fix: use memory logger instance when disabled

src/logger/logger.ts

@@ -147,6 +147,8 @@ export class Logger {
    * `Logger`.
    */
   public constructor(optionsOrName: LoggerOptions | string) {
+    const enabled = process.env.SFDX_DISABLE_LOG_FILE !== 'true' && process.env.SF_DISABLE_LOG_FILE !== 'true';
+
     const options: LoggerOptions =
       typeof optionsOrName === 'string'
         ? { name: optionsOrName, level: Logger.DEFAULT_LEVEL, fields: {} }
@@ -167,9 +169,9 @@ export class Logger {
         name: options.name ?? Logger.ROOT_NAME,
         base: options.fields ?? {},
         level,
-        enabled: process.env.SFDX_DISABLE_LOG_FILE !== 'true' && process.env.SF_DISABLE_LOG_FILE !== 'true',
+        enabled,
       };
-      if (options.useMemoryLogger || Global.getEnvironmentMode() === Mode.TEST) {
+      if (options.useMemoryLogger || Global.getEnvironmentMode() === Mode.TEST || !enabled) {
         this.memoryLogger = new MemoryLogger();
         this.pinoLogger = pino(
           {

test/unit/loggerTest.ts

@@ -45,6 +45,23 @@ describe('Logger', () => {
       const logger2 = await Logger.root();
       expect(logger2).to.not.equal(logger1);
     });
+
+    describe('DISABLE_LOG_FILE', () => {
+      const LOG_FILES_DISABLED = process.env.SF_DISABLE_LOG_FILE;
+      before(() => {
+        process.env.SF_DISABLE_LOG_FILE = 'true';
+      });
+      after(() => {
+        process.env.SF_DISABLE_LOG_FILE = LOG_FILES_DISABLED;
+      });
+      it('should construct a new named logger', async () => {
+        const logger1 = new Logger({ name: 'testLogger-noop' });
+        expect(logger1).to.be.instanceof(Logger);
+        // @ts-expect-error testing a private property
+        expect(logger1.memoryLogger).to.be.ok;
+        expect(logger1.getName()).to.equal('testLogger-noop');
+      });
+    });
   });
 
   describe('levels', () => {