Merge pull request #1746 from o1-labs/feature/conditional-emit-event

Conditional emit event

CHANGELOG.md

@@ -17,6 +17,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased](https://github.com/o1-labs/o1js/compare/1c736add...HEAD)
 
+### Added
+
+- `SmartContract.emitEventIf()` to conditionally emit an event https://github.com/o1-labs/o1js/pull/1746
+
 ## [1.5.0](https://github.com/o1-labs/o1js/compare/ed198f305...1c736add) - 2024-07-09
 
 ### Breaking changes

src/lib/mina/zkapp.ts

@@ -968,9 +968,15 @@ super.init();
 
   // TODO: not able to type event such that it is inferred correctly so far
   /**
-   * Emits an event. Events will be emitted as a part of the transaction and can be collected by archive nodes.
+   * Conditionally emits an event.
+   *
+   * Events will be emitted as a part of the transaction and can be collected by archive nodes.
    */
-  emitEvent<K extends keyof this['events']>(type: K, event: any) {
+  emitEventIf<K extends keyof this['events']>(
+    condition: Bool,
+    type: K,
+    event: any
+  ) {
     let accountUpdate = this.self;
     let eventTypes: (keyof this['events'])[] = Object.keys(this.events);
     if (eventTypes.length === 0)
@@ -997,12 +1003,22 @@ super.init();
       // if there is more than one event type, also store its index, like in an enum, to identify the type later
       eventFields = [Field(eventNumber), ...eventType.toFields(event)];
     }
-    accountUpdate.body.events = Events.pushEvent(
-      accountUpdate.body.events,
-      eventFields
+    let newEvents = Events.pushEvent(accountUpdate.body.events, eventFields);
+    accountUpdate.body.events = Provable.if(
+      condition,
+      Events,
+      newEvents,
+      accountUpdate.body.events
     );
   }
 
+  /**
+   * Emits an event. Events will be emitted as a part of the transaction and can be collected by archive nodes.
+   */
+  emitEvent<K extends keyof this['events']>(type: K, event: any) {
+    this.emitEventIf(Bool(true), type, event);
+  }
+
   /**
    * Asynchronously fetches events emitted by this {@link SmartContract} and returns an array of events with their corresponding types.
    * @async