Jira Plugin override system javascript file

Matthias Günter

I'm about to release a plugin, but currently have problems with a PolyFill in Internet Explorer. My frontend of the plugin works with a JavaScript Model driven state management [MobX](https://github.com/mobxjs/mobx). It depends on an ES6 function [`Array.prototype.find`](https://github.com/paulmillr/Array.prototype.find). This polyfill is described as follow in Jira core:

module-key = 'jira.webresources:find-polyfill'
location = '/static/lib/polyfills/find/find-polyfill.js'

When I have a look at the content of that file the polyfill is incorrect:

<span>if</span> <span>(!</span><span>Array</span><span>.</span><span>prototype</span><span>.</span><span>find</span><span>)</span> <span>{</span>
    <span>Object</span><span>.</span><span>defineProperty</span><span>(</span><span>Array</span><span>.</span><span>prototype</span><span>,</span> <span>'find'</span><span>,</span> <span>{</span><span>        value</span><span>:</span> <span>function</span><span>(</span><span>predicate</span><span>)</span> <span>{</span>
            <span>// 1. Let O be ? ToObject(this value).</span>
            <span>if</span> <span>(</span><span>this</span> <span>==</span> <span>null</span><span>)</span> <span>{</span>
                <span>throw</span> <span>new</span> <span>TypeError</span><span>(</span><span>'"this" is null or not defined'</span><span>);</span>
            <span>}</span>

            <span>var</span><span> o </span><span>=</span> <span>Object</span><span>(</span><span>this</span><span>);</span>

            <span>// 2. Let len be ? ToLength(? Get(O, "length")).</span>
            <span>var</span><span> len </span><span>=</span><span> o</span><span>.</span><span>length </span><span>>>></span> <span>0</span><span>;</span>

            <span>// 3. If IsCallable(predicate) is false, throw a TypeError exception.</span>
            <span>if</span> <span>(</span><span>typeof</span><span> predicate </span><span>!==</span> <span>'function'</span><span>)</span> <span>{</span>
                <span>throw</span> <span>new</span> <span>TypeError</span><span>(</span><span>'predicate must be a function'</span><span>);</span>
            <span>}</span>

            <span>// 4. If thisArg was supplied, let T be thisArg; else let T be undefined.</span>
            <span>var</span><span> thisArg </span><span>=</span><span> arguments</span><span>[</span><span>1</span><span>];</span>

            <span>// 5. Let k be 0.</span>
            <span>var</span><span> k </span><span>=</span> <span>0</span><span>;</span>

            <span>// 6. Repeat, while k < len</span>
            <span>while</span> <span>(</span><span>k </span><span><</span><span> len</span><span>)</span> <span>{</span>
                <span>// a. Let Pk be ! ToString(k).</span>
                <span>// b. Let kValue be ? Get(O, Pk).</span>
                <span>// c. Let testResult be ToBoolean(? Call(predicate, T, kValue, k, O )).</span>
                <span>// d. If testResult is true, return kValue.</span>
                <span>var</span><span> kValue </span><span>=</span><span> o</span><span>[</span><span>k</span><span>];</span>
                <span>if</span> <span>(</span><span>predicate</span><span>.</span><span>call</span><span>(</span><span>thisArg</span><span>,</span><span> kValue</span><span>,</span><span> k</span><span>,</span><span> o</span><span>))</span> <span>{</span>
                    <span>return</span><span> kValue</span><span>;</span>
                <span>}</span>
                <span>// e. Increase k by 1.</span><span>                k</span><span>++;</span>
            <span>}</span>

            <span>// 7. Return undefined.</span>
            <span>return</span> <span>undefined</span><span>;</span>
        <span>}</span>
    <span>});</span>
<span>}</span>

According to the community, I quote the erroneous behavior:

[...] by the spec, `Array.prototype.find` descriptor should be `{writable: true, enumerable: false, configurable: true}` and `core-js` use it. [...] - zloirock

Is there any possibility to:

- Change the system file /static/lib/polyfills/find/find-polyfill.js?
- Load a web resource before the jira.webresources:find-polyfill resource so I can hook with the correct polyfill?
- Override the web resource via atlassian-plugin.xml?

The correct implementation of the polyfill is described here: https://github.com/mobxjs/mobx/issues/1028#issuecomment-378940977

This is a duplicate post of https://stackoverflow.com/questions/54721948/jira-plugin-override-system-file