fix(registry): support not-empty validation

authlib fails if essential claim is empty, new implementation may choose to
accept empty strings.

in most cases empty value should not be accepted, it is handy to be able to
these.

raise InvalidClaimError when not_empty=True claim option:

    def test_essential_empty_value(self):
        claims_requests = jwt.JWTClaimsRegistry(sub={"essential": True, "not_empty": True})
        self.assertRaises(InvalidClaimError, claims_requests.validate, {"sub": ""})

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>

src/joserfc/rfc7519/registry.py

@@ -25,6 +25,10 @@ def __init__(self, **kwargs: ClaimsOption):
     def check_value(self, claim_name: str, value: Any) -> None:
         option = self.options.get(claim_name)
         if option:
+            option_not_empty = option.get("not_empty")
+            if option_not_empty and not value:
+                raise InvalidClaimError(claim_name)
+
             option_value = option.get("value")
             if option_value and value != option_value:
                 raise InvalidClaimError(claim_name)

tests/jwt/test_claims.py

@@ -46,6 +46,12 @@ def test_essential_claims(self):
 
         claims_requests.validate({"sub": "a", "iss": "a", "name": "joserfc"})
 
+    def test_essential_empty_value(self):
+        claims_requests = jwt.JWTClaimsRegistry(sub={"essential": True, "not_empty": True})
+        self.assertRaises(InvalidClaimError, claims_requests.validate, {"sub": ""})
+
+        claims_requests.validate({"sub": "a"})
+
     def test_option_value(self):
         claims_requests = jwt.JWTClaimsRegistry(sub={"essential": True, "value": "123"})
         self.assertRaises(InvalidClaimError, claims_requests.validate, {"sub": "a"})