nvim: add psoxizsh.lsp.core

Adds back some of the functionality of the late lsp.server, such that we
can paper over the exact implementation details of _how_ we're enabling
the language server.

In practice, this will allow us to create a bunch of preset
PsoxizshLspServer types, which users can then opt into enabling in their
plugin/* configs

nvim/lua/psoxizsh/lsp/core.lua

@@ -0,0 +1,95 @@
+
+---@class PsoxizshLspServer
+---@field id string The canonical name of the server
+---@field specs LazySpec Any other LazySpecs that will be included with ours
+---@field opts PsoxizshLspServerConfig This spec's config
+---@field callback PsoxizshLspPresetCallback Converts self.opts into a LazySpec
+---@field get fun(self: PsoxizshLspServer): LazySpec Return the materialized LazySpec for this server
+---@field with fun(self: PsoxizshLspServer, opts: PsoxizshLspServerConfig): LazySpec Return the materialized LazySpec for this server, with the given opts merged in
+---@operator call(PsoxizshLspServerConfig|nil): LazySpec
+
+---@class PsoxizshLspServerConfig
+---@field settings table The lspconfig settings for this server
+
+---@alias PsoxizshLspPresetCallback fun(string, PsoxizshLspServerConfig): LazySpec
+
+---@class psoxizsh.lsp.core
+local M = {}
+
+local S = {}
+
+---Merge the provided config into the normal neovim/nvim-lspconfig structure
+---@param server string
+---@param config table
+---@return table
+function M.make_server(server, config)
+  return { servers = { [server] = config } }
+end
+
+---Create a LazyPlugin spec override for neovim/nvim-lspconfig for the given
+---server and config
+---@param server string
+---@param opts PsoxizshLspServerConfig
+---@return LazySpec
+function M.lspconfig_server(server, opts)
+  return {
+    'neovim/nvim-lspconfig', opts = M.make_server(server, opts.settings)
+  }
+end
+
+---Create a new LSP server spec
+---@param id string
+---@param inherit LazySpec
+---@param cb PsoxizshLspPresetCallback
+---@return PsoxizshLspServer
+function M.preset(id, inherit, cb)
+  return S.new(id, inherit, cb)
+end
+
+---Create a new PsoxizshLspServer
+---@param id string
+---@param specs LazySpec
+---@param cb PsoxizshLspPresetCallback
+---@return PsoxizshLspServer
+function S.new(id, specs, cb)
+  local this = vim.deepcopy(S)
+
+  this.id = id
+  this.specs = specs
+  this.callback = cb
+  this.opts = { settings = {} }
+
+  setmetatable(this, {
+    __call = function(self, opts)
+      local hasopts = type(opts) == 'table' and next(opts) ~= 'nil' or type(opts) ~= 'nil'
+
+      return hasopts and self:with(opts) or self:get()
+    end
+  })
+
+  return this
+end
+
+---Get the LazyVim plugin spec(s) for this LspServer
+---@param self PsoxizshLspServer
+---@return LazySpec
+function S.get(self)
+  local unpack = table.unpack or unpack
+  local specs = type(self.specs) == 'string' and {{ import = self.specs }} or self.specs
+  local lsp = self.callback(self.id, self.opts)
+
+  return { unpack(specs), lsp }
+end
+
+---Get the LazyVim plugin spec(s) for this LspServer
+---@param self PsoxizshLspServer
+---@param opts PsoxizshLspServerConfig
+---@return LazySpec
+function S.with(self, opts)
+  local this = vim.deepcopy(self)
+  this.opts = vim.tbl_deep_extend('force', this.opts, opts)
+
+  return this:get()
+end
+
+return M