Adds performUpdate and defers update until connection
#368
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Fixes #290. The previous private `_validate` method has been made protected and named `performUpdate`. It's all now possible to return a promise from this method and doing so will block the update's completion until the promise is resolved. This allows control over the timing of update and integration with schedulers. Fixes #258. Updates are now deferred until element connection. This ensures that microtask checkpoints that may occur during element construction do not generate errors or cause extra update cycles.
src/lib/updating-element.ts
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| * to schedule updates to occur just before the next frame: | ||
| * | ||
| * ``` | ||
| * protected async scheduleUpdate(): Promise<unknown> { |
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shouldn't this be performUpdate() ?
| * } | ||
| * ``` | ||
| */ | ||
| protected performUpdate(): void|Promise<unknown> { | ||
| // Mixin instance properties once, if they exist. | ||
| if (this._instanceProperties) { |
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Could this be moved to the connectedCallback and take this check out of the every-render path?
src/lib/updating-element.ts
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| } | ||
| return this._invalidate(); | ||
| if (!this._hasRequestedUpdate && shouldRequestUpdate) { | ||
| this._setupUpdate(); |
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Naming: is _enqueueUpdate better?
| await previousUpdatePromise; | ||
| // Make sure the element has connected before updating. | ||
| if (!this._hasConnected) { | ||
| await new Promise((res) => this._hasConnectedResolver = res); |
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It seems unfortunate to need to introduce another promise to synchronize a pending update with connected, but I get that it is needed to keep the updateComplete promise pending to allow someone to await el.updateComplete before it is connected. I don't have a better idea, other than saving the _updatePromise resolver and letting connected's call to requestUpdate use the same promise. Not sure that's any better.
Would it be too weird to just document that the pending update system isn't ready until first connected, so updateComplete shouldn't be awaited until the element is connected? That would allow you to just bail in requestUpdate (since you'll always come back in when connected).
If you don't like either of those suggestions this code is fine, not that big of a deal. Just somehow feels more complicated than it should be and wanted to brainstorm a little.
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Acknowledged, but think it makes sense to keep as is.
Fixes #290. The previous private
_validatemethod has been made protected and namedperformUpdate. It's all now possible to return a promise from this method and doing so will block the update's completion until the promise is resolved. This allows control over the timing of update and integration with schedulers.Fixes #258. Updates are now deferred until element connection. This ensures that microtask checkpoints that may occur during element construction do not generate errors or cause extra update cycles.