sbt/main-settings/src
Ethan Atkins ed06e18fab Add InputGraph
This commit adds functionality to traverse the settings graph to find
all of the Inputs settings values for the transitive dependencies of the
task. We can use this to build up the list of globs that we must watch
when we are in a continuous build. Because the Inputs key is a setting,
it is actually quite fast to fetch all the values once the compiled map
is generated (O(2ms) in the scripted tests, though I did find that it
took O(20ms) to generate the compiled map).

One complicating factor is that dynamic tasks do not track any of
their dynamic dependencies. To work around this, I added the
transitiveDependencies key. If one does something like:
foo := {
  val _ = bar / transitiveDependencies
  val _ = baz / transitiveDependencies
  if (System.getProperty("some.prop", "false") == "true") Def.task(bar.value)
  else Def.task(baz.value)
}
then (foo / transitiveDependencies).value will return all of the inputs
and triggers for bar and baz as well as for foo.

To implement transitiveDependencies, I did something fairly similar to
streams where if the setting is referenced, I add a default
implementation. If the default implementation is not present, I fall
back on trying to extract the key from the commandLine. This allows the
user to run `show bar / transitiveDependencies` from the command line
even if `bar / transitiveDependencies` is not defined in the project.

It might be possible to coax transitiveDependencies into a setting, but
then it would have to be eagerly evaluated at project definition time
which might increase start up time too much.  Alternatively, we could
just define this task for every task in the build, but I'm not sure how
expensive that would be. At any rate, it should be straightforward to
make that change without breaking binary compatibility if need be. This
is something to possibly explore before the 1.3 release if there is any
spare time (unlikely).
2019-03-30 16:38:44 -07:00
..
main/scala/sbt Add InputGraph 2019-03-30 16:38:44 -07:00
test/scala/sbt Implement Append for Function1 2019-01-29 09:12:11 +00:00