feat(core): Add lifecycle hooks

Author: AbhiPrasad

packages/core/src/baseclient.ts

@@ -97,6 +97,8 @@ export abstract class BaseClient<O extends ClientOptions> implements Client<O> {
   /** Holds flushable  */
   private _outcomes: { [key: string]: number } = {};
 
+  private _hooks: Record<> = {};
+
   /**
    * Initializes this client instance.
    *
@@ -351,6 +353,8 @@ export abstract class BaseClient<O extends ClientOptions> implements Client<O> {
     }
   }
 
+  public on(): () => void {}
+
   /** Updates existing session based on the provided event */
   protected _updateSessionFromEvent(session: Session, event: Event): void {
     let crashed = false;

packages/types/src/client.ts

@@ -8,6 +8,7 @@ import type { Scope } from './scope';
 import type { SdkMetadata } from './sdkmetadata';
 import type { Session, SessionAggregates } from './session';
 import type { Severity, SeverityLevel } from './severity';
+import type { Transaction } from './transaction';
 import type { Transport } from './transport';
 
 /**
@@ -147,4 +148,13 @@ export interface Client<O extends ClientOptions = ClientOptions> {
    * @param event The dropped event.
    */
   recordDroppedEvent(reason: EventDropReason, dataCategory: DataCategory, event?: Event): void;
+
+  // HOOKS
+
+  on(
+    hook: 'startTransaction' | 'transactionFinish',
+    callback: (transaction: Transaction) => Transaction | null,
+  ): () => void;
+
+  emit(hook: Hooks, ...params: unknown[]): void;
 }

packages/types/src/hooks.ts

@@ -0,0 +1 @@
+export type Hooks = 'startTransaction' | 'transactionFinish';

packages/types/src/index.ts

@@ -96,3 +96,4 @@ export type { WrappedFunction } from './wrappedfunction';
 export type { Instrumenter } from './instrumenter';
 
 export type { BrowserClientReplayOptions } from './browseroptions';
+export type { Hooks } from './hooks';