`custom_element_props_identifier` warning appearing in non-custom elements

[adwher]

Describe the bug

I'm extending the base HTML elements by adding styles but exposing their base properties and using rest props, but since I updated from 5.32.1 to 5.33.13 the custom_element_props_identifier is showing up in all components even when I'm NOT using <svelte:options customElement /> at any part of my application. Compilation works, but is annoying to see the warning when I'm not even using that feature.

Alert on VS Code

Reproduction

Alert on VS Code

Component Code

<script module lang="ts">
  import { cva } from "class-variance-authority";
  import type { HTMLInputAttributes } from "svelte/elements";

  export interface InputProps extends Omit<HTMLInputAttributes, "size"> {
    /**
     * Size of the input.
     * @default "medium"
     */
    size?: "medium";

    /**
     * If `true`, the input will take up the full width of its container.
     * @default false
     */
    fullwidth?: boolean;
  }

  export const createInputStyle = cva(
    [
      "text-paragraph bg-paper transition-(shadow,colors) transition-200",
      "border border-solid border-divider",
      "outline-0 appearance-none",
      "focus:(border-violet-400 shadow-sm)",
    ],
    {
      variants: {
        size: {
          medium: ["px-3 h-10", "text-base", "rounded-md"],
        },

        fullwidth: {
          true: "w-full",
        },
      },

      defaultVariants: {
        size: "medium",
        fullwidth: false,
      },
    },
  );
</script>

<script lang="ts">
  let { size = "medium", fullwidth = false, ...props }: InputProps = $props();

  const classname = createInputStyle({ size, fullwidth, class: props.class });
</script>

<input {...props} class={classname} />

Logs

System Info

System:
    OS: macOS 15.5
    CPU: (8) arm64 Apple M1 Pro
    Memory: 268.22 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - ~/.local/state/fnm_multishells/1409_1748734535725/bin/node
    Yarn: 1.22.22 - ~/.local/state/fnm_multishells/1409_1748734535725/bin/yarn
    npm: 10.9.2 - ~/.local/state/fnm_multishells/1409_1748734535725/bin/npm
    pnpm: 10.7.1 - ~/.local/state/fnm_multishells/1409_1748734535725/bin/pnpm
    bun: 1.2.12 - /opt/homebrew/bin/bun
  Browsers:
    Chrome: 137.0.7151.55
    Safari: 18.5
  npmPackages:
    svelte: ^5.33.13 => 5.33.13
    @sveltejs/kit: ^2.21.1 => 2.21.1
    @sveltejs/adapter-auto: ^4.0.0 => 4.0.0
    @sveltejs/vite-plugin-svelte: ^5.0.3 => 5.0.3

Severity

annoyance

[paoloricciuti]

Are you compiling with customElement: true in your svelte config?

[dummdidumm]

Assuming customElement: true is indeed set: This is tricky - I would say the common case in that case is not exposing component without a <svelte:options /> as custom elements. In other words, that warning is an annoying false positive. I would be in favor of not showing it when a <svelte:options customElement=... /> isn't present.

[paoloricciuti]

Assuming customElement: true is indeed set: This is tricky - I would say the common case in that case is not exposing component without a <svelte:options /> as custom elements. In other words, that warning is an annoying false positive. I would be in favor of not showing it when a <svelte:options customElement=... /> isn't present.

I think I agree with Rich here : if you are compiling with customElement: true it means that component will be compiled as custom element regardless so the warning is still useful.

[adwher]

@paoloricciuti @dummdidumm The option is not set in my svelte.config.js, but even with the customElement: false shows the alert:

[adwher]

When I use the customElement: true it appears twice:

[paoloricciuti]

Mmm then I think we need an actual reproduction here, in the form of a GitHub repo

[adwher]

Sorry guys, problem solved! I assumed that probably is an issue with my eslint-plugin-svelte and it was true, I moved from 2.46.1 to 3.9.1 and it worked. Thank you all for your support! 🥳