function applyAction()

in packages/recoil/core/Recoil_RecoilValueInterface.js [132:173]
38 lines of code
6 McCabe index (conditional complexity)

function applyAction(store: Store, state: TreeState, action: Action<mixed>) {
  if (action.type === 'set') {
    const {recoilValue, valueOrUpdater} = action;
    const newValue = valueFromValueOrUpdater(
      store,
      state,
      recoilValue,
      valueOrUpdater,
    );

    const writes = setNodeValue(store, state, recoilValue.key, newValue);

    for (const [key, loadable] of writes.entries()) {
      writeLoadableToTreeState(state, key, loadable);
    }
  } else if (action.type === 'setLoadable') {
    const {
      recoilValue: {key},
      loadable,
    } = action;
    writeLoadableToTreeState(state, key, loadable);
  } else if (action.type === 'markModified') {
    const {
      recoilValue: {key},
    } = action;
    state.dirtyAtoms.add(key);
  } else if (action.type === 'setUnvalidated') {
    // Write value directly to state bypassing the Node interface as the node
    // definitions may not have been loaded yet when processing the initial snapshot.
    const {
      recoilValue: {key},
      unvalidatedValue,
    } = action;
    const node = getNodeMaybe(key);
    node?.invalidate?.(state);
    state.atomValues.delete(key);
    state.nonvalidatedAtoms.set(key, unvalidatedValue);
    state.dirtyAtoms.add(key);
  } else {
    recoverableViolation(`Unknown action ${action.type}`, 'recoil');
  }
}