Can't set type for input tag.

[stalkerg]

I am tring to generate input tag:

<input type="{{cond.field_type}}" placeholder="constant"
       value="{{cond.const}}" on:change="setCondConst(index, this)">

but svelte plugin output:

'svelte' plugin: 'type must be a static attribute

[Conduitry]

type needs to be static because in some cases fairly different code is generated depending on the input's type. Allowing type to vary would result in all that logic being pushed to the generated code. In addition to making the runtime code more complicated, it would also make the compiler code more complicated. The two versions of the code (doing different things based on the type at compile time, and doing different things based on the type at runtime) would have to be kept in sync. It seems to be a much larger surface for bugs, with not a lot of benefit. Rich may feel differently, but I doubt this is something we want to pursue.

If you need this sort of functionality, I would recommend having multiple {{#if}}...{{else}}...{{/if}} blocks around different instances of the <input> tag for all of the different types you need to support.

[Rich-Harris]

I think it only needs to be static if there's a two-way binding, because the change handler is dependent on the input type. In this case, I reckon it's fine for it to be dynamic.

The error is being raised here because of this block — note the TODO comment (mea culpa). That check should probably be more specific and happen in the validation phase.

[Rich-Harris]

This is fixed in 1.22.3, thanks

[ayZagen]

Is it feasible to make type attribute to be dynamic ? That would be great for having dynamic inputs like password fields.

For ex:

<input
  type={ passwordVisible ? 'text' : 'password'}
  bind:value={data.loginForm.password} />
<span on:click={() => passwordVisible = !passwordVisible} class="fa fa-fw {passwordVisible ? 'fa-eye-slash' : 'fa-eye' }"></span>

EDIT: Using svelte 3.6.7

[Conduitry]

I had thought there was an open issue already for that, but I can't find it right now. Because we don't want stuff to be completely dynamic at runtime, there'd be some restrictions on what you can do. Inputs with dynamic type would always be treated as text-type inputs - i.e., only have value bindings, which are updated by listening for the input event. I don't know whether those limitations would lead to too much confusion.

[stalkerg]

I don't know whether those limitations would lead to too much confusion.

It significant confusing and it should be in the documentation.