feat(lua): add vim.spell (#16620)

src/nvim/lua/spell.c

@@ -0,0 +1,99 @@
+
+#include <lua.h>
+#include <lauxlib.h>
+
+#include "nvim/spell.h"
+#include "nvim/vim.h"
+#include "nvim/lua/spell.h"
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "lua/spell.c.generated.h"
+#endif
+
+int nlua_spell_check(lua_State *lstate)
+{
+  if (lua_gettop(lstate) < 1) {
+    return luaL_error(lstate, "Expected 1 argument");
+  }
+
+  if (lua_type(lstate, 1) != LUA_TSTRING) {
+    luaL_argerror(lstate, 1, "expected string");
+  }
+
+  const char *str = lua_tolstring(lstate, 1, NULL);
+
+  // spell.c requires that 'spell' is enabled, so we need to temporarily enable
+  // it before we can call spell functions.
+  const int wo_spell_save = curwin->w_p_spell;
+
+  if (!curwin->w_p_spell) {
+    did_set_spelllang(curwin);
+    curwin->w_p_spell = true;
+  }
+
+  // Check 'spelllang'
+  if (*curwin->w_s->b_p_spl == NUL) {
+    emsg(_(e_no_spell));
+    curwin->w_p_spell = wo_spell_save;
+    return 0;
+  }
+
+  hlf_T attr = HLF_COUNT;
+  size_t len = 0;
+  size_t pos = 0;
+  int capcol = -1;
+  int no_res = 0;
+  const char * result;
+
+  lua_createtable(lstate, 0, 0);
+
+  while (*str != NUL) {
+    attr = HLF_COUNT;
+    len = spell_check(curwin, (char_u *)str, &attr, &capcol, false);
+    assert(len <= INT_MAX);
+
+    if (attr != HLF_COUNT) {
+      lua_createtable(lstate, 3, 0);
+
+      lua_pushlstring(lstate, str, len);
+      lua_rawseti(lstate, -2, 1);
+
+      result = attr == HLF_SPB ? "bad"   :
+               attr == HLF_SPR ? "rare"  :
+               attr == HLF_SPL ? "local" :
+               attr == HLF_SPC ? "caps"  :
+               NULL;
+
+      assert(result != NULL);
+
+      lua_pushstring(lstate, result);
+      lua_rawseti(lstate, -2, 2);
+
+      // +1 for 1-indexing
+      lua_pushinteger(lstate, (long)pos + 1);
+      lua_rawseti(lstate, -2, 3);
+
+      lua_rawseti(lstate, -2, ++no_res);
+    }
+
+    str += len;
+    pos += len;
+    capcol -= (int)len;
+  }
+
+  // Restore 'spell'
+  curwin->w_p_spell = wo_spell_save;
+  return 1;
+}
+
+static const luaL_Reg spell_functions[] = {
+  { "check", nlua_spell_check },
+  { NULL   , NULL }
+};
+
+int luaopen_spell(lua_State *L)
+{
+  lua_newtable(L);
+  luaL_register(L, NULL, spell_functions);
+  return 1;
+}

src/nvim/lua/spell.h

@@ -0,0 +1,12 @@
+#ifndef NVIM_LUA_SPELL_H
+#define NVIM_LUA_SPELL_H
+
+#include <lauxlib.h>
+#include <lua.h>
+#include <lualib.h>
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "lua/spell.h.generated.h"
+#endif
+
+#endif  // NVIM_LUA_SPELL_H

src/nvim/lua/stdlib.c

@@ -30,6 +30,7 @@
 #include "nvim/lua/stdlib.h"
 #include "nvim/lua/treesitter.h"
 #include "nvim/lua/xdiff.h"
+#include "nvim/lua/spell.h"
 #include "nvim/macros.h"
 #include "nvim/map.h"
 #include "nvim/memline.h"
@@ -518,6 +519,10 @@ void nlua_state_add_stdlib(lua_State *const lstate)
   lua_pushcfunction(lstate, &nlua_xdl_diff);
   lua_setfield(lstate, -2, "diff");
 
+  // vim.spell
+  luaopen_spell(lstate);
+  lua_setfield(lstate, -2, "spell");
+
   lua_cjson_new(lstate);
   lua_setfield(lstate, -2, "json");
 }