Allow takeSnapshot to specify specific stores

- Resolves Issue #54
- This enables snapshotting a subset of the app data
- `takeSnapshot` returns stringified JSON containing just the subset
  of data specified. The new snapshot is merged with the LAST_SNAPSHOT data
  to ensure that the last snapshot of the stores not specified in the subset
  is not lost. This also means that rollbacks will just work.

Author: jdlehman

README.md

@@ -529,12 +529,12 @@ Restart the loop by making your views kick off new actions.
 
 ### Snapshots
 
-`takeSnapshot :: String`
+`takeSnapshot :: ?...String -> String`
 
 Snapshots are a core component of alt. The idea is that at any given point in time you can `takeSnapshot` and have your entire application's state
 serialized for persistence, transferring, logging, or debugging.
 
-Taking a snapshot is as easy as calling `alt.takeSnapshot()`.
+Taking a snapshot is as easy as calling `alt.takeSnapshot()`. It can also take an optional number of arguments as strings which correspond to the store names you would like to include in the snapshot. This allows you to take a snapshot of a subset of your app's data.
 
 ### Bootstrapping
 

dist/alt-browser-with-addons.js

@@ -1258,7 +1258,12 @@ var setAppState = function (instance, data, onStore) {
 };
 
 var snapshot = function (instance) {
-  return JSON.stringify(Object.keys(instance.stores).reduce(function (obj, key) {
+  for (var _len = arguments.length, storeNames = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    storeNames[_key - 1] = arguments[_key];
+  }
+
+  var stores = storeNames.length ? storeNames : Object.keys(instance.stores);
+  return JSON.stringify(stores.reduce(function (obj, key) {
     var store = instance.stores[key];
     var customSnapshot = store[LIFECYCLE].serialize && store[LIFECYCLE].serialize();
     obj[key] = customSnapshot ? customSnapshot : store.getState();
@@ -1509,8 +1514,16 @@ var Alt = (function () {
     },
     takeSnapshot: {
       value: function takeSnapshot() {
-        var state = snapshot(this);
-        this[LAST_SNAPSHOT] = state;
+        for (var _len = arguments.length, storeNames = Array(_len), _key = 0; _key < _len; _key++) {
+          storeNames[_key] = arguments[_key];
+        }
+
+        var state = snapshot.apply(undefined, [this].concat(storeNames));
+        if (this[LAST_SNAPSHOT]) {
+          assign(this[LAST_SNAPSHOT], state);
+        } else {
+          this[LAST_SNAPSHOT] = state;
+        }
         return state;
       }
     },

dist/alt-browser.js

@@ -1002,7 +1002,12 @@ var setAppState = function (instance, data, onStore) {
 };
 
 var snapshot = function (instance) {
-  return JSON.stringify(Object.keys(instance.stores).reduce(function (obj, key) {
+  for (var _len = arguments.length, storeNames = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    storeNames[_key - 1] = arguments[_key];
+  }
+
+  var stores = storeNames.length ? storeNames : Object.keys(instance.stores);
+  return JSON.stringify(stores.reduce(function (obj, key) {
     var store = instance.stores[key];
     var customSnapshot = store[LIFECYCLE].serialize && store[LIFECYCLE].serialize();
     obj[key] = customSnapshot ? customSnapshot : store.getState();
@@ -1253,8 +1258,16 @@ var Alt = (function () {
     },
     takeSnapshot: {
       value: function takeSnapshot() {
-        var state = snapshot(this);
-        this[LAST_SNAPSHOT] = state;
+        for (var _len = arguments.length, storeNames = Array(_len), _key = 0; _key < _len; _key++) {
+          storeNames[_key] = arguments[_key];
+        }
+
+        var state = snapshot.apply(undefined, [this].concat(storeNames));
+        if (this[LAST_SNAPSHOT]) {
+          assign(this[LAST_SNAPSHOT], state);
+        } else {
+          this[LAST_SNAPSHOT] = state;
+        }
         return state;
       }
     },

dist/alt-with-runtime.js

@@ -257,7 +257,12 @@ var setAppState = function (instance, data, onStore) {
 };
 
 var snapshot = function (instance) {
-  return JSON.stringify(Object.keys(instance.stores).reduce(function (obj, key) {
+  for (var _len = arguments.length, storeNames = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    storeNames[_key - 1] = arguments[_key];
+  }
+
+  var stores = storeNames.length ? storeNames : Object.keys(instance.stores);
+  return JSON.stringify(stores.reduce(function (obj, key) {
     var store = instance.stores[key];
     var customSnapshot = store[LIFECYCLE].serialize && store[LIFECYCLE].serialize();
     obj[key] = customSnapshot ? customSnapshot : store.getState();
@@ -503,8 +508,16 @@ var Alt = (function () {
     },
     takeSnapshot: {
       value: function takeSnapshot() {
-        var state = snapshot(this);
-        this[LAST_SNAPSHOT] = state;
+        for (var _len = arguments.length, storeNames = Array(_len), _key = 0; _key < _len; _key++) {
+          storeNames[_key] = arguments[_key];
+        }
+
+        var state = snapshot.apply(undefined, [this].concat(storeNames));
+        if (this[LAST_SNAPSHOT]) {
+          assign(this[LAST_SNAPSHOT], state);
+        } else {
+          this[LAST_SNAPSHOT] = state;
+        }
         return state;
       }
     },

