<p dir="auto"><strong>Describe the bug</strong><br>
A clear and concise description of what the bug is. <strong>If your problem is not a bug, please file under Support or Usage Question</strong></p>
<p dir="auto"><strong>To Reproduce</strong><br>
Code snippet to reproduce, ideally that will work by pasting into something like <a href="https://npm.runkit.com/axios" rel="nofollow">https://npm.runkit.com/axios</a>, a hosted solution, or a repository that illustrates the issue. <strong>If your problem is not reproducible, please file under Support or Usage Question</strong></p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="// Example code here"><pre class="notranslate"><span class="pl-c">// Example code here</span></pre></div>
<p dir="auto"><strong>Expected behavior</strong><br>
A clear and concise description of what you expected to happen.</p>
<p dir="auto"><strong>Environment:</strong></p>
<ul dir="auto">
<li>Axios Version [e.g. 0.18.0]</li>
<li>OS: [e.g. iOS 12.1.0, OSX 10.13.4]</li>
<li>Browser [e.g. Chrome, Safari]</li>
<li>Browser Version [e.g. 22]</li>
<li>Additional Library Versions [e.g. React 16.7, React Native 0.58.0]</li>
</ul>
<p dir="auto"><strong>Additional context/Screenshots</strong><br>
Add any other context about the problem here. If applicable, add screenshots to help explain.</p>
<h4 dir="auto">Summary</h4>
<p dir="auto"><a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="301721609" data-permission-text="Title is private" data-url="https://github.com/axios/axios/issues/1395" data-hovercard-type="pull_request" data-hovercard-url="/axios/axios/pull/1395/hovercard" href="https://github.com/axios/axios/pull/1395">#1395</a> launched a fix that instance config may override global config, but it <a href="https://github.com/axios/axios/blob/master/lib/core/mergeConfig.js#L36">ignore custom configs</a>.<br>
So it will break something we'd like to attach into the config and access in interceptor (e.g. CookieJar).</p>
<p dir="auto">For example (<a href="https://codepen.io/anon/pen/gjZRdR?editors=1111" rel="nofollow">https://codepen.io/anon/pen/gjZRdR?editors=1111</a>):</p>
<div class="highlight highlight-source-js notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="const inst = axios.create();
inst.interceptors.request.use(config =&gt; {
  console.log('should be &quot;test&quot;, actual', config.testAttr);
})
inst.get('/', {
  testAttr: 'test',
});"><pre class="notranslate"><span class="pl-k">const</span> <span class="pl-s1">inst</span> <span class="pl-c1">=</span> <span class="pl-s1">axios</span><span class="pl-kos">.</span><span class="pl-en">create</span><span class="pl-kos">(</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-s1">inst</span><span class="pl-kos">.</span><span class="pl-c1">interceptors</span><span class="pl-kos">.</span><span class="pl-c1">request</span><span class="pl-kos">.</span><span class="pl-en">use</span><span class="pl-kos">(</span><span class="pl-s1">config</span> <span class="pl-c1">=&gt;</span> <span class="pl-kos">{</span>
  <span class="pl-smi">console</span><span class="pl-kos">.</span><span class="pl-en">log</span><span class="pl-kos">(</span><span class="pl-s">'should be "test", actual'</span><span class="pl-kos">,</span> <span class="pl-s1">config</span><span class="pl-kos">.</span><span class="pl-c1">testAttr</span><span class="pl-kos">)</span><span class="pl-kos">;</span>
<span class="pl-kos">}</span><span class="pl-kos">)</span>
<span class="pl-s1">inst</span><span class="pl-kos">.</span><span class="pl-en">get</span><span class="pl-kos">(</span><span class="pl-s">'/'</span><span class="pl-kos">,</span> <span class="pl-kos">{</span>
  <span class="pl-c1">testAttr</span>: <span class="pl-s">'test'</span><span class="pl-kos">,</span>
<span class="pl-kos">}</span><span class="pl-kos">)</span><span class="pl-kos">;</span></pre></div>
<h4 dir="auto">Context</h4>
<ul dir="auto">
<li>axios version: v0.19.0-beta.1</li>
<li>Environment: node &amp; chrome</li>
</ul>