g., the Woolworth's number or the 1962
+          promotional number).
+    
+    """
+    def clean(self, value):
+        super(USSocialSecurityNumberField, self).clean(value)
+        if value in EMPTY_VALUES:
+            return u''
+        msg = gettext(u'Enter a valid US Social Security number in XXX-XX-XXXX format')
+        match = re.match(ssn_re, value)
+        if not match:
+            raise ValidationError(msg)
+        area, group, serial = match.groupdict()['area'], match.groupdict()['group'], match.groupdict()['serial']
+        
+        # First pass: no blocks of all zeroes.
+        if area == '000' or \
+           group == '00' or \
+           serial == '0000':
+            raise ValidationError(msg)
+        
+        # Second pass: promotional and otherwise permanently invalid numbers.
+        if area == '666' or \
+           (area == '987' and group == '65' and \
+            4320 <= int(serial) <= 4329) or \
+           value == '078-05-1120' or \
+           value == '219-09-9999':
+            raise ValidationError(msg)
+        return u'%s-%s-%s' % (area, group, serial)
+
 class USStateField(Field):
     """
     A form field that validates its input is a U.S. state name or abbreviation.

tests/regressiontests/forms/localflavor.py

@@ -246,6 +246,18 @@ as its choices.
 <option value="WY">Wyoming</option>
 </select>
 
+# USSocialSecurityNumberField #################################################
+>>> from django.contrib.localflavor.usa.forms import USSocialSecurityNumberField
+>>> f = USSocialSecurityNumberField()
+>>> f.clean('987-65-4330')
+u'987-65-4330'
+>>> f.clean('987654330')
+u'987-65-4330'
+>>> f.clean('078-05-1120')
+Traceback (most recent call last):
+...
+ValidationError: [u'Enter a valid US Social Security number in XXX-XX-XXXX format']
+
 # UKPostcodeField #############################################################
 
 UKPostcodeField validates that the data is a valid UK postcode.