refactor(api): refactor more api functions to use arena return

Currently having two separate memory strategies for API return values is
a bit unnecessary, and mostly a consequence of converting the hot spot
cases which needed it first. But there is really no downside to using
arena everywhere (which implies also directly using strings which are
allocated earlier or even statically, without copy).

There only restriction is we need to know the size of arrays in advance,
but this info can often be passed on from some earlier stage if it is
missing.

This collects some "small" cases. The more complex stuff will get a PR
each.

8 files changed, 84 insertions, 98 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 7af2b7241c..751fc1c32d 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -1262,28 +1262,27 @@ Object nvim_buf_call(Buffer buffer, LuaRef fun, Error *err)
   return res;
 }
 
-Dictionary nvim__buf_stats(Buffer buffer, Error *err)
+Dictionary nvim__buf_stats(Buffer buffer, Arena *arena, Error *err)
 {
-  Dictionary rv = ARRAY_DICT_INIT;
-
   buf_T *buf = find_buffer_by_handle(buffer, err);
   if (!buf) {
-    return rv;
+    return (Dictionary)ARRAY_DICT_INIT;
   }
 
+  Dictionary rv = arena_dict(arena, 7);
   // Number of times the cached line was flushed.
   // This should generally not increase while editing the same
   // line in the same mode.
-  PUT(rv, "flush_count", INTEGER_OBJ(buf->flush_count));
+  PUT_C(rv, "flush_count", INTEGER_OBJ(buf->flush_count));
   // lnum of current line
-  PUT(rv, "current_lnum", INTEGER_OBJ(buf->b_ml.ml_line_lnum));
+  PUT_C(rv, "current_lnum", INTEGER_OBJ(buf->b_ml.ml_line_lnum));
   // whether the line has unflushed changes.
-  PUT(rv, "line_dirty", BOOLEAN_OBJ(buf->b_ml.ml_flags & ML_LINE_DIRTY));
+  PUT_C(rv, "line_dirty", BOOLEAN_OBJ(buf->b_ml.ml_flags & ML_LINE_DIRTY));
   // NB: this should be zero at any time API functions are called,
   // this exists to debug issues
-  PUT(rv, "dirty_bytes", INTEGER_OBJ((Integer)buf->deleted_bytes));
-  PUT(rv, "dirty_bytes2", INTEGER_OBJ((Integer)buf->deleted_bytes2));
-  PUT(rv, "virt_blocks", INTEGER_OBJ((Integer)buf_meta_total(buf, kMTMetaLines)));
+  PUT_C(rv, "dirty_bytes", INTEGER_OBJ((Integer)buf->deleted_bytes));
+  PUT_C(rv, "dirty_bytes2", INTEGER_OBJ((Integer)buf->deleted_bytes2));
+  PUT_C(rv, "virt_blocks", INTEGER_OBJ((Integer)buf_meta_total(buf, kMTMetaLines)));
 
   u_header_T *uhp = NULL;
   if (buf->b_u_curhead != NULL) {
@@ -1292,7 +1291,7 @@ Dictionary nvim__buf_stats(Buffer buffer, Error *err)
     uhp = buf->b_u_newhead;
   }
   if (uhp) {
-    PUT(rv, "uhp_extmark_size", INTEGER_OBJ((Integer)kv_size(uhp->uh_extmark)));
+    PUT_C(rv, "uhp_extmark_size", INTEGER_OBJ((Integer)kv_size(uhp->uh_extmark)));
   }
 
   return rv;
diff --git a/src/nvim/api/extmark.c b/src/nvim/api/extmark.c
index 0948abf065..94f6059014 100644
--- a/src/nvim/api/extmark.c
+++ b/src/nvim/api/extmark.c
@@ -70,15 +70,15 @@ Integer nvim_create_namespace(String name)
 /// Gets existing, non-anonymous |namespace|s.
 ///
 /// @return dict that maps from names to namespace ids.
-Dictionary nvim_get_namespaces(void)
+Dictionary nvim_get_namespaces(Arena *arena)
   FUNC_API_SINCE(5)
 {
-  Dictionary retval = ARRAY_DICT_INIT;
+  Dictionary retval = arena_dict(arena, map_size(&namespace_ids));
   String name;
   handle_T id;
 
