Guide devs on the various happy paths of an add-on lifecycle

[sacrosanctic]

create - clean workspace
add (update) - compatibility checks
addx2 (incremental update) - detect dependency, possibly bail.

For an add-on like eslint, it most likely has to bail as soon as it detects a discrepency during add and addx2. Loosely coupled packages like component libraries could be able to handle all 3, addx2 could be bumping dependencies and running codemod.

Not sure if this comes in the form of an API, util or just a pattern (and docs) we should to add to the official add-ons.

This came up in #1034. It wasn't immediately obvious to me that I should handle these cases.

[jycouet]

I'm not sure to get what you mean 👀

[sacrosanctic]

I'm talking about context the addon will run. If it runs from pnpm dlx sv create, its a clean environment. pnpm dlx sv add, some checks will be required. And if the user runs pnpm dlx sv add again, we should know and handle it accordingly.

I believe this is already all doable, just need some documentation of happy paths to consider. I would consider promoting it to an API since it seems pretty important to handle.

[jycouet]

Hooo, I see

It's already more or less the case (minor bugs 😅). I remember doing something for drizzle that if you already have it, we don't do things and log it if I recall.
With tailwind, you can add a plugin, and later add another plugin.

Did you see a few issues already that can be covered here ?
Yes, if eslint is already clnfigured (& different), we can say sorry. I think that real "migration" from eslint 7 to eslint 10 is not sv job today.

FYI, I have a custom plugin to scafold a route with a few files and content. I use it from time to time.

[sacrosanctic]

It's already more or less the case (minor bugs 😅). I remember doing something for drizzle that if you already have it, we don't do things and log it if I recall.

I couldnt spot this

Yes, if eslint is already clnfigured (& different), we can say sorry. I think that real "migration" from eslint 7 to eslint 10 is not sv job today.

Theoretically, add-on developers can use sv to do migrations.

Did you see a few issues already that can be covered here ?

How do I distinguish between sv add and sv create? I only want to write to README.md in sv create.

[jycouet]

It's the usage of cancel, for example https://github.com/sveltejs/cli/blob/main/packages/sv/src/addons/drizzle.ts#L118

Yes, sv could do migrations, what I mean, is that today no official add-ons are doing this.

Probably using fromCommand arg ? https://github.com/sveltejs/cli/blob/main/packages/sv/src/cli/add.ts#L654

Let me know if I can help 👍

[sacrosanctic]

Is fromCommand an internal API? Where do I access it?