feat($scrollRestoration): add feature to disable automatic scroll res…

…toration via manual: true optio

.eslintrc.js

@@ -55,6 +55,7 @@ module.exports = {
     'no-unused-vars': 1,
     'import/no-unresolved': 1,
     'flowtype/no-weak-types': 1,
+    'consistent-return': 1,
     semi: [2, 'never'],
     'no-console': [2, { allow: ['warn', 'error'] }],
     'flowtype/semi': [2, 'never'],

README.md

@@ -186,7 +186,7 @@ and you're free to make your own. Basically it passes the `href` on to **Redux F
 into a URL for you! The package is obvious enough once you get the hang of what's going on here--check it
 out when you're ready: [redux-first-router-link](http://github.com/faceyspacey/redux-first-router-link). And if 
 you're wondering, we don't offer route matching components like *React Router*--that's what state is for! 
-See our FAQ below.
+See our [FAQ](#faq) below.
 
 ## routesMap
 

src/action-creators/middlewareCreateAction.js

@@ -8,11 +8,11 @@ export default (
   action: Object,
   routesMap: RoutesMap,
   prevLocation: Location,
-  history: History
+  hist: History
 ): Action => {
   try {
     const pathname = actionToPath(action, routesMap)
-    const kind = getKind(pathname, history)
+    const [kind, history] = getKindAndHistory(!!hist.entries, pathname, hist)
     return nestAction(pathname, action, prevLocation, history, kind)
   }
   catch (e) {
@@ -25,49 +25,45 @@ export default (
       pathname,
       { type: NOT_FOUND, payload },
       prevLocation,
-      history
+      hist
     )
   }
 }
 
-const getKind = (pathname: string, history: History): ?string => {
-  const isMemoryHistory = !!history.entries
-
+// REACT NATIVE FEATURE:
+// emulate npm `history` package and `historyCreateAction`  so that actions
+// and state indicate the user went back or forward. The idea is if you are
+// going back or forward to a route you were just at, apps can determine
+// from `state.location.backNext` and `action.backNext` that things like
+// scroll position should be restored.
+// NOTE: for testability, history is also returned to make this a pure function
+const getKindAndHistory = (
+  isMemoryHistory: boolean,
+  pathname: string,
+  history: History
+): [?string, History] => {
   if (!isMemoryHistory) {
-    return undefined
+    return [undefined, history]
   }
 
-  const isLast = history.index === history.length - 1
-  const prev = history.entries[history.index - 1]
-  // REACT NATIVE FEATURE:
-  // emulate npm `history` package and `historyCreateAction`  so that actions
-  // and state indicate the user went back or forward. The idea is if you are
-  // going back or forward to a route you were just at, apps can determine
-  // from `state.location.backNext` and `action.backNext` that things like
-  // scroll position should be restored.
-  if (isLast && prev) {
-    const prevPath = prev.pathname
-    const isGoingBack = prevPath === pathname
-
-    if (isGoingBack) {
-      history.index--
-      return 'backNext'
-    }
-
-    return undefined
+  if (goingBack(pathname, history)) {
+    history.index--
+    return ['backNext', history]
+  }
+  else if (goingForward(pathname, history)) {
+    history.index++
+    return ['backNext', history]
   }
 
-  const next = history.entries[history.index + 1]
-
-  if (next) {
-    const nextPath = next.pathname
-    const isGoingForward = nextPath === pathname
+  return [undefined, history]
+}
 
-    if (isGoingForward) {
-      history.index++
-      return 'backNext'
-    }
-  }
+const goingBack = (pathname: string, history: History): boolean => {
+  const prev = history.entries[history.index - 1]
+  return prev && prev.pathname === pathname
+}
 
-  return undefined
+const goingForward = (pathname: string, history: History): boolean => {
+  const next = history.entries[history.index + 1]
+  return next && next.pathname === pathname
 }

src/connectRoutes.js

@@ -277,22 +277,8 @@ export default (
 
     history.listen(_historyAttemptDispatchAction.bind(null, store))
 
-    _updateScroll = () => {
-      if (scrollBehavior) {
-        scrollBehavior.updateScroll(prevState, nextState)
-      }
-      else if (process.env.NODE_ENV !== 'production') {
-        throw new Error(
-          `[redux-first-router] you must set the \`restoreScroll\` option before
-          you can call \`updateScroll\``
-        )
-      }
-    }
-
     // update the scroll position after initial rendering of page
-    if (scrollBehavior) {
-      setTimeout(_updateScroll, 0)
-    }
+    setTimeout(() => _updateScroll(false))
 
     // dispatch the first location-aware action so initial app state is based on the url on load
     if (!location.hasSSR || isServer()) {
@@ -337,14 +323,28 @@ export default (
       }
     }
 
-    if (scrollBehavior) {
-      _updateScroll()
-    }
+    _updateScroll(false)
   }
 
+  /* SIDE_EFFECTS - client-only state that must escape closure */
+
   _history = history
   _scrollBehavior = scrollBehavior
 
+  _updateScroll = (performedByUser: boolean = true) => {
+    if (scrollBehavior) {
+      if (!scrollBehavior.manual) {
+        scrollBehavior.updateScroll(prevState, nextState)
+      }
+    }
+    else if (process.env.NODE_ENV !== 'production' && performedByUser) {
+      throw new Error(
+        `[redux-first-router] you must set the \`restoreScroll\` option before
+        you can call \`updateScroll\``
+      )
+    }
+  }
+
   /* RETURN  */
 
   return {