Class BuildTask

Hook to allow the calling interface to display a message.

This hook gets called as part of preparing a task for execution
(that is, a Node to be built).  As part of figuring out what Node
should be built next, the actually target list may be altered,
along with a message describing the alteration.  The calling
interface can subclass Task and provide a concrete implementation
of this method to see those messages.

Overrides: Taskmaster.Task.display

(inherited documentation)

Called just before the task is executed.

This is mainly intended to give the target Nodes a chance to
unlink underlying files and make all necessary directories before
the Action is actually called to build the targets.

Overrides: Taskmaster.Task.prepare

(inherited documentation)

Called to determine whether the task's execute() method should
be run.

This method allows one to skip the somethat costly execution
of the execute() method in a seperate thread. For example,
that would be unnecessary for up-to-date targets.

Overrides: Taskmaster.Task.needs_execute

(inherited documentation)

Called to execute the task.

This method is called from multiple threads in a parallel build,
so only do thread safe stuff here.  Do thread unsafe stuff in
prepare(), executed() or failed().

Overrides: Taskmaster.Task.execute

(inherited documentation)

Called when the task has been successfully executed and
the Taskmaster instance wants to call the Node's callback
methods.

This may have been a do-nothing operation (to preserve build
order), so we must check the node's state before deciding whether
it was "built", in which case we call the appropriate Node method.
In any event, we always call "visited()", which will handle any
post-visit actions that must take place regardless of whether
or not the target was an actual built target or a source Node.

Overrides: Taskmaster.Task.executed_with_callbacks

(inherited documentation)

Default action when a task fails:  stop the build.

Note: Although this function is normally invoked on nodes in
the executing state, it might also be invoked on up-to-date
nodes when using Configure().

Overrides: Taskmaster.Task.failed

(inherited documentation)

Post-processes a task after it's been executed.

This examines all the targets just built (or not, we don't care
if the build was successful, or even if there was no build
because everything was up-to-date) to see if they have any
waiting parent Nodes, or Nodes waiting on a common side effect,
that can be put back on the candidates list.

Overrides: Taskmaster.Task.postprocess

(inherited documentation)

Make a task ready for execution

Overrides: Taskmaster.Task.make_ready_current