Optional arguments supplied with ~ are completed with ? instead

[bcc32]

When requesting completion for a function's optional labeled argument, which the user intends to pass with ~, OCaml-LSP's completion suggestion uses ? instead and replaces the original intended meaning, e.g.:

let f ?abc ~def () = assert false

let () = f ~

If, at the end of that snippet, the user presses TAB (or whatever completion key), OCaml-LSP suggests:

?abc : 'a option
~def : 'b

as some of the completion results. Selecting ?abc causes the code to now look like:

let () = f ?abc

whereas the expected behavior is more likely:

let () = f ~abc

This issue also occurs if the user has typed some prefix of the optional argument label first.

Here's the event log item I got from Emacs:

(:jsonrpc "2.0" :id 176 :method "textDocument/completion" :params
          (:textDocument
           (:uri "file:///home/azeng/z.ml")
           :position
           (:line 8 :character 12)
           :context
           (:triggerKind 1)))
[server-reply] (id:176) Tue Sep 12 16:49:13 2023:
(:id 176 :jsonrpc "2.0" :result
     (:isIncomplete :json-false :items
                    [(:data
                      (:position
                       (:character 12 :line 8)
                       :textDocument
                       (:uri "file:///home/azeng/z.ml"))
                      :deprecated :json-false :detail "'a option" :kind 5 :label "?abc" :sortText "0000" :textEdit
                      (:newText "?abc" :range
                                (:end
                                 (:character 12 :line 8)
                                 :start
                                 (:character 10 :line 8))))
                     (:data
                      (:position
                       (:character 12 :line 8)
                       :textDocument
                       (:uri "file:///home/azeng/z.ml"))
                      :deprecated :json-false :detail "'b" :kind 5 :label "~def" :sortText "0001" :textEdit
                      (:newText "~def" :range
                                (:end
                                 (:character 12 :line 8)
                                 :start
                                 (:character 10 :line 8))))
                     (:data
                      (:position
                       (:character 12 :line 8)
                       :textDocument
                       (:uri "file:///home/azeng/z.ml"))
                      :deprecated :json-false :detail "'_weak42" :kind 5 :label "~a" :sortText "0002" :textEdit
                      (:newText "~a" :range
                                (:end
                                 (:character 12 :line 8)
                                 :start
                                 (:character 10 :line 8))))]))

I think maybe the label should remain ?abc but the newText should be ~abc instead?

[jfeser]

Or we could offer completions for ?abc, ~abc, and ~def.

[ddickstein]

In Neovim ?abc doesn't even appear as a completion option. I agree with @bcc32 though; newText should be ~abc. @jfeser I'm not sure adding ?abc as an additional completion candidate adds more value than noise, as the user has already signaled how they want to pass the argument.