withr 3.0.0

Performance of withr

• defer() is now a thin wrapper around base::on.exit(). This is
  possible thanks to two contributions that we made to R 3.5:

  • We added an argument for FIFO cleanup: on.exit(after = FALSE).
  • Calling sys.on.exit() elsewhere than top-level didn't work. This
    is needed for manual invokation with deferred_run().

  Following this change, defer() is now much faster (although still
  slower than on.exit() which is a primitive function and about as
  fast as it gets). This also increases the compatibility of defer()
  with on.exit() (all handlers are now run in the expected order
  even if they are registered with on.exit()) and standalone
  versions of defer().

Breaking change

• When source() is used with a local environment, as opposed to
  globalenv() (the default), you now need to set
  options(withr.hook_source = TRUE) to get proper withr support
  (running defer() or local_ functions at top-level of a script).
  THis support is disabled by default in local environments to avoid a
  performance penalty in normal usage of withr features.

Other features and bugfixes

• deferred_run() now reports the number of executed expressions with
  a message.

• deferred_run() can now be run at any point in a knitr file (#235).

,* local_tempfile() now writes lines in UTF-8 (#210) and always uses
\n for newlines (#216).

• local_pdf() and friends now correctly restore to the previously
  active device (#138).

• local_() now works even if withr isn't attached (#207).

• local_par() and with_par() now work if you don't set any parameters
  (#238).

• with_language() now properly resets the translation cache (#213).

• Fixes for Debian packaging.