E2E Tests: Intermittent failure in "Allowed Blocks Setting on InnerBlocks"

[aduth]

Example:

• https://travis-ci.com/github/WordPress/gutenberg/jobs/300173148

FAIL packages/e2e-tests/specs/editor/plugins/inner-blocks-allowed-blocks.test.js (12.448s)
  Allowed Blocks Setting on InnerBlocks 
    ✓ allows all blocks if the allowed blocks setting was not set (4146ms)
    ✓ allows the blocks if the allowed blocks setting was set (3206ms)
    ✕ correctly applies dynamic allowed blocks restrictions (3588ms)
  ● Allowed Blocks Setting on InnerBlocks  › correctly applies dynamic allowed blocks restrictions
    expect(received).toEqual(expected) // deep equality
    - Expected
    + Received
      Array [
    -   "Gallery",
    -   "Video",
    +   "Image",
    +   "List",
      ]
      76 | 		await page.click( appenderSelector );
      77 | 		await openAllBlockInserterCategories();
    > 78 | 		expect( await getAllBlockInserterItemTitles() ).toEqual( [
         | 		                                                ^
      79 | 			'Gallery',
      80 | 			'Video',
      81 | 		] );
      at Object.toEqual (specs/editor/plugins/inner-blocks-allowed-blocks.test.js:78:51)
          at runMicrotasks (<anonymous>)

[aduth]

The test attempts to verify that after a block is inserted in a parent block, the parent updates the settings of its InnerBlocks to restrain the allowed blocks.

There's a couple known async behaviors in here which could be causing race conditions:

1. Async rendering of the block list may only rerender parent or appender after scheduled delay.
   • That said, I seem recall there being some logic explicitly handling synchronous rendering of a block's own parent.
2. Settings are only updated after the next render of InnerBlocks, during componentDidUpdate (source)

[aduth]

Async rendering of the block list may only rerender parent or appender after scheduled delay.

• That said, I seem recall there being some logic explicitly handling synchronous rendering of a block's own parent.

This synchronous rendering of parents was removed as of #19343, so it's quite likely this is related (if not the direct cause).