dist/alt.js

@@ -271,7 +271,12 @@ var setAppState = function (instance, data, onStore) {
 };
 
 var snapshot = function (instance) {
-  return JSON.stringify(Object.keys(instance.stores).reduce(function (obj, key) {
+  for (var _len = arguments.length, storeNames = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
+    storeNames[_key - 1] = arguments[_key];
+  }
+
+  var stores = storeNames.length ? storeNames : Object.keys(instance.stores);
+  return JSON.stringify(stores.reduce(function (obj, key) {
     var store = instance.stores[key];
     var customSnapshot = store[LIFECYCLE].serialize && store[LIFECYCLE].serialize();
     obj[key] = customSnapshot ? customSnapshot : store.getState();
@@ -520,8 +525,16 @@ var Alt = (function () {
     },
     takeSnapshot: {
       value: function takeSnapshot() {
-        var state = snapshot(this);
-        this[LAST_SNAPSHOT] = state;
+        for (var _len = arguments.length, storeNames = Array(_len), _key = 0; _key < _len; _key++) {
+          storeNames[_key] = arguments[_key];
+        }
+
+        var state = snapshot.apply(undefined, [this].concat(storeNames));
+        if (this[LAST_SNAPSHOT]) {
+          assign(this[LAST_SNAPSHOT], state);
+        } else {
+          this[LAST_SNAPSHOT] = state;
+        }
         return state;
       }
     },

docs/takeSnapshot.md

@@ -7,13 +7,14 @@ permalink: /docs/takeSnapshot/
 
 # takeSnapshot
 
-> (): string
+> (...storeNames: ?string): string
 
-Take snapshot provides you with the entire application's state serialized to JSON.
+Take snapshot provides you with the entire application's state serialized to JSON, by default, but you may also pass in store names to take a snapshot of a subset of the application's state.
 
 Snapshots are a core component of alt. The idea is that at any given point in time you can `takeSnapshot` and have your entire application's state
-serialized for persistence, transfering, logging, or debugging.
+serialized for persistence, transferring, logging, or debugging.
 
 ```js
 var snapshot = alt.takeSnapshot();
+var partialSnapshot = alt.takeSnapshot('Store1', 'Store3');
 ```

src/alt.js

@@ -239,9 +239,10 @@ const setAppState = (instance, data, onStore) => {
   })
 }
 
-const snapshot = (instance) => {
+const snapshot = (instance, ...storeNames) => {
+  const stores = storeNames.length ? storeNames : Object.keys(instance.stores)
   return JSON.stringify(
-    Object.keys(instance.stores).reduce((obj, key) => {
+    stores.reduce((obj, key) => {
       const store = instance.stores[key]
       const customSnapshot = store[LIFECYCLE].serialize && store[LIFECYCLE].serialize()
       obj[key] = customSnapshot ? customSnapshot : store.getState()
@@ -456,9 +457,14 @@ class Alt {
     }, exportObj)
   }
 
-  takeSnapshot() {
-    const state = snapshot(this)
-    this[LAST_SNAPSHOT] = state
+  takeSnapshot(...storeNames) {
+    const state = snapshot(this, ...storeNames)
+    if(this[LAST_SNAPSHOT]) {
+      assign(this[LAST_SNAPSHOT], state)
+    }
+    else {
+      this[LAST_SNAPSHOT] = state
+    }
     return state
   }
 

test/index.js

@@ -473,6 +473,12 @@ const tests = {
     assert(JSON.parse(snapshot).MyStore.name === 'bear', 'the snapshot is not affected by action')
   },
 
+  'specifying stores to snapshot'() {
+    const snapshot = alt.takeSnapshot('MyStore', 'AltSecondStore')
+    assert.deepEqual(Object.keys(JSON.parse(snapshot)), ['MyStore', 'AltSecondStore'], 'the snapshot includes specified stores')
+    assert.isFalse(Object.keys(JSON.parse(snapshot)).includes('LifeCycleStore'), 'the snapshot does not include unspecified stores')
+  },
+
   'serializing/deserializing snapshot/bootstrap data'(){
     myActions.updateAnotherVal(11)
     const snapshot = alt.takeSnapshot()