Fixes for docs rendering (pyauth#145)

* adds `sphinx.ext.intersphinx` to link types back to
https://docs.python.org/3/library/typing.html
* Remove a default value in the `TOTP` / `HOTP` classes so the type
hints get rendered correctly (this is likely a bug in `sphinx` and just
working around it).

docs/conf.py

@@ -10,10 +10,13 @@
 release = ""
 language = "en"
 master_doc = "index"
-extensions = ["sphinx.ext.autodoc", "sphinx.ext.viewcode"]
+extensions = ["sphinx.ext.autodoc", "sphinx.ext.viewcode", "sphinx.ext.intersphinx"]
 source_suffix = [".rst", ".md"]
 exclude_patterns = ["_build", "Thumbs.db", ".DS_Store"]
 pygments_style = "sphinx"
+intersphinx_mapping = {
+    "https://docs.python.org/3": None,
+}
 
 if "readthedocs.org" in os.getcwd().split("/"):
     with open("index.rst", "w") as fh:

src/pyotp/hotp.py

@@ -14,7 +14,7 @@ def __init__(
         self,
         s: str,
         digits: int = 6,
-        digest: Any = hashlib.sha1,
+        digest: Any = None,
         name: Optional[str] = None,
         issuer: Optional[str] = None,
         initial_count: int = 0,
@@ -23,10 +23,13 @@ def __init__(
         :param s: secret in base32 format
         :param initial_count: starting HMAC counter value, defaults to 0
         :param digits: number of integers in the OTP. Some apps expect this to be 6 digits, others support more.
-        :param digest: digest function to use in the HMAC (expected to be sha1)
+        :param digest: digest function to use in the HMAC (expected to be SHA1)
         :param name: account name
         :param issuer: issuer
         """
+        if digest is None:
+            digest = hashlib.sha1
+
         self.initial_count = initial_count
         super().__init__(s=s, digits=digits, digest=digest, name=name, issuer=issuer)
 

src/pyotp/totp.py

@@ -17,7 +17,7 @@ def __init__(
         self,
         s: str,
         digits: int = 6,
-        digest: Any = hashlib.sha1,
+        digest: Any = None,
         name: Optional[str] = None,
         issuer: Optional[str] = None,
         interval: int = 30,
@@ -26,18 +26,23 @@ def __init__(
         :param s: secret in base32 format
         :param interval: the time interval in seconds for OTP. This defaults to 30.
         :param digits: number of integers in the OTP. Some apps expect this to be 6 digits, others support more.
-        :param digest: digest function to use in the HMAC (expected to be sha1)
+        :param digest: digest function to use in the HMAC (expected to be SHA1)
         :param name: account name
         :param issuer: issuer
         """
+        if digest is None:
+            digest = hashlib.sha1
+
         self.interval = interval
         super().__init__(s=s, digits=digits, digest=digest, name=name, issuer=issuer)
 
     def at(self, for_time: Union[int, datetime.datetime], counter_offset: int = 0) -> str:
         """
         Accepts either a Unix timestamp integer or a datetime object.
 
-        To get the time until the next timecode change (seconds until the current OTP expires), use this instead::
+        To get the time until the next timecode change (seconds until the current OTP expires), use this instead:
+
+        .. code:: python
 
             totp = pyotp.TOTP(...)
             time_remaining = totp.interval - datetime.datetime.now().timestamp() % totp.interval