v0.28.0

Full Changelog: v0.27.0...v0.28.0

Bugfixes

• :func:inspect.iscoroutinefunction and the like now give correct answers when
  called on KI-protected functions. (#2670)

• Rework KeyboardInterrupt protection to track code objects, rather than frames,
  as protected or not. The new implementation no longer needs to access
  frame.f_locals dictionaries, so it won't artificially extend the lifetime of
  local variables. Since KeyboardInterrupt protection is now imposed statically
  (when a protected function is defined) rather than each time the function runs,
  its previously-noticeable performance overhead should now be near zero.
  The lack of a call-time wrapper has some other benefits as well:

  • :func:inspect.iscoroutinefunction and the like now give correct answers when
    called on KI-protected functions.

  • Calling a synchronous KI-protected function no longer pushes an additional stack
    frame, so tracebacks are clearer.

  • A synchronous KI-protected function invoked from C code (such as a weakref
    finalizer) is now guaranteed to start executing; previously there would be a brief
    window in which KeyboardInterrupt could be raised before the protection was
    established.

  One minor drawback of the new approach is that multiple instances of the same
  closure share a single KeyboardInterrupt protection state (because they share a
  single code object). That means that if you apply
  trio.lowlevel.enable_ki_protection to some of them
  and not others, you won't get the protection semantics you asked for. See the
  documentation of trio.lowlevel.enable_ki_protection
  for more details and a workaround. (#3108)

• Rework foreign async generator finalization to track async generator
  ids rather than mutating ag_frame.f_locals. This fixes an issue
  with the previous implementation: locals' lifetimes will no longer be
  extended by materialization in the ag_frame.f_locals dictionary that
  the previous finalization dispatcher logic needed to access to do its work. (#3112)

• Ensure that Pyright recognizes our underscore prefixed attributes for attrs classes. (#3114)

• Fix trio.testing.RaisesGroup's typing. (#3141)

Improved documentation

• Improve error message when run after gevent's monkey patching. (#3087)
• Document that trio.sleep_forever is guaranteed to raise an exception now. (#3113)

Removals without deprecations

• Remove workaround for OpenSSL 1.1.1 DTLS ClientHello bug. (#3097)
• Drop support for Python 3.8. (#3104) (#3106)

Miscellaneous internal changes

• Switch to using PEP570 for positional-only arguments for trio.socket.SocketType's methods. (#3094)
• Improve type annotations in several places by removing Any usage. (#3121)
• Get and enforce 100% coverage (#3159)