Fix ssn provider for zh_TW (#1851)

faker/providers/ssn/zh_TW/__init__.py

@@ -1,8 +1,45 @@
 from .. import Provider as SsnProvider
 
 
-class Provider(SsnProvider):
-    ssn_formats = ("?#########",)
+def checksum(s: str) -> int:
+    def _get_alphabet_weight(c: str) -> int:
+        """A=10, B=11, ...., H=17,
+        I=34,
+        J=18, K=19, ..., N=22,
+        O=35,
+        P=23, Q=24, ..., V=29,
+        W=32,
+        X=30, Y=31, Z=33
+        """
+        if ord(c) < 73:  # A-H
+            return ord(c) - 55
+        if ord(c) == 73:  # I
+            return ord(c) - 39
+        if ord(c) < 79:  # J-N
+            return ord(c) - 56
+        if ord(c) == 79:  # O
+            return ord(c) - 44
+        if ord(c) < 87:  # P-V
+            return ord(c) - 57
+        if ord(c) == 87:  # W
+            return ord(c) - 55
+        if ord(c) < 90:  # X, Y
+            return ord(c) - 58
+        return ord(c) - 57  # Z
+
+    res = 0
+    for i, c in enumerate(s):
+        if i == 0:
+            res = _get_alphabet_weight(c) % 10 * 9 + _get_alphabet_weight(c) // 10
+        elif i < 9:
+            res += int(c) * (9 - i)
+        else:
+            res += int(c)
+    return res
 
+
+class Provider(SsnProvider):
     def ssn(self) -> str:
-        return self.bothify(self.random_element(self.ssn_formats)).upper()
+        ssn_without_last_char = self.numerify(self.random_uppercase_letter() + str(self.random_int(1, 2)) + "#######")
+        last_char = str((10 - checksum(ssn_without_last_char) % 10) % 10)
+        return ssn_without_last_char + last_char

tests/providers/test_ssn.py

@@ -34,6 +34,7 @@
 from faker.providers.ssn.pt_BR import checksum as pt_checksum
 from faker.providers.ssn.ro_RO import ssn_checksum as ro_ssn_checksum
 from faker.providers.ssn.ro_RO import vat_checksum as ro_vat_checksum
+from faker.providers.ssn.zh_TW import checksum as tw_checksum
 from faker.utils.checksums import luhn_checksum
 
 
@@ -1271,3 +1272,25 @@ def check_length(self):
     def test_vat_id(self):
         for _ in range(100):
             assert re.search(r"^LV\d{11}$", self.fake.vat_id())
+
+
+class TestZhTW(unittest.TestCase):
+    num_sample_runs = 10
+
+    def setUp(self):
+        self.fake = Faker("zh_TW")
+        Faker.seed(0)
+        self.samples = [self.fake.ssn() for _ in range(self.num_sample_runs)]
+
+    def test_length(self):
+        for sample in self.samples:
+            assert len(sample) == 10
+
+    def test_gender(self):
+        """only '1' and '2' are allowed in the second char"""
+        for sample in self.samples:
+            assert sample[1] == "1" or sample[1] == "2"
+
+    def test_checksum(self):
+        for sample in self.samples:
+            assert tw_checksum(sample) % 10 == 0