OBSERVATION: fromJS in combineReducers not successfully converting to Map in node (but works in browser)

[AshCoolman]

Observation

Problem

Note: using immutable ^3.8.1

Creating store works fine in browser.

But in node v9.2.0 test environment, combineReducers was complaining that finalReducers.filter is not a function.

TypeError: finalReducers.filter is not a function

at combineReducers (node_modules/redux-immutablejs/lib/utils/combineReducers.js:83:33)

Research

I instrumented combineReducers thus:

// redux-immutablejs/lib/utils/combineReducers.js
function combineReducers(reducers) {
  var finalReducers = isImmutable(reducers) ? reducers : _immutable2['default'].fromJS(reducers);
  console.log(`

    reducers was a ${typeof reducers}
    reducers ${isImmutable(reducers) ? 'is' : 'is not' } immutable
    reducers keys: ${Object.keys(reducers).length}

    finalReducers is a ${typeof finalReducers}
    finalReducers ${_immutable2['default'].Map.isMap(finalReducers) ? 'is' : 'is not'} a Map
    fromJS(finalReducers) is a ${
      _immutable2['default'].Map.isMap(
        _immutable2['default'].fromJS(reducers)
      )
      ? 'Map' 
      : _immutable2['default'].List.isList(
        _immutable2['default'].fromJS(reducers)
      )
      ? 'List'
      : 'not list or map?'
    }
    `      
  )
  finalReducers = finalReducers.filter(function (v) {
    return typeof v === 'function';
  });
// ...

Browser (Chrome) output:

      reducers was a object
      reducers is not immutable
      reducers keys: 29

      finalReducers is a object
      finalReducers is a Map

On node v9.2.0 Error

      reducers was a object
      reducers is not immutable
      reducers keys: 29

      finalReducers is a object
      finalReducers is not a Map

Work-around

I just convert to map before I pass into combineReducers

Naive suggestion

It must be something to do with the node environment (babel?). But perhaps for safety's sake:

var finalReducers = isImmutable(reducers) ? reducers : _immutable2['default'].fromJS(reducers);

could be changed to:

  var finalReducers = isImmutable(reducers) ? reducers : _immutable2['default'].Map(reducers);