Regression: can no longer specify custom cljs REPL code via variable

[weavejester]

Older versions of CIDER had a cider-cljs-lein-repl variable, but this appears to be deprecated in favour of REPL types, leading to a regression in functionality.

If we want to specify our own code to initiate a cljs REPL, then we have to use cider-register-cljs-repl-type. However, this is not easily useable from .dir-locals.el. Ideally we want to be able to allow projects to specify their own cljs setup, as was the case in earlier versions of CIDER.

A possible solution is to add a cider-cljs-custom-repl variable, which when set would be used instead of the REPL types.

On Slack "ag" pointed me toward a hacky workaround using eval:

((nil . ((eval . (with-eval-after-load 'cider
                   (cider-register-cljs-repl-type
                    'fw-cc
                    "(do (start) (start-fw) (use 'figwheel-sidecar.repl-api) (cljs-repl))")
                   (setq cider-default-cljs-repl 'fw-cc))))))

However, that's not exactly elegant!

While I appreciate the need to improve features and streamline functionality, it's a touch frustrating to grab a new version of CIDER and find out that it breaks my workflow because functionality has been removed.

[bbatsov]

The registration function is meant to be used in your Emacs config, so in .dir-locals you’d just have to set one var as before. The old variable was removed simply because the build tool used and the cljs repl used are completely orthogonal. I’m sorry that this caused some frustration for you, but I think there was no easy way to retain the old behavior and provide the desired behavior at the same time.

[weavejester]

The registration function is meant to be used in your Emacs config, so in .dir-locals you’d just have to set one var as before.

What variable would I set in .dir-locals.el? If I've missed a variable I apologize, but from my reading of the source there didn't seem to be a way to set a custom initialization string, except by triggering an eval and adding a new cljs REPL type.

The old way of doing it would be to add something like this to .dir-locals.el.

((nil . ((cider-cljs-lein-repl . "(do (custom-init) (cljs-repl))"))))

But since cider-cljs-lein-repl has been deprecated, is there a variable that we should be using instead that does the same thing?

[bbatsov]

My point was that REPL types should normally be registered globally - e.g. in init.el. You’d just refer to the REPL type in .dir-locals.el, you won’t be registering it there. The basic premise is that’s it’s very unlikely that someone would use REPL init forms that are unique to a single project, so it makes sense to register those globally. Does this make sense? I don’t have a computer with me and I can’t write detailed examples.

Currently there’s no way to do exactly what cider-cljs-lein-repl did, but we can provide something if it’s warranted.

[weavejester]

The basic premise is that’s it’s very unlikely that someone would use REPL init forms that are unique to a single project, so it makes sense to register those globally.

I agree it's not likely that a REPL init form will be limited to a single project; however, it is likely that there will be projects where the required REPL init form is not included in CIDER by default. For example, any project that uses Duct (hence my interest!).

Before, we could include a .dir-locals.el file in the directory, and anyone using Emacs and CIDER who opens the project will automatically be able to load in a ClojureScript REPL. With the current change to the REPL init form, I have to manually tell users how to set it up, with code to copy and paste into their init.el. If anything goes awry, they'll raise an issue.

So hopefully you can see why I'm so keen on a solution that can fit in a .dir-locals.el - because it provides per-project, automatic configuration.

[kommen]

The basic premise is that’s it’s very unlikely that someone would use REPL init forms that are unique to a single project, so it makes sense to register those globally.

Just adding a data point: we need this too.

Our solution right now is that our wrapper bash script, which starts the project's clojure app in development, uses emacsclient to add our custom cljs repl type to cider-cljs-repl-types. Not pretty, but it does the job.

[bbatsov]

I guess a good option might be to add something called cider-cljs-repl-form (or whatever) that'd would point to a form and would take precedence over the default type. We can also change cider-cljs-default-repl to be behave differently if it's a symbol or a string.

Basically, changing this is simple but we need to decide on the best "API". :-)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution and understanding!

[bbatsov]

After some consideration I've decided the best approach for this would be adding 'init-form as a cider-default-cljs-repl type and cider-cljs-repl-init-form variable that goes along with it. This fits nice within the current approach and will solve cleanly the problem in question. Expect a fix soon. This comment is mostly a reminder for myself, but everyone's welcome to beat me to implementing this simple fix.

[bbatsov]

In the end I've decided to just recycle the existing custom repl type:

((nil
  (cider-custom-cljs-repl-init-form . "(do (foo) (bar))"
  (cider-default-cljs-repl . custom)))

I think you'll all agree that's simple enough.