Confused about config = on new plugins

[florentc]

Hello,

I am confused about how to use packer in the following case:

Starting from an empty configuration:

require('packer').startup(function()
    use 'wbthomason/packer.nvim'
end

I want to use a new plugin theplugin and configure it. I add something like:

require('packer').startup(function()
    use 'wbthomason/packer.nvim'
    use {
        'theauthor/theplugin',
        config = require('theplugin').setup { ... }
    }
end

I need to source the modified file or restart nvim before I can run :PackerCompile or :PackerSync. Since the plugin has yet to be installed, I get a module 'theplugin' not found. Running :PackerCompile and/or :PackerSync does not work then.

I have to remove config = require('theplugin').setup { ... }, compile/sync to install the plugin, and then I can put the config line back (and this time obviously the module is found because the plugin has been installed). Just like with traditional vim plugin managers.

Therefore, I don't get the point of the config key. I thought the config function would only be called if the plugin is installed and its modules ready for use.

Am I missing something?

Thank you for your help.

[wbthomason]

This is a reasonable question - partially, the flow you used is a bit different than the usual, and partially, config doesn't do quite what you think (though perhaps this should change).

Usually, for a new plugin install, I would

1. Write the plugin spec
2. Load the plugin specification file (restarting Neovim if I have to because of Lua's module caching)
3. Run PackerSync to first clone the plugin and then generate (and source) the compiled file

In this case, everything goes "as expected". I'm guessing that you probably ran PackerCompile first, which generated an invalid compiled file because the plugin wasn't installed? (that said, the try_loadstring function we use in packer_compiled should have prevented a failing config from affecting others, so I'm not sure why you were unable to run packer commands, as you say).

The other bit of this is that, right now, config etc. does not check if a plugin is installed before trying to run. This might be worth adding; let me throw together a quick PR with an idea I have and see if it works as you'd hope.

[wbthomason]

Ok, check out #508 which makes config behave more like you (reasonably) expect!

[florentc]

Thank you very much for your quick reply and implementing a new dedicated feature that fast!

I switched to the feature branch and did the following:

1. Add a new plugin to the plugin spec

use {
    'theauthor/theplugin',
    config = require('theplugin').setup { ... }
}

2. Save the file
3. Restart neovim

I get the "module not found error" at startup as before. Before I can run PackerSync and PackerCompile. If I run PackerSync it offers to remove the plugins specified after the error line.

I guess the new feature prevents issues when calling compile then sync (as I used to do) but it seems I am also doing something wrong before compilation is involved.

[wbthomason]

Ah, I see - this is a slightly different problem. Here, the issue is just normal Lua evaluation - when you run the plugin spec, Lua eagerly evaluates the config key's value to get the config function (note: this is not the same as running the config function). I should've noticed and commented on this in your original post, but your config key is slightly wrong - config (and setup) must be either strings or functions, whereas your spec eagerly evaluates a function call to setup. You probably want config = function() require('theplugin').setup {} end instead.

[florentc]

Oh OK I see! I am so sorry to have bothered you and wasted time about such a basic mistake. In the documentation of packer and other plugins, such calls are always encapsulated inside a function. My brain has repeatedly ignored that for some reason. Thank you again for your help and your work. The new feature does come in handy.

[wbthomason]

No, no worries! packer has a definite learning curve; I'm happy to help. I'm glad things are working now.