Function mountComponent

packages/react-devtools-shared/src/backend/legacy/renderer.js:223–268

(fn, args)

    // React 15
    oldReconcilerMethods = decorateMany(renderer.Reconciler, {
      mountComponent(fn, args) {
        const internalInstance = args[0];
        const hostContainerInfo = args[3];
        if (getElementType(internalInstance) === ElementTypeOtherOrUnknown) {
          // $FlowFixMe[object-this-reference] found when upgrading Flow
          return fn.apply(this, args);
        }
        if (hostContainerInfo._topLevelWrapper === undefined) {
          // SSR
          // $FlowFixMe[object-this-reference] found when upgrading Flow
          return fn.apply(this, args);
        }

        const id = getID(internalInstance);
        // Push the operation.
        const parentID =
          parentIDStack.length > 0
            ? parentIDStack[parentIDStack.length - 1]
            : 0;
        recordMount(internalInstance, id, parentID);
        parentIDStack.push(id);

        // Remember the root.
        internalInstanceToRootIDMap.set(
          internalInstance,
          getID(hostContainerInfo._topLevelWrapper),
        );

        try {
          // $FlowFixMe[object-this-reference] found when upgrading Flow
          const result = fn.apply(this, args);
          parentIDStack.pop();
          return result;
        } catch (err) {
          parentIDStack = [];
          throw err;
        } finally {
          if (parentIDStack.length === 0) {
            const rootID = internalInstanceToRootIDMap.get(internalInstance);
            if (rootID === undefined) {
              throw new Error('Expected to find root ID.');
            }
            flushPendingEvents(rootID);
          }
        }
      },
      performUpdateIfNecessary(fn, args) {
        const internalInstance = args[0];
        if (getElementType(internalInstance) === ElementTypeOtherOrUnknown) {