Component & file names comment markup is missing in svelte v5

[harshmandan]

Describe the bug

In svelte v4, the markup in dev mode would contain the file name & components names in the html markup as comments. Here's a screenshot:

But in svelte v5, the markup now omits the file name & comment names in dev mode, making it hard to parse the markup in large apps.

Reproduction

For v4:
https://stackblitz.com/edit/sveltejs-kit-template-default-k8mk4s?file=package.json

For v5:
https://stackblitz.com/edit/sveltejs-kit-template-default-xkgpk8fk?file=package.json

Logs

No response

System Info

System:
    OS: macOS 15.2
    CPU: (8) arm64 Apple M1 Pro
    Memory: 123.53 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.11.0 - ~/.nvm/versions/node/v20.11.0/bin/node
    npm: 10.2.4 - ~/.nvm/versions/node/v20.11.0/bin/npm
    pnpm: 9.15.3 - ~/.nvm/versions/node/v20.11.0/bin/pnpm

Severity

blocking an upgrade

[dummdidumm]

I can't reproduce this - opening your Stackblitz link for v4 does not show any comments, nor can I remember that we ever had something like this in dev mode. Could this be from another source? An extension adding these, etc ?

[Conduitry]

I'm seeing those comments in the v4 StackBlitz. I do also recall seeing them before. I don't have any extensions that would be adding them. I'm seeing them both in Firefox and in Chromium.

[Thiagolino8]

I'm also seeing those comments in the v4 StackBlitz and I do also recall seeing them before.

[harshmandan]

The screenshots are from the stackblitz repo. Are you inspecting the correct element? (It should be inside an iframe)

[dummdidumm]

Apologies, I must've looked in the wrong place, I see them too, though I really don't recall that part of the compiler. @Conduitry is this some dev only thing that was present once? Looking at the compiler output of v4 there's nothing obvious standing out.

[harshmandan]

Could it be a HMR thing? Meaning, does it depend on vite somehow?

[harshmandan]

Looking at the compiler output of v4 there's nothing obvious standing out.

I also couldn't find the logic anywhere. I looked in svelte-4 branch & in the vite-plugin-svelte repo.

[harshmandan]

Any update on as to what's causing this new behaviour?

[stemaDev]

Same issue for us. We updated to svelte5, and there are these empty comments (I don't even think they align with where the components would be), but I don't see the component indicating comments which is VERY helpful when debugging.

[DreaminDani]

This is happening for us too. I think it might be something that svelte inspector added? Maybe the latest version of inspector doesn't include those in the markdown anymore? Either way, empty comments add more noise than and helpful, so it'd be nice to know how to fix this (or remove the comment lines altogether)

[JohnScience]

We recently switched to Svelte 5. Now I'm considering downgrading because of this. Can anyone provide any info on where the relevant code is?