feat(lua): print source locations of lua callbacks (#19597)

Co-authored-by: ii14 <ii14@users.noreply.github.com>

src/nvim/api/command.c

@@ -944,7 +944,7 @@ void create_user_command(String name, Object command, Dict(user_command) *opts,
   cmd_addr_T addr_type_arg = ADDR_NONE;
   int compl = EXPAND_NOTHING;
   char *compl_arg = NULL;
-  char *rep = NULL;
+  const char *rep = NULL;
   LuaRef luaref = LUA_NOREF;
   LuaRef compl_luaref = LUA_NOREF;
   LuaRef preview_luaref = LUA_NOREF;
@@ -1116,8 +1116,7 @@ void create_user_command(String name, Object command, Dict(user_command) *opts,
     if (opts->desc.type == kObjectTypeString) {
       rep = opts->desc.data.string.data;
     } else {
-      snprintf((char *)IObuff, IOSIZE, "<Lua function %d>", luaref);
-      rep = (char *)IObuff;
+      rep = "";
     }
     break;
   case kObjectTypeString:

src/nvim/autocmd.c

@@ -196,9 +196,16 @@ static void aupat_show(AutoPat *ap, event_T event, int previous_group)
     if (ac->desc != NULL) {
       size_t msglen = 100;
       char *msg = (char *)xmallocz(msglen);
-      snprintf(msg, msglen, "%s [%s]", exec_to_string, ac->desc);
+      if (ac->exec.type == CALLABLE_CB) {
+        msg_puts_attr(exec_to_string, HL_ATTR(HLF_8));
+        snprintf(msg, msglen, " [%s]", ac->desc);
+      } else {
+        snprintf(msg, msglen, "%s [%s]", exec_to_string, ac->desc);
+      }
       msg_outtrans(msg);
       XFREE_CLEAR(msg);
+    } else if (ac->exec.type == CALLABLE_CB) {
+      msg_puts_attr(exec_to_string, HL_ATTR(HLF_8));
     } else {
       msg_outtrans(exec_to_string);
     }

src/nvim/eval/typval.c

@@ -1657,13 +1657,14 @@ void callback_copy(Callback *dest, Callback *src)
 /// Generate a string description of a callback
 char *callback_to_string(Callback *cb)
 {
-  size_t msglen = 100;
+  if (cb->type == kCallbackLua) {
+    return nlua_funcref_str(cb->data.luaref);
+  }
+
+  const size_t msglen = 100;
   char *msg = (char *)xmallocz(msglen);
 
   switch (cb->type) {
-  case kCallbackLua:
-    snprintf(msg, msglen, "<lua: %d>", cb->data.luaref);
-    break;
   case kCallbackFuncref:
     // TODO(tjdevries): Is this enough space for this?
     snprintf(msg, msglen, "<vim function: %s>", cb->data.funcref);
@@ -1672,7 +1673,7 @@ char *callback_to_string(Callback *cb)
     snprintf(msg, msglen, "<vim partial: %s>", cb->data.partial->pt_name);
     break;
   default:
-    snprintf(msg, msglen, "%s", "");
+    *msg = '\0';
     break;
   }
   return msg;

src/nvim/ex_docmd.c

@@ -5440,7 +5440,7 @@ char *uc_validate_name(char *name)
 /// This function takes ownership of compl_arg, compl_luaref, and luaref.
 ///
 /// @return  OK if the command is created, FAIL otherwise.
-int uc_add_command(char *name, size_t name_len, char *rep, uint32_t argt, long def, int flags,
+int uc_add_command(char *name, size_t name_len, const char *rep, uint32_t argt, long def, int flags,
                    int compl, char *compl_arg, LuaRef compl_luaref, LuaRef preview_luaref,
                    cmd_addr_T addr_type, LuaRef luaref, bool force)
   FUNC_ATTR_NONNULL_ARG(1, 3)
@@ -5762,6 +5762,16 @@ static void uc_list(char *name, size_t name_len)
       IObuff[len] = '\0';
       msg_outtrans((char *)IObuff);
 
