Add subproblems to errors (#7046) (#9258)

* Add subproblems to errors (#7046)

* Fix can't assign attribute

* Tidy up string representations of errors and add decoders for subproblems / identifiers

* Add missing attributes to docstring

* Move change to 1.27.0 in changelog

2 files changed, 85 insertions, 52 deletions

diff --git a/acme/acme/messages.py b/acme/acme/messages.py
index 286178d63..9b9ef5de2 100644
--- a/acme/acme/messages.py
+++ b/acme/acme/messages.py
@@ -79,6 +79,55 @@ def is_acme_error(err: BaseException) -> bool:
     return False
 
 
+class _Constant(jose.JSONDeSerializable, Hashable):
+    """ACME constant."""
+    __slots__ = ('name',)
+    POSSIBLE_NAMES: Dict[str, '_Constant'] = NotImplemented
+
+    def __init__(self, name: str) -> None:
+        super().__init__()
+        self.POSSIBLE_NAMES[name] = self  # pylint: disable=unsupported-assignment-operation
+        self.name = name
+
+    def to_partial_json(self) -> str:
+        return self.name
+
+    @classmethod
+    def from_json(cls, jobj: str) -> '_Constant':
+        if jobj not in cls.POSSIBLE_NAMES:  # pylint: disable=unsupported-membership-test
+            raise jose.DeserializationError(f'{cls.__name__} not recognized')
+        return cls.POSSIBLE_NAMES[jobj]
+
+    def __repr__(self) -> str:
+        return f'{self.__class__.__name__}({self.name})'
+
+    def __eq__(self, other: Any) -> bool:
+        return isinstance(other, type(self)) and other.name == self.name
+
+    def __hash__(self) -> int:
+        return hash((self.__class__, self.name))
+
+
+class IdentifierType(_Constant):
+    """ACME identifier type."""
+    POSSIBLE_NAMES: Dict[str, _Constant] = {}
+
+
+IDENTIFIER_FQDN = IdentifierType('dns')  # IdentifierDNS in Boulder
+IDENTIFIER_IP = IdentifierType('ip') # IdentifierIP in pebble - not in Boulder yet
+
+
+class Identifier(jose.JSONObjectWithFields):
+    """ACME identifier.
+
+    :ivar IdentifierType typ:
+    :ivar str value:
+
+    """
+    typ: IdentifierType = jose.field('type', decoder=IdentifierType.from_json)
+    value: str = jose.field('value')
+
+
 class Error(jose.JSONObjectWithFields, errors.Error):
     """ACME error.
 
@@ -87,11 +136,23 @@ class Error(jose.JSONObjectWithFields, errors.Error):
     :ivar str typ:
     :ivar str title:
     :ivar str detail:
+    :ivar Identifier identifier:
+    :ivar tuple subproblems: An array of ACME Errors which may be present when the CA
+            returns multiple errors related to the same request, `tuple` of `Error`.
 
     """
     typ: str = jose.field('type', omitempty=True, default='about:blank')
     title: str = jose.field('title', omitempty=True)
     detail: str = jose.field('detail', omitempty=True)
+    identifier: Optional['Identifier'] = jose.field(
+        'identifier', decoder=Identifier.from_json, omitempty=True)
+    subproblems: Optional[Tuple['Error', ...]] = jose.field('subproblems', omitempty=True)
+
+    # Mypy does not understand the josepy magic happening here, and falsely claims
+    # that subproblems is redefined. Let's ignore the type check here.
+    @subproblems.decoder  # type: ignore
+    def subproblems(value: List[Dict[str, Any]]) -> Tuple['Error', ...]:  # type: ignore[misc]  # pylint: disable=no-self-argument,missing-function-docstring
+        return tuple(Error.from_json(subproblem) for subproblem in value)
 
     @classmethod
     def with_code(cls, code: str, **kwargs: Any) -> 'Error':
@@ -135,39 +196,16 @@ class Error(jose.JSONObjectWithFields, errors.Error):
         return None
 
