Support custom nrepl ops for different evaluation styles

[jaidetree]

Problem

What if I'm in my editor and I want to send some forms to REBL and some only to the REPL?

Proposed Solution

If we create custom nrepl ops we can allow editors and users to select which forms they want to send to REBL.

For instance setting up an additional, separate key binding to eval a top level form in REBL.

Related Resources

• https://cljdoc.org/d/nrepl/nrepl/0.5.2/doc/built-in-ops

[RickMoynihan]

What custom ops do you suggest?

I was thinking:

• rebl-start-ui (already implemented) calls (rebl/ui) for you.
• rebl-toggle-follow (would require cognitect to give us a hook for this) equivalent to pushing the follow checkbox button (but from your editor)
• rebl-submit-form (for sending a form direct to REBL skipping your editor's REPL).

[jaidetree]

I have no objections to those but I think it can be helpful to think them through as user stories:

As a user familiar with REBL I want to create a keybinding to open the REBL UI so that I can quickly inspect eval results whenever I need it.

• Sends nrebl-start-ui op to middleware.

As a beginner REBL user I expect it to automatically receive any forms sent to my REPL so I can quickly get familiar and use my pre-existing REPL process and keybindings.

• Will help sell the experience seen in Stu's REBL demo video
• Sends nrebl-toggle-follow to middleware
• Active by default?

As an advanced REBL user I expect to be able to specify which forms I inspect in REBL as not all evaluations are valuable to inspect. I want to create a keybinding to select which forms should be inspected.

• Sends nrebl-submit-form op to middleware
• Question: Would the result of it be evaluated against the REPL environment at all or just inspect it as a value?

As a moderate REBL user I expect to be able to clear the REBL eval history after running it for a long time and having collected a lot of data that needs to be held in memory.

• Sends nrebl-clear-history op to middleware
• May need support from Cognitect if such a function does not exist.
• Definitely helpful if follow mode is active

[RickMoynihan]

Yes thanks for that.

I agree that we probably also want an nrebl-clear-history, though I've not seen any such function exposed. Also this might be achievable simply by closing the REBL window, though there's no function hook to do that, that I'm aware of either.

Regarding nrebl-submit-form:

Would the result of it be evaluated against the REPL environment at all or just inspect it as a value?

I'd thought about this too and think we really need to do a read and eval as I think users will normally expect evaluating a form like (let [x 10] x) to return 10 not the s-expression. And an un evaluated form won't have any datafy metadata on it. If you have a form in your editor it'll normally be small enough to view in your editor anyway. Finally if you had evaluated a value and bound it to a var, then sent the var back to REBL it could easily contain unprintable values, and thus is unlikely to work as expected.

[RickMoynihan]

Also we should rename all the above to be prefixed with nrebl-, as they're really instructions for our middleware not rebl itself.

[jaidetree]

That sounds good to me. We may not be able to provide nrebl-clear-history without support but Is there a way to fake it by creating a function that closes and reopens rebl?