Replace Snapshot.prevStates with Machine.getPrevStates()

README.md

@@ -8,7 +8,7 @@ seamless integration with TypeScript. It facilitates deterministic behavior by o
 encapsulated state machine, user-defined actions and state transformers, as well as automatic stale
 snapshot invalidation.
 
-_✅ 508 B with all dependencies, minified and gzipped._
+_✅ 511 B with all dependencies, minified and gzipped._
 
 ## Installation
 

package.json

@@ -44,19 +44,19 @@
   "size-limit": [
     {
       "name": "brotli compression",
-      "limit": "460 B",
+      "limit": "463 B",
       "path": "./lib/mod.js",
       "brotli": true
     },
     {
       "name": "gzip compression",
-      "limit": "508 B",
+      "limit": "511 B",
       "path": "./lib/mod.js",
       "gzip": true
     },
     {
       "name": "no compression",
-      "limit": "460 B",
+      "limit": "463 B",
       "path": "./lib/mod.js",
       "gzip": false
     }

src/create_machine.test.ts

@@ -94,17 +94,17 @@ describe(`createMachine()`, () => {
   });
 
   test(`prev states`, () => {
-    const isRed = trafficLightMachine.assert(`isRed`);
+    const prevStates = trafficLightMachine.getPrevStates(`isRed`);
 
     // @ts-expect-error ts(1360)
-    void (isRed.prevStates satisfies ReadonlyArray<'isRed'>);
+    void (prevStates satisfies ReadonlyArray<'isRed'>);
     // @ts-expect-error ts(1360)
-    void (isRed.prevStates satisfies ReadonlyArray<'isTurningGreen'>);
+    void (prevStates satisfies ReadonlyArray<'isTurningGreen'>);
     // @ts-expect-error ts(1360)
-    void (isRed.prevStates satisfies ReadonlyArray<'isGreen'>);
-    void (isRed.prevStates satisfies ReadonlyArray<'isTurningRed'>);
+    void (prevStates satisfies ReadonlyArray<'isGreen'>);
+    void (prevStates satisfies ReadonlyArray<'isTurningRed'>);
 
-    expect(isRed.prevStates).toEqual([`isTurningRed`]);
+    expect(prevStates).toEqual([`isTurningRed`]);
   });
 
   test(`subscriptions`, () => {
@@ -194,7 +194,6 @@ describe(`createMachine()`, () => {
     expect(() => isRed.state).toThrow(errorMessage);
     expect(() => isRed.value).toThrow(errorMessage);
     expect(() => isRed.actions).toThrow(errorMessage);
-    expect(() => isRed.prevStates).toThrow(errorMessage);
     expect(() => actions.turnGreen).toThrow(errorMessage);
     expect(() => turnGreen(`#FFFF00`)).toThrow(errorMessage);
   });

src/create_machine.ts

@@ -27,6 +27,10 @@ export type Machine<
     listener: () => void,
     options?: { readonly signal?: AbortSignal | undefined },
   ): () => void;
+
+  getPrevStates<TState extends keyof TTransformerMap>(
+    state: TState,
+  ): readonly InferPrevStateUnion<TTransformerMap, TTransitionsMap, TState>[];
 };
 
 export type TransformerMap = Readonly<Record<string, (...args: any[]) => any>>;
@@ -49,8 +53,6 @@ export interface Snapshot<
       ...args: Parameters<TTransformerMap[TTransitionsMap[TState][TActionName]]>
     ) => Snapshot<TTransformerMap, TTransitionsMap, TTransitionsMap[TState][TActionName]>;
   };
-
-  readonly prevStates: readonly InferPrevStateUnion<TTransformerMap, TTransitionsMap, TState>[];
 }
 
 export type InferPrevStateUnion<
@@ -201,12 +203,6 @@ export function createMachine<
 
         return actions;
       },
-
-      get prevStates() {
-        assertVersion();
-
-        return prevStatesMap[currentState as string] as any;
-      },
     };
   }
 
@@ -237,5 +233,9 @@ export function createMachine<
 
       return unsubscribe;
     },
+
+    getPrevStates(state) {
+      return prevStatesMap[state as string] as any;
+    },
   };
 }