In Angular, a circular dependency occurs when two or more modules or components have interdependent references to each other, forming a loop. This means that Module A depends on Module B, and Module B depends on Module A, resulting in an unresolved reference and potential runtime issues.

Circular dependencies can cause various problems in an Angular application, such as:

1. Initialization errors: Angular needs to resolve dependencies before creating instances of components or services. Circular dependencies can lead to initialization errors because Angular cannot determine which module or component should be instantiated first.
2. Runtime errors: If modules or components depend on each other in a circular manner, it can cause runtime errors or infinite loops when trying to resolve the dependencies.

There are may ways To find circular dependencies in an Angular application.

Alternative 1

 npx madge --circular --extensions ts .

By running a cli command npx madge –circular –extensions ts ./ we can quickly get a list of circular dependencies of all . ts files in current directory and its subdirectories. That’s it! Now you see where you have circular dependencies and can go and fix it.

Alternative 2

• Enable strict mode: Circular dependencies are not allowed in Angular by default, but you can enable strict mode to receive warnings about them. Open the tsconfig.json file in the root directory of your Angular project and ensure that the "angularCompilerOptions" section includes "strictInjectionParameters": true.

• Build the application: Run the build process for your Angular application by executing the following command in the terminal:

ng build

This will compile your application and check for any circular dependencies. If circular dependencies are detected, you will see warnings or errors in the console.

• Inspect build output: After the build process completes, inspect the build output in the terminal. Look for any warnings or errors related to circular dependencies. The build output will indicate the affected files or components involved in the circular dependencies.

• Analyze imports and dependencies: Review the affected files and their import statements to identify the circular dependencies. Angular dependencies are typically managed through import statements in Angular modules or component files. Look for any mutual or cyclic imports between files.

• Resolve circular dependencies: Once you have identified the circular dependencies, you need to resolve them. There are a few strategies you can use:
  • Refactor code: Analyze the dependencies and consider refactoring your code to eliminate the circular dependencies. This might involve reorganizing code, extracting shared functionality into separate modules, or creating service providers.
  • Use a shared service: If you have components that depend on each other, consider introducing a shared service to manage the communication between them. This can help break the circular dependency and provide a clean separation of concerns.
  • Review module structure: Review the structure of your Angular modules. Ensure that modules are organized in a logical and hierarchical manner, with clear boundaries and dependencies. Make sure that modules only import what they require and avoid unnecessary imports.
  • Use lazy loading: If circular dependencies occur between feature modules, consider using lazy loading to load modules on-demand. This can help break the circular dependencies by delaying the loading of modules until they are actually needed.
  • Test and validate: After resolving the circular dependencies, rebuild your application and test it throughly to ensure that everything works as expected.