Notebook cell execution model

[jrieken]

Somewhat a continuation of #103713

Today, execution results are parts metadata and output and execution itself is done via kernels which come from kernel providers. We should try to model execution results into a single entity, e.g execution status (idle, running, scheduled? etc)

[jrieken]

One thing that we should do is to allow the executeCell-functions to return a promise. The promise should resolve that execution has been successfully started. It would allow to show feedback on the run button in cases in which the kernel needs to be resolved or isn't idle.

[roblourens]

Some execution API TODOs that I didn't have time to put into code, including some suggestions from Kai a few weeks ago

• Rethink naming to be more explicit in the intent. Write all the jsdoc to explain the usage to check whether a normal person can follow the flow. Get someone else on the team to review it. Check which words are used in the explanation and use those in names.
  • Should the execution object be called "execution", maybe it is a "task".
  • "executeCells" could be "executeCellsRequest" because it really is just a request
• Normalize "run" vs "execution" name
• createNotebookCellExecution - only a kernel can access this, and only the active kernel can trigger an execution.
  • The kernel is provided some factory somehow, how does this work?
• Because of [Notebook] Execution timer starts with negative value #117460, maybe we can't use absolute times to drive the timer

[roblourens]

Two things not in the PR

• Preemptively setting a cell as "pending" as soon as it is clicked, not having to wait for a Task to be created. We discussed this some, but in trying to implement it and explain it in the API jsdoc, I was wondering whether it's really worth the extra complexity. Even if there are a few hundred ms of latency, I don't know that it's worth the effort. Will leave it alone for now until we really think it's an issue.
• Canceling executions when a cell is deleted. Just because I'm not sure of the right place to implement this. Cancel cell execution task when cell is deleted #119504

[roblourens]

@jrieken maybe you can call this verified since you implemented it and filed some issues