[py] Fix remaining mypy errors and enable CI for type checking (#16837)

Author: cgoldberg

.github/workflows/ci-python.yml

@@ -52,7 +52,7 @@ jobs:
           pip install tox
       - name: Run type checking
         run: |
-          tox -c py/tox.ini || true
+          tox -c py/tox.ini
         env:
           TOXENV: typecheck
 

py/BUILD.bazel

@@ -314,11 +314,14 @@ py_wheel(
     python_requires = ">=3.10",
     python_tag = "py3",
     requires = [
-        "urllib3[socks]>=2.5.0,<3.0",
+        "certifi>=2025.10.5",
         "trio>=0.31.0,<1.0",
         "trio-websocket>=0.12.2,<1.0",
-        "certifi>=2025.10.5",
+        "trio-typing>=0.10.0",
+        "types-certifi>=2021.10.8.3",
+        "types-urllib3>=1.26.25.14",
         "typing_extensions>=4.15.0,<5.0",
+        "urllib3[socks]>=2.6.0,<3.0",
         "websocket-client>=1.8.0,<2.0",
     ],
     strip_path_prefixes = [

py/pyproject.toml

@@ -26,11 +26,14 @@ classifiers = [
     "Programming Language :: Python :: 3.14",
 ]
 dependencies = [
-    "urllib3[socks]>=2.6.0,<3.0",
+    "certifi>=2025.10.5",
     "trio>=0.31.0,<1.0",
     "trio-websocket>=0.12.2,<1.0",
-    "certifi>=2025.10.5",
+    "trio-typing>=0.10.0",
+    "types-certifi>=2021.10.8.3",
+    "types-urllib3>=1.26.25.14",
     "typing_extensions>=4.15.0,<5.0",
+    "urllib3[socks]>=2.6.0,<3.0",
     "websocket-client>=1.8.0,<2.0",
 ]
 
@@ -48,10 +51,6 @@ lint = [
 ]
 typecheck = [
     "mypy==1.19.1",
-    "types-urllib3==1.26.25.14",
-    "types-certifi==2021.10.8.3",
-    "trio-typing==0.10.0",
-    "trio-websocket>=0.12.2,<1.0",
 ]
 validate = [
     "validate-pyproject==0.24.1",
@@ -111,14 +110,11 @@ testpaths = ["test"]
 # mypy global options
 [tool.mypy]
 exclude = "selenium/webdriver/common/devtools"
-# The aim in future here is we would be able to turn (most) of these flags on, however the typing technical
-# debt is quite colossal right now.  For now we should maybe get everything working with the config here
-# then look at going after partially or completely untyped defs as a phase-2.
-files = "selenium"
+# The aim in future is we would be able to turn (most) of these flags on
 # warn about per-module sections in the config file that do not match any files processed.
 warn_unused_configs = true
 # disallows subclassing of typing.Any.
-disallow_subclassing_any = false
+disallow_subclassing_any = true
 # disallow usage of generic types that do not specify explicit type parameters.
 disallow_any_generics = false
 # disallow calling functions without type annotations from functions that have type annotations.
@@ -132,7 +128,7 @@ check_untyped_defs = false
 # reports an error whenever a function with type annotations is decorated with a decorator without annotations.
 disallow_untyped_decorators = false
 # changes the treatment of arguments with a default value of None by not implicitly making their type `typing.Optional`.
-no_implicit_optional = false
+no_implicit_optional = true
 # warns about casting an expression to it's inferred type.
 warn_redundant_casts = true
 # warns about unneeded `# type: ignore` comments.

py/requirements.txt

@@ -51,8 +51,11 @@ sortedcontainers==2.4.0
 tomli==2.3.0
 tox==4.32.0
 trio==0.32.0
+trio-typing==0.10.0
 trio-websocket==0.12.2
 twine==6.2.0
+types-certifi==2021.10.8.3
+types-urllib3==1.26.25.14
 typing_extensions==4.15.0
 urllib3[socks]==2.6.2
 virtualenv==20.35.4

