Implementing View Encapsulation in Angular Components

Angular's view encapsulation feature is crucial for maintaining component isolation and preventing style conflicts. This challenge asks you to create a simple Angular component that demonstrates and utilizes different view encapsulation modes to understand their impact on styling and component interaction. Successfully completing this challenge will solidify your understanding of how to control the scope of CSS styles within Angular components.

Problem Description

You are tasked with building a simple Angular component called MyComponent that displays a list of items. This component should have its own CSS styles. The goal is to implement this component with different view encapsulation modes (None, Emulated, and ShadowDom) and observe how the styles affect the component and its parent. You need to create three separate components, each using a different encapsulation mode, and demonstrate how styles defined within each component are scoped. The parent component, AppComponent, will also have some styles. You need to verify that the MyComponent styles do not bleed into the AppComponent and vice versa, and that the different encapsulation modes behave as expected.

Key Requirements:

• Create three Angular components: MyComponentNone, MyComponentEmulated, and MyComponentShadowDom.
• Each component should display a list of at least three items (e.g., using <ul> and <li>).
• Each component should have its own CSS styles applied to the list items (e.g., different colors, fonts).
• The AppComponent should also have some CSS styles applied to its own elements.
• Demonstrate that the styles within each MyComponent are encapsulated and do not affect the styles of the AppComponent or other MyComponent instances.
• Verify that ShadowDom encapsulation creates a shadow DOM, isolating the component's styles completely.

Expected Behavior:

• MyComponentNone: Styles are global and can affect other components and the parent component.
• MyComponentEmulated: Styles are scoped to the component using CSS variables and attribute selectors.
• MyComponentShadowDom: Styles are encapsulated within a shadow DOM, providing the strongest isolation.

Edge Cases to Consider:

• Global styles defined in styles.css or styleUrls in angular.json should not be affected by the component styles.
• Styles defined in the parent component (AppComponent) should not be affected by the component styles.
• Verify that styles defined within a ShadowDom component are truly isolated and cannot be accessed from outside the component.

Examples

Example 1: MyComponentEmulated

Input:  AppComponent with a paragraph "Hello from App!" and MyComponentEmulated displaying a list of items with a red color.
Output: App Component displays "Hello from App!" in its default style. MyComponentEmulated displays its list items in red.  The "Hello from App!" paragraph is *not* red.
Explanation: Emulated encapsulation prevents the red color from leaking out of MyComponentEmulated.

Example 2: MyComponentShadowDom

Input: AppComponent with a paragraph "Hello from App!" and MyComponentShadowDom displaying a list of items with a blue color.
Output: App Component displays "Hello from App!" in its default style. MyComponentShadowDom displays its list items in blue. The "Hello from App!" paragraph is *not* blue.
Explanation: ShadowDom encapsulation provides complete isolation, preventing the blue color from affecting the parent component.

Example 3: MyComponentNone

Input: AppComponent with a paragraph "Hello from App!" and MyComponentNone displaying a list of items with a green color.
Output: App Component displays "Hello from App!" in green. MyComponentNone displays its list items in green.
Explanation:  No encapsulation means the green color leaks out and affects the parent component.

Constraints

• The solution must be implemented using TypeScript.
• The Angular version should be 14 or higher.
• The solution should be modular and well-structured.
• The code should be readable and maintainable.
• The solution should demonstrate the correct behavior for all three view encapsulation modes.
• The solution should not introduce any unnecessary dependencies.

Notes

• Consider using Angular CLI to generate the components.
• Pay close attention to the encapsulation property in the @Component decorator.
• Use your browser's developer tools to inspect the DOM and CSS styles to verify the encapsulation behavior.
• The focus is on demonstrating the effect of each encapsulation mode, not on creating a complex application. Keep the component's functionality simple.
• You can use simple HTML elements (e.g., <ul>, <li>, <p>) for the component's content.