nvim: add support for “nerdfonts”

.config/nvim/lua/my/functions.lua

@@ -106,4 +106,12 @@ function M.get_hl_hex(hl_group)
     return hl_hex
 end
 
+-- return true if 'Symbols Nerd Font' is known to fontconfig
+function M.nerdfont_installed()
+    if os.execute([[fc-list -q 'Symbols Nerd Font']]) == 0 then
+        return true
+    end
+    return false
+end
+
 return M

.config/nvim/lua/my/plugins.lua

@@ -83,9 +83,19 @@ require('packer').startup(function(use)
     }
     use {
         'https://github.com/kyazdani42/nvim-tree.lua',
-        tag = '*'
+        tag = '*',
+        requires = {
+            'https://github.com/ryanoasis/vim-devicons',
+            opt = true
+        }
+    }
+    use {
+        'https://github.com/nvim-lualine/lualine.nvim',
+        requires = {
+            'https://github.com/ryanoasis/vim-devicons',
+            opt = true
+        }
     }
-    use { 'https://github.com/nvim-lualine/lualine.nvim' }
 
     -- coding
     use {

.config/nvim/lua/my/tools.lua

@@ -36,6 +36,8 @@ map('n', '<Leader>tm', t_builtin.man_pages, 'Man pages')
 map('n', '<Leader>tr', t_builtin.registers, 'Registers')
 map('n', '<Leader>tp', telescope.extensions.projects.projects, 'Projects')
 
+local nerdfont_installed = require('my.functions').nerdfont_installed()
+
 require("nvim-tree").setup({
     filters = {
         dotfiles = false
@@ -49,10 +51,10 @@ require("nvim-tree").setup({
     renderer = {
         icons = {
             show = {
-                file = false,
-                folder = false,
-                folder_arrow = false,
-                git = false
+                file = nerdfont_installed,
+                folder = nerdfont_installed,
+                folder_arrow = nerdfont_installed,
+                git = nerdfont_installed
             }
         }
     }
@@ -70,9 +72,10 @@ require('lualine').setup({
     },
     sections = {
         lualine_a = { 'mode' },
-        lualine_b = { 'branch', { 'diagnostics', icons_enabled = false } },
+        lualine_b = { 'branch',
+            { 'diagnostics', icons_enabled = nerdfont_installed } },
         lualine_c = { { 'filename', path = 1 } },
-        lualine_x = { { 'filetype', icons_enabled = false } },
+        lualine_x = { { 'filetype', icons_enabled = nerdfont_installed } },
         lualine_y = { 'progress' },
         lualine_z = { 'location' }
     },