fix: assure only one clone ever exists in memory

Clones are now handled in the same way that instances are.  If you call clone twice on the same object, the return value is always the same clone.  This assures that only one clone ever exists in memory, creating a very consistent API.  (Of course, more clones can always be stored anywhere in an app by manual use of a cloning utility like fast-copy)

Author: marshallswain

src/service-module/make-model.ts

@@ -46,6 +46,7 @@ export default function makeModel(options: FeathersVuexOptions) {
     // Think of these as abstract static properties
     public static servicePath: string
     public static namespace: string
+    public static keepCopiesInStore = options.keepCopiesInStore
     // eslint-disable-next-line
     public static instanceDefaults(data, { models, store }) {
       return data
@@ -79,20 +80,30 @@ export default function makeModel(options: FeathersVuexOptions) {
     public constructor(data, options: BaseModelInstanceOptions) {
       // You have to pass at least an empty object to get a tempId.
       const originalData = data
+      data = data || {}
       options = Object.assign({}, defaultOptions, options)
+
       const {
         store,
+        keepCopiesInStore,
+        copiesById: copiesByIdOnModel,
         models,
         instanceDefaults,
         idField,
+        tempIdField,
         setupInstance,
         getFromStore,
+        namespace,
         _commit
       } = this.constructor as typeof BaseModel
       const id = getId(data, idField)
       const hasValidId = id !== null && id !== undefined
+      const tempId = data && data.hasOwnProperty(tempIdField) && data[tempIdField]
+      const hasValidTempId = tempId !== null && tempId !== undefined
+      const copiesById = keepCopiesInStore
+        ? store.state[namespace].copiesById
+        : copiesByIdOnModel
 
-      data = data || {}
 
       const existingItem = hasValidId && !options.clone
         ? getFromStore.call(this.constructor, id)
@@ -105,6 +116,16 @@ export default function makeModel(options: FeathersVuexOptions) {
         return existingItem
       }
 
+      // If cloning and a clone already exists, update and return the original clone. Only one clone is allowed.
+      const existingClone = (hasValidId || hasValidTempId) && options.clone
+        ? copiesById[id] || copiesById[tempId]
+        : null
+      if (existingClone) {
+        // This must be done in a mutation to avoid Vuex errors.
+        _commit.call(this.constructor, 'merge', { dest: existingClone, source: data })
+        return existingClone
+      }
+
       // Mark as a clone
       if (options.clone) {
         Object.defineProperty(this, '__isClone', {

src/service-module/service-module.mutations.ts

@@ -113,8 +113,13 @@ export default function makeServiceMutations() {
     }
   }
 
+  function merge(state, { dest, source }) {
+    mergeWithAccessors(dest, source)
+  }
+
   return {
     mergeInstance,
+    merge,
     addItem(state, item) {
       addItems(state, [item])
     },