Fix Suspense Hydration

[developit]

Instead of annotating the VNode at a suspend point (a component that threw during render) with _hydrateDom, annotate the VNode at the Suspense boundary (the component that implemented componentDidCatch()). When re-rendering a component, if its owner vnode has a boolean ._hydrating property value, that means we should attempt to resume from the VNode's current ._dom reference.

You can try this PR by checking out the suspense-hydration-testing branch of preactjs/cli-demo. Clone, then run npm i && npm link ../preact && npm run build && http-server -s -p 8080 build

Note: looking at this, I believe I need to change src/component.js L129 in order to enable resumption for trees that suspended during non-hydrate rendering:

vnode._hydrating != null ? [oldDom] : null

To-Do

• [ ] Fix test failures
• [ ] Add MutationObserver-based test from the cli-demo repo
• [ ] Test on preact-www

[github-actions[bot]]

Size Change: +28 B (0%)

Total Size: 38.4 kB

Filename	Size	Change
dist/preact.js	3.74 kB	+5 B (0%)
dist/preact.min.js	3.74 kB	+5 B (0%)
dist/preact.module.js	3.76 kB	+10 B (0%)
dist/preact.umd.js	3.8 kB	+8 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
compat/dist/compat.js	2.95 kB	0 B
compat/dist/compat.module.js	2.97 kB	0 B
compat/dist/compat.umd.js	3 kB	0 B
debug/dist/debug.js	3.08 kB	0 B
debug/dist/debug.module.js	3.07 kB	0 B
debug/dist/debug.umd.js	3.14 kB	0 B
devtools/dist/devtools.js	175 B	0 B
devtools/dist/devtools.module.js	185 B	0 B
devtools/dist/devtools.umd.js	252 B	0 B
hooks/dist/hooks.js	1.06 kB	0 B
hooks/dist/hooks.module.js	1.08 kB	0 B
hooks/dist/hooks.umd.js	1.12 kB	0 B
test-utils/dist/testUtils.js	390 B	0 B
test-utils/dist/testUtils.module.js	392 B	0 B
test-utils/dist/testUtils.umd.js	469 B	0 B

_{compressed-size-action}

[coveralls]

Coverage increased (+0.0002%) to 99.809% when pulling 1f88e722f76ee82a1122071afada5c45e5a3d418 on fix-progressive-hydration into 8f679f076f689a247e58d578d9c0e8f4709b4c10 on prateekbh/suspense-hydration.