4 files changed, 303 insertions, 0 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index ce9c4e27ad..bacb991c4b 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -1273,6 +1273,63 @@ Object nvim_buf_call(Buffer buffer, LuaRef fun, Error *err)
   return res;
 }
 
+/// Create a new user command |user-commands| in the given buffer.
+///
+/// @param  buffer  Buffer handle, or 0 for current buffer.
+/// @param[out] err Error details, if any.
+/// @see nvim_add_user_command
+void nvim_buf_add_user_command(Buffer buffer, String name, Object command,
+                               Dict(user_command) *opts, Error *err)
+  FUNC_API_SINCE(9)
+{
+  buf_T *target_buf = find_buffer_by_handle(buffer, err);
+  if (ERROR_SET(err)) {
+    return;
+  }
+
+  buf_T *save_curbuf = curbuf;
+  curbuf = target_buf;
+  add_user_command(name, command, opts, UC_BUFFER, err);
+  curbuf = save_curbuf;
+}
+
+/// Delete a buffer-local user-defined command.
+///
+/// Only commands created with |:command-buffer| or
+/// |nvim_buf_add_user_command()| can be deleted with this function.
+///
+/// @param  buffer  Buffer handle, or 0 for current buffer.
+/// @param  name    Name of the command to delete.
+/// @param[out] err Error details, if any.
+void nvim_buf_del_user_command(Buffer buffer, String name, Error *err)
+  FUNC_API_SINCE(9)
+{
+  garray_T *gap;
+  if (buffer == -1) {
+    gap = &ucmds;
+  } else {
+    buf_T *buf = find_buffer_by_handle(buffer, err);
+    gap = &buf->b_ucmds;
+  }
+
+  for (int i = 0; i < gap->ga_len; i++) {
+    ucmd_T *cmd = USER_CMD_GA(gap, i);
+    if (!STRCMP(name.data, cmd->uc_name)) {
+      free_ucmd(cmd);
+
+      gap->ga_len -= 1;
+
+      if (i < gap->ga_len) {
+        memmove(cmd, cmd + 1, (size_t)(gap->ga_len - i) * sizeof(ucmd_T));
+      }
+
+      return;
+    }
+  }
+
+  api_set_error(err, kErrorTypeException, "No such user-defined command: %s", name.data);
+}
+
 Dictionary nvim__buf_stats(Buffer buffer, Error *err)
 {
   Dictionary rv = ARRAY_DICT_INIT;
diff --git a/src/nvim/api/keysets.lua b/src/nvim/api/keysets.lua
index f3e7f2f1dc..e47dec9eb7 100644
--- a/src/nvim/api/keysets.lua
+++ b/src/nvim/api/keysets.lua
@@ -33,6 +33,18 @@ return {
   get_commands = {
     "builtin";
   };
+  user_command = {
+    "addr";
+    "bang";
+    "bar";
+    "complete";
+    "count";
+    "desc";
+    "force";
+    "nargs";
+    "range";
+    "register";
+  };
   float_config = {
     "row";
     "col";
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 9b407eab8b..962fce6952 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -961,6 +961,10 @@ Object copy_object(Object obj)
 
   case kObjectTypeDictionary:
     return DICTIONARY_OBJ(copy_dictionary(obj.data.dictionary));
+
+  case kObjectTypeLuaRef:
+    return LUAREF_OBJ(api_new_luaref(obj.data.luaref));
+
   default:
     abort();
   }
@@ -1342,3 +1346,184 @@ const char *get_default_stl_hl(win_T *wp)
     return "StatusLineNC";
   }
 }
+
+void add_user_command(String name, Object command, Dict(user_command) *opts, int flags, Error *err)
+{
+  uint32_t argt = 0;
+  long def = -1;
+  cmd_addr_T addr_type_arg = ADDR_NONE;
+  int compl = EXPAND_NOTHING;
+  char *compl_arg = NULL;
+  char *rep = NULL;
+  LuaRef luaref = LUA_NOREF;
+  LuaRef compl_luaref = LUA_NOREF;
+
+  if (HAS_KEY(opts->range) && HAS_KEY(opts->count)) {
+    api_set_error(err, kErrorTypeValidation, "'range' and 'count' are mutually exclusive");
+    goto err;
+  }
+
+  if (opts->nargs.type == kObjectTypeInteger) {
+    switch (opts->nargs.data.integer) {
+    case 0:
+      // Default value, nothing to do
+      break;
+    case 1:
+      argt |= EX_EXTRA | EX_NOSPC | EX_NEEDARG;
+      break;
+    default:
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'nargs'");
