fix(gx): visual selection, expand env vars

---
Rejected experiment: move vim.ui.open() to vim.env.open()

Problem:
`vim.ui` is where user-interface "providers" live, which can be
overridden. It would also be useful to have a "providers" namespace for
platform-specific features such as "open", clipboard, python, and the other
providers listed in `:help providers`. We could overload `vim.ui` to
serve that purpose as the single "providers" namespace, but
`vim.ui.nodejs()` for example seems awkward.

Solution:
`vim.env` currently has too narrow of a purpose. Overload it to also be
a namespace for `vim.env.open`.

diff --git a/runtime/lua/vim/_meta.lua b/runtime/lua/vim/_meta.lua
index 913f1fe20348..17d05ff37595 100644
--- a/runtime/lua/vim/_meta.lua
+++ b/runtime/lua/vim/_meta.lua
@@ -37,8 +37,28 @@ local options_info = setmetatable({}, {
   end,
 })

-vim.env = setmetatable({}, {
-  __index = function(_, k)
+vim.env = setmetatable({
+  open = setmetatable({}, {
+      __call = function(_, uri)
+        print('xxxxx'..uri)
+        return true
+      end,
+      __tostring = function()
+        local v = vim.fn.getenv('open')
+        if v == vim.NIL then
+          return nil
+        end
+        return v
+      end,
+    })
+  },
+  {
+  __index = function(t, k, ...)
+    if k == 'open' then
+      error()
+      -- vim.print({...})
+      -- return rawget(t, k)
+    end
     local v = vim.fn.getenv(k)
     if v == vim.NIL then
       return nil

7 files changed, 82 insertions, 78 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index f180471bde..b09e308e80 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -2344,28 +2344,26 @@ input({opts}, {on_confirm})                                   *vim.ui.input()*
                       entered), or `nil` if the user aborted the dialog.
 
 open({path})                                                   *vim.ui.open()*
-    Opens a path in the system's default handler. This function utilizes
-    `xdg-open`, `wslview`, `explorer`, or `open` commands depending on the
-    system to open the provided path.
+    Opens `path` with the system default handler (macOS `open`, Windows
+    `explorer.exe`, Linux `xdg-open`, …), or shows a message on failure.
 
-    Notifies the user if unsuccessful
+    Expands "~/" and environment variables in filesystem paths.
 
-    Example: >lua
+    Examples: >lua
 
      vim.ui.open("https://neovim.io/")
-
-     vim.ui.open("/path/to/file")
+     vim.ui.open("~/path/to/file")
+     vim.ui.open("$VIMRUNTIME")
 <
 
     Parameters: ~
-      • {path}  (string) Path to be opened
+      • {path}  (string) Path or URL to open
 
     Return: ~
-        SystemCompleted|nil result Result of command, if an appropriate one
-        could be found.
+        SystemCompleted|nil result Command result, or nil if not found.
 
     See also: ~
-      • |vim.system|
+      • |vim.system()|
 
 select({items}, {opts}, {on_choice})                         *vim.ui.select()*
     Prompts the user to pick from a list of items, allowing arbitrary
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index ed797f94ba..24e9dc917b 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -105,10 +105,10 @@ The following new APIs and features were added.
   https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_inlayHint
 
 • Bundled treesitter parser and queries (highlight, folds) for Markdown,
-Python, and Bash.
+  Python, and Bash.
 
 • |vim.ui.open()| opens URIs using the system default handler (macOS `open`,
-Windows `explorer`, Linux `xdg-open`, etc.)
+  Windows `explorer`, Linux `xdg-open`, etc.)
 
 ==============================================================================
 CHANGED FEATURES                                                 *news-changed*
@@ -146,8 +146,9 @@ The following changes to existing APIs or features add new behavior.
 
 • |:Man| now respects 'wrapmargin'
 
-• The |gx| command now uses |vim.ui.open()| and not netrw. Continue using
-netrw with `vim.g.use_lua_gx = false`.
+• |gx| now uses |vim.ui.open()| and not netrw. To customize, you can redefine
+  `vim.ui.open` or remap `gx`. To continue using netrw (deprecated): >vim
+  :call netrw#BrowseX(expand(exists("g:netrw_gx")? g:netrw_gx : '<cfile>'), netrw#CheckIfRemote())<CR>
 
 ==============================================================================
 REMOVED FEATURES                                                 *news-removed*
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index de1c21b310..956c37fc0f 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -98,13 +98,14 @@ g8			Print the hex values of the bytes used in the
 			command won't move the cursor.
 
