feat: allow partial patching with params.data

## Partial data on patch

As of version 3.9.0, you can provide an object as `params.data`, and Feathers-Vuex will use `params.data` as the patch data.  This change was made to the service-module, itself, so it will work for `patch` across all of feathers-vuex.  Here's an example of patching with partial data:

```js
import { models } from 'feathers-vuex'
const { Todo } = models.api

const todo = new Todo({ description: 'Do Something', isComplete: false })

todo.patch({ data: { isComplete: true } })

// also works for patching with instance.save
todo.save({ data: { isComplete: true } })
```

Author: marshallswain

docs/2.0-major-release.md

@@ -163,6 +163,8 @@ I have not been able to find a diffing algorithm that works equally well acroos
 
 ## Model Classes: BYOD (Bring Your Own Diffing)
 
+> Note: As of `[email protected]`, you can also pass `params.data` to the patch object to implement partial patching on objects.  You might choose to use `params.data` instead of `diffOnPatch`.
+
 First, why do any diffing?  On the API server, an `update` request replaces an entire object, but a `patch` request only overwrites the attributes that are provided in the data.  For services with simple schemas, it doesn't really matter.  But if your schema grows really large, it can be supportive to only send the updates instead of the entire object.
 
 A new `diffOnPatch` method is available to override in your extended models.  `diffOnPatch` gets called just before sending the data to the API server.  It gets called with the data and must return the diffed data.  By default, it is set to `diffOnPatch: data => data`.

docs/3.0-major-release.md

@@ -16,6 +16,21 @@ Version 3.0 of Feathers-Vuex is the Vue Composition API release!  There were qui
 
 And now it has become the best way to perform queries with Feathers-Vuex.  To find out how to take advantage of the new functionality in your apps, read the [Feather-Vuex Composition API docs](./composition-api.md).
 
+## Partial data on patch <Badge text="3.9.0+" />
+As of version 3.9.0, you can provide an object as `params.data`, and Feathers-Vuex will use `params.data` as the patch data.  This change was made to the service-module, itself, so it will work for `patch` across all of feathers-vuex.  Here's an example of patching with partial data:
+
+```js
+import { models } from 'feathers-vuex'
+const { Todo } = models.api
+
+const todo = new Todo({ description: 'Do Something', isComplete: false })
+
+todo.patch({ data: { isComplete: true } })
+
+// also works for patching with instance.save
+todo.save({ data: { isComplete: true } })
+```
+
 ## FeathersVuexPagination Component <Badge text="3.8.0+" />
 
 To assist with Server Side Pagination support, Feathers-Vuex now includes the `<FeathersVuexPagination>` component.  It's a renderless component that removes the boilerplate behind handling pagination in the UI.  Read about it in the [Composition API Docs](/composition-api.html#feathersvuexpagination).

docs/model-classes.md

@@ -302,6 +302,7 @@ The `patch` method calls the `patch` action (service method) using the instance
 
 Similar to the `.create()` method, you might not ever need to use `.patch()` if you just use `.save()` and let `feathers-vuex` figure out how to handle it.
 
+
 ```js
 const { Todo } = this.$FeathersVuex.api
 const todo = new Todo({ id: 1, description: 'Do something!' })
@@ -311,7 +312,16 @@ todo.description = 'Do something else'
 todo.patch() // --> Sends a `patch` request the with the id and description.
 ```
 
-*Note: Currently, patch sends all data, not just what has changed. In a future update, it will only send the fields that have changed.*
+<Badge text="3.9.0+" /> As of version 3.9.0, you can provide an object as `params.data`, and Feathers-Vuex will use `params.data` as the patch data.  This allows patching with partial data:
+
+```js
+import { models } from 'feathers-vuex'
+const { Todo } = models.api
+
+const todo = new Todo({ description: 'Do Something', isComplete: false })
+
+todo.patch({ data: { isComplete: true } })
+```
 
 ### `instance.update(params)`
 

docs/service-plugin.md

@@ -363,7 +363,7 @@ Patch (merge in changes) one or more records
 - `paramArray {Array}` - array containing the three parameters patch takes.
   - `id {Number|String}` - the `id` of the existing record being requested from the API server.
   - `data {Object}` - the data that will be merged into the existing record
-  - `params {Object}` - An object containing a `query` object.
+  - `params {Object}` - An object containing a `query` object. If params.data is provided, it will be used as the patch data, providing a simple way to patch with partial data.
 
 ```js
 let data = {description: 'write your tests', completed: true}

src/service-module/service-module.actions.ts

@@ -145,14 +145,21 @@ export default function makeServiceActions(service) {
         })
     },
 
+    /**
+     * If params.data is provided, it will be passed as the patch data (instead of the `data` arg).
+     * This provides a simple way to patch with partial data.
+     */
     patch({ commit, dispatch, state }, [id, data, params]) {
       commit('setPending', 'patch')
 
       params = fastCopy(params)
 
-      if (service.FeathersVuexModel) {
+      if (service.FeathersVuexModel && params && !params.data) {
         data = service.FeathersVuexModel.diffOnPatch(data)
       }
+      if (params && params.data) {
+        data = params.data
+      }
 
       return service
         .patch(id, data, params)

test/service-module/service-module.actions.test.ts

@@ -995,6 +995,44 @@ describe('Service Module - Actions', () => {
         })
     })
 
+    it('overrides patch data with params.data', done => {
+      const { makeServicePlugin, Todo } = makeContext()
+      const store = new Vuex.Store<RootState>({
+        plugins: [
+          makeServicePlugin({
+            servicePath: 'my-todos',
+            Model: Todo,
+            service: feathersClient.service('my-todos')
+          })
+        ]
+      })
+      const actions = mapActions('my-todos', ['create', 'patch'])
+      const originalData = { description: 'Do something', test: true }
+
+      actions.create.call({ $store: store }, originalData).then(() => {
+        const data = {
+          description:
+            'This description should not be patched since params.data is provided'
+        }
+        const params = { data: { test: false } }
+        actions.patch
+          .call({ $store: store }, [0, data, params])
+          .then(responseFromPatch => {
+            assert.equal(
+              responseFromPatch.description,
+              originalData.description,
+              'description should not have changed'
+            )
+            assert.equal(
+              responseFromPatch.test,
+              false,
+              'Providing params.data should have set the test attribute to false.'
+            )
+            done()
+          })
+      })
+    })
+
     it('updates store state on service success', done => {
       const { makeServicePlugin, Todo } = makeContext()
       const store = new Vuex.Store<RootState>({