[RFC]: WatchScheduler

Overview

We should expose a new scheduler that has the ability to invalidate parts of a target graph to trigger runs of targets and dependent targets on file system changes. Another detail is detecting changes of a graph itself if package.json files are moved around.

Goals & non-goals

Goals

• let the WrappedTarget's status have states: modified, added, removed
• modify upstream deps or wrap around it to execute the fn's correctly
• may have to modify upstream p-graph to separate the queue running into a separate package
• investigate whether we can leverage @lage-run/worker-threads-pool to execute runners rather than relying on p-graph
• investigate whether the scheduling from p-graph needs to be moved out

Upstream Deps

• p-graph: currently p-graph is the software that executes the task fn's in topological order

Test Plan

• this is heavily unit testable, we should be able to utilize the different lage packages / upstream package node.js APIs to test out the functionality