refactor(ui): simplify stdin handling

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");
 

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;
-}

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) {

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

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();
   }