plugins.lsp: automatically remove unsupported servers

A new update script will check which "old" files do not have an
equivalent "new" file, then the plugins.lsp module will create a
removal assertion for any servers that are listed in the generated
file.

ci/generate.nix

@@ -51,6 +51,7 @@ writeShellApplication {
 
     generate_json "${conform-formatters}" "conform-formatters"
     generate_json "${lspconfig-servers}" "lspconfig-servers"
+    generate_json "${lspconfig-servers.unsupported}" "unsupported-lspconfig-servers"
 
     if [ -n "$commit" ]; then
       cd "$generated_dir"

ci/nvim-lspconfig/default.nix

@@ -1,5 +1,6 @@
 {
   lib,
+  callPackage,
   vimPlugins,
   neovimUtils,
   wrapNeovimUnstable,
@@ -31,6 +32,7 @@ runCommand "lspconfig-servers"
       pandoc
       python3
     ];
+    passthru.unsupported = callPackage ./unsupported.nix { };
   }
   ''
     export HOME=$(realpath .)

ci/nvim-lspconfig/unsupported.nix

@@ -0,0 +1,24 @@
+{
+  runCommand,
+  jq,
+  vimPlugins,
+}:
+/**
+  Produces a JSON array of all nvim-lspconfig server configs that don't yet
+  support the new system.
+
+  I.e., files in the old `lua/lspconfig/configs/` directory, that aren't
+  present in the new `lsp/` directory.
+*/
+runCommand "unsupported-lspconfig-servers"
+  {
+    nativeBuildInputs = [ jq ];
+    lspconfig = vimPlugins.nvim-lspconfig;
+  }
+  ''
+    for file in "$lspconfig"/lua/lspconfig/configs/*.lua
+    do
+      name=$(basename --suffix=.lua "$file")
+      [ -f "$lspconfig"/lsp/"$name".lua ] || echo "$name"
+    done | jq --raw-input . | jq --slurp [.] > "$out"
+  ''