fix: do not always autostart servers with explicit user config

[WieeRd]

Current State

When an explicit configuration is given for a server through setup(), availability check for that server is skipped, and it will be always setup when an associated filetype is triggered. The rationale behind this is that some server configurations in lspconfig dynamically changes cmd based on other fields or environment variables. It is hard to predict what the actual cmd is going to be. So I choose to skip the executable check in order to avoid false negatives of not picking up actually available servers.

Problem

False positives. After deploying my dotfiles on fresh Arch setup, opening nvim config immediately resulted in auto-lsp trying to setup lua_ls and failing, because I have explicit configs for lua_ls but didn't have it installed yet. It's only mildly annoying, but I'd still like to get rid of it.

Solution

some server configurations in lspconfig dynamically changes cmd based on other fields or environment variables.

Turns out there is a clear sign that tells this will happen or not. The on_new_config field is responsible for dynamic adjustments to the default config. I can take note if this field is present when iterating through configs during mappings generation. "Always setup if explicit user config is given" should be only applied to these servers.