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.

1 files changed, 19 insertions, 38 deletions

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)