Allow variable substitution in logger

src/loggers/console.js

@@ -30,7 +30,33 @@ class ConsoleLogger {
     if (levels.indexOf(this._level) > levels.indexOf(level)) {
       return;
     }
+    if (this.hasError(args)) {
+      // If the arguments contain an error object, send them directly
+      // to preserve the stack trace.
+      loggerFn(...this.getParts(level), ...args);
+    } else {
+      const [message, ...rest] = args;
+      // Otherwise wrap the message to allow for variable substitution.
+      loggerFn(this.wrapMessage(message, level), ...rest);
+    }
+  }
+
+  hasError(args) {
+    return args.some((arg) => {
+      return arg instanceof Error;
+    });
+  }
+
 
+  wrapMessage(message, level) {
+    return [
+      ...this.getParts(level),
+      message,
+    ].join(' ');
+  }
+
+
+  getParts(level) {
     let levelStr = level.toUpperCase().padStart(5, " ");
     if (["warn"].includes(level)) {
       levelStr = klour.yellow(levelStr);
@@ -39,15 +65,14 @@ class ConsoleLogger {
     } else {
       levelStr = klour.gray(levelStr);
     }
-
-    loggerFn(
+    return [
       klour.gray(`[${getLocalDate()}]`),
       levelStr,
       ...Object.keys(this.props).map((key) => {
         return `${key}: ${this.props[key]}`;
       }),
-      ...args
-    );
+    ];
+
   }
 
   trace(...args) {