+      goto err;
+    }
+  } else if (opts->nargs.type == kObjectTypeString) {
+    if (opts->nargs.data.string.size > 1) {
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'nargs'");
+      goto err;
+    }
+
+    switch (opts->nargs.data.string.data[0]) {
+    case '*':
+      argt |= EX_EXTRA;
+      break;
+    case '?':
+      argt |= EX_EXTRA | EX_NOSPC;
+      break;
+    case '+':
+      argt |= EX_EXTRA | EX_NEEDARG;
+      break;
+    default:
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'nargs'");
+      goto err;
+    }
+  } else if (HAS_KEY(opts->nargs)) {
+    api_set_error(err, kErrorTypeValidation, "Invalid value for 'nargs'");
+    goto err;
+  }
+
+  if (HAS_KEY(opts->complete) && !argt) {
+    api_set_error(err, kErrorTypeValidation, "'complete' used without 'nargs'");
+    goto err;
+  }
+
+  if (opts->range.type == kObjectTypeBoolean) {
+    if (opts->range.data.boolean) {
+      argt |= EX_RANGE;
+      addr_type_arg = ADDR_LINES;
+    }
+  } else if (opts->range.type == kObjectTypeString) {
+    if (opts->range.data.string.data[0] == '%' && opts->range.data.string.size == 1) {
+      argt |= EX_RANGE | EX_DFLALL;
+      addr_type_arg = ADDR_LINES;
+    } else {
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'range'");
+      goto err;
+    }
+  } else if (opts->range.type == kObjectTypeInteger) {
+    argt |= EX_RANGE | EX_ZEROR;
+    def = opts->range.data.integer;
+    addr_type_arg = ADDR_LINES;
+  } else if (HAS_KEY(opts->range)) {
+    api_set_error(err, kErrorTypeValidation, "Invalid value for 'range'");
+    goto err;
+  }
+
+  if (opts->count.type == kObjectTypeBoolean) {
+    if (opts->count.data.boolean) {
+      argt |= EX_COUNT | EX_ZEROR | EX_RANGE;
+      addr_type_arg = ADDR_OTHER;
+      def = 0;
+    }
+  } else if (opts->count.type == kObjectTypeInteger) {
+    argt |= EX_COUNT | EX_ZEROR | EX_RANGE;
+    addr_type_arg = ADDR_OTHER;
+    def = opts->count.data.integer;
+  } else if (HAS_KEY(opts->count)) {
+    api_set_error(err, kErrorTypeValidation, "Invalid value for 'count'");
+    goto err;
+  }
+
+  if (opts->addr.type == kObjectTypeString) {
+    if (parse_addr_type_arg((char_u *)opts->addr.data.string.data, (int)opts->addr.data.string.size,
+                            &addr_type_arg) != OK) {
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'addr'");
+      goto err;
+    }
+
+    if (addr_type_arg != ADDR_LINES) {
+      argt |= EX_ZEROR;
+    }
+  } else if (HAS_KEY(opts->addr)) {
+    api_set_error(err, kErrorTypeValidation, "Invalid value for 'addr'");
+    goto err;
+  }
+
+  if (api_object_to_bool(opts->bang, "bang", false, err)) {
+    argt |= EX_BANG;
+  } else if (ERROR_SET(err)) {
+    goto err;
+  }
+
+  if (api_object_to_bool(opts->bar, "bar", false, err)) {
+    argt |= EX_TRLBAR;
+  } else if (ERROR_SET(err)) {
+    goto err;
+  }
+
+
+  if (api_object_to_bool(opts->register_, "register", false, err)) {
+    argt |= EX_REGSTR;
+  } else if (ERROR_SET(err)) {
+    goto err;
+  }
+
+  bool force = api_object_to_bool(opts->force, "force", false, err);
+  if (ERROR_SET(err)) {
+    goto err;
+  }
+
+  if (opts->complete.type == kObjectTypeLuaRef) {
+    compl = EXPAND_USER_LUA;
+    compl_luaref = api_new_luaref(opts->complete.data.luaref);
+  } else if (opts->complete.type == kObjectTypeString) {
+    if (parse_compl_arg((char_u *)opts->complete.data.string.data,
+                        (int)opts->complete.data.string.size, &compl, &argt,
+                        (char_u **)&compl_arg) != OK) {
+      api_set_error(err, kErrorTypeValidation, "Invalid value for 'complete'");
+      goto err;
+    }
+  } else if (HAS_KEY(opts->complete)) {
+    api_set_error(err, kErrorTypeValidation, "Invalid value for 'complete'");
