withState hoc

src/combineEpics.js

@@ -15,7 +15,8 @@ export const combineEpics = epicsArray => (actions, store) => {
       throw new TypeError('The array passed to combineEpics must contain only Epics (functions).')
     }
 
-    const out = epic(actions, store)
+    // withState HOC support
+    const out = epic.length === 1 ? epic(actions) : epic(store, actions)
 
     if (!out || !out.source) {
       const epicIdentifier = epic.name

src/index.js

@@ -5,3 +5,4 @@ export { EPIC_END } from './constants'
 export { select } from './select'
 export { selectArray } from './selectArray'
 export { withState } from './withState'
+export { mergeState } from './mergeState'

src/mergeState.js

@@ -0,0 +1,5 @@
+import { snapshot } from '@most/core'
+
+const toArray = (state, action) => [state, action]
+
+export const mergeState = snapshot(toArray)

src/withState.js

@@ -1,5 +1,8 @@
-import { snapshot } from '@most/core'
+const unCurry2 = fn => (arg1, arg2) =>
+  fn.length === 1 ? fn(arg1)(arg2) : fn(arg1, arg2)
 
-const toArray = (state, action) => [state, action]
-
-export const withState = snapshot(toArray)
+// withState :: (s$ -> a$ -> a$) -> s$ -> a$ -> a$
+export const withState = epic => {
+  const uncurriedEpic = unCurry2(epic)
+  return (state$, action$) => uncurriedEpic(state$, action$)
+}

tests/combineEpics.test.js

@@ -1,7 +1,7 @@
 import test from 'ava'
 import { map, tap, runEffects, never, MulticastSource } from '@most/core'
 import { newDefaultScheduler } from '@most/scheduler'
-import { combineEpics, select } from '../src/'
+import { combineEpics, select, withState } from '../src/'
 
 test('combineEpics should combine an array of epics', t => {
   const ACTION_1 = 'ACTION_1'
@@ -10,14 +10,18 @@ test('combineEpics should combine an array of epics', t => {
   const DELEGATED_2 = 'DELEGATED_2'
   const MOCKED_STORE = { I: 'am', a: 'store' }
 
-  const epic1 = (actions$, store) => map(
-    action => ({ type: DELEGATED_1, action, store }),
-    select(ACTION_1, actions$)
+  const epic1 = withState(
+    (store, actions$) => map(
+      action => ({ type: DELEGATED_1, action, store }),
+      select(ACTION_1, actions$)
+    )
   )
 
-  const epic2 = (actions$, store) => map(
-    action => ({ type: DELEGATED_2, action, store }),
-    select(ACTION_2, actions$)
+  const epic2 = withState(
+    (store, actions$) => map(
+      action => ({ type: DELEGATED_2, action, store }),
+      select(ACTION_2, actions$)
+    )
   )
 
   const epic = combineEpics([