Allow disabling of "credentialless" on iframeAttr

[chendo]

Is your feature request related to a problem? Please describe.

We're trying to upgrade from our licensed Fancybox v4 to v6. We have run into an issue where we are using iframes with credentials as a captcha mechanism, however due to the default value of credentialless being enabled, this is causing the captcha to not be able to persist a cookie across all browsers.

Describe the solution you'd like

I propose that if the value of a key in iframeAttr is falsey, it should not be set on the iframe.

Describe alternatives you've considered

I've tried the following:

Html: {
  iframeAttr: {
     credentialless: false
  }
}

Html: {
  iframeAttr: {
     credentialless: "no", 
  }
}

Html: {
  iframeAttr: {
     credentialless: null, // sets credentials="null"
  }
}

I've tried crossorigin="use-credentials", which does override credentialless in Safari, but doesn't work in Chrome.

I have also tried to use various hooks to try to modify the iframe before it gets attached to the DOM to no avail.

Additional context

No response

[fancyapps]

Hi,

The Html plugin has been moved to the Carousel to allow for an "inline Fancybox" effect. So you can set the parameters like this:

Fancybox.bind("[data-fancybox]", {
  Carousel : {
    Html : {
      iframeAttr: {
        allow: "autoplay; fullscreen",
        scrolling: "auto"
      }
    }
  }
});

[chendo]

@fancyapps We use Fancybox.show to invoke in this scenario, and I had left out the Carousel bit in my example to keep it cleaner, but that was what I was doing, and the problem is that I cannot remove the default credentialless: "" definition due to how the defaults are merged and the attributes applied.

// defaults definition
const a = {
    iframeAttr: {
      allow: "autoplay; fullscreen",
      scrolling: "auto",
      credentialless: ""
    }
  },

// ...

// code that merges and applies attributes
for (const [e, o] of Object.entries(function () {
  const e = null == i ? void 0 : i.getOptions().Html;
  return t(e) ? Object.assign(Object.assign({}, a), e) : a;
}().iframeAttr || {})) l.setAttribute(e, o);

If the above snippet was modified to something like if (o) { l.setAttribute(e, o) } so only truthy values were set, then that would resolve my issue.

[chendo]

Closing as I was unable to reproduce the error after revisiting the issue