 							*gx*
-gx			Open the current path or URL under the cursor in the 
-			system's default handler with |vim.ui.open|.
+gx			Opens the current filepath or URL (decided by
+			|<cfile>|, 'isfname') at cursor using the system
+			default handler, by calling |vim.ui.open()|.
+
+							*v_gx*
+{Visual}gx		Opens the selected text using the system default
+			handler, by calling |vim.ui.open()|.
 
-			To use the netrw keymap, set `use_lua_gx` to false:
->lua
-    vim.g.use_lua_gx = false
-<
 						*:p* *:pr* *:print* *E749*
 :[range]p[rint] [flags]
 			Print [range] lines (default current line).
diff --git a/runtime/lua/vim/lsp/handlers.lua b/runtime/lua/vim/lsp/handlers.lua
index 9b102c0f84..79d3f7aab0 100644
--- a/runtime/lua/vim/lsp/handlers.lua
+++ b/runtime/lua/vim/lsp/handlers.lua
@@ -576,12 +576,12 @@ M['window/showDocument'] = function(_, result, ctx, _)
 
     local ret = vim.ui.open(uri)
 
-    if ret.code ~= 0 or ret == nil then
+    if ret == nil or ret.code ~= 0 then
       return {
         success = false,
         error = {
           code = protocol.ErrorCodes.UnknownErrorCode,
-          message = ret and ret.stderr or 'No handler could be found',
+          message = ret and ret.stderr or 'No handler found',
         },
       }
     end
@@ -593,7 +593,7 @@ M['window/showDocument'] = function(_, result, ctx, _)
   local client = vim.lsp.get_client_by_id(client_id)
   local client_name = client and client.name or string.format('id=%d', client_id)
   if not client then
-    err_message({ 'LSP[', client_name, '] client has shut down after sending ', ctx.method })
+    err_message('LSP[', client_name, '] client has shut down after sending ', ctx.method)
     return vim.NIL
   end
 
diff --git a/runtime/lua/vim/ui.lua b/runtime/lua/vim/ui.lua
index 2200ee7bc3..3ffa329f74 100644
--- a/runtime/lua/vim/ui.lua
+++ b/runtime/lua/vim/ui.lua
@@ -104,69 +104,54 @@ function M.input(opts, on_confirm)
   end
 end
 
---- Opens a path in the system's default handler.
---- This function utilizes `xdg-open`, `wslview`, `explorer`, or `open` commands
---- depending on the system to open the provided path.
+--- Opens `path` with the system default handler (macOS `open`, Windows `explorer.exe`, Linux
+--- `xdg-open`, …), or shows a message on failure.
 ---
---- Notifies the user if unsuccessful
+--- Expands "~/" and environment variables in filesystem paths.
 ---
----@param path string Path to be opened
----
----@return SystemCompleted|nil result Result of command, if an appropriate one
----could be found.
----
----@see |vim.system|
----
---- Example:
+--- Examples:
 --- <pre>lua
 --- vim.ui.open("https://neovim.io/")
----
---- vim.ui.open("/path/to/file")
+--- vim.ui.open("~/path/to/file")
+--- vim.ui.open("$VIMRUNTIME")
 --- </pre>
+---
+---@param path string Path or URL to open
+---
+---@return SystemCompleted|nil result Command result, or nil if not found.
+---
+---@see |vim.system()|
 function M.open(path)
-  if not path or path == '' then
-    vim.notify('os_open: No path provided', vim.log.levels.ERROR)
-    return nil
+  vim.validate{
+    path={path, 'string'}
+  }
+  local is_uri = path:match('%w+:')
+  if not is_uri then
+    path = vim.fn.expand(path)
   end
 
   local cmd
 
-  if vim.fn.has('macunix') == 1 then
+  if vim.fn.has('mac') == 1 then
     cmd = { 'open', path }
   elseif vim.fn.has('win32') == 1 then
     cmd = { 'explorer', path }
+  elseif vim.fn.executable('wslview') == 1 then
+    cmd = { 'wslview', path }
+  elseif vim.fn.executable('xdg-open') == 1 then
+    cmd = { 'xdg-open', path }
   else
-    if vim.fn.executable('wslview') == 1 then
-      cmd = { 'wslview', path }
-    elseif vim.fn.executable('xdg-open') == 1 then
-      cmd = { 'xdg-open', path }
-    else
-      vim.notify(
-        'os_open: Could not find an appropriate command to use (Is xdg-open installed?)',
-        vim.log.levels.ERROR
-      )
-
-      return nil
-    end
+    vim.notify('vim.ui.open: no handler found (tried: wslview, xdg-open)', vim.log.levels.ERROR)
+    return nil
   end
 
