feat: added format override to log messages

Added the ability to override a log message format on a per-message basis. You have to provide an optional `LogFormatter` parameter to the message. For example logger.info('INFO MESSAGE', formatting.format`${formatting.date}:${formatting.msg}`);.

Related #4

Author: tegefaulkes

src/Handler.ts

@@ -13,8 +13,8 @@ abstract class Handler {
     this.formatter = formatter;
   }
 
-  public handle(record: LogRecord): void {
-    const output = this.format(record);
+  public handle(record: LogRecord, format?: LogFormatter): void {
+    const output = format != null ? format(record) : this.format(record);
     this.emit(output);
   }
 

src/Logger.ts

@@ -1,4 +1,4 @@
-import type { ToString, LogRecord } from './types';
+import type { ToString, LogRecord, LogFormatter } from './types';
 import type Handler from './Handler';
 
 import { LogLevel } from './types';
@@ -74,26 +74,26 @@ class Logger {
     }
   }
 
-  public debug(data: ToString): void {
-    this.log(data.toString(), LogLevel.DEBUG);
+  public debug(data: ToString, format?: LogFormatter): void {
+    this.log(data.toString(), LogLevel.DEBUG, format);
   }
 
-  public info(data: ToString): void {
-    this.log(data.toString(), LogLevel.INFO);
+  public info(data: ToString, format?: LogFormatter): void {
+    this.log(data.toString(), LogLevel.INFO, format);
   }
 
-  public warn(data: ToString): void {
-    this.log(data.toString(), LogLevel.WARN);
+  public warn(data: ToString, format?: LogFormatter): void {
+    this.log(data.toString(), LogLevel.WARN, format);
   }
 
-  public error(data: ToString): void {
-    this.log(data.toString(), LogLevel.ERROR);
+  public error(data: ToString, format?: LogFormatter): void {
+    this.log(data.toString(), LogLevel.ERROR, format);
   }
 
-  protected log(msg: string, level: LogLevel): void {
+  protected log(msg: string, level: LogLevel, format?: LogFormatter): void {
     const record = this.makeRecord(msg, level);
     if (level >= this.getEffectiveLevel()) {
-      this.callHandlers(record);
+      this.callHandlers(record, format);
     }
   }
 
@@ -107,12 +107,12 @@ class Logger {
     };
   }
 
-  protected callHandlers(record: LogRecord): void {
+  protected callHandlers(record: LogRecord, format?: LogFormatter): void {
     for (const handler of this.handlers) {
-      handler.handle(record);
+      handler.handle(record, format);
     }
     if (this.parent) {
-      this.parent.callHandlers(record);
+      this.parent.callHandlers(record, format);
     }
   }
 }

src/formatting.ts

@@ -34,9 +34,19 @@ function format(
       } else if (value === level) {
         result += levelToString(record.level);
       } else if (value === trace) {
-        const errorStack = new Error().stack ?? '';
-        const formattedStack = errorStack.split('\n').splice(7).join('\n');
-        result += '\n' + formattedStack;
+        const errorStack = new Error().stack;
+        if (errorStack != null) {
+          const splitErrorStack = errorStack.split('\n');
+          const position =
+            splitErrorStack.findIndex((value) => /Logger\.log/.test(value)) ??
+            0;
+          const formattedStack = splitErrorStack
+            .splice(position + 2)
+            .join('\n');
+          result += '\n' + formattedStack;
+        } else {
+          result += '';
+        }
       } else {
         result += value.toString();
       }

tests/index.test.ts

@@ -114,4 +114,16 @@ describe('index', () => {
     );
     expect(consoleSpy).toHaveBeenCalledWith(expect.stringContaining('at'));
   });
+  test('Testing overriding log format', () => {
+    const consoleSpy = jest.spyOn(console, 'log');
+    const logger = new Logger('root', LogLevel.NOTSET);
+    logger.debug('DEBUG MESSAGE', formatting.format`OVERRIDDEN`);
+    expect(consoleSpy).toHaveBeenCalledWith('OVERRIDDEN');
+    logger.info('INFO MESSAGE', formatting.format`OVERRIDDEN`);
+    expect(consoleSpy).toHaveBeenCalledWith('OVERRIDDEN');
+    logger.warn('WARN MESSAGE', formatting.format`OVERRIDDEN`);
+    expect(consoleSpy).toHaveBeenCalledWith('OVERRIDDEN');
+    logger.error('ERROR MESSAGE', formatting.format`OVERRIDDEN`);
+    expect(consoleSpy).toHaveBeenCalledWith('OVERRIDDEN');
+  });
 });