Harden mypy/ruff tooling and improve typing

Toolchain:
- Bump the pinned linters that CI enforces: ruff 0.2.0 -> 0.15.8 and the
  mypy pre-commit hook 1.8.0 -> 1.20.2 (aligning the package type-check with
  the `mypy>=1.20` floor the test suite now requires), and switch to the
  non-deprecated `ruff-check` hook id (updating the hatch lint:build script
  to match).
- Enable additional mypy error codes: truthy-iterable, possibly-undefined,
  redundant-self, unused-awaitable.
- Drop ruff rules removed upstream (UP038, PT004, PT005); ignore PLC0415
  (traitlets relies on lazy/optional imports); relax RUF059/PLW0108/B024
  for tests, matching the existing per-file test allowances.

Typing / correctness:
- parse_notifier_name / observe / unobserve: Iterable -> Collection, so the
  `not names` / `All in names` checks are honest (a generator was a latent
  bug) and truthy-iterable is satisfied.
- SingletonConfigurable.instance now returns Self instead of a bespoke
  TypeVar (PYI019).
- _CallbackWrapper gets a __hash__ consistent with __eq__ (PLW1641).
- Use `is` instead of `==` for exact trait-type comparisons (E721).
- Correct/remove stale `type: ignore` codes and unused noqa directives
  surfaced by the newer mypy.

Cleanups:
- Modernize %-formatting and str.format to f-strings (UP031/UP032), across
  traitlets/, tests/, examples/ and docs/.
- Replace dict-index iteration with .items() (PLC0206), iterable unpacking
  (RUF005), and lazy %-args for a logging call (G004).
- Reformat with the newer ruff-format.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TBmDBHmq8vVSGig4i37KK7

Author: claude

.pre-commit-config.yaml

@@ -51,7 +51,7 @@ repos:
         args: ["-L", "sur,nd"]
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: "v1.8.0"
+    rev: "v1.20.2"
     hooks:
       - id: mypy
         files: "^traitlets"
@@ -67,9 +67,9 @@ repos:
       - id: rst-inline-touching-normal
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.2.0
+    rev: v0.15.8
     hooks:
-      - id: ruff
+      - id: ruff-check
         types_or: [python, jupyter]
         args: ["--fix", "--show-fixes"]
       - id: ruff-format

docs/sphinxext/github.py

@@ -13,6 +13,7 @@
 * Doug Hellmann
 * Min RK
 """
+
 #
 # Original Copyright (c) 2010 Doug Hellmann.  All rights reserved.
 #
@@ -42,9 +43,7 @@ def make_link_node(rawtext, app, type, slug, options):
         if not base.endswith("/"):
             base += "/"
     except AttributeError as err:
-        raise ValueError(
-            "github_project_url configuration value is not set (%s)" % str(err)
-        ) from err
+        raise ValueError(f"github_project_url configuration value is not set ({err!s})") from err
 
     ref = base + type + "/" + slug + "/"
     set_classes(options)
@@ -79,7 +78,7 @@ def ghissue_role(name, rawtext, text, lineno, inliner, options=None, content=Non
     except ValueError:
         msg = inliner.reporter.error(
             "GitHub issue number must be a number greater than or equal to 1; "
-            '"%s" is invalid.' % text,
+            f'"{text}" is invalid.',
             line=lineno,
         )
         prb = inliner.problematic(rawtext, rawtext, msg)
@@ -92,7 +91,7 @@ def ghissue_role(name, rawtext, text, lineno, inliner, options=None, content=Non
         category = "issues"
     else:
         msg = inliner.reporter.error(
-            'GitHub roles include "ghpull" and "ghissue", "%s" is invalid.' % name, line=lineno
+            f'GitHub roles include "ghpull" and "ghissue", "{name}" is invalid.', line=lineno
         )
         prb = inliner.problematic(rawtext, rawtext, msg)
         return [prb], [msg]
@@ -149,9 +148,7 @@ def ghcommit_role(name, rawtext, text, lineno, inliner, options=None, content=No
         if not base.endswith("/"):
             base += "/"
     except AttributeError as err:
-        raise ValueError(
-            "github_project_url configuration value is not set (%s)" % str(err)
-        ) from err
+        raise ValueError(f"github_project_url configuration value is not set ({err!s})") from err
 
     ref = base + text
     node = nodes.reference(rawtext, text[:6], refuri=ref, **options)

examples/argcomplete_app.py

@@ -63,6 +63,7 @@
 If completions are not showing, you can set the environment variable ``_ARC_DEBUG=1``
 to assist in debugging argcomplete. This was last checked with ``argcomplete==1.12.3``.
 """
+
 from __future__ import annotations
 
 import json

examples/docs/aliases.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of using Application aliases, for docs"""
+
 from __future__ import annotations
 
 from traitlets import Bool

examples/docs/container.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of using container traits in Application command-line"""
+
 from __future__ import annotations
 
 from traitlets import Dict, Integer, List, Unicode

examples/docs/flags.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of using Application flags, for docs"""
+
 from __future__ import annotations
 
 from traitlets import Bool

examples/docs/from_string.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of using TraitType.from_string, for docs"""
+
 from __future__ import annotations
 
 from binascii import a2b_hex

examples/docs/load_config_app.py

@@ -16,6 +16,7 @@
     $ ./examples/docs/load_config_app.py -c ""
     The school MIT has a rank of 1.
 """
+
 from __future__ import annotations
 
 from pathlib import Path

examples/docs/multiple_apps.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of one application calling another"""
+
 from __future__ import annotations
 
 from traitlets.config import Application

examples/docs/subcommands.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # PYTHON_ARGCOMPLETE_OK
 """A simple example of using Application subcommands, for docs"""
+
 from __future__ import annotations
 
 from traitlets.config import Application