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Add interactive command for case splitting #112

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Add interactive command for case splitting #112

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19 changes: 19 additions & 0 deletions lsp-haskell.el
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Expand Up @@ -228,6 +228,25 @@ if projectile way fails"
(user-error "Couldn't find cabal file, using: %s" dir)
dir))))


;; ---------------------------------------------------------------------
;; Interactive commands

(defun lsp-haskell-case-split ()
"Case split on an identifier.
To use this, place make sure the point is over a type hole."
(interactive)
(let* ((case-split-regex "Case split on \\(.*\\)")
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This feels a little fragile. I think the right way to do this is to use code action kinds: they're explicitly there to allow filtering by the client (i.e. us). We might need to teach the tactics plugin to add a kind, though.

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I can update the tactics plugin with kinds, good call!

(actions (-filter (lambda (action) (s-matches-p case-split-regex (lsp:code-action-title action))) (lsp-code-actions-at-point))))
(lsp-execute-code-action (cond ((seq-empty-p actions) (signal 'lsp-no-code-actions nil))
((and (eq (seq-length actions) 1) lsp-auto-execute-action)
(lsp-seq-first actions))
(t (lsp--completing-read "Identifier: "
(seq-into actions 'list)
(lambda (action)
(cadr (s-match case-split-regex (lsp:code-action-title action))))
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Hmm, you do rather rely on the regex here. I guess I don't have a better suggestion, then, since AFAICT there's no proper way to include some extra structured data in a CodeAction...

I guess we could avoid the regex by just using the code action title as is, for something like:

Pick a case-splitting action:
1. Case split on x
2. Case split on y

but I guess that's a worse UX.

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If it is too fragile, then we can remove it! Shame that the spec doesn't let us communicate more in the kind.

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Yeah, I just want to avoid the situation where someone changes the title, rightly reasoning that it's a user-facing string that can be changed freely, and then this function breaks.

nil t))))))

;; ---------------------------------------------------------------------
;; Starting the server and registration with lsp-mode

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