Function getLContext

packages/core/src/render3/context_discovery.ts:42–130

(target: any)

 * @param target Component, Directive or DOM Node.
 */
export function getLContext(target: any): LContext | null {
  let mpValue = readPatchedData(target);
  if (mpValue) {
    // only when it's an array is it considered an LView instance
    // ... otherwise it's an already constructed LContext instance
    if (isLView(mpValue)) {
      const lView: LView = mpValue!;
      let nodeIndex: number;
      let component: any = undefined;
      let directives: any[] | null | undefined = undefined;

      if (isComponentInstance(target)) {
        nodeIndex = findViaComponent(lView, target);
        if (nodeIndex == -1) {
          throw new Error('The provided component was not found in the application');
        }
        component = target;
      } else if (isDirectiveInstance(target)) {
        nodeIndex = findViaDirective(lView, target);
        if (nodeIndex == -1) {
          throw new Error('The provided directive was not found in the application');
        }
        directives = getDirectivesAtNodeIndex(nodeIndex, lView);
      } else {
        nodeIndex = findViaNativeElement(lView, target as RElement);
        if (nodeIndex == -1) {
          return null;
        }
      }

      // the goal is not to fill the entire context full of data because the lookups
      // are expensive. Instead, only the target data (the element, component, container, ICU
      // expression or directive details) are filled into the context. If called multiple times
      // with different target values then the missing target data will be filled in.
      const native = unwrapRNode(lView[nodeIndex]);
      const existingCtx = readPatchedData(native);
      const context: LContext =
        existingCtx && !Array.isArray(existingCtx)
          ? existingCtx
          : createLContext(lView, nodeIndex, native);

      // only when the component has been discovered then update the monkey-patch
      if (component && context.component === undefined) {
        context.component = component;
        attachPatchData(context.component, context);
      }

      // only when the directives have been discovered then update the monkey-patch
      if (directives && context.directives === undefined) {
        context.directives = directives;
        for (let i = 0; i < directives.length; i++) {
          attachPatchData(directives[i], context);
        }
      }

      attachPatchData(context.native, context);
      mpValue = context;
    }