New neovim config.

I've been using neovim for a while but the config got messy so here is a
cleaner config.

Signed-off-by: Louis Hollingworth <louis@hollingworth.nl>

after/plugin/lsp.lua

@@ -0,0 +1,135 @@
+local keymap = vim.keymap.set
+
+require('mason').setup({
+    ui = {
+        icons = {
+            server = " ",
+            lsp = " ",
+            linter = " ",
+            formatter = " ",
+
+            package_installed = "✓",
+            package_pending = "➜",
+            package_uninstalled = "✗"
+        },
+    },
+})
+
+require("mason-lspconfig").setup({
+    automatic_installation = true,
+})
+
+local lsp = require('lspconfig')
+
+local cmp = require('cmp')
+local cmp_select = {behavior = cmp.SelectBehavior.Select}
+
+local opts = { noremap=true, silent=true }
+--keymap('i', '<C-Space>', vim.diagnostic.open_float, opts)
+--keymap('i', '<C-p>', vim.diagnostic.goto_prev, opts)
+--keymap('i', '<C-n>', vim.diagnostic.goto_next, opts)
+--keymap('i', '<C-Space>', cmp.mapping.complete(), opts)
+--keymap('i', '<CR>', vim.diagnostic.setloclist, opts)
+keymap('n', '<C-Space>', vim.diagnostic.open_float, opts)
+keymap('n', '<C-p>', vim.diagnostic.goto_prev, opts)
+keymap('n', '<C-n>', vim.diagnostic.goto_next, opts)
+--keymap('i', '<C-Space>', cmp.mapping.complete(), opts)
+keymap('n', '<CR>', vim.diagnostic.setloclist, opts)
+
+cmp.setup({
+    snippet = {
+        expand = function(args)
+            require('luasnip').lsp_expand(args.body)
+        end,
+    },
+    mapping = {
+        ['<C-p>'] = cmp.mapping.select_prev_item(cmp_select),
+        ['<C-n>'] = cmp.mapping.select_next_item(cmp_select),
+        ['<C-Space>'] = cmp.mapping.complete(cmp_select),
+        ['<C-e>'] = cmp.mapping.close(),
+        ['<CR>'] = cmp.mapping.confirm({
+            behavior = cmp.ConfirmBehavior.Replace,
+            select = true,
+        }),
+    },
+    sources = {
+        { name = 'nvim_lsp' },
+        { name = 'luasnip' },
+        { name = 'buffer' },
+    },
+})
+
+vim.diagnostic.config({
+    virtual_text = true,
+})
+
+local on_attach = function(client, bufnr)
+    local function buf_set_keymap(...)
+		vim.api.nvim_buf_set_keymap(bufnr, ...)
+	end
+
+	-- Mappings.
+	local opts = { noremap = true, silent = true, buffer = bufnr}
+
+	-- See `:help vim.lsp.*` for documentation on any of the below functions
+	vim.keymap.set("n", "gd", "<cmd>Telescope lsp_definitions<CR>", opts)
+	vim.keymap.set("n", "gr", "<cmd>Telescope lsp_references<CR>", opts)
+
+	vim.keymap.set("n", "<C-j>", "<cmd>Telescope lsp_document_symbols<CR>", opts)
+	vim.keymap.set("n", "<C-k>", "<cmd>lua vim.lsp.buf.signature_help()<CR>", opts)
+
+	vim.keymap.set("n", "gi", "<cmd>Telescope lsp_implementations<CR>", opts)
+	vim.keymap.set("n", "K", "<cmd>lua vim.lsp.buf.hover()<CR>", opts)
+	vim.keymap.set("n", "<leader>D", "<cmd>Telescope lsp_type_definitions<CR>", opts)
+	vim.keymap.set("n", "<leader>rn", "<cmd>lua vim.lsp.buf.rename()<CR>", opts)
+	vim.keymap.set("n", "<leader>ca", "<cmd>Telescope lsp_code_actions<CR>", opts)
+	vim.keymap.set("n", "gt", vim.lsp.buf.type_definition, {buffer=0})
+	vim.keymap.set("n", "gi", vim.lsp.buf.implementation, {buffer=0})
+	vim.keymap.set("n", "<leader>dj", vim.diagnostic.goto_next, {buffer=0})
+	vim.keymap.set("n", "<leader>dk", vim.diagnostic.goto_prev, {buffer=0})
+	vim.keymap.set("n", "<leader>dl", "<cmd>Telescope diagnostics<cr>", {buffer=0})
+	vim.keymap.set("n", "<leader>r", vim.lsp.buf.rename, {buffer=0})
+	vim.keymap.set("n", "<leader>ca", vim.lsp.buf.code_action, {buffer=0})
+
+    -- Set autocommands conditional on server_capabilities
+	if client.server_capabilities.document_highlight then
+		vim.cmd([[
+			augroup lsp_document_highlight
+				autocmd! * <buffer>
+				autocmd CursorHold <buffer> lua vim.lsp.buf.document_highlight()
+				autocmd CursorMoved <buffer> lua vim.lsp.buf.clear_references()
+			augroup END
+		]])
+	end
+end
+
+lsp.gopls.setup({
+    on_attach = on_attach,
+    flags = lsp_flags,
+    settings = {
+        gopls = {
+            analyses = {
+                unusedparams = true,
+            },
+            staticcheck = true,
+        },
+    },
+})
+
+lsp['lua_ls'].setup{
+    on_attach = on_attach,
+    flags = lsp_flags,
+}
+
+lsp['rust_analyzer'].setup{
+    on_attach = on_attach,
+    flags = lsp_flags,
+    cmd = {
+        "rustup", "run", "stable", "rust-analyzer",
+    }
+}
+
+lsp.tsserver.setup{
+    on_attach = on_attach,
+    flags = lsp_flags,
+}