updates:
- [github.com/asottile/pyupgrade: v2.21.2 → v2.23.0](https://github.com/asottile/pyupgrade/compare/v2.21.2...v2.23.0)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

* Removing MSVC C4996 from pragma block at the top of pybind11.h

* localtime_thread_safe, PYBIND11_COMPAT_STRDUP

* Adding #include <ctime> (attempt to fix MSVC 2015, 2017 errors).

* Specified encoding in setup.py calls of open()

* Fix for Python2

Co-authored-by: Karsten Bock <karsten.bock@dlr.de>

* Move item instead of copy.

* Make Clang 3.6 happy.

Co-authored-by: c99 <email@dummy.com>

updates:
- [github.com/asottile/pyupgrade: v2.21.0 → v2.21.2](https://github.com/asottile/pyupgrade/compare/v2.21.0...v2.21.2)
- [github.com/psf/black: 21.6b0 → 21.7b0](https://github.com/psf/black/compare/21.6b0...21.7b0)
- https://gitlab.com/pycqa/flake8 → https://github.com/PyCQA/flake8

* Introducing PYBIND11_VERSION_HEX (better late than never!)

* PYBIND11_VERSION_HEX consistency check in setup.py

The docutils 0.17+ release uses more semantic HTML5 tags, which
the RTD theme does not (yet) know.

This breaks side bar, lists and other elements.

* Enable -Wstrict-aliasing warning

* Narrow down the scope of -Wstrict-aliasing

* Go home, MSVC, you're drunk

* Make sure "pragma GCC" is not executed on ICC

Co-authored-by: Yannick Jadoul <yannick.jadoul@belgacom.net>

* style: disallow PyTest (should be pytest)

* style: cleanup spell checking a bit

* style: add a few items to the .gitignore

* Raise codec errors when casting to std::string

Allow the codec's exception to be raised instead of RuntimeError when
casting from py::str to std::string.

PY2 allows ucs surrogates in UTF-8 conversion

Signed-off-by: Shane Loretz <sloretz@openrobotics.org>
Signed-off-by: Shane Loretz <sloretz@osrfoundation.org>

* Attempt to fix py2 error

* Revert all unicode literals

* Fixed

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* Removing stray semicolons (discovered by running clang-format v12 followed by tools/check-style.sh). (#3087)

* Manually moving `// NOLINT` comments so that clang-format does not move them to the wrong places.

* Manually reformatting comments related to `static_assert`s so that clang-format does not need two passes.

* Empty lines between #includes, to prevent clang-format from shuffling the order and thereby confusing MSVC 2015.

* git diff -U0 --no-color HEAD^ | python3 $HOME/clone/llvm-project/clang/tools/clang-format/clang-format-diff.py -p1 -style=file -i

For single-file extensions, a convenient pattern offered by cython
is to place the source files directly in the python source tree
(`foo/__init__.py`, `foo/ext.pyx`), deriving the package names from
their filesystem location.  Adapt this pattern for pybind11, using an
`intree_extensions` helper, which should be thought of as the moral
equivalent to `cythonize`.

Differences with cythonize: I chose not to include globbing support
(`intree_extensions(glob.glob("**/*.cpp"))` seems sufficient), nor to
provide extension-customization kwargs (directly setting the attributes
on the resulting Pybind11Extension objects seems sufficient).

We could choose to have `intree_extension` (singular instead) and make
users write `[*map(intree_extension, glob.glob("**/*.cpp"))]`; no strong
opinion here.

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

* Improve documentation of discard_as_unraisable() API

* Update pytypes.h

Remove "the above"

* Update pytypes.h

Fix precommit error

Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>

fix(clang-tidy): Add cppcoreguidelines-init-vars,slicing, and throw-by-value-catch-by-reference checks (#3094)

* clang-tidy: guard against more UB behavior

* Remove slicing check for now

* docs: update changelog

* docs: add one more and merge tidy

* Adding test_return_vector_bool_raw_ptr to test_stl.py.

* First attempt to make the documentation more accurate, but not trying to be comprehensive, to not bloat the reference table with too many details.

* Fixing minor oversights.

* Applying reviewer suggestion.

* chore: add nox support

* chore: add more lines to CODEOWNERS

Fixing spelling errors that went undetected because the pre-commit spell check was added after the CI for PR #2995 last ran. (#3103)

* Adding iostream.h thread-safety documentation.

* Restoring `TestThread` code with added `std::lock_guard<std::mutex>`.

* Updating new comments to reflect new information.

* Fixing up `git rebase -X theirs` accidents.

* Copying from prework_no_rst branch (PR #3087): test_numpy_array.cpp, test_stl.cpp

* Manual changes reducing NOLINTs.

* clang-format-diff.py

* Minor adjustment to avoid MSVC warning C4702: unreachable code

[skip ci]

* py::pickle typo

* correct dots and parentheses

Go all the way fixing clang-tidy issues to avoid the NOLINTNEXTLINE clutter and clang-format issues. This was really meant to be part of PR #3051 but was held back either out of an abundance of caution, or because of confusion caused by stray semicolons. (#3086)

* Enable clang-tidy else-after-return and redundant void checks

* Fix remaining else-after

* Address reviewer comments

* Fix indentation

* Rerun clang-tidy post merge

* Splitting out pybind11/stl/filesystem.h.

To solve breakages like: https://github.com/deepmind/open_spiel/runs/2999582108

Mostly following the suggestion here: https://github.com/pybind/pybind11/pull/2730#issuecomment-750507575

Except using pybind11/stl/filesystem.h instead of pybind11/stlfs.h, as decided via chat.

stl.h restored to the exact state before merging PR #2730 via:
```
git checkout 733f8de2 stl.h
```

* Properly including new stl subdirectory in pip wheel config.

This now passes interactively:
```
pytest tests/extra_python_package/
```

* iwyu cleanup.

iwyuh.py -c -std=c++17 -DPYBIND11_TEST_BOOST -Ipybind11/include -I/usr/include/python3.9 -I/usr/include/eigen3 include/pybind11/stl/filesystem.h

* Adding PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL.

* Eliminating else after return.

* Unify cast_error message thrown by [simple|unpacking]_collector

simple_collector and unpacking_collector throw different error messages
when the casting of an argument failed: While the former mentions make_tuple(),
the latter emphasises the call argument (and its name/position).

* Consolidating "Unable to convert call argument" error reporting code to guarantee uniformity.

Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>