Traits Futures 0.3.1

This is a bugfix release which fixes a regression introduced in Traits Futures 0.3.0, namely that subclasses of BaseFuture could not be instantiated without any arguments.

Traits Futures 0.3.0

This is a feature release of Traits Futures, with a some minor backwards incompatible changes that users should be aware of. New features include multiprocessing support, wxPython support, support for delivering events using an asyncio event loop in place of a GUI toolkit event loop, and better support for synchronous executor shutdown.

Migration guide

The majority of existing code using Traits Futures 0.2.0 should continue to work with Traits Futures 0.3.0 with no changes. However, there are some minor changes that could affect current code, and some major backwards-incompatible changes for anyone making use of the ITaskSpecification interface to create their own background task types. For the ITaskSpecification changes, see the detailed changelog in the documentation.

• The cancel method on a future no longer raise a RuntimeError exception when a future is not cancellable; instead, it silently does nothing. Code that needs to distinguish can use the new return value of the cancel method to determine whether the cancel call actually caused cancellation to occur. Code that currently checks the cancellable property before cancelling should be able to safely drop that check.
• The executor_state trait of a |TraitsExecutor| is no longer writable.
• The executor and callable parameters to the submit_call, submit_iteration and submit_progress functions may become positional-only in a future version of Traits Futures. If you're passing arguments by name instead of by position, for example using submit_call(executor=my_executor, callable=do_calculation, ...), you should fix your code to pass by position instead: submit_call(my_executor, do_calculation, ...).

See the changelog in the documentation for a full list of changes.

Traits Futures 0.2.0

This is a feature release of Traits Futures. The main features of this
release are:

• Improved support for user-defined background task types.
• Easier creation of background calculations that can be (cooperatively)
  cancelled mid-calculation.
• Significant internal refactoring and cleanup, aimed at eventual support
  for alternative front ends (GUI event loops other than the Qt event
  loop) and back ends (e.g., multiprocessing).
• Improved and expanded documentation.

There are no immediately API-breaking changes in this release: existing working
code using Traits Futures 0.1.1 should continue to work with no changes
required. However, some parts of the existing API have been deprecated, and
will be removed in a future release. See the Changes section below for more
details.

Detailed changes follow. Note that the list below is not exhaustive: many
more minor PRs have been omitted.

Features

• Users can now easily create their own background task types to supplement
  the provided task types (background calls, background iterations and
  background progress). A combination of a new ITaskSpecification
  interface and a convenience BaseFuture base class support this.
  (#198)
• The submit_iteration function now supports generator functions that
  return a result. This provides an easy way to submit background computations
  that can be cancelled mid-calculation. (#167)
• The TraitsExecutor class now accepts a max_workers argument,
  which specifies the maximum number of workers for a worker pool created
  by the executor. (#125)
• There are new task submission functions submit_call,
  submit_iteration and submit_progress. These functions replace
  the eponymous existing TraitsExecutor methods, which are now
  deprecated. (#166)
• There's a new IFuture interface class in the
  traits_futures.api module, to aid in typing and Trait declarations.
  (#169)
• A new IParallelContext interface supports eventual addition
  of alternative back ends. The new MultithreadingContext class
  implements this interface and provides the default threading back-end.
  (#149)

Changes

• The state trait on CallFuture, IterationFuture and ProgressFuture is
  now read-only. It used to be writable.
• The default number of workers in an owned worker pool (that is, a worker pool
  created by a TraitsExecutor) has changed. Previously it was
  hard-coded as 4. Now it defaults to whatever Python's
  concurrent.futures executors give, but can be controlled by passing
  the max_workers argument. (#125)
• The submit_call, submit_iteration and submit_progress
  methods on the TraitsExecutor have been deprecated. Use the
  submit_call, submit_iteration and submit_progress
  convenience functions instead. (#159)
• The thread_pool argument to TraitsExecutor has been renamed
  to worker_pool. The original name is still available for backwards
  compatibility, but its use is deprecated. (#144, #148)
• Python 2.7 is no longer supported. Traits Futures requires Python >= 3.5,
  and has been tested with Python 3.5 through Python 3.9. (#123, #130, #131,
  #132, #133, #138, #145)

Fixes

• Don't create a new MessageRouter at executor shutdown time. (#187)

Tests

• Fix some intermittent test failures due to test interactions. (#176)
• The 'null' backend that's used for testing in the absence of a Qt backend
  now uses a asyncio-based event loop instead of a custom event loop.
  (#107, #179)
• Rewrite the Qt GuiTestAssistant to react rather than polling. This
  significantly speeds up the test run. (#153)
• Ensure that all tests properly stop the executors they create. (#108, #146)
• Refactor the test structure in preparation for multiprocessing
  support. (#135, #141)
• Test the GuiTestAssistant class. (#109)

Developer tooling

• Add a new python -m ci shell click cmd. (#204)
• Update edm version in CI. (#205)
• Add checks for missing or malformed copyright headers in Python files (and
  fix existing copyright headers). (#193)
• Add import order checks (and fix existing import order bugs). (#161)
• Add separate "build" and "ci" modes for setting up the development
  environment. (#104)
• Don't pin dependent packages in the build environment. (#99)

Documentation

• Update docs to use the Enthought Sphinx Theme. (#128)
• Autogenerated API documentation is now included in the documentation
  build. (#177, #181)
• Restructure the documentation to avoid nesting 'User Guide'
  under 'User Documentation'. (#191)
• Document creation of new background task types. (#198)
• Document use of submit_iteration for interruptible tasks. (#188)