add ability to pause history

README.md

@@ -142,6 +142,25 @@ console.log(tryUndoState.present); // [{ id: 1, title: "Dune" }]
 
 Just like undoable functions, these methods will act mutably when passed an immer draft and immutably otherwise.
 
+### Pausing history
+
+If you need to make changes to the state without affecting the history, you can use the `pause` and `resume` methods.
+
+```ts
+const pausedState = booksHistoryAdapter.pause(resetState);
+
+const withBook = addBook(pausedState, { id: 2, title: "Foundation" });
+
+const resumedState = booksHistoryAdapter.resume(withBook);
+
+const undoneState = booksHistoryAdapter.undo(resumedState);
+
+// changes while paused cannot be undone
+console.log(undoneState.present); // [{ id: 1, title: "Dune" }, { id: 2, title: "Foundation" }]
+```
+
+Changes will still be made to the data while paused (including `undo` and `redo`), but they won't be recorded in the history.
+
 ## Redux helper methods
 
 If imported from `"history-adapter/redux"`, the history adapter will have additional methods to assist use with Redux, specifically with Redux Toolkit.
@@ -247,7 +266,7 @@ dispatch(addBook(book, true)); // action.meta.undoable === true
 dispatch(addBook(book, false)); // action.meta.undoable === false
 ```
 
-As a tip, `undo`, `redo` and `clearHistory` are all valid reducers due to not needing an argument. The version of `jump` on a Redux history adapter allows for either a number or payload action, making it also valid.
+As a tip, `undo`, `redo`, `pause`, `resume` and `clearHistory` are all valid reducers due to not needing an argument. The version of `jump` on a Redux history adapter allows for either a number or payload action, making it also valid.
 
 ```ts
 const booksSlice = createSlice({
@@ -257,6 +276,8 @@ const booksSlice = createSlice({
     undo: booksHistoryAdapter.undo,
     redo: booksHistoryAdapter.redo,
     jump: booksHistoryAdapter.jump,
+    pause: booksHistoryAdapter.pause,
+    resume: booksHistoryAdapter.resume,
     clearHistory: booksHistoryAdapter.clearHistory,
     addBook: {
       prepare: booksHistoryAdapter.withPayload<Book>(),
@@ -275,20 +296,24 @@ const booksSlice = createSlice({
 A method which returns some useful selectors.
 
 ```ts
-const { selectCanUndo, selectCanRedo, selectPresent } =
+const { selectCanUndo, selectCanRedo, selectPresent, selectPaused } =
   booksHistoryAdapter.getSelectors();
 
 console.log(
   selectPresent(initialState), // []
   selectCanUndo(initialState), // false
   selectCanRedo(initialState), // false
+  selectPaused(initialState), // false
 );
 
 console.log(
   selectPresent(nextState), // [{ id: 1, title: "Dune" }]
   selectCanUndo(nextState), // true
   selectCanRedo(nextState), // false
+  selectPaused(nextState), // false
 );
+
+console.log(selectPaused(pausedState)); // true
 ```
 
 If an input selector is provided, the selectors will be combined using [reselect](https://github.com/reduxjs/reselect).
@@ -301,7 +326,7 @@ const { selectPresent } = booksHistoryAdapter.getSelectors(
 console.log(selectPresent({ books: initialState })); // []
 ```
 
-The instance of `createSelector` used can be customised:
+The instance of `createSelector` used can be customised, and defaults to RTK's [`createDraftSafeSelector`](https://redux-toolkit.js.org/api/createSelector#createdraftsafeselector):
 
 ```ts
 import { createSelectorCreator, lruMemoize } from "reselect";

src/creator.test.ts

@@ -58,6 +58,8 @@ describe("Slice creators", () => {
         undo,
         redo,
         jump,
+        pause,
+        resume,
         clearHistory,
         reset,
         addBook,
@@ -109,6 +111,16 @@ describe("Slice creators", () => {
     store.dispatch(reset());
 
