Unexpected Rendering Failure When Injecting Custom SPFx Component Into List Form

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Unexpected Rendering Failure When Injecting Custom SPFx Component Into List Form

Gwendolyn Denton 140

while developing an SPFx customization for a SharePoint Online list form. I’m using a custom SPFx application customizer to dynamically inject a React component into the modern list form using the placeholder API. The component loads correctly on most pages, but in certain list forms especially those with custom column formatting or non-default content types the placeholder fails to render.

When this happens, the React component doesn’t mount at all, and no errors appear in the browser console except a generic “placeholder not available” message.

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Answer 1

Hi Gwendolyn Denton

Thank you for reaching out to Microsoft Q&A forum

As states in Overview of SharePoint Framework Extensions and Build your first Form Customizer extension, the root cause of this behavior is Application Customizers can render only into the well‑known Top/Bottom page placeholders on modern pages, however, list forms sometimes render in reduced chrome (panel/dialog or full‑page minimal layout), or the experience may switch to classic or be overridden by Power Apps, in which cases those placeholders are not available, so tryCreateContent returns null and your React component never mounts.

In this context, you can follow below two approaches to see if it can resolve this behavior:

1/ Use SPFx Form Customizer for form pages

You can consider refactoring the customization to a Form Customizer and associate it with the affected list’s content types so it renders consistently on New/Edit/Display forms, independent of page placeholders. Deployment can be automated (PnP script) by setting the content‑type properties NewFormClientSideComponentId, EditFormClientSideComponentId, and DisplayFormClientSideComponentId.

Link reference: Build your first Form Customizer extension

2/ Harden the Application Customizer for page/route changes and missing placeholders.

In your onInit, listen to placeholderChangedEvent and application.navigatedEvent; on each callback, attempt tryCreateContent(Top|Bottom) and gracefully skip when null. This avoids stale mounts after SPA transitions and prevents errors when forms don’t expose placeholders.


// in Application Customizer
public async onInit(): Promise<void> {
  this.context.placeholderProvider.placeholderChangedEvent.add(this, this.renderPlaceholders);
  this.context.application.navigatedEvent.add(this, () => { this.disposePlaceholders(); this.renderPlaceholders(); });
}
private renderPlaceholders() {
  const top = this.context.placeholderProvider.tryCreateContent(PlaceholderName.Top, { onDispose: this.onDispose });
  if (top?.domElement) ReactDOM.render(<MyBanner/>, top.domElement);

For your information:

https://dori-uw-1.kuma-moon.com/en-us/sharepoint/dev/spfx/extensions/get-started/using-page-placeholder-with-extensions

https://nanddeepnachanblogs.com/posts/2020-04-10-handle-navigation-in-sharepoint-framework-application-customizer/

Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

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Gwendolyn Denton 140 Reputation points

2025-12-11T13:52:29.57+00:00

Many thanks for your detail answer

Answer 2

The issue you're experiencing with the SPFx application customizer not rendering the React component in certain list forms could be related to the specific configurations of those forms. Here are a few considerations that might help you troubleshoot the problem:

Custom Column Formatting: If the list forms have custom column formatting, it might interfere with the placeholder API. Ensure that the placeholder you are trying to inject into is available and not being overridden by the custom formatting.
Non-default Content Types: Different content types can have varying layouts and structures. Make sure that the placeholder you are targeting is compatible with the content types being used in those forms. It may not be available in all scenarios.
Check Placeholder Availability: The generic “placeholder not available” message indicates that the placeholder you are trying to use might not be present in the DOM when your component is attempting to mount. You can add checks in your code to verify the existence of the placeholder before attempting to inject your component.
Debugging: Even though no errors appear in the console, consider adding additional logging within your code to track the rendering process and identify at which point it fails. This can help you pinpoint whether the issue is with the placeholder or the component itself.
Testing on Different Forms: Test your SPFx component on various list forms to see if the issue is consistent across all forms with custom formatting or specific content types. This can help you determine if the problem is isolated to certain configurations.

If the problem persists, you may want to consult the Microsoft Community for further assistance, as they may have additional insights or updates regarding known issues with SPFx components in SharePoint Online.

References:

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Unexpected Rendering Failure When Injecting Custom SPFx Component Into List Form

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