[Components] Adds support for rendering async components - #6708
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javiercn
commented
Jan 15, 2019
javiercn
commented
- Converts SetParameters to SetParametersAsync
- Captures all the returned task produced by SetParametersAsync of each component to properly await them.
- Introduces RenderRootComponentAsync to render the root component and deterministically wait for all async work to be done.
- Protects the state in Renderer from concurrent modifications.
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Could this fix the following issue? #5592 (comment) |
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Question I forgot to ask elsewhere, how will this handle encoding? |
@rynowak The HTML renderer gets a Func<string,string> encoder that does the encoding. Due to the fact that this lives in Microsoft.AspNetCore.Components and we don't want to bring a dependency to the webencoders in that package. Mvc just provides the htmlEncoder resolved from DI |
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Ok cool beans |
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| private int _nextComponentId = 0; // TODO: change to 'long' when Mono .NET->JS interop supports it | ||
| private bool _isBatchInProgress; | ||
| private int _lastEventHandlerId = 0; | ||
| private List<Task> _pendingTasks = new List<Task>(); |
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I might be missing something, but it looks like in the non-HtmlRenderer case, this list will grow infinitely and is never cleared after the initial render.
Should we do something so that only HtmlRenderer actually populates this list, and the others do nothing in AddToPendingTasks? The AddToPendingTasks could be changed to a virtual method that no-ops in the default case.
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This gets cleaned up in all code paths as
void RenderRootComponent(int componentId, ParameterCollection initialParameters)
{
ReportAsyncExceptions(RenderRootComponentAsync(componentId, initialParameters));
}Internally makes sure that all the cleanup happens.
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I thought that only happened on the first render cycle. When some event like a button click happens later in the other renderers, this code path doesn't execute, does it?
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Ah, I see what you mean. You're right. But it has an easy fix
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I null the list after RenderRootComponentAsync is done
SteveSandersonMS
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SteveSandersonMS
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Looking great! Hopefully the remaining points won't be hugely disruptive to resolve. Thanks for tracking down so many fine details about the lifecycle method execution process.
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Updated |
| // reason we have OnAfterRenderAsync is so that the developer doesn't | ||
| // have to use "async void" and do their own exception handling in | ||
| // the case where they want to start an async task. | ||
| var taskWithHandledException = HandleAfterRenderException(onAfterRenderTask); |
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Looks like we don't need the taskWithHandledException var, or do we?
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The compiler complains if we take it out
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_ = HandleAfterRenderException(...);
* Updates the IComponent interface to rename Init into Configure * Updates the IComponent interface to change SetParameters for SetParametersAsync and make it return a Task that represents when the component is done applying the parameters and potentially triggering one or more renders. * Updates ComponentBase SetParametersAsync to ensure that OnInit(Async) runs before OnParametersSet(Async). * Introduces ParameterCollection.FromDictionary to generate a parameter collection from a dictionary of key value pairs. * Introduces RenderComponentAsync on HtmlRenderer to support prerrendering of async components. * Introduces RenderRootComponentAsync on the renderer to allow for asynchronous prerrendering of the root component.
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This is blocked waiting on this unrelated failing test: @natemcmaster Is there something we can do here? I've triggered several builds already |
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If the flaky test is blocking you, log an issue and mark it as skipped. |
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Merging in as this is blocked on an unrelated test. |
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