Angular Circular Dependency Detector

Angular applications, especially larger ones, can sometimes suffer from a subtle but detrimental issue: circular dependencies between components, services, or other injectables. These circular dependencies can lead to unexpected runtime errors during bootstrapping or module initialization, making debugging difficult and potentially breaking your application. This challenge asks you to implement a mechanism to detect and report these circular dependencies.

Problem Description

You need to develop a TypeScript utility that can analyze an Angular application's module structure and identify any circular dependencies between its providers. This utility should be able to process a representation of your Angular application's modules and their dependencies and output a clear report of any detected circularities.

Key Requirements:

• The utility should accept a data structure representing Angular modules, their declarations (components, directives, pipes), and their providers (services, etc.).
• It should traverse the dependency graph of providers.
• It must identify cycles in this dependency graph.
• The output should be a human-readable report listing the modules involved in each detected circular dependency.

Expected Behavior:

When provided with a valid representation of an Angular application's module and provider structure, the utility should accurately pinpoint all circular dependencies. If no circular dependencies are found, it should indicate that.

Edge Cases:

• Modules with no providers.
• Modules with providers that don't depend on anything.
• Complex dependency chains that might eventually form a cycle.
• Scenarios where a provider is declared in multiple modules.

Examples

Example 1:

Input:
{
  "AppModule": {
    "providers": ["ServiceA", "ServiceB"],
    "imports": []
  },
  "ServiceA": {
    "dependencies": ["ServiceB"]
  },
  "ServiceB": {
    "dependencies": ["ServiceA"]
  }
}

Output:
Circular dependency detected:
  - AppModule -> ServiceA -> ServiceB -> ServiceA

Explanation: ServiceA depends on ServiceB, and ServiceB depends on ServiceA, creating a direct circular dependency within the context of AppModule.

Example 2:

Input:
{
  "AppModule": {
    "providers": ["ServiceA"],
    "imports": ["FeatureModule"]
  },
  "FeatureModule": {
    "providers": ["ServiceB"],
    "imports": []
  },
  "ServiceA": {
    "dependencies": ["ServiceB"]
  },
  "ServiceB": {
    "dependencies": ["ServiceC"]
  },
  "ServiceC": {
    "dependencies": ["ServiceA"]
  }
}

Output:
Circular dependency detected:
  - AppModule -> FeatureModule -> ServiceA -> ServiceB -> ServiceC -> ServiceA

Explanation: Even though the direct dependencies are between services, the cycle is formed through the import of FeatureModule into AppModule. ServiceA (in AppModule) depends on ServiceB (in FeatureModule), ServiceB depends on ServiceC, and ServiceC ultimately depends back on ServiceA.

Example 3:

Input:
{
  "AppModule": {
    "providers": ["ServiceA", "ServiceB"],
    "imports": []
  },
  "ServiceA": {
    "dependencies": []
  },
  "ServiceB": {
    "dependencies": []
  }
}

Output:
No circular dependencies detected.

Explanation: ServiceA and ServiceB have no dependencies on each other or any other services that would form a cycle.

Constraints

• The input data structure will be a JSON object representing modules and their providers/dependencies.
• Provider names and module names will be strings.
• The depth of dependency chains will not exceed 1000 for performance reasons.
• The number of modules and providers will not exceed 1000 each.

Notes

You can model the Angular application's structure using interfaces in TypeScript. Consider how you would represent the graph of providers. Algorithms for cycle detection in directed graphs, such as Depth First Search (DFS), would be highly relevant here. Think about how to handle the mapping between modules and the services they provide, as dependencies are often expressed implicitly through module imports.