   map_foreach(&namespace_ids, name, id, {
-    PUT(retval, name.data, INTEGER_OBJ(id));
+    PUT_C(retval, name.data, INTEGER_OBJ(id));
   })
 
   return retval;
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index b1bfdd79e7..1453de30d4 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -1351,14 +1351,13 @@ Integer nvim_get_color_by_name(String name)
 /// (e.g. 65535).
 ///
 /// @return Map of color names and RGB values.
-Dictionary nvim_get_color_map(void)
+Dictionary nvim_get_color_map(Arena *arena)
   FUNC_API_SINCE(1)
 {
-  Dictionary colors = ARRAY_DICT_INIT;
+  Dictionary colors = arena_dict(arena, ARRAY_SIZE(color_name_table));
 
   for (int i = 0; color_name_table[i].name != NULL; i++) {
-    PUT(colors, color_name_table[i].name,
-        INTEGER_OBJ(color_name_table[i].color));
+    PUT_C(colors, color_name_table[i].name, INTEGER_OBJ(color_name_table[i].color));
   }
   return colors;
 }
@@ -1438,16 +1437,16 @@ Object nvim_load_context(Dictionary dict, Error *err)
 /// "blocking" is true if Nvim is waiting for input.
 ///
 /// @returns Dictionary { "mode": String, "blocking": Boolean }
-Dictionary nvim_get_mode(void)
+Dictionary nvim_get_mode(Arena *arena)
   FUNC_API_SINCE(2) FUNC_API_FAST
 {
-  Dictionary rv = ARRAY_DICT_INIT;
-  char modestr[MODE_MAX_LENGTH];
+  Dictionary rv = arena_dict(arena, 2);
+  char *modestr = arena_alloc(arena, MODE_MAX_LENGTH, false);
   get_mode(modestr);
   bool blocked = input_blocking();
 
-  PUT(rv, "mode", CSTR_TO_OBJ(modestr));
-  PUT(rv, "blocking", BOOLEAN_OBJ(blocked));
+  PUT_C(rv, "mode", CSTR_AS_OBJ(modestr));
+  PUT_C(rv, "blocking", BOOLEAN_OBJ(blocked));
 
   return rv;
 }
@@ -1848,14 +1847,14 @@ Float nvim__id_float(Float flt)
 /// Gets internal stats.
 ///
 /// @return Map of various internal stats.
-Dictionary nvim__stats(void)
-{
-  Dictionary rv = ARRAY_DICT_INIT;
-  PUT(rv, "fsync", INTEGER_OBJ(g_stats.fsync));
-  PUT(rv, "log_skip", INTEGER_OBJ(g_stats.log_skip));
-  PUT(rv, "lua_refcount", INTEGER_OBJ(nlua_get_global_ref_count()));
-  PUT(rv, "redraw", INTEGER_OBJ(g_stats.redraw));
-  PUT(rv, "arena_alloc_count", INTEGER_OBJ((Integer)arena_alloc_count));
+Dictionary nvim__stats(Arena *arena)
+{
+  Dictionary rv = arena_dict(arena, 5);
+  PUT_C(rv, "fsync", INTEGER_OBJ(g_stats.fsync));
+  PUT_C(rv, "log_skip", INTEGER_OBJ(g_stats.log_skip));
+  PUT_C(rv, "lua_refcount", INTEGER_OBJ(nlua_get_global_ref_count()));
+  PUT_C(rv, "redraw", INTEGER_OBJ(g_stats.redraw));
+  PUT_C(rv, "arena_alloc_count", INTEGER_OBJ((Integer)arena_alloc_count));
   return rv;
 }
 
@@ -2151,7 +2150,7 @@ Array nvim_get_mark(String name, Dict(empty) *opts, Error *err)
 ///                     |Dictionary| with these keys:
 ///           - start: (number) Byte index (0-based) of first character that uses the highlight.
 ///           - group: (string) Name of highlight group.
-Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *err)
+Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Arena *arena, Error *err)
   FUNC_API_SINCE(8) FUNC_API_FAST
 {
   Dictionary result = ARRAY_DICT_INIT;
@@ -2260,58 +2259,61 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
                                      && global_stl_height() > 0)) ? Columns : wp->w_width;
   }
 
