Remove IE8 plugin

[zeitgeist87]

Remove IE8 plugin and drop IE8 support

[zeitgeist87]

I've just spent more than 3 hours, trying to get Prism to work in IE8 with the ie8 plugin. I had some minor success, but I had to make substantial changes to prism-core.js to get anything to work. I added a few extra polyfills to the ie8 plugin and rewrote some of the existing ones.

Then an unfixable issue cropped up. IE8 removes newline characters with innerHTML und textContent. Unfortunately there is no good solution for that problem. So I concluded, that IE8 support is not possible, even with polyfills and plugins. We may just as well drop it entirely.

[Golmote]

I'd just like to say that there is a difference between deleting the IE8 plugin (that has never worked and was not officially public) and triggering errors in IE8.

I think @LeaVerou was in favor of not triggering errors in IE8, even if Prism would not work. But maybe she changed her mind?

I personally do agree we should drop support for IE8 entirely and stop caring about triggering errors on this browser, though.

[zeitgeist87]

I think @LeaVerou was in favor of not triggering errors in IE8, even if Prism would not work. But maybe she changed her mind?

Well I tested it, and we are triggering lots of errors in IE8 right now. We would have to make substantial changes to prism-core.js to change that. Or some IE8 specific code like:

if (document.documentMode < 9)
    return null;

[zeitgeist87]

I may have overstated my case in the previous post. These things cause errors in prism-core.js in IE8:

You cannot slice DOM elements. We would have to use a bit more code to get the current script:

[].slice.call(document.getElementsByTagName("script")).pop();

Object.defineProperty only works on DOM elements. We would have to use obj['__id'] instead, which makes the __id property enumerable and we have to check for it in other parts of the code:

Object.defineProperty(obj, '__id', { value: ++uniqueId });

But there are numerous other things wrong with the plugins. The file-highlight plugin causes an error because IE8 has no document.addEventListener. We would have to put an if (document.addEventListener) statement there.

[Golmote]

You're right. And we already removed some of the IE8 checks in the past...
I'd like to hear @LeaVerou's opinion on this, but having to keep being error-proof on IE8 really is a pain in the neck. :/

[LeaVerou]

Prism was released in 2012, when IE8 mattered more. In 2016, to hell with IE8. Also, indeed the plugin never worked. It was an abandoned WIP which I gave up on when I discovered the same newline issue. Feel free to remove it, as it's kind of misleading.
As for triggering errors, if there's a simple check that we can put in the beginning (I.e. If X not supported, return), fine. Anything more than that is way too much for way too little benefit.

[Golmote]

Merged!

[svlima777]

Thank You!