Handle More Types

examples/myapp.py

@@ -93,6 +93,7 @@ def start(self):
         print("app.config:")
         print(self.config)
         print("try running with --help-all to see all available flags")
+        assert self.log is not None
         self.log.info("Info Mesage")
         self.log.debug("DebugMessage")
         self.log.critical("Warning")

traitlets/config/application.py

@@ -28,6 +28,7 @@
     PyFileConfigLoader,
 )
 from traitlets.traitlets import (
+    Any,
     Bool,
     Dict,
     Enum,
@@ -94,8 +95,10 @@
 
 IS_PYTHONW = sys.executable and sys.executable.endswith("pythonw.exe")
 
+T = t.TypeVar("T", bound=t.Callable[..., t.Any])
 
-def catch_config_error(method):
+
+def catch_config_error(method: T) -> T:
     """Method decorator for catching invalid config (Trait/ArgumentErrors) during init.
 
     On a TraitError (generally caused by bad config), this will print the trait's
@@ -113,7 +116,7 @@ def inner(app, *args, **kwargs):
             app.log.debug("Config at the time: %s", app.config)
             app.exit(1)
 
-    return inner
+    return t.cast(T, inner)
 
 
 class ApplicationError(Exception):
@@ -148,6 +151,8 @@ class Application(SingletonConfigurable):
     # line application
     name: t.Union[str, Unicode] = Unicode("application")
 
+    log = Any(help="Logger or LoggerAdapter instance", allow_none=False)
+
     # The description of the application that is printed at the beginning
     # of the help.
     description: t.Union[str, Unicode] = Unicode("This is an application.")
@@ -198,19 +203,19 @@ def _classes_inc_parents(self, classes=None):
     )
 
     # The log level for the application
-    log_level: t.Union[str, int, Enum] = Enum(
+    log_level: t.Union[str, int, Enum] = Enum(  # type:ignore[assignment]
         (0, 10, 20, 30, 40, 50, "DEBUG", "INFO", "WARN", "ERROR", "CRITICAL"),
         default_value=logging.WARN,
         help="Set the log level by value or name.",
     ).tag(config=True)
 
     _log_formatter_cls = LevelFormatter
 
-    log_datefmt: t.Union[str, Unicode] = Unicode(
+    log_datefmt: t.Union[str, Unicode] = Unicode(  # type:ignore[assignment]
         "%Y-%m-%d %H:%M:%S", help="The date format used by logging formatters for %(asctime)s"
     ).tag(config=True)
 
-    log_format: t.Union[str, Unicode] = Unicode(
+    log_format: t.Union[str, Unicode] = Unicode(  # type:ignore[assignment]
         "[%(name)s]%(highlevel)s %(message)s",
         help="The Logging format template",
     ).tag(config=True)
@@ -234,7 +239,7 @@ def get_default_logging_config(self):
                 "console": {
                     "class": "logging.StreamHandler",
                     "formatter": "console",
-                    "level": logging.getLevelName(self.log_level),
+                    "level": logging.getLevelName(self.log_level),  # type:ignore[arg-type]
                     "stream": "ext://sys.stderr",
                 },
             },
@@ -393,7 +398,7 @@ def _log_default(self):
     # and the second being the help string for the subcommand
     subcommands: t.Union[t.Dict[str, t.Tuple[str, str]], Dict] = Dict()
     # parse_command_line will initialize a subapp, if requested
-    subapp = Instance("traitlets.config.application.Application", allow_none=True)
+    subapp: Instance[t.Any] = Instance("traitlets.config.application.Application", allow_none=True)
 
     # extra command-line arguments that don't set config values
     extra_args: t.Union[t.List[str], List] = List(Unicode())
@@ -411,11 +416,11 @@ def _log_default(self):
 
     _loaded_config_files = List()
 
-    show_config: t.Union[bool, Bool] = Bool(
+    show_config: t.Union[bool, Bool] = Bool(  # type:ignore[assignment]
         help="Instead of starting the Application, dump configuration to stdout"
     ).tag(config=True)
 
-    show_config_json: t.Union[bool, Bool] = Bool(
+    show_config_json: t.Union[bool, Bool] = Bool(  # type:ignore[assignment]
         help="Instead of starting the Application, dump configuration to stdout (as JSON)"
     ).tag(config=True)
 

traitlets/config/configurable.py

@@ -5,6 +5,7 @@
 
 
 import logging
+import typing as t
 import warnings
 from copy import deepcopy
 from textwrap import dedent
@@ -44,8 +45,10 @@ class MultipleInstanceError(ConfigurableError):
 
 class Configurable(HasTraits):
 
-    config = Instance(Config, (), {})
-    parent = Instance("traitlets.config.configurable.Configurable", allow_none=True)
+    config: Instance[Config] = Instance(Config, (), {})
+    parent: Instance[t.Any] = Instance(
+        "traitlets.config.configurable.Configurable", allow_none=True
+    )
 
     def __init__(self, **kwargs):
         """Create a configurable given a config config.
@@ -183,6 +186,7 @@ def _load_config(self, cfg, section_names=None, traits=None):
                     from difflib import get_close_matches
 
                     if isinstance(self, LoggingConfigurable):
+                        assert self.log is not None
                         warn = self.log.warning
                     else:
                         warn = lambda msg: warnings.warn(msg, stacklevel=9)  # noqa[E371]
@@ -460,6 +464,7 @@ def _validate_log(self, proposal):
     @default("log")
     def _log_default(self):
         if isinstance(self.parent, LoggingConfigurable):
+            assert self.parent is not None
             return self.parent.log
         from traitlets import log
 

traitlets/config/loader.py

@@ -96,9 +96,9 @@ class LazyConfigValue(HasTraits):
     _value = None
 
     # list methods
-    _extend = List()
-    _prepend = List()
-    _inserts = List()
+    _extend: List = List()
+    _prepend: List = List()
+    _inserts: List = List()
 
     def append(self, obj):
         """Append an item to a List"""

traitlets/tests/test_typing.py

@@ -1,9 +1,8 @@
-from lib2to3 import pytree
-
 import pytest
 from typing_extensions import reveal_type
 
 from traitlets import Bool, HasTraits, TCPAddress
+from traitlets.config import Application
 
 
 @pytest.mark.mypy_testing