-  char buf[MAXPATHL];
+  result = arena_dict(arena, 3);
+  char *buf = arena_alloc(arena, MAXPATHL, false);
   stl_hlrec_t *hltab;
+  size_t hltab_len = 0;
 
   // Temporarily reset 'cursorbind' to prevent side effects from moving the cursor away and back.
   int p_crb_save = wp->w_p_crb;
   wp->w_p_crb = false;
 
-  int width = build_stl_str_hl(wp, buf, sizeof(buf), str.data, -1, 0, fillchar, maxwidth,
-                               opts->highlights ? &hltab : NULL, NULL,
+  int width = build_stl_str_hl(wp, buf, MAXPATHL, str.data, -1, 0, fillchar, maxwidth,
+                               opts->highlights ? &hltab : NULL, &hltab_len, NULL,
                                statuscol_lnum ? &statuscol : NULL);
 
-  PUT(result, "width", INTEGER_OBJ(width));
+  PUT_C(result, "width", INTEGER_OBJ(width));
 
   // Restore original value of 'cursorbind'
   wp->w_p_crb = p_crb_save;
 
   if (opts->highlights) {
-    Array hl_values = ARRAY_DICT_INIT;
-    const char *grpname;
+    Array hl_values = arena_array(arena, hltab_len + 1);
     char user_group[15];  // strlen("User") + strlen("2147483647") + NUL
 
     // If first character doesn't have a defined highlight,
     // add the default highlight at the beginning of the highlight list
     if (hltab->start == NULL || (hltab->start - buf) != 0) {
-      Dictionary hl_info = ARRAY_DICT_INIT;
-      grpname = get_default_stl_hl(opts->use_tabline ? NULL : wp, opts->use_winbar, stc_hl_id);
+      Dictionary hl_info = arena_dict(arena, 2);
+      const char *grpname = get_default_stl_hl(opts->use_tabline ? NULL : wp,
+                                               opts->use_winbar, stc_hl_id);
 
-      PUT(hl_info, "start", INTEGER_OBJ(0));
-      PUT(hl_info, "group", CSTR_TO_OBJ(grpname));
+      PUT_C(hl_info, "start", INTEGER_OBJ(0));
+      PUT_C(hl_info, "group", CSTR_AS_OBJ((char *)grpname));
 
-      ADD(hl_values, DICTIONARY_OBJ(hl_info));
+      ADD_C(hl_values, DICTIONARY_OBJ(hl_info));
     }
 
     for (stl_hlrec_t *sp = hltab; sp->start != NULL; sp++) {
-      Dictionary hl_info = ARRAY_DICT_INIT;
+      Dictionary hl_info = arena_dict(arena, 2);
 
-      PUT(hl_info, "start", INTEGER_OBJ(sp->start - buf));
+      PUT_C(hl_info, "start", INTEGER_OBJ(sp->start - buf));
 
+      const char *grpname;
       if (sp->userhl == 0) {
         grpname = get_default_stl_hl(opts->use_tabline ? NULL : wp, opts->use_winbar, stc_hl_id);
       } else if (sp->userhl < 0) {
         grpname = syn_id2name(-sp->userhl);
       } else {
         snprintf(user_group, sizeof(user_group), "User%d", sp->userhl);
-        grpname = user_group;
+        grpname = arena_memdupz(arena, user_group, strlen(user_group));
       }
-      PUT(hl_info, "group", CSTR_TO_OBJ(grpname));
-      ADD(hl_values, DICTIONARY_OBJ(hl_info));
+      PUT_C(hl_info, "group", CSTR_AS_OBJ((char *)grpname));
+      ADD_C(hl_values, DICTIONARY_OBJ(hl_info));
     }
-    PUT(result, "highlights", ARRAY_OBJ(hl_values));
+    PUT_C(result, "highlights", ARRAY_OBJ(hl_values));
   }
-  PUT(result, "str", CSTR_TO_OBJ(buf));
+  PUT_C(result, "str", CSTR_AS_OBJ(buf));
 