py/requirements_lock.txt

@@ -4,6 +4,10 @@
 #
 #    bazel run //py:requirements.update
 #
+async-generator==1.10 \
+    --hash=sha256:01c7bf666359b4967d2cda0000cc2e4af16a0ae098cbffcb8472fb9e8ad6585b \
+    --hash=sha256:6ebb3d106c12920aaae42ccb6f787ef5eefdcdd166ea3d628fa8476abe712144
+    # via trio-typing
 attrs==25.4.0 \
     --hash=sha256:16d5969b87f0859ef33a48b35d55ac1be6e42ae49d5e853b597db70c35c57e11 \
     --hash=sha256:adcf7e2a1fb3b36ac48d97835bb6d8ade15b8dcce26aba8bf1d14847b57a3373
@@ -360,6 +364,7 @@ importlib-metadata==8.7.1 \
     # via
     #   -r py/requirements.txt
     #   keyring
+    #   trio-typing
 inflection==0.5.1 \
     --hash=sha256:1a29730d366e996aaacffb2f1f1cb9593dc38e2ddd30c91250c6dde09ea9b417 \
     --hash=sha256:f38b2b640938a4f35ade69ac3d053042959b62a0f1076a5bbaa1b9526605a8a2
@@ -420,6 +425,10 @@ more-itertools==10.8.0 \
     #   -r py/requirements.txt
     #   jaraco-classes
     #   jaraco-functools
+mypy-extensions==1.1.0 \
+    --hash=sha256:1be4cccdb0f2482337c4743e60421de3a356cd97508abadd57d47403e94f5505 \
+    --hash=sha256:52e68efc3284861e772bbcd66823fde5ae21fd2fdb51c62a211403730b916558
+    # via trio-typing
 nh3==0.3.2 \
     --hash=sha256:019ecbd007536b67fdf76fab411b648fb64e2257ca3262ec80c3425c24028c80 \
     --hash=sha256:03d617e5c8aa7331bd2659c654e021caf9bba704b109e7b2b28b039a00949fe5 \
@@ -466,6 +475,7 @@ packaging==25.0 \
     #   pyproject-api
     #   pytest
     #   tox
+    #   trio-typing
     #   twine
 platformdirs==4.5.1 \
     --hash=sha256:61d5cdcc6065745cdd94f0f878977f8de9437be93de97c1c12f853c9c0cdcbda \
@@ -640,7 +650,12 @@ trio==0.32.0 \
     # via
     #   -r py/requirements.txt
     #   pytest-trio
+    #   trio-typing
     #   trio-websocket
+trio-typing==0.10.0 \
+    --hash=sha256:065ee684296d52a8ab0e2374666301aec36ee5747ac0e7a61f230250f8907ac3 \
+    --hash=sha256:6d0e7ec9d837a2fe03591031a172533fbf4a1a95baf369edebfc51d5a49f0264
+    # via -r py/requirements.txt
 trio-websocket==0.12.2 \
     --hash=sha256:22c72c436f3d1e264d0910a3951934798dcc5b00ae56fc4ee079d46c7cf20fae \
     --hash=sha256:df605665f1db533f4a386c94525870851096a223adcb97f72a07e8b4beba45b6
@@ -649,6 +664,14 @@ twine==6.2.0 \
     --hash=sha256:418ebf08ccda9a8caaebe414433b0ba5e25eb5e4a927667122fbe8f829f985d8 \
     --hash=sha256:e5ed0d2fd70c9959770dce51c8f39c8945c574e18173a7b81802dab51b4b75cf
     # via -r py/requirements.txt
+types-certifi==2021.10.8.3 \
+    --hash=sha256:72cf7798d165bc0b76e1c10dd1ea3097c7063c42c21d664523b928e88b554a4f \
+    --hash=sha256:b2d1e325e69f71f7c78e5943d410e650b4707bb0ef32e4ddf3da37f54176e88a
+    # via -r py/requirements.txt
+types-urllib3==1.26.25.14 \
+    --hash=sha256:229b7f577c951b8c1b92c1bc2b2fdb0b49847bd2af6d1cc2a2e3dd340f3bda8f \
+    --hash=sha256:9683bbb7fb72e32bfe9d2be6e04875fbe1b3eeec3cbb4ea231435aa7fd6b4f0e
+    # via -r py/requirements.txt
 typing-extensions==4.15.0 \
     --hash=sha256:0cea48d173cc12fa28ecabc3b837ea3cf6f38c6d1136f85cbaaf598984861466 \
     --hash=sha256:f0fa19c6845758ab08074a0cfa8b7aecb71c999ca73d62883bc25cc018c4e548
@@ -657,6 +680,7 @@ typing-extensions==4.15.0 \
     #   cryptography
     #   exceptiongroup
     #   tox
+    #   trio-typing
     #   virtualenv
 urllib3[socks]==2.6.2 \
     --hash=sha256:016f9c98bb7e98085cb2b4b17b87d2c702975664e4f060c6532e64d1c1a5e797 \

py/selenium/webdriver/chrome/remote_connection.py

@@ -28,7 +28,7 @@ def __init__(
         self,
         remote_server_addr: str,
         keep_alive: bool = True,
-        ignore_proxy: bool | None = False,
+        ignore_proxy: bool = False,
         client_config: ClientConfig | None = None,
     ) -> None:
         super().__init__(

py/selenium/webdriver/chrome/webdriver.py

@@ -15,7 +15,6 @@
 # specific language governing permissions and limitations
 # under the License.
 