     def __str__(self) -> str:
-        return b' :: '.join(
+        result = b' :: '.join(
             part.encode('ascii', 'backslashreplace') for part in
             (self.typ, self.description, self.detail, self.title)
             if part is not None).decode()
-
-
-class _Constant(jose.JSONDeSerializable, Hashable):
-    """ACME constant."""
-    __slots__ = ('name',)
-    POSSIBLE_NAMES: Dict[str, '_Constant'] = NotImplemented
-
-    def __init__(self, name: str) -> None:
-        super().__init__()
-        self.POSSIBLE_NAMES[name] = self  # pylint: disable=unsupported-assignment-operation
-        self.name = name
-
-    def to_partial_json(self) -> str:
-        return self.name
-
-    @classmethod
-    def from_json(cls, jobj: str) -> '_Constant':
-        if jobj not in cls.POSSIBLE_NAMES:  # pylint: disable=unsupported-membership-test
-            raise jose.DeserializationError(f'{cls.__name__} not recognized')
-        return cls.POSSIBLE_NAMES[jobj]
-
-    def __repr__(self) -> str:
-        return f'{self.__class__.__name__}({self.name})'
-
-    def __eq__(self, other: Any) -> bool:
-        return isinstance(other, type(self)) and other.name == self.name
-
-    def __hash__(self) -> int:
-        return hash((self.__class__, self.name))
+        if self.identifier:
+            result = f'Problem for {self.identifier.value}: ' + result # pylint: disable=no-member
+        if self.subproblems and len(self.subproblems) > 0:
+            for subproblem in self.subproblems:
+                result += f'\n{subproblem}'
+        return result
 
 
 class Status(_Constant):
@@ -185,26 +223,6 @@ STATUS_READY = Status('ready')
 STATUS_DEACTIVATED = Status('deactivated')
 
 
-class IdentifierType(_Constant):
-    """ACME identifier type."""
-    POSSIBLE_NAMES: Dict[str, _Constant] = {}
-
-
-IDENTIFIER_FQDN = IdentifierType('dns')  # IdentifierDNS in Boulder
-IDENTIFIER_IP = IdentifierType('ip') # IdentifierIP in pebble - not in Boulder yet
-
-
-class Identifier(jose.JSONObjectWithFields):
-    """ACME identifier.
-
-    :ivar IdentifierType typ:
-    :ivar str value:
-
-    """
-    typ: IdentifierType = jose.field('type', decoder=IdentifierType.from_json)
-    value: str = jose.field('value')
-
-
 class HasResourceType(Protocol):
     """
     Represents a class with a resource_type class parameter of type string.
diff --git a/acme/tests/messages_test.py b/acme/tests/messages_test.py
index 3f0f29215..cf7e7629a 100644
--- a/acme/tests/messages_test.py
+++ b/acme/tests/messages_test.py
@@ -17,7 +17,7 @@ class ErrorTest(unittest.TestCase):
     """Tests for acme.messages.Error."""
 
     def setUp(self):
-        from acme.messages import Error, ERROR_PREFIX
+        from acme.messages import Error, ERROR_PREFIX, Identifier, IDENTIFIER_FQDN
         self.error = Error.with_code('malformed', detail='foo', title='title')
         self.jobj = {
             'detail': 'foo',
@@ -25,6 +25,9 @@ class ErrorTest(unittest.TestCase):
             'type': ERROR_PREFIX + 'malformed',
         }
         self.error_custom = Error(typ='custom', detail='bar')
+        self.identifier = Identifier(typ=IDENTIFIER_FQDN, value='example.com')
+        self.subproblem = Error.with_code('caa', detail='bar', title='title', identifier=self.identifier)
+        self.error_with_subproblems = Error.with_code('malformed', detail='foo', title='title', subproblems=[self.subproblem])
         self.empty_error = Error()
 
     def test_default_typ(self):
@@ -39,6 +42,14 @@ class ErrorTest(unittest.TestCase):
         from acme.messages import Error
         hash(Error.from_json(self.error.to_json()))
 
+    def test_from_json_with_subproblems(self):
+        from acme.messages import Error
+
+        parsed_error = Error.from_json(self.error_with_subproblems.to_json())
+
+        self.assertEqual(1, len(parsed_error.subproblems))
+        self.assertEqual(self.subproblem, parsed_error.subproblems[0])
+
     def test_description(self):
         self.assertEqual('The request message was malformed', self.error.description)
         self.assertIsNone(self.error_custom.description)
@@ -73,7 +84,11 @@ class ErrorTest(unittest.TestCase):
             str(self.error),
             u"{0.typ} :: {0.description} :: {0.detail} :: {0.title}"
             .format(self.error))
-
+        self.assertEqual(
+            str(self.error_with_subproblems),
+            (u"{0.typ} :: {0.description} :: {0.detail} :: {0.title}\n"+
+            u"Problem for {1.identifier.value}: {1.typ} :: {1.description} :: {1.detail} :: {1.title}").format(
+        self.error_with_subproblems, self.subproblem))
 
 class ConstantTest(unittest.TestCase):
     """Tests for acme.messages._Constant."""