job: Let vimL jobsend() accept a list.

Use save_tv_as_string(), same as vimL system(). This also makes
jobsend() more liberal in what it can accept. For example,
`jobsend(j, 123)` is now valid.

Closes #1176

runtime/doc/eval.txt

@@ -4014,8 +4014,15 @@ items({dict})						*items()*
 
 jobsend({job}, {data})					{Nvim} *jobsend()*
 		Send data to {job} by writing it to the stdin of the process.
+		Returns 1 if the write succeeded, 0 otherwise.
 		See |job-control| for more information.
 
+		{data} may be a string, string convertible, or a list.  If
+		{data} is a list, the items will be separated by newlines and
+		any newlines in an item will be sent as a NUL.  For example: >
+			:call jobsend(j, ["abc", "123\n456"])
+< 		will send "abc<NL>123<NUL>456<NL>".
+
 jobstart({name}, {prog}[, {argv}])			{Nvim} *jobstart()*
 		Spawns {prog} as a job and associate it with the {name} string,
 		which will be used to match the "filename pattern" in

src/nvim/eval.c

@@ -10593,9 +10593,9 @@ static void f_jobsend(typval_T *argvars, typval_T *rettv)
     return;
   }
 
-  if (argvars[0].v_type != VAR_NUMBER || argvars[1].v_type != VAR_STRING) {
+  if (argvars[0].v_type != VAR_NUMBER || argvars[1].v_type == VAR_UNKNOWN) {
-    // First argument is the job id and second is the string to write to 
+    // First argument is the job id and second is the string or list to write
-    // the job's stdin
+    // to the job's stdin
     EMSG(_(e_invarg));
     return;
   }
@@ -10608,10 +10608,15 @@ static void f_jobsend(typval_T *argvars, typval_T *rettv)
     return;
   }
 
-  WBuffer *buf = wstream_new_buffer(xstrdup((char *)argvars[1].vval.v_string),
+  ssize_t input_len;
-                                    strlen((char *)argvars[1].vval.v_string),
+  char *input = (char *) save_tv_as_string(&argvars[1], &input_len, true);
-                                    1,
+  if (input_len < 0) {
-                                    free);
+    return;  // Error handled by save_tv_as_string().
+  } else if (input_len == 0) {
+    return;  // Not an error, but nothing to do.
+  }
+
+  WBuffer *buf = wstream_new_buffer(input, input_len, 1, free);
   rettv->vval.v_number = job_write(job, buf);
 }
 
@@ -14469,7 +14474,7 @@ static void get_system_output_as_rettv(typval_T *argvars, typval_T *rettv,
 
   // get input to the shell command (if any), and its length
   ssize_t input_len;
-  char *input = (char *) save_tv_as_string(&argvars[1], &input_len);
+  char *input = (char *) save_tv_as_string(&argvars[1], &input_len, false);
   if (input_len == -1) {
     return;
   }
@@ -15158,9 +15163,10 @@ static bool write_list(FILE *fd, list_T *list, bool binary)
 ///
 /// @param[in]  tv   A value to store as a string.
 /// @param[out] len  The length of the resulting string or -1 on error.
+/// @param[in]  endnl If true, the output will end in a newline (if a list).
 /// @returns an allocated string if `tv` represents a VimL string, list, or
 ///          number; NULL otherwise.
-static char_u *save_tv_as_string(typval_T *tv, ssize_t *len)
+static char_u *save_tv_as_string(typval_T *tv, ssize_t *len, bool endnl)
   FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_ALL
 {
   if (tv->v_type == VAR_UNKNOWN) {
@@ -15192,13 +15198,13 @@ static char_u *save_tv_as_string(typval_T *tv, ssize_t *len)
     return NULL;
   }
 
-  char_u *ret = xmalloc(*len);
+  char_u *ret = xmalloc(*len + endnl);
   char_u *end = ret;
   for (listitem_T *li = list->lv_first; li != NULL; li = li->li_next) {
     for (char_u *s = get_tv_string(&li->li_tv); *s != NUL; s++) {
       *end++ = (*s == '\n') ? NUL : *s;
     }
-    if (li->li_next != NULL) {
+    if (endnl || li->li_next != NULL) {
       *end++ = '\n';
     }
   }

test/functional/job/job_spec.lua

@@ -44,11 +44,33 @@ describe('jobs', function()
     eq({'notification', 'stdout', {{'abc'}}}, next_message())
     nvim('command', 'call jobsend(j, "123\\nxyz\\n")')
     eq({'notification', 'stdout', {{'123', 'xyz'}}}, next_message())
+    nvim('command', 'call jobsend(j, [123, "xyz"])')
+    eq({'notification', 'stdout', {{'123', 'xyz'}}}, next_message())
     nvim('command', notify_str('v:job_data[1])'))
     nvim('command', "call jobstop(j)")
     eq({'notification', 'exit', {}}, next_message())
   end)
 
+  it('preserves NULs', function()
+    -- Make a file with NULs in it.
+    local filename = os.tmpname()
+    local file = io.open(filename, "w")
+    file:write("abc\0def\n")
+    file:close()
+
+    -- v:job_data preserves NULs.
+    nvim('command', notify_str('v:job_data[1]', 'v:job_data[2]'))
+    nvim('command', "let j = jobstart('xxx', 'cat', ['"..filename.."'])")
+    eq({'notification', 'stdout', {{'abc\ndef'}}}, next_message())
+    os.remove(filename)
+
+    -- jobsend() preserves NULs.
+    nvim('command', "let j = jobstart('xxx', 'cat', ['-'])")
+    nvim('command', [[call jobsend(j, ["123\n456"])]])
+    eq({'notification', 'stdout', {{'123\n456'}}}, next_message())
+    nvim('command', "call jobstop(j)")
+  end)
+
   it('will hold data if it does not end in a newline', function()
     nvim('command', notify_str('v:job_data[1]', 'v:job_data[2]'))
     nvim('command', "let j = jobstart('xxx', 'cat', ['-'])")
@@ -58,7 +80,6 @@ describe('jobs', function()
     eq({'notification', 'stdout', {{'xyz'}}}, next_message())
   end)
 
-
   it('will not allow jobsend/stop on a non-existent job', function()
     eq(false, pcall(eval, "jobsend(-1, 'lol')"))
     eq(false, pcall(eval, "jobstop(-1, 'lol')"))