Change element type at runtime - aurelia

Question

Is it possible to dynamically define the type of an element inside a custom components template at runtime?
I'd like to avoid duplication of the inner contents of the button and a element in the following example:
<template>
<button if.bind="!isLinkBtn">
<span class="btn-icon">${icon}</span>
<span class="btn-text">${contentText}</span>
</button>
<a if.bind="isLinkBtn">
<!--
The content is a 1:1 duplicate of the button above which should be prevented
somehow in order to keep the view DRY
-->
<span class="btn-icon">${icon}</span>
<span class="btn-text">${contentText}</span>
</a>
</template>
Is it possible to write something like this:
<template>
<!--
The type of element should be defined at runtime and can be a standard HTML "button"
or an anchor "a"
-->
<element type.bind="${isLinkBtn ? 'a' : 'button'}">
<span class="btn-icon">${icon}</span>
<span class="btn-text">${contentText}</span>
</element>
</template>
I'm aware of dynamic composition with <compose view="${widget.type}-view.html"></compose> but as far as I know, this won't allow me to create default HTML elements but only custom components, correct?
I've asked this question on the Aurelia Gitter where Erik Lieben suggested to use a #processContent(function) decorator, replace the content within the given function and return true to let Aurelia process it.
Unfortunately I don't know how to actually apply those instructions and am hoping for some alternative approaches here or some details about how to actually accomplish this.
Edit
I've created a corresponding feature request. Even though possible solutions have been provided, I'd love to see some simpler way to solve this ;)

Answer 1

When you want to reuse HTML snippets, use compose. Doing so does not create a new custom element. It simply includes the HTML at the location of each compose element. As such, the view-model for the included HTML is the same as for the element into which it is composed.
Take a look at this GistRun: https://gist.run/?id=36cf2435d39910ff709de05e5e1bedaf
custom-link.html
<template>
<button if.bind="!isLinkBtn">
<compose view="./custom-link-icon-and-text.html"></compose>
</button>
<a if.bind="isLinkBtn" href="#">
<compose view="./custom-link-icon-and-text.html"></compose>
</a>
</template>
custom-link.js
import {bindable} from 'aurelia-framework';
export class CustomLink {
#bindable() contentText;
#bindable() icon;
#bindable() isLinkBtn;
}
custom-link-icon-and-text.html
<template>
<span class="btn-icon">${icon}</span>
<span class="btn-text">${contentText}</span>
</template>
consumer.html
<template>
<require from="./custom-link"></require>
<custom-link content-text="Here is a button"></custom-link>
<custom-link is-link-btn.bind="true" content-text="Here is a link"></custom-link>
</template>
You may want to split these into separate elements, like <custom-button> and <custom-link> instead of controlling their presentation using an is-link-btn attribute. You can use the same technique to reuse common HTML parts and composition with decorators to reuse the common code.
See this GistRun: https://gist.run/?id=e9572ad27cb61f16c529fb9425107a10
Response to your "less verbose" comment
You can get it down to one file and avoid compose using the techniques in the above GistRun and the inlineView decorator:
See this GistRun: https://gist.run/?id=4e325771c63d752ef1712c6d949313ce
All you would need is this one file:
custom-links.js
import {bindable, inlineView} from 'aurelia-framework';
function customLinkElement() {
return function(target) {
bindable('contentText')(target);
bindable('icon')(target);
}
}
const tagTypes = {button: 'button', link: 'a'};
#inlineView(viewHtml(tagTypes.button))
#customLinkElement()
export class CustomButton {
}
#inlineView(viewHtml(tagTypes.link))
#customLinkElement()
export class CustomLink {
}
function viewHtml(tagType) {
let result = `
<template>
<${tagType}${tagType === tagTypes.link ? ' href="#"' : ''}>
<span class="btn-icon">\${icon}</span>
<span class="btn-text">\${contentText}</span>
</${tagType}>
</template>
`;
return result;
}

Answer 2

Sorry, I was doing 2 things at once while looking at gitter, which I am not good at apparently :-)
For the thing you wanted to accomplish in the end, could this also work?
I am not an a11y expert or have a lot of knowledge on that area, but from what I understand, this will accomplish what you want. The browser will look at the role attribute and handle it as a link or button and ignores the actual element type itself / won't care if it is button or anchor it will act as if it is of the type defined in role.
Then you can style it like a button or link tag with css.
<a role.bind="type"><span>x</span><span>y</span></a>
where type is either link or button, see this: https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_link_role