+    goto err;
+  }
+
+  switch (command.type) {
+  case kObjectTypeLuaRef:
+    luaref = api_new_luaref(command.data.luaref);
+    if (opts->desc.type == kObjectTypeString) {
+      rep = opts->desc.data.string.data;
+    } else {
+      snprintf((char *)IObuff, IOSIZE, "<Lua function %d>", luaref);
+      rep = (char *)IObuff;
+    }
+    break;
+  case kObjectTypeString:
+    rep = command.data.string.data;
+    break;
+  default:
+    api_set_error(err, kErrorTypeValidation, "'command' must be a string or Lua function");
+    goto err;
+  }
+
+  if (uc_add_command((char_u *)name.data, name.size, (char_u *)rep, argt, def, flags,
+                     compl, (char_u *)compl_arg, compl_luaref, addr_type_arg, luaref,
+                     force) != OK) {
+    api_set_error(err, kErrorTypeException, "Failed to create user command");
+    goto err;
+  }
+
+  return;
+
+err:
+  NLUA_CLEAR_REF(luaref);
+  NLUA_CLEAR_REF(compl_luaref);
+}
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index fb59e0fb44..dfc606f927 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -2363,3 +2363,52 @@ Dictionary nvim_eval_statusline(String str, Dict(eval_statusline) *opts, Error *
 
   return result;
 }
+
+/// Create a new user command |user-commands|
+///
+/// {name} is the name of the new command. The name must begin with an uppercase letter.
+///
+/// {command} is the replacement text or Lua function to execute.
+///
+/// Example:
+/// <pre>
+///    :call nvim_add_user_command('SayHello', 'echo "Hello world!"', {})
+///    :SayHello
+///    Hello world!
+/// </pre>
+///
+/// @param  name    Name of the new user command. Must begin with an uppercase letter.
+/// @param  command Replacement command to execute when this user command is executed. When called
+///                 from Lua, the command can also be a Lua function. The function is called with a
+///                 single table argument that contains the following keys:
+///                 - args: (string) The args passed to the command, if any |<args>|
+///                 - bang: (boolean) "true" if the command was executed with a ! modifier |<bang>|
+///                 - line1: (number) The starting line of the command range |<line1>|
+///                 - line2: (number) The final line of the command range |<line2>|
+///                 - range: (number) The number of items in the command range: 0, 1, or 2 |<range>|
+///                 - count: (number) Any count supplied |<count>|
+///                 - reg: (string) The optional register, if specified |<reg>|
+///                 - mods: (string) Command modifiers, if any |<mods>|
+/// @param  opts    Optional command attributes. See |command-attributes| for more details. To use
+///                 boolean attributes (such as |:command-bang| or |:command-bar|) set the value to
+///                 "true". When using a Lua function for {command} you can also provide a "desc"
+///                 key that will be displayed when listing commands. In addition to the string
+///                 options listed in |:command-complete|, the "complete" key also accepts a Lua
+///                 function which works like the "customlist" completion mode
+///                 |:command-complete-customlist|.
+/// @param[out] err Error details, if any.
+void nvim_add_user_command(String name, Object command, Dict(user_command) *opts, Error *err)
+  FUNC_API_SINCE(9)
+{
+  add_user_command(name, command, opts, 0, err);
+}
+
+/// Delete a user-defined command.
+///
+/// @param  name    Name of the command to delete.
+/// @param[out] err Error details, if any.
+void nvim_del_user_command(String name, Error *err)
+  FUNC_API_SINCE(9)
+{
+  nvim_buf_del_user_command(-1, name, err);
+}