startup: treat stdin as input instead of commands

Treat stdin as input by default (so the "-" file is not needed):
    echo foo | nvim

It works even if file args are given:
    echo foo | nvim file1.txt file2.txt

When you want to execute commands, use `-s -` instead:
    echo ifoo | nvim -s -

Why? Because:
- Execution of input is (1) almost always unintentional/confusing,
  and (2) potentially destructive.
- Avoids the need for time-delayed warning.  #7659
- The *common* case is to open text in a buffer, not send commands.

Other alternatives for executing commands:
  - Replay a register. E.g. the following mostly works, except @q aborts
    on any "beep" (e.g. if the cursor can't move).
    nvim -c '%d q|norm @q' -
  - Future: Let `:%source` work with unsaved buffer contents?

closes #2087
closes #7659

src/nvim/main.c

@@ -281,12 +281,6 @@ int main(int argc, char **argv)
 
   full_screen = true;
 
-  // When starting in Ex mode and commands come from a file, set Silent mode.
-  // is active input a terminal?
-  if (!headless_mode && exmode_active && !params.input_isatty) {
-    silent_mode = true;
-  }
-
   /*
    * Set the default values for the options that use Rows and Columns.
    */
@@ -1097,7 +1091,7 @@ static void command_line_scan(mparm_T *parmp)
               mch_exit(2);
             }
             int error;
-            if (STRCMP(argv[0], "-") == 0) {
+            if (strequal(argv[0], "-")) {
               const int stdin_dup_fd = os_dup(STDIN_FILENO);
 #ifdef WIN32
               // On Windows, replace the original stdin with the
@@ -1212,6 +1206,21 @@ static void command_line_scan(mparm_T *parmp)
     set_vim_var_string(VV_SWAPCOMMAND, swcmd, -1);
     xfree(swcmd);
   }
+
+  // Handle "foo | nvim". #6299
+  if (!headless_mode
+      && !embedded_mode
+      && !parmp->input_isatty
+      && !exmode_active       // `-es` was not given.
+      && scriptin[0] == NULL  // `-s -` was not given.
+      ) {
+    if (parmp->edit_type == EDIT_NONE || parmp->edit_type == EDIT_FILE) {
+      parmp->edit_type = EDIT_STDIN;
+    } else if (parmp->edit_type != EDIT_STDIN) {
+      mainerr(err_too_many_args, "stdin");
+    }
+  }
+
   TIME_MSG("parsing arguments");
 }
 
@@ -1407,6 +1416,10 @@ static void read_stdin(void)
   no_wait_return = TRUE;
   i = msg_didany;
   set_buflisted(TRUE);
+  if (buf_valid(curbuf)) {  // Files were loaded; create new buffer for stdin.
+    do_cmdline_cmd(":enew");
+  }
+
   (void)open_buffer(TRUE, NULL, 0);     /* create memfile and read file */
   no_wait_return = FALSE;
   msg_didany = i;
@@ -1886,7 +1899,6 @@ static void usage(void)
 
   mch_msg(_("Usage:\n"));
   mch_msg(_("  nvim [options] [file ...]      Edit file(s)\n"));
-  mch_msg(_("  nvim [options] -               Read text from stdin\n"));
   mch_msg(_("  nvim [options] -t <tag>        Edit file where tag is defined\n"));
   mch_msg(_("  nvim [options] -q [errorfile]  Edit file with first error\n"));
   mch_msg(_("\nOptions:\n"));
@@ -1920,7 +1932,7 @@ static void usage(void)
   mch_msg(_("  --api-info            Write msgpack-encoded API metadata to stdout\n"));
   mch_msg(_("  --embed               Use stdin/stdout as a msgpack-rpc channel\n"));
   mch_msg(_("  --headless            Don't start a user interface\n"));
-  mch_msg(_("  --listen <address>    Start RPC server at this address\n"));
+  mch_msg(_("  --listen <address>    Serve RPC API from this address\n"));
 #if !defined(UNIX)
   mch_msg(_("  --literal             Don't expand wildcards\n"));
 #endif

test/functional/core/startup_spec.lua

@@ -9,11 +9,13 @@ local nvim_prog = helpers.nvim_prog
 local nvim_set = helpers.nvim_set
 local read_file = helpers.read_file
 local retry = helpers.retry
+local sleep = helpers.sleep
 local iswin = helpers.iswin
 
