Class Scope

packages/compiler/src/render3/view/t2_binder.ts:290–520

* Represents a binding scope within a template. * * Any variables, references, or other named entities declared within the template will * be captured and available by name in `namedEntities`. Additionally, child templates will * be analyzed and have their child `Scope`s available in `childScope

 * be analyzed and have their child `Scope`s available in `childScopes`.
 */
class Scope implements Visitor {
  /**
   * Named members of the `Scope`, such as `Reference`s or `Variable`s.
   */
  readonly namedEntities = new Map<string, TemplateEntity>();

  /**
   * Set of element-like nodes that belong to this scope.
   */
  readonly elementLikeInScope = new Set<Element | Component>();

  /**
   * Child `Scope`s for immediately nested `ScopedNode`s.
   */
  readonly childScopes = new Map<ScopedNode, Scope>();

  /** Whether this scope is deferred or if any of its ancestors are deferred. */
  readonly isDeferred: boolean;

  private constructor(
    readonly parentScope: Scope | null,
    readonly rootNode: ScopedNode | null,
  ) {
    this.isDeferred =
      parentScope !== null && parentScope.isDeferred ? true : rootNode instanceof DeferredBlock;
  }

  static newRootScope(): Scope {
    return new Scope(null, null);
  }

  /**
   * Process a template (either as a `Template` sub-template with variables, or a plain array of
   * template `Node`s) and construct its `Scope`.
   */
  static apply(template: ScopedNode | Node[]): Scope {
    const scope = Scope.newRootScope();
    scope.ingest(template);
    return scope;
  }

  /**
   * Internal method to process the scoped node and populate the `Scope`.
   */
  private ingest(nodeOrNodes: ScopedNode | Node[]): void {
    if (nodeOrNodes instanceof Template) {
      // Variables on an <ng-template> are defined in the inner scope.
      nodeOrNodes.variables.forEach((node) => this.visitVariable(node));

      // Process the nodes of the template.
      nodeOrNodes.children.forEach((node) => node.visit(this));
    } else if (nodeOrNodes instanceof IfBlockBranch) {
      if (nodeOrNodes.expressionAlias !== null) {
        this.visitVariable(nodeOrNodes.expressionAlias);
      }
      nodeOrNodes.children.forEach((node) => node.visit(this));
    } else if (nodeOrNodes instanceof ForLoopBlock) {
      this.visitVariable(nodeOrNodes.item);