kakoune: rework plugin support

The previous implementation of plugin-support for the kakoune derivation
was based on generating, at build time, a `plugins.kak` file that would
source all .kak files in the list of plugins, and wrap the `kak` binary
in a script that would add some command-line arguments so that this
file gets loaded on start-up. The main problem with this approach
is that the plugins' code get executed *after* the user's configuration
file is loaded, so effectively one cannot automatically activate/configure
these plugins.

The idiomatic way of loading plugins is ensuring they end up installed
somwhere under `share/kak/autoload`. Because plugins are already being
packaged to have their code in `share/kak/autoload/plugins/<name-of-plugin>`,
we can obtain a derivation that includes the plugins simply by doing a
`symlinkJoin` of `kakoune-unwrapped` and all the requested plugins.

For this to work, we need to fix two issues:

  1. By default, kakoune makes `share/kak/autoload` a symbolic link to
     `share/kak/rc`, which contains all builtin definitions. We need
     to patch this to put the symlink under `share/kak/autoload/rc`, so that
     the join works.

  2. By default kakoune expects the `autoload` directory to be in
     `../share/kak/autoload` relative to the location of the `kak` binary.
     We need to set the `KAKOUNE_RUNTIME` to point the symlinked
     share/kak for this to work.

doc/builders/packages/kakoune.xml

@@ -6,9 +6,7 @@
  <para>
   Kakoune can be built to autoload plugins:
 <programlisting>(kakoune.override {
-  configure = {
+  plugins = with pkgs.kakounePlugins; [ parinfer-rust ];
-    plugins = with pkgs.kakounePlugins; [ parinfer-rust ];
-  };
 })</programlisting>
  </para>
 </section>

pkgs/applications/editors/kakoune/default.nix

@@ -30,6 +30,15 @@ stdenv.mkDerivation rec {
     $out/bin/kak -ui json -E "kill 0"
   '';
 
+  postInstall = ''
+    # make share/kak/autoload a directory, so we can use symlinkJoin with plugins
+    cd "$out/share/kak"
+    autoload_target=$(readlink autoload)
+    rm autoload
+    mkdir autoload
+    ln -s --relative "$autoload_target" autoload
+  '';
+
   meta = {
     homepage = "http://kakoune.org/";
     description = "A vim inspired text editor";

pkgs/applications/editors/kakoune/wrapper.nix

@@ -1,44 +1,24 @@
-{ stdenv, bash }:
+{ symlinkJoin, makeWrapper, kakoune, plugins ? [], configure ? {} }:
-with stdenv.lib;
-
-kakoune:
 
 let
-  getPlugins = { plugins ? [] }: plugins;
+  # "plugins" is the preferred way, but some configurations may be
+  # using "configure.plugins", so accept both
+  requestedPlugins = plugins ++ (configure.plugins or []);
 
-  wrapper = { configure ? {} }:
+in
-  stdenv.mkDerivation rec {
+  symlinkJoin {
-    pname = "kakoune";
+    name = "kakoune-${kakoune.version}";
-    version = getVersion kakoune;
 
-    src = ./.;
+    buildInputs = [ makeWrapper ];
-    buildCommand = ''
-      mkdir -p $out/share/kak
-      for plugin in ${strings.escapeShellArgs (getPlugins configure)}; do
-        if [[ -d $plugin/share/kak/autoload ]]; then
-          find "$plugin/share/kak/autoload" -type f -name '*.kak'| while read rcfile; do
-            printf 'source "%s"\n' "$rcfile"
-          done
-        fi
-      done >>$out/share/kak/plugins.kak
 
-      mkdir -p $out/bin
+    paths = [ kakoune ] ++ requestedPlugins;
-      substitute ${src}/wrapper.sh $out/bin/kak \
+
-        --subst-var-by bash "${bash}" \
+    postBuild = ''
-        --subst-var-by kakoune "${kakoune}" \
+      # location of kak binary is used to find ../share/kak/autoload,
-        --subst-var-by out "$out"
+      # unless explicitly overriden with KAKOUNE_RUNTIME
-      chmod +x $out/bin/kak
+      rm "$out/bin/kak"
+      makeWrapper "${kakoune}/bin/kak" "$out/bin/kak" --set KAKOUNE_RUNTIME "$out/share/kak"
     '';
 
-    preferLocalBuild = true;
+    meta = kakoune.meta // { priority = (kakoune.meta.priority or 0) - 1; };
-    buildInputs = [ bash kakoune ];
+  }
-    passthru = { unwrapped = kakoune; };
-
-    meta = kakoune.meta // {
-      # prefer wrapper over the package
-      priority = (kakoune.meta.priority or 0) - 1;
-      hydraPlatforms = [];
-    };
-  };
-in
-  makeOverridable wrapper

pkgs/applications/editors/kakoune/wrapper.sh

@@ -1,30 +0,0 @@
-#!@bash@/bin/bash
-
-# We use the -E option to load plugins.  This only makes sense when we are
-# starting a new session, so we detect that.  Also, Kakoune can only handle
-# one -E option, so we prepend loading plugins to an existing one.
-args=( "$@" )
-loadPlugins=true
-EValueOffset=-1
-pluginScript='@out@/share/kak/plugins.kak'
-
-for (( i = 0; i < ${#args[@]}; i++ )); do
-    case "${args[i]}" in
-        -n|-c|-l|-p|-clear|-version) loadPlugins=false;;
-        -E)                          EValueOffset=$(( i + 1 ));;
-        --)                          break;;
-    esac
-    case "${args[i]}" in
-        -E|-c|-e|-s|-p|-f|-i|-ui|-debug) i=$(( i + 1 ));;
-    esac
-done
-
-if [[ $loadPlugins = true ]]; then
-    if (( EValueOffset >= 0 )); then
-        args[EValueOffset]="source '$pluginScript'"$'\n'"${args[EValueOffset]}"
-    else
-        args=( "-E" "source '$pluginScript'" "${args[@]}" )
-    fi
-fi
-
-exec @kakoune@/bin/kak "${args[@]}"

pkgs/top-level/all-packages.nix

@@ -4905,10 +4905,12 @@ in
 
   kalibrate-hackrf = callPackage ../applications/radio/kalibrate-hackrf { };
 
-  wrapKakoune = callPackage ../applications/editors/kakoune/wrapper.nix { };
+  wrapKakoune = kakoune: attrs: callPackage ../applications/editors/kakoune/wrapper.nix (attrs // { inherit kakoune; });
   kakounePlugins = callPackage ../applications/editors/kakoune/plugins { };
   kakoune-unwrapped = callPackage ../applications/editors/kakoune { };
-  kakoune = wrapKakoune kakoune-unwrapped { };
+  kakoune = wrapKakoune kakoune-unwrapped {
+    plugins = [ ];  # override with the list of desired plugins
+  };
 
   kak-lsp = callPackage ../tools/misc/kak-lsp { };