feat: make loglevel types stricter

Author: dreamorosi

Diff for: packages/logger/src/Logger.ts

@@ -117,7 +117,7 @@ class Logger extends Utility implements ClassThatLogs {
 
   private customConfigService?: ConfigServiceInterface;
 
-  private static readonly defaultLogLevel: LogLevel = 'INFO';
+  private static readonly defaultLogLevel: Uppercase<LogLevel> = 'INFO';
 
   // envVarsService is always initialized in the constructor in setOptions()
   private envVarsService!: EnvironmentVariablesService;
@@ -128,7 +128,7 @@ class Logger extends Utility implements ClassThatLogs {
 
   private logIndentation: number = LogJsonIndent.COMPACT;
 
-  private logLevel?: LogLevel;
+  private logLevel?: Uppercase<LogLevel>;
 
   private readonly logLevelThresholds: LogLevelThresholds = {
     DEBUG: 8,
@@ -554,12 +554,16 @@ class Logger extends Utility implements ClassThatLogs {
 
   /**
    * It returns the log level set for the Logger instance.
+   * 
+   * Even though logLevel starts as undefined, it will always be set to a value
+   * during the Logger instance's initialization. So, we can safely use the non-null
+   * assertion operator here.
    *
    * @private
    * @returns {LogLevel}
    */
-  private getLogLevel(): LogLevel {
-    return <LogLevel> this.logLevel;
+  private getLogLevel(): Uppercase<LogLevel> {
+    return this.logLevel!;
   }
 
   /**
@@ -619,14 +623,14 @@ class Logger extends Utility implements ClassThatLogs {
   }
 
   /**
-   * It returns true if the provided log level is valid.
+   * It returns true and type guards the log level if a given log level is valid.
    *
    * @param {LogLevel} logLevel
    * @private
    * @returns {boolean}
    */
-  private isValidLogLevel(logLevel?: LogLevel): boolean {
-    return typeof logLevel === 'string' && logLevel.toUpperCase() in this.logLevelThresholds;
+  private isValidLogLevel(logLevel?: LogLevel | string): logLevel is LogLevel {
+    return typeof logLevel === 'string' && logLevel in this.logLevelThresholds;
   }
 
   /**
@@ -648,7 +652,8 @@ class Logger extends Utility implements ClassThatLogs {
    * It prints a given log with given log level.
    *
    * @param {LogLevel} logLevel
-   * @param {LogItem} log
+   * @param {LogItemMessage} input
+   * @param {LogItemExtraInput} extraInput
    * @private
    */
   private processLogItem(logLevel: LogLevel, input: LogItemMessage, extraInput: LogItemExtraInput): void {
@@ -744,19 +749,19 @@ class Logger extends Utility implements ClassThatLogs {
    */
   private setLogLevel(logLevel?: LogLevel): void {
     if (this.isValidLogLevel(logLevel)) {
-      this.logLevel = (<LogLevel>logLevel).toUpperCase();
+      this.logLevel = logLevel?.toUpperCase() as Uppercase<LogLevel>;
 
       return;
     }
     const customConfigValue = this.getCustomConfigService()?.getLogLevel();
     if (this.isValidLogLevel(customConfigValue)) {
-      this.logLevel = (<LogLevel>customConfigValue).toUpperCase();
+      this.logLevel = customConfigValue?.toUpperCase() as Uppercase<LogLevel>;
 
       return;
     }
     const envVarsValue = this.getEnvVarsService().getLogLevel();
     if (this.isValidLogLevel(envVarsValue)) {
-      this.logLevel = (<LogLevel>envVarsValue).toUpperCase();
+      this.logLevel = envVarsValue?.toUpperCase() as Uppercase<LogLevel>;
 
       return;
     }
@@ -845,14 +850,15 @@ class Logger extends Utility implements ClassThatLogs {
   /**
    * It checks whether the current log item should/can be printed.
    *
-   * @param {string} serviceName
-   * @param {Environment} environment
-   * @param {LogAttributes} persistentLogAttributes
+   * @param {LogLevel} logLevel
    * @private
    * @returns {boolean}
    */
   private shouldPrint(logLevel: LogLevel): boolean {
-    if (this.logLevelThresholds[logLevel] >= this.logLevelThresholds[this.getLogLevel()]) {
+    if (
+      this.logLevelThresholds[logLevel.toUpperCase() as Uppercase<LogLevel>] >=
+      this.logLevelThresholds[this.getLogLevel()]
+    ) {
       return true;
     }
 

Diff for: packages/logger/src/types/Log.ts

@@ -3,10 +3,10 @@ type LogLevelInfo = 'INFO';
 type LogLevelWarn = 'WARN';
 type LogLevelError = 'ERROR';
 
-type LogLevel = LogLevelDebug | LogLevelInfo | LogLevelWarn | LogLevelError | string;
+type LogLevel = LogLevelDebug | Lowercase<LogLevelDebug> | LogLevelInfo | Lowercase<LogLevelInfo> | LogLevelWarn | Lowercase<LogLevelWarn> | LogLevelError | Lowercase<LogLevelError>;
 
 type LogLevelThresholds = {
-  [key in LogLevel]: number;
+  [key in Uppercase<LogLevel>]: number;
 };
 
 type LogAttributeValue = unknown;

Diff for: packages/logger/tests/unit/Logger.test.ts

@@ -1419,7 +1419,7 @@ describe('Class: Logger', () => {
       };
       const childLoggerWithSampleRateEnabled = parentLogger.createChild(optionsWithSampleRateEnabled);
 
-      const optionsWithErrorLogLevel = {
+      const optionsWithErrorLogLevel: ConstructorOptions = {
         logLevel: 'ERROR',
       };
       const childLoggerWithErrorLogLevel = parentLogger.createChild(optionsWithErrorLogLevel);

Diff for: packages/logger/tests/unit/formatter/PowertoolLogFormatter.test.ts

@@ -23,7 +23,7 @@ describe('Class: PowertoolLogFormatter', () => {
 
       // Prepare
       const formatter = new PowertoolLogFormatter();
-      const unformattedAttributes = {
+      const unformattedAttributes: UnformattedAttributes = {
         sampleRateValue: undefined,
         awsRegion: 'eu-west-1',
         environment: '',

Diff for: packages/logger/tests/unit/helpers.test.ts

@@ -56,7 +56,7 @@ describe('Helper: createLogger function', () => {
     test('when no parameters are set, returns a Logger instance with the correct properties', () => {
 
       // Prepare
-      const loggerOptions = {
+      const loggerOptions: ConstructorOptions = {
         logLevel: 'WARN',
         serviceName: 'my-lambda-service',
         sampleRateValue: 1,