refactor(ui): simplify stdin handling

9 files changed, 106 insertions, 53 deletions

diff --git a/runtime/doc/ui.txt b/runtime/doc/ui.txt
index f9110cd59b..8014199dc5 100644
--- a/runtime/doc/ui.txt
+++ b/runtime/doc/ui.txt
@@ -52,6 +52,11 @@ with these (optional) keys:
 	`term_name`		Sets the name of the terminal 'term'.
 	`term_colors`		Sets the number of supported colors 't_Co'.
 	`term_background`	Sets the default value of 'background'.
+	`stdin_fd`		Read buffer from `fd` as if it was a stdin pipe
+				This option can only used by |--embed| ui,
+				see |ui-startup-stdin|.
+
+
 
 Specifying an unknown option is an error; UIs can check the |api-metadata|
 `ui_options` key for supported options.
@@ -140,6 +145,19 @@ procedure:
    Inside this request handler, the UI can safely do any initialization before
    entering normal mode, for example reading variables set by init.vim.
 
+							   *ui-startup-stdin*
+An UI can support the native read from stdin feature as invoked with
+`command | nvim -` for the builtin TUI. |--|
+The embedding process can detect that its stdin is open to a file which
+not is a terminal, just like nvim does. It then needs to forward this fd
+to Nvim. As fd=0 is already is used to send rpc data from the embedder to
+Nvim, it needs to use some other file descriptor, like fd=3 or higher.
+
+Then, `stdin_fd` option should be passed to `nvim_ui_attach` and nvim will
+implicitly read it as a buffer. This option can only be used when Nvim is
+launched with `--embed` option, as described above.
+
+
 ==============================================================================
 Global Events							    *ui-global*
 
diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 997f0c218a..f449ccc3c7 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -283,6 +283,22 @@ static void ui_set_option(UI *ui, bool init, String name, Object value, Error *e
     return;
   }
 
+  if (strequal(name.data, "stdin_fd")) {
+    if (value.type != kObjectTypeInteger || value.data.integer < 0) {
+      api_set_error(error, kErrorTypeValidation, "stdin_fd must be a non-negative Integer");
+      return;
+    }
+
+    if (starting != NO_SCREEN) {
+      api_set_error(error, kErrorTypeValidation,
+                    "stdin_fd can only be used with first attached ui");
+      return;
+    }
+
+    stdin_fd = (int)value.data.integer;
+    return;
+  }
+
   // LEGACY: Deprecated option, use `ext_cmdline` instead.
   bool is_popupmenu = strequal(name.data, "popupmenu_external");
 
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 9c34c912c0..061653c5af 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2661,35 +2661,3 @@ end:
   xfree(cmdline);
   return result;
 }
-
-/// Invokes the nvim server to read from stdin when it is not a tty
-///
-/// It enables functionalities like:
-/// - echo "1f u c4n r34d th1s u r34lly n33d t0 g37 r357"| nvim -
-/// - cat path/to/a/file | nvim -
-/// It has to be called before |nvim_ui_attach()| is called in order
-/// to ensure proper functioning.
-///
-/// @param channel_id: The channel id of the GUI-client
-/// @param filedesc: The file descriptor of the GUI-client process' stdin
-/// @param implicit: Tells if read_stdin call is implicit.
-///                  i.e for cases like `echo xxx | nvim`
-/// @param[out] err Error details, if any
-void nvim_read_stdin(uint64_t channel_id, Integer filedesc, Error *err)
-FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY
-{
-  if (starting != NO_SCREEN) {
-    api_set_error(err, kErrorTypeValidation,
-                  "nvim_read_stdin must be called before nvim_ui_attach");
-    return;
-  }
-  if (filedesc < 0) {
-    api_set_error(err, kErrorTypeValidation,
-                  "file descriptor must be non-negative");
-    return;
-  }
-
-  stdin_filedesc = (int)filedesc;
-  implicit_readstdin = implicit;
-  return;
-}
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 7ca7abccdc..95c373ec5c 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -176,7 +176,7 @@ void filemess(buf_T *buf, char_u *name, char_u *s, int attr)
 int readfile(char_u *fname, char_u *sfname, linenr_T from, linenr_T lines_to_skip,
              linenr_T lines_to_read, exarg_T *eap, int flags, bool silent)
 {
-  int fd = 0;
+  int fd = stdin_fd >= 0 ? stdin_fd : 0;
   int newfile = (flags & READ_NEW);
   int check_readonly;
   int filtering = (flags & READ_FILTER);
@@ -1722,17 +1722,19 @@ failed:
   xfree(buffer);
 
