Sort code action completions by importance

This is inspired by a recent change in [Helix] that fixes sorting of
code actions.
We have the same problem; we use ":prompt -shell-script-candidates"
to show code actions.
For example, on this Rust file:

	fn main() {
	    let f: FnOnce(HashMap<i32, i32>);
	}

with the cursor on "HashMap", a ":lsp-code-actions" will offer two
code actions (from rust-analyzer):

	Extract type as type alias"
	Import `std::collections::HashMap`

The first one is a refactoring and the second one is a quickfix.

A proposed Kakoune patch allows users to define completion priorities.
Use it to fix the order of such code actions.

[Helix]: helix-editor/helix#4134

rc/lsp.kak

@@ -196,10 +196,16 @@ define-command -hidden lsp-menu -params 1.. -docstring "Like menu but with promp
             cases=
             completion=
             nl=$(printf '\n.'); nl=${nl%.}
+            priority=1
             while [ $# -gt 0 ]; do
                 title=$1; shift
                 command=$1; shift
-                completion="${completion}${title}${nl}"
+                if $kak_opt_lsp_have_kakoune_feature_completion_priority; then
+                    completion="${completion}$(printf %s "${title}" | sed 's/\\|/\\|/g')|$priority${nl}"
+                    priority=$((priority + 1))
+                else
+                    completion="${completion}${title}${nl}"
+                fi
                 cases="${cases}
                 $(shellquote "$title" s/¶/¶¶/g))
                     printf '%s\\n' $(shellquote "$command" s/¶/¶¶/g)
@@ -214,9 +220,9 @@ define-command -hidden lsp-menu -params 1.. -docstring "Like menu but with promp
                 ¶
             §" "$cases"
             printf ' %s' "$on_abort"
-            printf ' -menu -shell-script-candidates %%§
+            printf ' -menu %s -shell-script-candidates %%§
                 printf %%s %s
-                §\n' "$(shellquote "$completion")"
+                §\n' "$($kak_opt_lsp_have_kakoune_feature_completion_priority && printf %s -priority)" "$(shellquote "$completion")"
         }
     } catch %{
         evaluate-commands %sh{
@@ -359,6 +365,13 @@ ${lsp_draft}\"\"\"
     }
 }}
 
+declare-option -hidden bool lsp_have_kakoune_feature_completion_priority
+declare-option -hidden completions lsp_have_kakoune_feature_completion_priority_tmp
+try %{
+    set-option global lsp_have_kakoune_feature_completion_priority_tmp 1.1@0 insert_text|on_select|menu|1
+    set-option global lsp_have_kakoune_feature_completion_priority true
+}
+
 define-command -hidden lsp-completion -docstring "Request completions for the main cursor position" %{
 try %{
     # Fail if preceding character is a whitespace (by default; the trigger could be customized).

src/language_features/code_action.rs

@@ -144,7 +144,7 @@ fn editor_code_actions(
         return;
     }
 
-    let actions: Vec<_> = results
+    let mut actions: Vec<_> = results
         .into_iter()
         .flat_map(|(server_name, cmd)| {
             let cmd: Vec<_> = cmd
@@ -222,6 +222,25 @@ fn editor_code_actions(
         return;
     }
 
+    actions.sort_by_key(|(_server, ca)| {
+        // TODO Group by server?
+        let empty = CodeActionKind::EMPTY;
+        let kind = match ca {
+            CodeActionOrCommand::Command(_) => &empty,
+            CodeActionOrCommand::CodeAction(action) => action.kind.as_ref().unwrap_or(&empty),
+        };
+        // TODO These loosely follow what VSCode does, we should be more accurate.
+        match kind.as_str() {
+            "quickfix" => 0,
+            "refactor" => 1,
+            "refactor.extract" => 2,
+            "refactor.inline" => 3,
+            "refactor.rewrite" => 4,
+            "source" => 5,
+            "source.organizeImports" => 6,
+            _ => 7,
+        }
+    });
     let titles_and_commands = actions
         .iter()
         .map(|(server_name, c)| {