fix(logger): warn only once on ALC log level mismatch

packages/logger/src/Logger.ts

@@ -236,6 +236,11 @@ class Logger extends Utility implements LoggerInterface {
     refreshedTimes: 0,
   };
 
+  /**
+   * Map used to store the warning messages that have already been logged.
+   */
+  readonly #warnOnceMap = new Map<string, boolean>();
+
   /**
    * Log level used by the current instance of Logger.
    *
@@ -714,6 +719,17 @@ class Logger extends Utility implements LoggerInterface {
     this.processLogItem(LogLevelThreshold.WARN, input, extraInput);
   }
 
+  /**
+   * Log a warning message once per unique message.
+   *
+   * @param message - The log message.
+   */
+  #warnOnce(message: string): void {
+    if (this.#warnOnceMap.has(message)) return;
+    this.#warnOnceMap.set(message, true);
+    this.warn(message);
+  }
+
   /**
    * Factory method for instantiating logger instances. Used by `createChild` method.
    * Important for customization and subclassing. It allows subclasses, like `MyOwnLogger`,
@@ -811,7 +827,7 @@ class Logger extends Utility implements LoggerInterface {
         this.isValidLogLevel(selectedLogLevel) &&
         this.logLevel > LogLevelThreshold[selectedLogLevel]
       ) {
-        this.warn(
+        this.#warnOnce(
           `Current log level (${selectedLogLevel}) does not match AWS Lambda Advanced Logging Controls minimum log level (${awsLogLevel}). This can lead to data loss, consider adjusting them.`
         );
       }
@@ -1153,7 +1169,10 @@ class Logger extends Utility implements LoggerInterface {
   private setInitialLogLevel(logLevel?: ConstructorOptions['logLevel']): void {
     const constructorLogLevel = logLevel?.toUpperCase();
 
-    if (this.awsLogLevelShortCircuit(constructorLogLevel)) return;
+    if (this.awsLogLevelShortCircuit(constructorLogLevel)) {
+      this.#initialLogLevel = this.logLevel;
+      return;
+    }
 
     if (this.isValidLogLevel(constructorLogLevel)) {
       this.logLevel = LogLevelThreshold[constructorLogLevel];
@@ -1469,6 +1488,7 @@ class Logger extends Utility implements LoggerInterface {
    * logger.setCorrelationId('my-correlation-id'); // sets the correlation ID directly with the first argument as value
    * ```
    *
+   * @example
    * ```typescript
    * import { Logger } from '@aws-lambda-powertools/logger';
    * import { search } from '@aws-lambda-powertools/logger/correlationId';
@@ -1483,7 +1503,7 @@ class Logger extends Utility implements LoggerInterface {
   public setCorrelationId(value: unknown, correlationIdPath?: string): void {
     if (typeof correlationIdPath === 'string') {
       if (!this.#correlationIdSearchFn) {
-        this.warn(
+        this.#warnOnce(
           'correlationIdPath is set but no search function was provided. The correlation ID will not be added to the log attributes.'
         );
         return;

packages/logger/tests/unit/injectLambdaContext.test.ts

@@ -297,7 +297,7 @@ describe('Inject Lambda Context', () => {
     expect(logger.getCorrelationId()).toBe('12345-test-id');
   });
 
-  it('warns when correlationIdPath is provided but no search function is available', async () => {
+  it('warns once when correlationIdPath is provided but no search function is available', async () => {
     // Prepare
     const logger = new Logger(); // No search function provided
     const warnSpy = vi.spyOn(logger, 'warn');
@@ -306,7 +306,7 @@ describe('Inject Lambda Context', () => {
         'x-correlation-id': '12345-test-id',
       },
     };
-    // Act - Use middleware which will internally call setCorrelationIdFromPath
+    // Act
     const handler = middy(async () => {
       logger.info('Hello, world!');
     }).use(
@@ -315,12 +315,14 @@ describe('Inject Lambda Context', () => {
       })
     );
 
+    await handler(testEvent, context);
     await handler(testEvent, context);
 
     // Assess
     expect(warnSpy).toHaveBeenCalledWith(
       'correlationIdPath is set but no search function was provided. The correlation ID will not be added to the log attributes.'
     );
+    expect(warnSpy).toHaveBeenCalledTimes(1);
   });
 
   it('does not set correlation ID when search function returns falsy value', async () => {