   if (read_stdin) {
-    close(0);
+    close(fd);
+    if (stdin_fd < 0) {
 #ifndef WIN32
-    // On Unix, use stderr for stdin, makes shell commands work.
-    vim_ignored = dup(2);
+      // On Unix, use stderr for stdin, makes shell commands work.
+      vim_ignored = dup(2);
 #else
-    // On Windows, use the console input handle for stdin.
-    HANDLE conin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
-                              FILE_SHARE_READ, (LPSECURITY_ATTRIBUTES)NULL,
-                              OPEN_EXISTING, 0, (HANDLE)NULL);
-    vim_ignored = _open_osfhandle(conin, _O_RDONLY);
+      // On Windows, use the console input handle for stdin.
+      HANDLE conin = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE,
+                                FILE_SHARE_READ, (LPSECURITY_ATTRIBUTES)NULL,
+                                OPEN_EXISTING, 0, (HANDLE)NULL);
+      vim_ignored = _open_osfhandle(conin, _O_RDONLY);
 #endif
+    }
   }
 
   if (tmpname != NULL) {
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 8d03bdf000..3ae0d32d8f 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -507,6 +507,9 @@ EXTERN int v_dying INIT(= 0);
 EXTERN int stdin_isatty INIT(= true);
 // is stdout a terminal?
 EXTERN int stdout_isatty INIT(= true);
+/// filedesc set by embedder for reading first buffer like `cmd | nvim -`
+EXTERN int stdin_fd INIT(= -1);
+
 // true when doing full-screen output, otherwise only writing some messages.
 // volatile because it is used in a signal handler.
 EXTERN volatile int full_screen INIT(= false);
@@ -704,7 +707,6 @@ EXTERN int RedrawingDisabled INIT(= 0);
 
 EXTERN int readonlymode INIT(= false);      // Set to true for "view"
 EXTERN int recoverymode INIT(= false);      // Set to true for "-r" option
-EXTERN int stdin_filedesc INIT(= -1);       // stdin filedesc set by embedder
 
 // typeahead buffer
 EXTERN typebuf_T typebuf INIT(= { NULL, NULL, 0, 0, 0, 0, 0, 0, 0 });
@@ -848,10 +850,6 @@ EXTERN linenr_T printer_page_num;
 EXTERN bool typebuf_was_filled INIT(= false);     // received text from client
                                                   // or from feedkeys()
 
-EXTERN bool implicit_readstdin INIT(= false);     // Used in embed job created
-                                                  // by TUI process only in
-                                                  // builtin tui
-
 #ifdef BACKSLASH_IN_FILENAME
 EXTERN char psepc INIT(= '\\');            // normal path separator character
 EXTERN char psepcN INIT(= '/');            // abnormal path separator character
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 253a89467e..5a496a10b4 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -454,7 +454,7 @@ int main(int argc, char **argv)
   // writing end of the pipe doesn't like, e.g., in case stdin and stderr
   // are the same terminal: "cat | vim -".
   // Using autocommands here may cause trouble...
-  if ((params.edit_type == EDIT_STDIN || implicit_readstdin) && !recoverymode) {
+  if ((params.edit_type == EDIT_STDIN || stdin_fd >= 0) && !recoverymode) {
     read_stdin();
   }
 
diff --git a/test/functional/helpers.lua b/test/functional/helpers.lua
index 173fc54af5..b0b2dac9fd 100644
--- a/test/functional/helpers.lua
+++ b/test/functional/helpers.lua
@@ -361,14 +361,15 @@ local function remove_args(args, args_rm)
   return new_args
 end
 
