Warning: Can't perform a React state update on an unmounted component when SCRIPT_DEBUG true

[bobbingwide]

Describe the bug
When SCRIPT_DEBUG is defined as true then the following message is written to the console log when performing trivial actions such as Duplicate block or Remove block.

backend.js:6 Warning: Can't perform a React state update on an unmounted component. 
This is a no-op, but it indicates a memory leak in your application. 
To fix, cancel all subscriptions and asynchronous tasks in the componentWillUnmount method.

The stack trace seems to vary.

    in SlotComponent (created by Context.Consumer)
    in Slot (created by __experimentalBlockSettingsMenuPluginsExtensionSlot)
    in __experimentalBlockSettingsMenuPluginsExtensionSlot (created by Dropdown)
    in div (created by MenuGroup)
    in div (created by MenuGroup)
    in MenuGroup (created by WithInstanceId(MenuGroup))
    in WithInstanceId(MenuGroup) (created by Dropdown)
    in div (created by NavigableContainer)
    in NavigableContainer (created by ForwardRef(NavigableContainer))
    in ForwardRef(NavigableContainer) (created by ForwardRef(NavigableMenu))
    in ForwardRef(NavigableMenu) (created by Dropdown)
    in div (created by Animate)
    in div (created by IsolatedEventContainer)
    in IsolatedEventContainer (created by Animate)
    in Animate (created by Popover)
    in PopoverDetectOutside (created by WithFocusOutside(PopoverDetectOutside))
    in div (created by WithFocusOutside(PopoverDetectOutside))
    in WithFocusOutside(PopoverDetectOutside) (created by Popover)
    in Unknown (created by FocusReturn)
    in div (created by FocusReturn)
    in FocusReturn (created by Context.Consumer)
    in WithFocusReturn(Component) (created by WithConstrainedTabbing(WithFocusReturn(Component)))
    in div (created by WithConstrainedTabbing(WithFocusReturn(Component)))
    in WithConstrainedTabbing(WithFocusReturn(Component)) (created by Popover)
    in fill_FillComponent (created by Context.Consumer)
    in Fill (created by Context.Consumer)
    in span (created by Context.Consumer)
    in Popover (created by Dropdown)
    in div (created by Dropdown)
    in Dropdown (created by DropdownMenu)
    in DropdownMenu (created by BlockActions)
    in div (created by ToolbarContainer)
    in ToolbarContainer (created by Toolbar)
    in Toolbar (created by BlockActions)
    in BlockActions (created by WithDispatch(BlockActions))
    in WithDispatch(BlockActions)
    in Unknown (created by WithSelect(WithDispatch(BlockActions)))
    in WithSelect(WithDispatch(BlockActions)) (created by BlockSettingsMenu)
    in BlockSettingsMenu (created by BlockToolbar)
    in div (created by BlockToolbar)
    in BlockToolbar
    in Unknown (created by WithSelect(BlockToolbar))
    in WithSelect(BlockToolbar) (created by BlockContextualToolbar)
    in div (created by NavigableContainer)
    in NavigableContainer (created by ForwardRef(NavigableContainer))
    in ForwardRef(NavigableContainer) (created by ForwardRef(NavigableMenu))
    in ForwardRef(NavigableMenu) (created by NavigableToolbar)
    in NavigableToolbar (created by BlockContextualToolbar)
    in BlockContextualToolbar (created by block_BlockListBlock)

To reproduce
Steps to reproduce the behavior:

1. define( 'SCRIPT_DEBUG', true ); in wp-config.php
2. Add new post.
3. Inspect
4. Create a paragraph
5. Choose More options > Duplicate.
6. See the Warning in the Console log.

Expected behavior
Either some documentation explaining which messages are expected and why.
Or no message for this action.

Screenshots
This is a screenshot when Gutenberg 7.2.0 is activated. In this post I deleted a paragraph.

Desktop (please complete the following information):

• OS: [e.g. iOS] Windows
• Browser [e.g. chrome, safari] Chrome
• Version [e.g. 22] current

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Initially mentioned in #18977 and on Slack https://wordpress.slack.com/archives/C02QB2JS7/p1578996401066300

• It happens with WordPresss core 5.3.2 and default theme Twenty Twenty.
• Not resolved with Gutenberg 7.2.0 (built version).

[seanvarnham]

Has there been a resolution to this @bobbingwide ? I have the exact same issue when building a Gutenberg plugin on Mac OS using Chrome version 79.0.3945.130 (Official Build) (64-bit)

[bobbingwide]

Has there been a resolution to this

It hasn't even been triaged @blt-sean. Workaround is to set SCRIPT_DEBUG false.

[talldan]

Was able to reproduce this. It shouldn't cause any issues in usage, but yep, we'd want to fix a potential memory leak.

It looks like this is actually a duplicate of #17355 which is tracking these issues, so I'll close in favour of that.