Defer Loading Does Not Work With Normal Ng Serve, But Works With Ng Serve --no-hmr

by ADMIN 83 views

Defer Loading in Angular: Understanding the Issue with ng serve

Angular provides a feature called defer loading, which allows developers to lazy load components and modules. This feature is particularly useful for improving the performance of applications by reducing the initial load time. However, some developers have reported issues with defer loading when using the ng serve command with Hot Module Replacement (HMR) enabled. In this article, we will explore the problem and provide a solution.

When creating a new Angular project and running ng serve with HMR enabled, the components in the defer block are not lazy loaded. Instead, they are included in the main chunk along with other components. This behavior is unexpected, as the documentation for @defer suggests that components in the defer block should be lazy loaded.

However, when running ng serve with the --no-hmr flag, the components in the defer block are lazy loaded as expected. The same behavior is observed when building the application and serving it from the dist folder.

The Issue with ng serve and HMR

The problem appears to be related to the way ng serve handles HMR. When HMR is enabled, ng serve outputs a message to the console indicating that HMR is active. However, this does not seem to affect the behavior of defer loading.

The expected behavior is that components in the defer block should be lazy loaded when running ng serve with HMR enabled. This would allow developers to take advantage of the performance benefits of defer loading without having to disable HMR.

To resolve the issue, developers can use the --no-hmr flag when running ng serve. This will disable HMR and allow defer loading to work as expected.

Alternatively, developers can build the application and serve it from the dist folder. This will also allow defer loading to work as expected.

In conclusion, the issue with defer loading in Angular when using ng serve with HMR enabled is a known problem. To resolve the issue, developers can use the --no-hmr flag or build the application and serve it from the dist folder. We hope that this article has provided a helpful explanation of the issue and a solution.

Describe the problem that you experienced

In the documentation for @defer everything is described nicely, but when a new simple project is started with ng serve (v19), the components in the defer block are not lazy loaded, but are in the main chunk with all other "normal" components.

Enter the URL of the topic with the problem

https://angular.dev/guide/templates/defer

Describe what you were looking for in the documentation

No response

Describe the actions that led you to experience the problem

No response

Describe what you want to experience that would fix the problem

No response

Add a screenshot if that helps illustrate the problem

No response

If this problem caused an exception or error, please paste it here

If the problem is browser-specific, please specify the device, OS, browser, and version

Provide any additional information here in as much as detail as you can

If you are experiencing issues with defer loading in your Angular application, here are some steps you can take to troubleshoot the problem:

  1. Check the version of ng serve: Make sure you are using the latest version of ng serve. You can check the version by running ng --version.
  2. Check for HMR issues: If you are using HMR, try disabling it by running ng serve --no-hmr. If defer loading works as expected, then the issue is likely related to HMR.
  3. Check the defer block: Make sure that the components in the defer block are correctly configured. Check that the @defer directive is applied to the correct components and that the defer block is correctly defined in the module.
  4. Check the application configuration: Make sure that the application configuration is correct. Check that the @defer directive is not overridden by any other configuration.

To ensure that defer loading works correctly in your Angular application, follow these best practices:

  1. Use the latest version of ng serve: Make sure you are using the latest version of ng serve.
  2. Disable HMR when necessary: If you are experiencing issues with defer loading, try disabling HMR by running ng serve --no-hmr.
  3. Check the defer block: Make sure that the components in the defer block are correctly configured.
  4. Check the application configuration: Make sure that the application configuration is correct.

By following these best practices and troubleshooting steps, you should be able to resolve any issues with defer loading in your Angular application.
Defer Loading in Angular: Q&A

In our previous article, we explored the issue with defer loading in Angular when using ng serve with Hot Module Replacement (HMR) enabled. We also provided a solution to resolve the issue. In this article, we will answer some frequently asked questions (FAQs) related to defer loading in Angular.

Q: What is defer loading in Angular?

A: Defer loading is a feature in Angular that allows developers to lazy load components and modules. This feature is particularly useful for improving the performance of applications by reducing the initial load time.

Q: Why is defer loading not working with ng serve and HMR enabled?

A: The issue with defer loading when using ng serve with HMR enabled is a known problem. When HMR is enabled, ng serve outputs a message to the console indicating that HMR is active. However, this does not seem to affect the behavior of defer loading.

Q: How can I resolve the issue with defer loading?

A: To resolve the issue, you can use the --no-hmr flag when running ng serve. This will disable HMR and allow defer loading to work as expected. Alternatively, you can build the application and serve it from the dist folder.

Q: What is the expected behavior of defer loading?

A: The expected behavior of defer loading is that components in the defer block should be lazy loaded when running ng serve with HMR enabled. This would allow developers to take advantage of the performance benefits of defer loading without having to disable HMR.

Q: How can I troubleshoot issues with defer loading?

A: To troubleshoot issues with defer loading, you can follow these steps:

  1. Check the version of ng serve.
  2. Check for HMR issues.
  3. Check the defer block.
  4. Check the application configuration.

Q: What are some best practices for using defer loading in Angular?

A: To ensure that defer loading works correctly in your Angular application, follow these best practices:

  1. Use the latest version of ng serve.
  2. Disable HMR when necessary.
  3. Check the defer block.
  4. Check the application configuration.

Q: Can I use defer loading with other Angular features?

A: Yes, you can use defer loading with other Angular features such as lazy loading and tree shaking. However, you should ensure that the features are correctly configured and that the application configuration is correct.

Q: Are there any known issues with defer loading in Angular?

A: Yes, there are known issues with defer loading in Angular. The issue with defer loading when using ng serve with HMR enabled is a known problem. However, the Angular team is working to resolve the issue.

In conclusion, defer loading is a powerful feature in Angular that allows developers to lazy load components and modules. However, there are some known issues with defer loading when using ng serve with HMR enabled. By following the best practices and troubleshooting steps outlined in this article, you should be able to resolve any issues with defer loading in your Angular application.