refactor: move some functions out of eval.c (#29964)

- common_function() has always been in evalfunc.c in Vim
- return_register() has always been in evalfunc.c in Vim
- get_user_input() was moved to ex_getln.c in Vim 8.1.1957
- tv_get_lnum_buf() was moved to typval.c in Vim 8.2.0847

src/nvim/ex_getln.c

@@ -267,6 +267,18 @@ static void init_incsearch_state(incsearch_state_T *s)
   save_viewstate(curwin, &s->old_viewstate);
 }
 
+static void set_search_match(pos_T *t)
+{
+  // First move cursor to end of match, then to the start.  This
+  // moves the whole match onto the screen when 'nowrap' is set.
+  t->lnum += search_match_lines;
+  t->col = search_match_endcol;
+  if (t->lnum > curbuf->b_ml.ml_line_count) {
+    t->lnum = curbuf->b_ml.ml_line_count;
+    coladvance(curwin, MAXCOL);
+  }
+}
+
 // Return true when 'incsearch' highlighting is to be done.
 // Sets search_first_line and search_last_line to the address range.
 static bool do_incsearch_highlighting(int firstc, int *search_delim, incsearch_state_T *s,
@@ -4622,14 +4634,132 @@ char *script_get(exarg_T *const eap, size_t *const lenp)
   return (char *)ga.ga_data;
 }
 
-static void set_search_match(pos_T *t)
+/// This function is used by f_input() and f_inputdialog() functions. The third
+/// argument to f_input() specifies the type of completion to use at the
+/// prompt. The third argument to f_inputdialog() specifies the value to return
+/// when the user cancels the prompt.
+void get_user_input(const typval_T *const argvars, typval_T *const rettv, const bool inputdialog,
+                    const bool secret)
+  FUNC_ATTR_NONNULL_ALL
 {
-  // First move cursor to end of match, then to the start.  This
-  // moves the whole match onto the screen when 'nowrap' is set.
-  t->lnum += search_match_lines;
-  t->col = search_match_endcol;
-  if (t->lnum > curbuf->b_ml.ml_line_count) {
-    t->lnum = curbuf->b_ml.ml_line_count;
-    coladvance(curwin, MAXCOL);
+  rettv->v_type = VAR_STRING;
+  rettv->vval.v_string = NULL;
+
+  const char *prompt;
+  const char *defstr = "";
+  typval_T *cancelreturn = NULL;
+  typval_T cancelreturn_strarg2 = TV_INITIAL_VALUE;
+  const char *xp_name = NULL;
+  Callback input_callback = { .type = kCallbackNone };
+  char prompt_buf[NUMBUFLEN];
+  char defstr_buf[NUMBUFLEN];
+  char cancelreturn_buf[NUMBUFLEN];
+  char xp_name_buf[NUMBUFLEN];
+  char def[1] = { 0 };
+  if (argvars[0].v_type == VAR_DICT) {
+    if (argvars[1].v_type != VAR_UNKNOWN) {
+      emsg(_("E5050: {opts} must be the only argument"));
+      return;
+    }
+    dict_T *const dict = argvars[0].vval.v_dict;
+    prompt = tv_dict_get_string_buf_chk(dict, S_LEN("prompt"), prompt_buf, "");
+    if (prompt == NULL) {
+      return;
+    }
+    defstr = tv_dict_get_string_buf_chk(dict, S_LEN("default"), defstr_buf, "");
+    if (defstr == NULL) {
+      return;
+    }
+    dictitem_T *cancelreturn_di = tv_dict_find(dict, S_LEN("cancelreturn"));
+    if (cancelreturn_di != NULL) {
+      cancelreturn = &cancelreturn_di->di_tv;
+    }
+    xp_name = tv_dict_get_string_buf_chk(dict, S_LEN("completion"),
+                                         xp_name_buf, def);
+    if (xp_name == NULL) {  // error
+      return;
+    }
+    if (xp_name == def) {  // default to NULL
+      xp_name = NULL;
+    }
+    if (!tv_dict_get_callback(dict, S_LEN("highlight"), &input_callback)) {
+      return;
+    }
+  } else {
+    prompt = tv_get_string_buf_chk(&argvars[0], prompt_buf);
+    if (prompt == NULL) {
+      return;
+    }
+    if (argvars[1].v_type != VAR_UNKNOWN) {
+      defstr = tv_get_string_buf_chk(&argvars[1], defstr_buf);
+      if (defstr == NULL) {
+        return;
+      }
+      if (argvars[2].v_type != VAR_UNKNOWN) {
+        const char *const strarg2 = tv_get_string_buf_chk(&argvars[2], cancelreturn_buf);
+        if (strarg2 == NULL) {
+          return;
+        }
+        if (inputdialog) {
+          cancelreturn_strarg2.v_type = VAR_STRING;
+          cancelreturn_strarg2.vval.v_string = (char *)strarg2;
+          cancelreturn = &cancelreturn_strarg2;
+        } else {
+          xp_name = strarg2;
+        }
+      }
+    }
   }
+
+  int xp_type = EXPAND_NOTHING;
+  char *xp_arg = NULL;
+  if (xp_name != NULL) {
+    // input() with a third argument: completion
+    const int xp_namelen = (int)strlen(xp_name);
+
+    uint32_t argt = 0;
+    if (parse_compl_arg(xp_name, xp_namelen, &xp_type,
+                        &argt, &xp_arg) == FAIL) {
+      return;
+    }
+  }
+
+  const bool cmd_silent_save = cmd_silent;
+
+  cmd_silent = false;  // Want to see the prompt.
+  // Only the part of the message after the last NL is considered as
+  // prompt for the command line, unlsess cmdline is externalized
+  const char *p = prompt;
+  if (!ui_has(kUICmdline)) {
+    const char *lastnl = strrchr(prompt, '\n');
+    if (lastnl != NULL) {
+      p = lastnl + 1;
+      msg_start();
+      msg_clr_eos();
+      msg_puts_len(prompt, p - prompt, get_echo_attr());
+      msg_didout = false;
+      msg_starthere();
+    }
+  }
+  cmdline_row = msg_row;
+
+  stuffReadbuffSpec(defstr);
+
+  const int save_ex_normal_busy = ex_normal_busy;
+  ex_normal_busy = 0;
+  rettv->vval.v_string = getcmdline_prompt(secret ? NUL : '@', p, get_echo_attr(),
+                                           xp_type, xp_arg, input_callback);
+  ex_normal_busy = save_ex_normal_busy;
+  callback_free(&input_callback);
+
+  if (rettv->vval.v_string == NULL && cancelreturn != NULL) {
+    tv_copy(cancelreturn, rettv);
+  }
+
+  xfree(xp_arg);
+
+  // Since the user typed this, no need to wait for return.
+  need_wait_return = false;
+  msg_didout = false;
+  cmd_silent = cmd_silent_save;
 }