Perf: avoid expensive removeAll on unmount (#39)

* Perf: on unmount, call removeAll with no argument

Calling `removeAll` with no argument is vastly more performant when one
needs to remove all documents. Therefore, upon unmount, we now use the
performant no-arg version.

See #38

* Fix

* Clarify docs

* Add regression test for errors on unmount

README.md

@@ -24,6 +24,14 @@ yarn add react-minisearch
 
 There are three main ways to use `react-minisearch`: the `useMiniSearch` hook, the `withMiniSearch` higher-order component, or the `WithMiniSearch` wrapper component.
 
+All three way take the following arguments (or props for the wrapper component):
+
+  - The initial collection of documents to add to the index. Note: this is just
+    the initial collection, and mutating this argument won't cause reindexing.
+    To add or remove documents after initialization, use the functions
+    `add`/`addAll`/`remove`/`removeAll`/`discard`, etc.
+  - The `MiniSearch` configuration options
+
 #### Using the useMiniSearch hook:
 
 ```jsx

src/react-minisearch.test.tsx

@@ -195,6 +195,10 @@ const testComponent = (Component: React.FC<Props>) => {
 
     const items = wrap.update().find('.results li')
     expect(items).not.toExist()
+
+    expect(() => {
+      wrap.unmount()
+    }).not.toThrow()
   })
 
   it('removes a document by id', () => {

src/react-minisearch.tsx

@@ -22,7 +22,7 @@ export interface UseMiniSearch<T = any> {
   miniSearch: MiniSearch<T>
 }
 
-export function useMiniSearch<T = any> (documents: T[], options: Options<T>): UseMiniSearch<T> {
+export function useMiniSearch<T = any> (documents: readonly T[], options: Options<T>): UseMiniSearch<T> {
   const optionsRef = useRef(options)
   const miniSearchRef = useRef<MiniSearch<T>>(new MiniSearch<T>(options))
   const documentByIdRef = useRef<{ [key: string]: T }>({})
@@ -147,11 +147,7 @@ export function useMiniSearch<T = any> (documents: T[], options: Options<T>): Us
 
   useEffect(() => {
     utils.addAll(documents)
-
-    return () => {
-      utils.removeAll(documents)
-    }
-  }, [utils, documents])
+  }, []) // eslint-disable-line react-hooks/exhaustive-deps
 
   return {
     searchResults,