-function module.spawn(argv, merge, env, keep)
+--- @param io_extra used for stdin_fd, see :help ui-option
+function module.spawn(argv, merge, env, keep, io_extra)
   if session and not keep then
     session:close()
   end
 
   local child_stream = ChildProcessStream.spawn(
       merge and module.merge_args(prepend_argv, argv) or argv,
-      env)
+      env, io_extra)
   return Session.new(child_stream)
 end
 
@@ -415,8 +416,8 @@ end
 --    clear('-e')
 --    clear{args={'-e'}, args_rm={'-i'}, env={TERM=term}}
 function module.clear(...)
-  local argv, env = module.new_argv(...)
-  module.set_session(module.spawn(argv, nil, env))
+  local argv, env, io_extra = module.new_argv(...)
+  module.set_session(module.spawn(argv, nil, env, nil, io_extra))
 end
 
 -- Builds an argument list for use in clear().
@@ -426,6 +427,7 @@ function module.new_argv(...)
   local args = {unpack(module.nvim_argv)}
   table.insert(args, '--headless')
   local new_args
+  local io_extra
   local env = nil
   local opts = select(1, ...)
   if type(opts) == 'table' then
@@ -461,13 +463,14 @@ function module.new_argv(...)
       end
     end
     new_args = opts.args or {}
+    io_extra = opts.io_extra
   else
     new_args = {...}
   end
   for _, arg in ipairs(new_args) do
     table.insert(args, arg)
   end
-  return args, env
+  return args, env, io_extra
 end
 
 function module.insert(...)
diff --git a/test/functional/ui/embed_spec.lua b/test/functional/ui/embed_spec.lua
index 8218c8e12d..92f5beebf5 100644
--- a/test/functional/ui/embed_spec.lua
+++ b/test/functional/ui/embed_spec.lua
@@ -1,3 +1,5 @@
+local uv = require'luv'
+
 local helpers = require('test.functional.helpers')(after_each)
 local Screen = require('test.functional.ui.screen')
 
@@ -98,3 +100,49 @@ end
 
 describe('--embed UI on startup (ext_linegrid=true)', function() test_embed(true) end)
 describe('--embed UI on startup (ext_linegrid=false)', function() test_embed(false) end)
+
+describe('--embed UI', function()
+  it('can pass stdin', function()
+    local pipe = assert(uv.pipe())
+
+    local writer = assert(uv.new_pipe(false))
+    writer:open(pipe.write)
+
+    clear {args_rm={'--headless'}, io_extra=pipe.read}
+
+    -- attach immediately after startup, for early UI
+    local screen = Screen.new(40, 8)
+    screen:attach {stdin_fd=3}
+    screen:set_default_attr_ids {
+      [1] = {bold = true, foreground = Screen.colors.Blue1};
+      [2] = {bold = true};
+    }
+
+    writer:write "hello nvim\nfrom external input\n"
+    writer:shutdown(function() writer:close() end)
+
+    screen:expect{grid=[[
+      ^hello nvim                              |
+      from external input                     |
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+                                              |
+    ]]}
+
+    -- stdin (rpc input) still works
+    feed 'o'
+    screen:expect{grid=[[
+      hello nvim                              |
+      ^                                        |
+      from external input                     |
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {1:~                                       }|
+      {2:-- INSERT --}                            |
+    ]]}
+  end)
+end)
diff --git a/third-party/cmake/BuildLuarocks.cmake b/third-party/cmake/BuildLuarocks.cmake
index 0cef37736d..244d1d9fb8 100644
--- a/third-party/cmake/BuildLuarocks.cmake
+++ b/third-party/cmake/BuildLuarocks.cmake
@@ -225,7 +225,7 @@ if(USE_BUNDLED_BUSTED)
   # nvim-client: https://github.com/neovim/lua-client
   add_custom_command(OUTPUT ${ROCKS_DIR}/nvim-client
     COMMAND ${LUAROCKS_BINARY}
-    ARGS build nvim-client 0.2.2-1 ${LUAROCKS_BUILDARGS}
+    ARGS build nvim-client 0.2.3-1 ${LUAROCKS_BUILDARGS}
     DEPENDS luv)
   add_custom_target(nvim-client DEPENDS ${ROCKS_DIR}/nvim-client)