   return result;
 }
@@ -2336,15 +2338,15 @@ void nvim_error_event(uint64_t channel_id, Integer lvl, String data)
 /// @return Dictionary containing these keys:
 ///       - winid: (number) floating window id
 ///       - bufnr: (number) buffer id in floating window
-Dictionary nvim_complete_set(Integer index, Dict(complete_set) *opts)
+Dictionary nvim_complete_set(Integer index, Dict(complete_set) *opts, Arena *arena)
   FUNC_API_SINCE(12)
 {
-  Dictionary rv = ARRAY_DICT_INIT;
+  Dictionary rv = arena_dict(arena, 2);
   if (HAS_KEY(opts, complete_set, info)) {
     win_T *wp = pum_set_info((int)index, opts->info.data);
     if (wp) {
-      PUT(rv, "winid", WINDOW_OBJ(wp->handle));
-      PUT(rv, "bufnr", BUFFER_OBJ(wp->w_buffer->handle));
+      PUT_C(rv, "winid", WINDOW_OBJ(wp->handle));
+      PUT_C(rv, "bufnr", BUFFER_OBJ(wp->w_buffer->handle));
     }
   }
   return rv;
diff --git a/src/nvim/buffer.c b/src/nvim/buffer.c
index 00cb7272c0..7c0d415099 100644
--- a/src/nvim/buffer.c
+++ b/src/nvim/buffer.c
@@ -3326,7 +3326,7 @@ void maketitle(void)
     if (*p_titlestring != NUL) {
       if (stl_syntax & STL_IN_TITLE) {
         build_stl_str_hl(curwin, buf, sizeof(buf), p_titlestring,
-                         kOptTitlestring, 0, 0, maxlen, NULL, NULL, NULL);
+                         kOptTitlestring, 0, 0, maxlen, NULL, NULL, NULL, NULL);
         title_str = buf;
       } else {
         title_str = p_titlestring;
@@ -3431,7 +3431,7 @@ void maketitle(void)
     if (*p_iconstring != NUL) {
       if (stl_syntax & STL_IN_ICON) {
         build_stl_str_hl(curwin, icon_str, sizeof(buf), p_iconstring,
-                         kOptIconstring, 0, 0, 0, NULL, NULL, NULL);
+                         kOptIconstring, 0, 0, 0, NULL, NULL, NULL, NULL);
       } else {
         icon_str = p_iconstring;
       }
diff --git a/src/nvim/generators/gen_api_dispatch.lua b/src/nvim/generators/gen_api_dispatch.lua
index 14b4ecb1a3..da3010878d 100644
--- a/src/nvim/generators/gen_api_dispatch.lua
+++ b/src/nvim/generators/gen_api_dispatch.lua
@@ -535,7 +535,6 @@ for i = 1, #functions do
     end
 
     -- function call
-    local call_args = table.concat(args, ', ')
     output:write('\n  ')
     if fn.return_type ~= 'void' then
       -- has a return value, prefix the call with a declaration
@@ -545,58 +544,40 @@ for i = 1, #functions do
     -- write the function name and the opening parenthesis
     output:write(fn.name .. '(')
 
+    local call_args = {}
     if fn.receives_channel_id then
-      -- if the function receives the channel id, pass it as first argument
-      if #args > 0 or fn.can_fail then
-        output:write('channel_id, ')
-        if fn.receives_array_args then
-          -- if the function receives the array args, pass it the second argument
-          output:write('args, ')
-        end
-        output:write(call_args)
-      else
-        output:write('channel_id')
-        if fn.receives_array_args then
-          output:write(', args')
-        end
-      end
-    else
-      if fn.receives_array_args then
-        if #args > 0 or fn.call_fail then
-          output:write('args, ' .. call_args)
-        else
-          output:write('args')
-        end
-      else
-        output:write(call_args)
-      end
+      table.insert(call_args, 'channel_id')
+    end
+
+    if fn.receives_array_args then
+      table.insert(call_args, 'args')
+    end
+
+    for _, a in ipairs(args) do
+      table.insert(call_args, a)
     end
 
