Heavy memory usage of the Language Server

This is some sort of documentation of my experience with Svelte Language Server (SLS) that I think needs attention.

In my moderately large Svelte project I decided to try using the Svelte Atom extension (VS Code has proven to be the same in regards to this issue, which makes sense – it’s not the editor’s fault). After a few moments of coding I’ve noticed severe performance drops and system freezes. Turns out that the SLS process was using up to 2 GB of RAM. After pulling the project apart I’ve discovered that the files that are causing such heavy memory consumption are /jsconfig.json and /__sapper__/*. It’s worth noting that at the time I had both the development and the production builds compiled, so the __sapper__ folder was twice the size.

jsconfig.json had a particularly interesting field:

{
  "exclude": ["node_modules", "dist"]
}

Turns out that SLS was honoring this field somehow, in that:

• removing jsconfig.json altogether brought the memory consumption to acceptable (~350 MB)
• keeping it in this way was giving the ridiculous 2 GB of memory usage
• adding "__sapper__" into the array of excludes also brought the memory consumption to acceptable (same as when removing)

My thoughts on this:

• why is SLS affected by a bunch of .js files in the __sapper__ folder? (note that copypasting the same file in __sapper__/dev/client didn’t increase the memory consumption, so it’s not simply linearly increasing with respect to the amount of files)
• is all this consumed memory really necessary?
• how exactly does jsconfig.json affect SLS?
• perhaps it should be somehow made clearer how to tweak memory consumption if it gets out of control, possibly by documenting the usage of jsconfig.json

I don’t really know what to make of this issue, hoping for some sort of discussion and possibly documentation improvement, but feel free to close this.