improved from_string

Author: daniel-sanche

google/auth/crypt/rsa.py

@@ -75,7 +75,9 @@ def from_string(cls, public_key):
         Raises:
             ValueError: If the public_key can't be parsed.
         """
-        return _cryptography_rsa.RSAVerifier.from_string(public_key)
+        instance = cls.__new__(cls)
+        instance._impl = _cryptography_rsa.RSAVerifier.from_string(public_key)
+        return instance
 
 
 class RSASigner(base.Signer, base.FromServiceAccountMixin):
@@ -132,4 +134,6 @@ def from_string(cls, key, key_id=None):
             ValueError: If the key cannot be parsed as PKCS#1 or PKCS#8 in
                 PEM format.
         """
-        return _cryptography_rsa.RSASigner.from_string(key, key_id=key_id)
+        instance = cls.__new__(cls)
+        instance._impl = _cryptography_rsa.RSASigner.from_string(key, key_id=key_id)
+        return instance

tests/crypt/test_rsa.py

@@ -81,7 +81,7 @@ def test_from_string_cryptography(self, mock_crypto):
 
         result = rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
 
-        assert result == expected_verifier
+        assert result._impl == expected_verifier
         mock_crypto.RSAVerifier.from_string.assert_called_once_with(PUBLIC_KEY_BYTES)
 
 
@@ -125,7 +125,7 @@ def test_from_string_delegates_to_cryptography(self, mock_crypto):
 
         result = rsa.RSASigner.from_string(PRIVATE_KEY_BYTES, key_id="123")
 
-        assert result == expected_signer
+        assert result._impl == expected_signer
         mock_crypto.RSASigner.from_string.assert_called_once_with(
             PRIVATE_KEY_BYTES, key_id="123"
         )
@@ -137,8 +137,8 @@ def test_end_to_end_cryptography_lib(self):
         verifier = rsa.RSAVerifier.from_string(PUBLIC_KEY_BYTES)
         result = verifier.verify(message, sig)
         assert result is True
-        assert isinstance(verifier, _cryptography_rsa.RSAVerifier)
-        assert isinstance(signer, _cryptography_rsa.RSASigner)
+        assert isinstance(verifier._impl, _cryptography_rsa.RSAVerifier)
+        assert isinstance(signer._impl, _cryptography_rsa.RSASigner)
 
     def test_end_to_end_rsa_lib(self):
         signer = rsa.RSASigner(RSA_PRIVATE_KEY)