-
 from selenium.webdriver.chrome.options import Options
 from selenium.webdriver.chrome.service import Service
 from selenium.webdriver.chromium.webdriver import ChromiumDriver
@@ -36,7 +35,7 @@ def __init__(
         Starts the service and then creates new instance of chrome driver.
 
         Args:
-            options: This takes an instance of ChromeOptions.
+            options: Instance of Options.
             service: Service object for handling the browser driver if you need to pass extra details.
             keep_alive: Whether to configure ChromeRemoteConnection to use HTTP keep-alive.
         """

py/selenium/webdriver/chromium/remote_connection.py

@@ -26,7 +26,7 @@ def __init__(
         vendor_prefix: str,
         browser_name: str,
         keep_alive: bool = True,
-        ignore_proxy: bool | None = False,
+        ignore_proxy: bool = False,
         client_config: ClientConfig | None = None,
     ) -> None:
         client_config = client_config or ClientConfig(

py/selenium/webdriver/chromium/webdriver.py

@@ -15,7 +15,6 @@
 # specific language governing permissions and limitations
 # under the License.
 
-
 from selenium.webdriver.chromium.options import ChromiumOptions
 from selenium.webdriver.chromium.remote_connection import ChromiumRemoteConnection
 from selenium.webdriver.chromium.service import ChromiumService
@@ -29,8 +28,8 @@ class ChromiumDriver(LocalWebDriver):
 
     def __init__(
         self,
-        browser_name: str | None = None,
-        vendor_prefix: str | None = None,
+        browser_name: str,
+        vendor_prefix: str,
         options: ChromiumOptions | None = None,
         service: ChromiumService | None = None,
         keep_alive: bool = True,
@@ -40,17 +39,17 @@ def __init__(
         Args:
             browser_name: Browser name used when matching capabilities.
             vendor_prefix: Company prefix to apply to vendor-specific WebDriver extension commands.
-            options: This takes an instance of ChromiumOptions.
+            options: Instance of ChromiumOptions.
             service: Service object for handling the browser driver if you need to pass extra details.
             keep_alive: Whether to configure ChromiumRemoteConnection to use HTTP keep-alive.
         """
         self.service = service if service else ChromiumService()
-        options = options if options else ChromiumOptions()
+        self.options = options if options else ChromiumOptions()
 
-        finder = DriverFinder(self.service, options)
+        finder = DriverFinder(self.service, self.options)
         if finder.get_browser_path():
-            options.binary_location = finder.get_browser_path()
-            options.browser_version = None
+            self.options.binary_location = finder.get_browser_path()
+            self.options.browser_version = None
 
         self.service.path = self.service.env_path() or finder.get_driver_path()
         self.service.start()
@@ -60,11 +59,11 @@ def __init__(
             browser_name=browser_name,
             vendor_prefix=vendor_prefix,
             keep_alive=keep_alive,
-            ignore_proxy=options._ignore_local_proxy,
+            ignore_proxy=self.options._ignore_local_proxy,
         )
 
         try:
-            super().__init__(command_executor=executor, options=options)
+            super().__init__(command_executor=executor, options=self.options)
         except Exception:
             self.quit()
             raise

py/selenium/webdriver/common/bidi/cdp.py

@@ -300,6 +300,8 @@ def _handle_event(self, data: dict):
             data: event as a JSON dictionary
         """
         global devtools
+        if devtools is None:
+            raise RuntimeError("CDP devtools module not loaded. Call import_devtools() first.")
         event = devtools.util.parse_json_event(data)
         logger.debug("Received event: %s", event)
         to_remove = set()
@@ -424,6 +426,8 @@ async def open_session(self, target_id) -> AsyncIterator[CdpSession]:
     async def connect_session(self, target_id) -> "CdpSession":
         """Returns a new :class:`CdpSession` connected to the specified target."""
         global devtools
+        if devtools is None:
+            raise RuntimeError("CDP devtools module not loaded. Call import_devtools() first.")
         session_id = await self.execute(devtools.target.attach_to_target(target_id, True))
         session = CdpSession(self.ws, session_id, target_id)
         self.sessions[session_id] = session
@@ -435,6 +439,8 @@ async def _reader_task(self):
         Dispatches responses to commands and events to listeners.
         """
         global devtools
+        if devtools is None:
+            raise RuntimeError("CDP devtools module not loaded. Call import_devtools() first.")
         while True:
             try:
                 message = await self.ws.get_message()