feat: add ability to track signature help triggers for automatic signature help display

Author: mehalter

lua/astrolsp/config.lua

@@ -29,6 +29,7 @@
 ---@field codelens boolean? enable/disable codelens refresh on start (boolean; default = true)
 ---@field inlay_hints boolean? enable/disable inlay hints on start (boolean; default = false)
 ---@field semantic_tokens boolean? enable/disable semantic token highlighting (boolean; default = true)
+---@field signature_help boolean? enable/disable automatic signature help (boolean; default = false)
 
 ---@class AstroLSPFormatOnSaveOpts
 ---@field enabled boolean? enable or disable format on save globally
@@ -260,6 +261,7 @@ local M = {
     codelens = true,
     inlay_hints = false,
     semantic_tokens = true,
+    signature_help = false,
   },
   capabilities = {},
   ---@diagnostic disable-next-line: missing-fields

lua/astrolsp/init.lua

@@ -229,6 +229,39 @@ function M.setup(opts)
   -- TODO: remove check when dropping support for Neovim v0.9
   if vim.lsp.inlay_hint then vim.lsp.inlay_hint.enable(M.config.features.inlay_hints ~= false) end
 
+  -- Set up tracking of signature help trigger characters
+  local augroup = vim.api.nvim_create_augroup("track_signature_help_triggers", { clear = true })
+  vim.api.nvim_create_autocmd("LspAttach", {
+    group = augroup,
+    desc = "Add signature help triggers as language servers attach",
+    callback = function(args)
+      local client = vim.lsp.get_client_by_id(args.data.client_id)
+      if client and client.supports_method "textDocument/signatureHelp" then
+        vim.b[args.buf].signature_help_trigger = require("astrocore").list_insert_unique(
+          vim.b[args.buf].signature_help_trigger,
+          client.server_capabilities.signatureHelpProvider.triggerCharacters or {}
+        )
+      end
+    end,
+  })
+  vim.api.nvim_create_autocmd("LspDetach", {
+    group = augroup,
+    desc = "Safely remove LSP signature help triggers when language servers detach",
+    callback = vim.schedule_wrap(function(args)
+      if not vim.api.nvim_buf_is_valid(args.buf) then return end
+      local signature_help_trigger = {}
+      for _, client in pairs((vim.lsp.get_clients or vim.lsp.get_active_clients) { bufnr = args.buf }) do
+        if client.id ~= args.data.client_id and client.supports_method "textDocument/signatureHelp" then
+          require("astrocore").list_insert_unique(
+            signature_help_trigger,
+            client.server_capabilities.signatureHelpProvider.triggerCharacters or {}
+          )
+        end
+      end
+      vim.b[args.buf].signature_help_trigger = signature_help_trigger
+    end),
+  })
+
   vim.api.nvim_create_autocmd("LspDetach", {
     group = vim.api.nvim_create_augroup("astrolsp_detach", { clear = true }),
     desc = "Clear state when language server is detached like LSP progress messages",

lua/astrolsp/toggles.lua

@@ -89,4 +89,26 @@ function M.codelens(silent)
   ui_notify(silent, ("CodeLens %s"):format(bool2str(features.codelens)))
 end
 
+--- Toggle automatic signature help
+---@param silent? boolean if true then don't sent a notification
+function M.signature_help(silent)
+  config.features.signature_help = not config.features.signature_help
+  ui_notify(silent, ("Global signature help %s"):format(bool2str(config.features.signature_help)))
+end
+
+--- Toggle buffer local automatic signature help
+---@param bufnr? integer The buffer to toggle the auto signature help of, default the current buffer
+---@param silent? boolean if true then don't sent a notification
+function M.buffer_signature_help(bufnr, silent)
+  bufnr = bufnr or 0
+  local old_val = vim.b[bufnr].signature_help
+  if old_val == nil then old_val = config.features.signature_help end
+  if not next(vim.b[bufnr].signature_help_trigger) then
+    ui_notify(silent, "No LSP attached with signature help triggers")
+    return
+  end
+  vim.b[bufnr].signature_help = not old_val
+  ui_notify(silent, ("Buffer signature help %s"):format(bool2str(vim.b[bufnr].signature_help)))
+end
+
 return M