[Autocomplete] Fix listbox opened unexpectedly when component is disabled

[mj12albert]

Fixes #36867

Here is a sandbox with the original repro and a simplified one that shows the fix: https://codesandbox.io/s/https-github-com-mui-material-ui-pull-38611-3hygqs?file=/demo.tsx

I can hardly believe how simple this fix could be, but it make sense to block the popup from opening if the component is disabled:

   const handleInputMouseDown = (event) => {
-    if (inputValue === '' || !open) {
+    if (!disabledProp && (inputValue === '' || !open)) {
       handlePopupIndicator(event);
     }
   };

Here is the simplified repro (I colored different parts of it) showing the bug: https://codesandbox.io/s/https-github-com-mui-material-ui-issues-36867-m25xds?file=/demo.tsx

Both cases are reproducible:

1. Click on any part of the component that doesn't overlap (green area) with the input slot or the popupIndicator- it will open the popup.

Seems that when the click handler on the InputBase fires (it will even though the Autocomplete is disabled, reason here), it will trigger the handleInputMouseDown (here), and open the popup.

2. Press and hold the left mouse button anywhere on the component except for the popupIndicator (green or blue area), move the cursor until it is over the popup indicator (red area) then release the mouse button - it will open the popup.

Not 100% sure what's going on but since fixing case 1 automatically fixed this one, I guess it's still triggering the click handler of InputBase even though the cursor is no longer directly over it, and the disabled popup button doesn't block the mouseup/click phase of the user action 🤔

• I have followed (at least) the PR section of the contributing guide.

[mui-bot]

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[mj12albert]

Manually tested a prior issue affecting the pickers: https://codesandbox.io/s/pickers-hidden-label-click-test-9q8k4m?file=/demo.tsx

[michaldudak]

I agree, this looks very simple :)
I couldn't find anything wrong with it.

[oliviertassinari]

It looks nice 👍