     if fn.arena_return then
-      output:write(', arena')
+      table.insert(call_args, 'arena')
     end
 
     if fn.has_lua_imp then
-      if #args > 0 then
-        output:write(', NULL')
-      else
-        output:write('NULL')
-      end
+      table.insert(call_args, 'NULL')
     end
 
     if fn.can_fail then
+      table.insert(call_args, 'error')
+    end
+
+    output:write(table.concat(call_args, ', '))
+    output:write(');\n')
+
+    if fn.can_fail then
       -- if the function can fail, also pass a pointer to the local error object
-      if #args > 0 then
-        output:write(', error);\n')
-      else
-        output:write('error);\n')
-      end
       -- and check for the error
       output:write('\n  if (ERROR_SET(error)) {')
       output:write('\n    goto cleanup;')
       output:write('\n  }\n')
-    else
-      output:write(');\n')
     end
 
     local ret_type = real_type(fn.return_type)
diff --git a/src/nvim/highlight_group.h b/src/nvim/highlight_group.h
index 8a4eb83827..47d58d20f2 100644
--- a/src/nvim/highlight_group.h
+++ b/src/nvim/highlight_group.h
@@ -12,7 +12,7 @@ typedef struct {
   char *name;
   RgbValue color;
 } color_name_table_T;
-extern color_name_table_T color_name_table[];
+extern color_name_table_T color_name_table[700];
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "highlight_group.h.generated.h"
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 7ed840c2f9..0a716067c6 100644
--- a/src/nvim/statusline.c
+++ b/src/nvim/statusline.c
@@ -411,7 +411,7 @@ static void win_redr_custom(win_T *wp, bool draw_winbar, bool draw_ruler)
   // might change the option value and free the memory.
   stl = xstrdup(stl);
   build_stl_str_hl(ewp, buf, sizeof(buf), stl, opt_idx, opt_scope,
-                   fillchar, maxwidth, &hltab, &tabtab, NULL);
+                   fillchar, maxwidth, &hltab, NULL, &tabtab, NULL);
 
   xfree(stl);
   ewp->w_p_crb = p_crb_save;
@@ -880,7 +880,7 @@ int build_statuscol_str(win_T *wp, linenr_T lnum, linenr_T relnum, char *buf, st
   StlClickRecord *clickrec;
   char *stc = xstrdup(wp->w_p_stc);
   int width = build_stl_str_hl(wp, buf, MAXPATHL, stc, kOptStatuscolumn, OPT_LOCAL, 0,
-                               stcp->width, &stcp->hlrec, fillclick ? &clickrec : NULL, stcp);
+                               stcp->width, &stcp->hlrec, NULL, fillclick ? &clickrec : NULL, stcp);
   xfree(stc);
 
   if (fillclick) {
@@ -922,7 +922,7 @@ int build_statuscol_str(win_T *wp, linenr_T lnum, linenr_T relnum, char *buf, st
 /// @return  The final width of the statusline
 int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, OptIndex opt_idx,
                      int opt_scope, schar_T fillchar, int maxwidth, stl_hlrec_t **hltab,
-                     StlClickRecord **tabtab, statuscol_T *stcp)
+                     size_t *hltab_len, StlClickRecord **tabtab, statuscol_T *stcp)
 {
   static size_t stl_items_len = 20;  // Initial value, grows as needed.
   static stl_item_t *stl_items = NULL;
@@ -2132,6 +2132,9 @@ int build_stl_str_hl(win_T *wp, char *out, size_t outlen, char *fmt, OptIndex op
     sp->start = NULL;
     sp->userhl = 0;
   }
+  if (hltab_len) {
+    *hltab_len = (size_t)itemcnt;
+  }
 
   // Store the info about tab pages labels.
   if (tabtab != NULL) {
diff --git a/test/unit/statusline_spec.lua b/test/unit/statusline_spec.lua
index f1294e6b5a..83ba4176c5 100644
--- a/test/unit/statusline_spec.lua
+++ b/test/unit/statusline_spec.lua
@@ -43,6 +43,7 @@ describe('build_stl_str_hl', function()
       maximum_cell_count,
       NULL,
       NULL,
+      NULL,
       NULL
     )
   end