Use strict optional checking in misc.py

src/pip/_internal/network/session.py

@@ -419,15 +419,17 @@ def add_trusted_host(
                 msg += f" (from {source})"
             logger.info(msg)
 
-        host_port = parse_netloc(host)
-        if host_port not in self.pip_trusted_origins:
-            self.pip_trusted_origins.append(host_port)
+        parsed_host, parsed_port = parse_netloc(host)
+        if parsed_host is None:
+            raise ValueError(f"Trusted host URL must include a host part: {host!r}")
+        if (parsed_host, parsed_port) not in self.pip_trusted_origins:
+            self.pip_trusted_origins.append((parsed_host, parsed_port))
 
         self.mount(
             build_url_from_netloc(host, scheme="http") + "/", self._trusted_host_adapter
         )
         self.mount(build_url_from_netloc(host) + "/", self._trusted_host_adapter)
-        if not host_port[1]:
+        if not parsed_port:
             self.mount(
                 build_url_from_netloc(host, scheme="http") + ":",
                 self._trusted_host_adapter,

src/pip/_internal/utils/misc.py

@@ -1,6 +1,3 @@
-# The following comment should be removed at some point in the future.
-# mypy: strict-optional=False
-
 import contextlib
 import errno
 import getpass
@@ -339,17 +336,18 @@ def write_output(msg: Any, *args: Any) -> None:
 
 
 class StreamWrapper(StringIO):
-    orig_stream: TextIO = None
+    orig_stream: TextIO
 
     @classmethod
     def from_stream(cls, orig_stream: TextIO) -> "StreamWrapper":
-        cls.orig_stream = orig_stream
-        return cls()
+        ret = cls()
+        ret.orig_stream = orig_stream
+        return ret
 
     # compileall.compile_dir() needs stdout.encoding to print to stdout
-    # https://github.com/python/mypy/issues/4125
+    # type ignore is because TextIOBase.encoding is writeable
     @property
-    def encoding(self):  # type: ignore
+    def encoding(self) -> str:  # type: ignore
         return self.orig_stream.encoding
 
 
@@ -417,7 +415,7 @@ def build_url_from_netloc(netloc: str, scheme: str = "https") -> str:
     return f"{scheme}://{netloc}"
 
 
-def parse_netloc(netloc: str) -> Tuple[str, Optional[int]]:
+def parse_netloc(netloc: str) -> Tuple[Optional[str], Optional[int]]:
     """
     Return the host-port pair from a netloc.
     """
@@ -505,7 +503,9 @@ def _redact_netloc(netloc: str) -> Tuple[str]:
     return (redact_netloc(netloc),)
 
 
-def split_auth_netloc_from_url(url: str) -> Tuple[str, str, Tuple[str, str]]:
+def split_auth_netloc_from_url(
+    url: str,
+) -> Tuple[str, str, Tuple[Optional[str], Optional[str]]]:
     """
     Parse a url into separate netloc, auth, and url with no auth.