added rpc to collections

__tests__/Collection.spec.js

@@ -287,5 +287,38 @@ describe('Collection', () => {
         expect(collection.get(2).get('name')).toBe(newItem.name)
       })
     })
+
+    describe('rpc', () => {
+      it('sets the request', () => {
+        collection.rpc('foo')
+        expect(collection.request.label).toBe('updating')
+      })
+
+      describe('when it fails', () => {
+        beforeEach(reject)
+
+        it('sets the error', async () => {
+          try {
+            await collection.rpc('foo')
+          } catch (_error) {
+            expect(collection.error.label).toBe('updating')
+            expect(collection.error.body).toBe(error)
+          }
+        })
+      })
+
+      describe('when it succeeds', () => {
+        const mockResponse = [item, { id: 2, name: 'bob' }]
+
+        beforeEach(() => {
+          resolve(mockResponse)()
+        })
+
+        it('return the data', async () => {
+          const data = await collection.rpc('foo')
+          expect(data).toBe(mockResponse)
+        })
+      })
+    })
   })
 })

src/Collection.js

@@ -266,4 +266,44 @@ export default class Collection<T: Model> {
 
     return data
   }
+
+  /**
+   * Call an RPC action for all those
+   * non-REST endpoints that you may have in
+   * your API.
+   */
+  @action
+  async rpc (
+    method: string,
+    body?: {}
+  ): Promise<*> {
+    const label: Label = 'updating' // TODO: Maybe differentiate?
+    const { promise, abort } = apiClient().post(
+      `${this.url()}/${method}`,
+      body || {}
+    )
+
+    this.request = {
+      label,
+      abort: asReference(abort),
+      progress: 0
+    }
+
+    let response
+
+    try {
+      response = await promise
+    } catch (body) {
+      runInAction('accept-fail', () => {
+        this.request = null
+        this.error = { label, body }
+      })
+
+      throw body
+    }
+
+    this.request = null
+
+    return response
+  }
 }