+      if (cmd->uc_luaref != LUA_NOREF) {
+        char *fn = nlua_funcref_str(cmd->uc_luaref);
+        msg_puts_attr(fn, HL_ATTR(HLF_8));
+        xfree(fn);
+        // put the description on a new line
+        if (*cmd->uc_rep != NUL) {
+          msg_puts("\n                                               ");
+        }
+      }
+
       msg_outtrans_special(cmd->uc_rep, false,
                            name_len == 0 ? Columns - 47 : 0);
       if (p_verbose > 0) {

src/nvim/lua/executor.c

@@ -2076,3 +2076,34 @@ int nlua_do_ucmd(ucmd_T *cmd, exarg_T *eap, bool preview)
 
   return retv;
 }
+
+/// String representation of a Lua function reference
+///
+/// @return Allocated string
+char *nlua_funcref_str(LuaRef ref)
+{
+  lua_State *const lstate = global_lstate;
+  StringBuilder str = KV_INITIAL_VALUE;
+  kv_resize(str, 16);
+
+  if (!lua_checkstack(lstate, 1)) {
+    goto plain;
+  }
+  nlua_pushref(lstate, ref);
+  if (!lua_isfunction(lstate, -1)) {
+    lua_pop(lstate, 1);
+    goto plain;
+  }
+
+  lua_Debug ar;
+  if (lua_getinfo(lstate, ">S", &ar) && *ar.source == '@' && ar.linedefined >= 0) {
+    char *src = home_replace_save(NULL, ar.source + 1);
+    kv_printf(str, "<Lua %d: %s:%d>", ref, src, ar.linedefined);
+    xfree(src);
+    return str.items;
+  }
+
+plain:
+  kv_printf(str, "<Lua %d>", ref);
+  return str.items;
+}

src/nvim/mapping.c

@@ -196,9 +196,9 @@ static void showmap(mapblock_T *mp, bool local)
   // Use false below if we only want things like <Up> to show up as such on
   // the rhs, and not M-x etc, true gets both -- webb
   if (mp->m_luaref != LUA_NOREF) {
-    char msg[100];
-    snprintf(msg, sizeof(msg), "<Lua function %d>", mp->m_luaref);
-    msg_puts_attr(msg, HL_ATTR(HLF_8));
+    char *str = nlua_funcref_str(mp->m_luaref);
+    msg_puts_attr(str, HL_ATTR(HLF_8));
+    xfree(str);
   } else if (mp->m_str[0] == NUL) {
     msg_puts_attr("<Nop>", HL_ATTR(HLF_8));
   } else {
@@ -2110,10 +2110,7 @@ static void get_maparg(typval_T *argvars, typval_T *rettv, int exact)
         rettv->vval.v_string = str2special_save((char *)rhs, false, false);
       }
     } else if (rhs_lua != LUA_NOREF) {
-      size_t msglen = 100;
-      char *msg = (char *)xmalloc(msglen);
-      snprintf(msg, msglen, "<Lua function %d>", mp->m_luaref);
-      rettv->vval.v_string = msg;
+      rettv->vval.v_string = nlua_funcref_str(mp->m_luaref);
     }
   } else {
     tv_dict_alloc_ret(rettv);

src/nvim/os/env.c

@@ -1143,7 +1143,7 @@ size_t home_replace(const buf_T *const buf, const char *src, char *const dst, si
 /// Like home_replace, store the replaced string in allocated memory.
 /// @param buf When not NULL, check for help files
 /// @param src Input file name
-char *home_replace_save(buf_T *buf, char *src)
+char *home_replace_save(buf_T *buf, const char *src)
   FUNC_ATTR_NONNULL_RET
 {
   size_t len = 3;             // space for "~/" and trailing NUL

test/functional/api/keymap_spec.lua

@@ -822,7 +822,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
       vim.api.nvim_set_keymap ('n', 'asdf', '', {callback = function() print('jkl;') end })
     ]]
     assert.truthy(string.match(exec_lua[[return vim.api.nvim_exec(':nmap asdf', true)]],
-                  "^\nn  asdf          <Lua function %d+>"))
+                  "^\nn  asdf          <Lua %d+>"))
   end)
 
   it ('mapcheck() returns lua mapping correctly', function()
@@ -830,7 +830,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
       vim.api.nvim_set_keymap ('n', 'asdf', '', {callback = function() print('jkl;') end })
     ]]
     assert.truthy(string.match(funcs.mapcheck('asdf', 'n'),
-                  "^<Lua function %d+>"))
+                  "^<Lua %d+>"))
   end)
 
   it ('maparg() returns lua mapping correctly', function()
@@ -838,7 +838,7 @@ describe('nvim_set_keymap, nvim_del_keymap', function()
       vim.api.nvim_set_keymap ('n', 'asdf', '', {callback = function() print('jkl;') end })
     ]]
     assert.truthy(string.match(funcs.maparg('asdf', 'n'),
-                  "^<Lua function %d+>"))
+                  "^<Lua %d+>"))
     local mapargs = funcs.maparg('asdf', 'n', false, true)
     assert(type(mapargs.callback) == 'number', 'callback is not luaref number')
     mapargs.callback = nil