-  local ret = vim
-    .system(cmd, {
-      text = true,
-      detach = true,
-    })
-    :wait()
-
-  if ret.code ~= 0 then
-    local msg = {
-      'Failed to open path',
-      ret,
-      vim.inspect(cmd),
-    }
-    vim.notify(table.concat(msg, '\n'), vim.log.levels.ERROR)
+  local rv = vim.system(cmd, { text = true, detach = true, }):wait()
+  if rv.code ~= 0 then
+    local msg = ('vim.ui.open: command failed (%d): %s'):format(rv.code, vim.inspect(cmd))
+    vim.notify(msg, vim.log.levels.ERROR)
   end
 
-  return ret
+  return rv
 end
 
 return M
diff --git a/runtime/plugin/nvim.lua b/runtime/plugin/nvim.lua
index fcc1b016aa..9fff6246e3 100644
--- a/runtime/plugin/nvim.lua
+++ b/runtime/plugin/nvim.lua
@@ -19,10 +19,15 @@ vim.api.nvim_create_user_command('InspectTree', function(cmd)
   end
 end, { desc = 'Inspect treesitter language tree for buffer', count = true })
 
-if vim.g.use_lua_gx == nil or vim.g.use_lua_gx == true then
-  vim.keymap.set({ 'n', 'x' }, 'gx', function()
-    local uri = vim.fn.expand('<cfile>')
-
-    vim.ui.open(uri)
-  end, { desc = 'Open URI under cursor with system app' })
+-- TODO: use vim.region() when it lands... #13896 #16843
+local function get_visual_selection()
+  local save_a = vim.fn.getreginfo('a')
+  vim.cmd[[norm! "ay]]
+  local selection = vim.fn.getreg('a', 1)
+  vim.fn.setreg('a', save_a)
+  return selection
 end
+
+local gx_desc = 'Opens filepath or URI under cursor with the system handler (file explorer, web browser, …)'
+vim.keymap.set({ 'n' }, 'gx', function() vim.ui.open(vim.fn.expand('<cfile>')) end, { desc = gx_desc })
+vim.keymap.set({ 'x' }, 'gx', function() vim.ui.open(get_visual_selection()) end, { desc = gx_desc })
diff --git a/test/functional/lua/ui_spec.lua b/test/functional/lua/ui_spec.lua
index 9ee99b4905..0f66aad7b3 100644
--- a/test/functional/lua/ui_spec.lua
+++ b/test/functional/lua/ui_spec.lua
@@ -1,5 +1,6 @@
 local helpers = require('test.functional.helpers')(after_each)
 local eq = helpers.eq
+local matches = helpers.matches
 local exec_lua = helpers.exec_lua
 local clear = helpers.clear
 local feed = helpers.feed
@@ -11,8 +12,7 @@ describe('vim.ui', function()
     clear()
   end)
 
-
-  describe('select', function()
+  describe('select()', function()
     it('can select an item', function()
       local result = exec_lua[[
         local items = {
@@ -47,7 +47,7 @@ describe('vim.ui', function()
     end)
   end)
 
-  describe('input', function()
+  describe('input()', function()
     it('can input text', function()
       local result = exec_lua[[
         local opts = {
@@ -130,4 +130,18 @@ describe('vim.ui', function()
     end)
 
   end)
+
+  describe('open()', function()
+    it('validation', function()
+      exec_lua[[vim.ui.open('non-existent-file')]]
+      matches('vim.ui.open: command failed %(%d%): { "[^"]+", "non%-existent%-file" }', eval('v:errmsg'))
+
+      exec_lua[[
+        vim.fn.has = function() return 0 end
+        vim.fn.executable = function() return 0 end
+      ]]
+      exec_lua[[vim.ui.open('foo')]]
+      eq('vim.ui.open: no handler found (tried: wslview, xdg-open)', eval('v:errmsg'))
+    end)
+  end)
 end)