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]

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.