4ff63a7960
TC 0.7.0 introduces a new `TaskData` type that maps to Taskwarrior's `Task` type more cleanly. It also introduces the idea of gathering lists of operations and "committing" them to a replica. A consequence of this change is that TaskChampion no longer automatically maintains dependency information, so Taskwarrior must do so, with its `TDB2::dependency_sync` method. This method does a very similar thing to what TaskChampion had been doing, so this is a shift of responsibility but not a major performance difference. Cxx is .. not great. It is missing a lot of useful things that make a general-purpose bridge impractical: - no support for trait objects - no support for `Option<T>` (https://github.com/dtolnay/cxx/issues/87) - no support for `Vec<Box<..>>` As a result, some creativity is required in writing the bridge, for example returning a `Vec<OptionTaskData>` from `all_task_data` to allow individual `TaskData` values to be "taken" from the vector. That said, Cxx is the current state-of-the-art, and does a good job of ensuring memory safety, at the cost of some slightly awkward APIs. Subsequent work can remove the "TDB2" layer and allow commands and other parts of Taskwarrior to interface directly with the `Replica`.
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Rust and C++
Taskwarrior has historically been a C++ project, but as of taskwarrior-3.0.0, the storage backend is now provided by a Rust library called TaskChampion.
TaskChampion
TaskChampion implements storage and access to "replicas" containing a user's tasks. It defines an abstract model for this data, and also provides a simple Rust API for manipulating replicas. It also defines a method of synchronizing replicas and provides an implementation of that method in the form of a sync server.
Other applications, besides Taskwarrior, can use TaskChampion to manage tasks. Taskwarrior is just one application using the TaskChampion interface.
Taskwarrior's use of TaskChampion
Taskwarrior's interface to TaskChampion is in src/taskchampion-cpp.
This links to taskchampion as a Rust dependency, and uses cxx to build a C++ API for it.
That API is defined, and documented, in src/taskchampion-cpp/src/lib.rs, and available in the tc namespace in C++ code.