add typing with mypy

1 files changed, 28 insertions, 12 deletions

diff --git a/src/itsdangerous/exc.py b/src/itsdangerous/exc.py
index 8c9021d..c38a6af 100644
--- a/src/itsdangerous/exc.py
+++ b/src/itsdangerous/exc.py
@@ -1,3 +1,10 @@
+import typing as _t
+from datetime import datetime
+
+_t_opt_any = _t.Optional[_t.Any]
+_t_opt_exc = _t.Optional[Exception]
+
+
 class BadData(Exception):
     """Raised if bad data of any sort was encountered. This is the base
     for all exceptions that ItsDangerous defines.
@@ -5,20 +12,18 @@ class BadData(Exception):
     .. versionadded:: 0.15
     """
 
-    message = None
-
-    def __init__(self, message):
+    def __init__(self, message: str):
         super().__init__(message)
         self.message = message
 
-    def __str__(self):
+    def __str__(self) -> str:
         return self.message
 
 
 class BadSignature(BadData):
     """Raised if a signature does not match."""
 
-    def __init__(self, message, payload=None):
+    def __init__(self, message: str, payload: _t_opt_any = None):
         super().__init__(message)
 
         #: The payload that failed the signature test. In some
@@ -26,7 +31,7 @@ class BadSignature(BadData):
         #: you know it was tampered with.
         #:
         #: .. versionadded:: 0.14
-        self.payload = payload
+        self.payload: _t_opt_any = payload
 
 
 class BadTimeSignature(BadSignature):
@@ -34,7 +39,12 @@ class BadTimeSignature(BadSignature):
     of :class:`BadSignature`.
     """
 
-    def __init__(self, message, payload=None, date_signed=None):
+    def __init__(
+        self,
+        message: str,
+        payload: _t_opt_any = None,
+        date_signed: _t.Optional[datetime] = None,
+    ):
         super().__init__(message, payload)
 
         #: If the signature expired this exposes the date of when the
@@ -62,16 +72,22 @@ class BadHeader(BadSignature):
     .. versionadded:: 0.24
     """
 
-    def __init__(self, message, payload=None, header=None, original_error=None):
+    def __init__(
+        self,
+        message: str,
+        payload: _t_opt_any = None,
+        header: _t_opt_any = None,
+        original_error: _t_opt_exc = None,
+    ):
         super().__init__(message, payload)
 
         #: If the header is actually available but just malformed it
         #: might be stored here.
-        self.header = header
+        self.header: _t_opt_any = header
 
         #: If available, the error that indicates why the payload was
         #: not valid. This might be ``None``.
-        self.original_error = original_error
+        self.original_error: _t_opt_exc = original_error
 
 
 class BadPayload(BadData):
@@ -83,9 +99,9 @@ class BadPayload(BadData):
     .. versionadded:: 0.15
     """
 
-    def __init__(self, message, original_error=None):
+    def __init__(self, message: str, original_error: _t_opt_exc = None):
         super().__init__(message)
 
         #: If available, the error that indicates why the payload was
         #: not valid. This might be ``None``.
-        self.original_error = original_error
+        self.original_error: _t_opt_exc = original_error