feat: enable HMR of persistentReducedStreams (opt in)

src/config.ts

@@ -0,0 +1,21 @@
+interface ConfigMap {
+  enableHotModuleReload: boolean;
+}
+type ConfigKeys = keyof ConfigMap;
+
+function createGlobalConfig() {
+  const config: ConfigMap = {
+    enableHotModuleReload: false,
+  };
+
+  return {
+    setProperty: <Key extends ConfigKeys>(key: Key, value: ConfigMap[Key]) => {
+      config[key] = value;
+    },
+    getProperty: <Key extends ConfigKeys>(key: Key) => {
+      return config[key];
+    },
+  };
+}
+
+export const rxBeachConfig = createGlobalConfig();

src/persistentReducedStream.ts

@@ -6,6 +6,7 @@ import {
   ReducedStreamOptions,
   reducedStream as reducedStreamInternal,
 } from './internal/reducedStream';
+import { rxBeachConfig } from './config';
 
 /**
  * Creates and registers a persistent reduced state stream
@@ -48,9 +49,31 @@ export const persistentReducedStream = <State>(
     tag(name)
   );
 
-  const stream = new ObservableState(name, source$, initialState);
+  try {
+    const stream = new ObservableState(name, source$, initialState);
+    stateStreamRegistry.register(stream);
+    return stream;
+  } catch (error) {
+    if (
+      rxBeachConfig.getProperty('enableHotModuleReload') &&
+      error instanceof Error &&
+      error.message.startsWith('Duplicate stream name: ')
+    ) {
+      // The following enables Hot Module Reloading (HMR) of persistentReducedStream by
+      // handling the "duplicate stream" error that is thrown when reusing a stream name.
+      console.warn(
+        `[HMR] Replacing stream "${name}", if you see this warning when your ` +
+          `application boots the first time you have used the same name twice!`
+      );
+      const prevState =
+        stateStreamRegistry.streams.get(name)?.state ?? initialState;
+      const newStream = new ObservableState(name, source$, prevState);
 
-  stateStreamRegistry.register(stream);
+      stateStreamRegistry.unregister(name);
+      stateStreamRegistry.register(newStream);
+      return newStream;
+    }
 
-  return stream;
+    throw error;
+  }
 };

src/stateStreamRegistry.ts

@@ -27,6 +27,22 @@ export class StateStreamRegistry {
     this.streams.set(stream.name, stream);
   }
 
+  /**
+   * Unregister a stream from the registry
+   * 
+   * @param name The name of the stream
+   * @returns void
+   */
+  unregister(name: string) {
+    var stream = this.streams.get(name)
+    if (!stream) {
+        return;
+    }
+
+    this.streams.delete(name)
+    stream.unsubscribe();
+};
+
   /**
    * Start the registered reduced state streams.
    *