     expect(selectLastBook(store.getState())).toBeUndefined();
+
+    store.dispatch(pause());
+
+    store.dispatch(addBook(book1));
+
+    store.dispatch(resume());
+
+    store.dispatch(undo());
+
+    expect(selectLastBook(store.getState())).toEqual(book1);
   });
   it("works with nested state", () => {
     const bookSlice = createAppSlice({
@@ -144,6 +156,8 @@ describe("Slice creators", () => {
         undo,
         redo,
         jump,
+        pause,
+        resume,
         clearHistory,
         reset,
         addBook,
@@ -195,6 +209,14 @@ describe("Slice creators", () => {
     store.dispatch(reset());
 
     expect(selectLastBook(store.getState())).toBeUndefined();
+
+    store.dispatch(pause());
+
+    store.dispatch(addBook(book1));
+
+    store.dispatch(resume());
+
+    expect(selectLastBook(store.getState())).toEqual(book1);
   });
   it("can be destructured", () => {
     const bookSlice = createAppSlice({

src/creator.ts

@@ -23,6 +23,8 @@ const undoableCreatorsCreatorType = Symbol("undoableCreatorsCreator");
 interface HistoryReducers<State> {
   undo: CaseReducerDefinition<State, PayloadAction>;
   redo: CaseReducerDefinition<State, PayloadAction>;
+  pause: CaseReducerDefinition<State, PayloadAction>;
+  resume: CaseReducerDefinition<State, PayloadAction>;
   jump: CaseReducerDefinition<State, PayloadAction<number>>;
   clearHistory: CaseReducerDefinition<State, PayloadAction>;
   reset: ReducerDefinition<typeof historyMethodsCreatorType> & {
@@ -153,12 +155,14 @@ export const historyMethodsCreator: ReducerCreator<
     {
       selectHistoryState = (state) => state as HistoryState<Data>,
     }: HistoryMethodsCreatorConfig<State, Data> = {},
-  ) {
+  ): HistoryReducers<State> {
     const createReducer = makeScopedReducerCreator(selectHistoryState);
     return {
       undo: createReducer(adapter.undo),
       redo: createReducer(adapter.redo),
       jump: createReducer(adapter.jump),
+      pause: createReducer(adapter.pause),
+      resume: createReducer(adapter.resume),
       clearHistory: createReducer(adapter.clearHistory),
       reset: {
         _reducerDefinitionType: historyMethodsCreatorType,

