refactor(logger): mark private members as readonly and fix code quality issues (#4350)

Author: kawaaaas

packages/logger/src/Logger.ts

@@ -117,7 +117,7 @@ class Logger extends Utility implements LoggerInterface {
   /**
    * Custom config service instance used to configure the logger.
    */
-  private customConfigService?: ConfigServiceInterface;
+  private readonly customConfigService?: ConfigServiceInterface;
   /**
    * Whether to print the Lambda invocation event in the logs.
    */
@@ -149,7 +149,7 @@ class Logger extends Utility implements LoggerInterface {
   /**
    * Standard attributes managed by Powertools that will be logged in all log items.
    */
-  private powertoolsLogData: PowertoolsLogData = <PowertoolsLogData>{
+  private readonly powertoolsLogData: PowertoolsLogData = <PowertoolsLogData>{
     sampleRateValue: 0,
   };
   /**
@@ -169,14 +169,14 @@ class Logger extends Utility implements LoggerInterface {
   /**
    * Flag used to determine if the logger is initialized.
    */
-  #isInitialized = false;
+  readonly #isInitialized: boolean = false;
   /**
    * Map used to hold the list of keys and their type.
    *
    * Because keys of different types can be overwritten, we keep a list of keys that were added and their last
    * type. We then use this map at log preparation time to pick the last one.
    */
-  #keys: Map<string, 'temp' | 'persistent'> = new Map();
+  readonly #keys: Map<string, 'temp' | 'persistent'> = new Map();
   /**
    * This is the initial log leval as set during the initialization of the logger.
    *
@@ -263,7 +263,9 @@ class Logger extends Utility implements LoggerInterface {
   public constructor(options: ConstructorOptions = {}) {
     super();
     const { customConfigService, ...rest } = options;
-    this.setCustomConfigService(customConfigService);
+    this.customConfigService = customConfigService
+      ? customConfigService
+      : undefined;
     // all logs are buffered until the logger is initialized
     this.setOptions(rest);
     this.#isInitialized = true;
@@ -1135,20 +1137,6 @@ class Logger extends Utility implements LoggerInterface {
     };
   }
 
-  /**
-   * Set the Logger's customer config service instance, which will be used
-   * to fetch environment variables.
-   *
-   * @param customConfigService - The custom config service
-   */
-  private setCustomConfigService(
-    customConfigService?: ConfigServiceInterface
-  ): void {
-    this.customConfigService = customConfigService
-      ? customConfigService
-      : undefined;
-  }
-
   /**
    * Set the initial Logger log level based on the following order:
    * 1. If a log level is set using AWS Lambda Advanced Logging Controls, it sets it.
@@ -1199,8 +1187,6 @@ class Logger extends Utility implements LoggerInterface {
     if (this.isValidLogLevel(logLevelValue)) {
       this.logLevel = LogLevelThreshold[logLevelValue];
       this.#initialLogLevel = this.logLevel;
-
-      return;
     }
   }
 

packages/logger/src/formatter/LogFormatter.ts

@@ -183,7 +183,7 @@ abstract class LogFormatter {
    *
    * @param timezone - IANA time zone identifier (e.g., "Asia/Dhaka").
    */
-  #getDateFormatter = (timezone: string): Intl.DateTimeFormat => {
+  readonly #getDateFormatter = (timezone: string): Intl.DateTimeFormat => {
     const twoDigitFormatOption = '2-digit';
     const validTimeZone = Intl.supportedValuesOf('timeZone').includes(timezone)
       ? timezone

packages/logger/src/formatter/PowertoolsLogFormatter.ts

@@ -24,7 +24,7 @@ class PowertoolsLogFormatter extends LogFormatter {
    *
    * This can be a set of keys or an array of keys.
    */
-  #logRecordOrder?: LogRecordOrderKeys;
+  readonly #logRecordOrder?: LogRecordOrderKeys;
 
   public constructor(options?: PowertoolsLogFormatterOptions) {
     super();

packages/logger/tests/e2e/basicFeatures.middy.test.ts

@@ -269,12 +269,10 @@ describe('Logger E2E tests, basic functionalities middy usage', () => {
         const logMessages = invocationLogs[i].getFunctionLogs();
 
         // Check that the X-Ray Trace ID is logged on every log
-        const traceIds: string[] = [];
         for (const message of logMessages) {
           const log = TestInvocationLogs.parseFunctionLog(message);
           expect(log).toHaveProperty('xray_trace_id');
           expect(log.xray_trace_id).toMatch(XRAY_TRACE_ID_REGEX);
-          traceIds.push(log.xray_trace_id as string);
         }
       }
     });