Could someone please elucidate how "merging" specs works and what "parent specs" are?

[NiklasKappel]

The docs mention that specs can be merged with "parent specs", but I can not wrap my head around what is meant by that exactly.

I created a file plugins/which-key.lua

return {
	"folke/which-key.nvim",
	dependencies = { "nvim-tree/nvim-web-devicons", opts = {} },
	opts = {
		spec = {
			{ "<C-h>", "<C-w>h" },
			{ "<C-j>", "<C-w>j" },
			{ "<C-k>", "<C-w>k" },
			{ "<C-l>", "<C-w>l" },
		},
	},
}

and a file plugins/tree.lua, which also defines a keymap spec

return {
	{
		"nvim-tree/nvim-tree.lua",
		dependencies = {
			{ "nvim-tree/nvim-web-devicons", opts = {} },
		},
		opts = {},
	},
	{
		"folke/which-key.nvim",
		opts = {
			spec = { "<Leader>e", vim.cmd.NvimTreeFindFileToggle, desc = "explorer" },
		},
	},
}

with the intention of having plugin configuration and keymaps close together. From the docs, I expected the which-key opts to be merged, but this is not the case. With this setup, only the window navigation keys work and the NvimTree keymap is ignored.

I think LazyVim does the same thing e.g. here, but I don't know what it does differently to make it work. Could someone please explain how I can actually merge plugin specs from different files?

[dpetka2001]

The problem in your case is that only key-value tables can be merged. list-like tables will be overridden normally (and which-key opts.spec is a list-like table).

But lazy.nvim has another fairly recent feature and that is opts_extend. With this you can define list-like tables that will be merged by lazy.nvim as well instead of overwritten. That is what LazyVim also uses (see here).

But you should make sure that opts_extend is present in the parent spec (I believe?? Not 100% sure about that). lazy.nvim parses the files alphabetically, so the first file that will be parsed and has a which-key spec in it will be considered as the parent spec.

[NiklasKappel]

Thanks, it works with opts_extend! I will just go ahead and add it to every which-key spec, so that it works independent of load order.