src/index.test.ts

@@ -28,6 +28,7 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [],
         future: [],
+        paused: false,
       });
     });
   });
@@ -52,6 +53,7 @@ describe("createHistoryAdapter", () => {
         past: [aPatchState],
         present: [book1],
         future: [],
+        paused: false,
       });
     });
     it("handles nothing value to return undefined", () => {
@@ -63,6 +65,7 @@ describe("createHistoryAdapter", () => {
         past: [aPatchState],
         present: undefined,
         future: [],
+        paused: false,
       });
     });
     it("allows deriving from arguments whether update should be undoable", () => {
@@ -78,6 +81,7 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [book1],
         future: [],
+        paused: false,
       });
     });
     it("can be used as a mutator if already working with drafts", () => {
@@ -92,6 +96,7 @@ describe("createHistoryAdapter", () => {
         past: [aPatchState],
         present: [book1],
         future: [],
+        paused: false,
       });
     });
     it("can be provided with a selector if working with nested state", () => {
@@ -113,6 +118,7 @@ describe("createHistoryAdapter", () => {
           past: [aPatchState],
           present: [book1],
           future: [],
+          paused: false,
         },
       });
     });
@@ -130,6 +136,7 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [],
         future: [aPatchState],
+        paused: false,
       });
     });
     it("can be used as a mutator if already working with drafts", () => {
@@ -141,6 +148,7 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [],
         future: [aPatchState],
+        paused: false,
       });
     });
   });
@@ -159,6 +167,7 @@ describe("createHistoryAdapter", () => {
         past: [aPatchState],
         present: [book1],
         future: [],
+        paused: false,
       });
     });
     it("can be used as a mutator if already working with drafts", () => {
@@ -170,6 +179,7 @@ describe("createHistoryAdapter", () => {
         past: [aPatchState],
         present: [book1],
         future: [],
+        paused: false,
       });
     });
   });
@@ -187,6 +197,7 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [],
         future: [aPatchState, aPatchState],
+        paused: false,
       });
       const jumpedForwardState = booksHistoryAdapter.jump(jumpedState, 2);
       expect(jumpedForwardState).toEqual(secondState);
@@ -200,6 +211,96 @@ describe("createHistoryAdapter", () => {
         past: [],
         present: [],
         future: [aPatchState, aPatchState],
+        paused: false,
+      });
+    });
+  });
+  describe("pause", () => {
+    it("can be used to pause history tracking", () => {
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      const pausedState = booksHistoryAdapter.pause(initialState);
+      expect(pausedState).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [],
+        future: [],
+        paused: true,
+      });
+    });
+    it("can be used as a mutator if already working with drafts", () => {
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      expect(
+        produce(initialState, (draft) => {
+          booksHistoryAdapter.pause(draft);
+        }),
+      ).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [],
+        future: [],
+        paused: true,
+      });
+    });
+    it("is respected by undoable functions", () => {
+      const addBook = booksHistoryAdapter.undoable((books, book: Book) => {
+        books.push(book);
+      });
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      const pausedState = booksHistoryAdapter.pause(initialState);
+      const nextState = addBook(pausedState, book1);
+      expect(nextState).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [book1],
+        future: [],
+        paused: true,
+      });
+    });
+  });
+  describe("resume", () => {
+    it("can be used to resume history tracking", () => {
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      const pausedState = booksHistoryAdapter.pause(initialState);
+      const resumedState = booksHistoryAdapter.resume(pausedState);
+      expect(resumedState).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [],
+        future: [],
+        paused: false,
+      });
+    });
+    it("can be used as a mutator if already working with drafts", () => {
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      const pausedState = booksHistoryAdapter.pause(initialState);
+      expect(
+        produce(pausedState, (draft) => {
+          booksHistoryAdapter.resume(draft);
+        }),
+      ).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [],
+        future: [],
+        paused: false,
+      });
+    });
+    it("is respected by undoable functions", () => {
+      const addBook = booksHistoryAdapter.undoable((books, book: Book) => {
+        books.push(book);
+      });
+      const initialState = booksHistoryAdapter.getInitialState([]);
+      const pausedState = booksHistoryAdapter.pause(initialState);
+      const withBook = addBook(pausedState, book1);
+      expect(withBook).toEqual<HistoryState<Array<Book>>>({
+        past: [],
+        present: [book1],
+        future: [],
+        paused: true,
+      });
+
+      const resumedState = booksHistoryAdapter.resume(withBook);
+      const nextState = addBook(resumedState, book2);
+      expect(nextState).toEqual<HistoryState<Array<Book>>>({
+        past: [aPatchState],
+        present: [book1, book2],
+        future: [],
+        paused: false,
       });
     });
   });

src/index.ts

@@ -26,6 +26,7 @@ export interface HistoryState<Data> {
   past: Array<PatchState>;
   present: Data;
   future: Array<PatchState>;
+  paused: boolean;
 }
 
 export type MaybeDraftHistoryState<Data> =
@@ -130,6 +131,17 @@ export interface HistoryAdapter<Data> {
     state: State,
     ...args: Args
   ) => State;
+
+  /**
+   * Pauses the history, preventing any new patches from being added.
+   * @param state History state shape, with patches
+   */
+  pause<State extends MaybeDraftHistoryState<Data>>(state: State): State;
+  /**
+   * Resumes the history, allowing new patches to be added.
+   * @param state History state shape, with patches
+   */
+  resume<State extends MaybeDraftHistoryState<Data>>(state: State): State;
 }
 
 /**
@@ -142,6 +154,7 @@ export function getInitialState<Data>(initialData: Data): HistoryState<Data> {
     past: [],
     present: initialData,
     future: [],
+    paused: false,
   };
 }
 
@@ -210,6 +223,9 @@ export function createHistoryAdapter<Data>({
         });
         state.present = present;
 
+        // if paused, don't add to history
+        if (state.paused) return;
+
         const undoable = isUndoable?.(...args) ?? true;
         if (undoable) {
           const lengthWithoutFuture = state.past.length + 1;
@@ -221,5 +237,11 @@ export function createHistoryAdapter<Data>({
         }
       });
     },
+    pause: makeStateOperator<HistoryState<Data>>((state) => {
+      state.paused = true;
+    }),
+    resume: makeStateOperator<HistoryState<Data>>((state) => {
+      state.paused = false;
+    }),
   };
 }