 describe('startup', function()
   before_each(function()
     clear()
+    os.remove('Xtest_startup_ttyout')
   end)
   after_each(function()
     os.remove('Xtest_startup_ttyout')
@@ -46,8 +48,8 @@ describe('startup', function()
     end
     -- Running in :terminal
     command([[exe printf("terminal %s -u NONE -i NONE --cmd \"]]
-            ..nvim_set..[[\" ]]
-            ..[[-c \"echo has('ttyin') has('ttyout')\""]]
+            ..nvim_set..[[\"]]
+            ..[[ -c \"echo has('ttyin') has('ttyout')\""]]
             ..[[, shellescape(v:progpath))]])
     screen:expect([[
       ^                         |
@@ -56,41 +58,74 @@ describe('startup', function()
     ]])
   end)
   it('output to pipe: has("ttyin")==1 has("ttyout")==0', function()
-    local screen = Screen.new(25, 5)
-    screen:attach()
     if iswin() then
       command([[set shellcmdflag=/s\ /c shellxquote=\"]])
     end
     -- Running in :terminal
     command([[exe printf("terminal %s -u NONE -i NONE --cmd \"]]
-            ..nvim_set..[[\" ]]
-            ..[[-c \"call writefile([has('ttyin'), has('ttyout')], 'Xtest_startup_ttyout')\"]]
-            ..[[-c q | cat -v"]]  -- Output to a pipe.
+            ..nvim_set..[[\"]]
+            ..[[ -c \"call writefile([has('ttyin'), has('ttyout')], 'Xtest_startup_ttyout')\"]]
+            ..[[ -c q | cat -v"]]  -- Output to a pipe.
             ..[[, shellescape(v:progpath))]])
     retry(nil, 3000, function()
-      screen:sleep(1)
+      sleep(1)
       eq('1\n0\n',  -- stdin is a TTY, stdout is a pipe
          read_file('Xtest_startup_ttyout'))
     end)
   end)
   it('input from pipe: has("ttyin")==0 has("ttyout")==1', function()
-    local screen = Screen.new(25, 5)
-    screen:attach()
     if iswin() then
       command([[set shellcmdflag=/s\ /c shellxquote=\"]])
     end
     -- Running in :terminal
     command([[exe printf("terminal echo foo | ]]  -- Input from a pipe.
             ..[[%s -u NONE -i NONE --cmd \"]]
-            ..nvim_set..[[\" ]]
-            ..[[-c \"call writefile([has('ttyin'), has('ttyout')], 'Xtest_startup_ttyout')\"]]
-            ..[[-c q -- -"]]
+            ..nvim_set..[[\"]]
+            ..[[ -c \"call writefile([has('ttyin'), has('ttyout')], 'Xtest_startup_ttyout')\"]]
+            ..[[ -c q -- -"]]
             ..[[, shellescape(v:progpath))]])
     retry(nil, 3000, function()
-      screen:sleep(1)
+      sleep(1)
       eq('0\n1\n',  -- stdin is a pipe, stdout is a TTY
          read_file('Xtest_startup_ttyout'))
     end)
   end)
+  it('input from pipe (implicit) #7679', function()
+    local screen = Screen.new(25, 3)
+    screen:attach()
+    if iswin() then
+      command([[set shellcmdflag=/s\ /c shellxquote=\"]])
+    end
+    -- Running in :terminal
+    command([[exe printf("terminal echo foo | ]]  -- Input from a pipe.
+            ..[[%s -u NONE -i NONE --cmd \"]]
+            ..nvim_set..[[\"]]
+            ..[[ -c \"echo has('ttyin') has('ttyout')\""]]
+            ..[[, shellescape(v:progpath))]])
+    screen:expect([[
+      ^foo                      |
+      0 1                      |
+                               |
+    ]])
+  end)
+  it('input from pipe (implicit) + file args #7679', function()
+    local screen = Screen.new(25, 3)
+    screen:attach()
+    if iswin() then
+      command([[set shellcmdflag=/s\ /c shellxquote=\"]])
+    end
+    command([[exe "terminal echo ohyeah | "]]  -- Input from a pipe.
+            ..[[.shellescape(v:progpath)." -u NONE -i NONE --cmd \"]]
+            ..nvim_set..[[\"]]
+            ..[[ -c \"echo has('ttyin') has('ttyout') 'bufs='.bufnr('$')\"]]
+            ..[[ -- test/functional/fixtures/shell-test.c]]
+            ..[[    test/functional/fixtures/tty-test.c]]
+            ..[["]])
+    screen:expect([[
+      ^ohyeah                   |
+      0 1 bufs=3               |
+                               |
+    ]])
+  end)
 end)