Feature - optionally include Error.cause property

lib/winston/logger.js

@@ -78,7 +78,7 @@
    * @param {!Object} options - TODO: add param description.
    * @returns {undefined}
    */
   configure({
     silent,
     format,
     defaultMeta,
@@ -204,7 +204,7 @@
    *
    */
   /* eslint-enable valid-jsdoc */
   log(level, msg, ...splat) {
     // eslint-disable-line max-params
     // Optimize for the hotpath of logging JSON literals
     if (arguments.length === 1) {
@@ -248,6 +248,7 @@
 
         if (meta.message) info.message = `${info.message} ${meta.message}`;
         if (meta.stack) info.stack = meta.stack;
+        if (meta.cause) info.cause = meta.cause;
 
         this.write(info);
         return this;

test/unit/winston/logger.test.js

@@ -1016,6 +1016,19 @@ describe('Logger Instance', function () {
 
         logger.log('info', '%d%% such %s %j', 100, 'wow', {much: 'javascript'}, {thisIsMeta: true});
       });
+
+      it(`.log(level, new Error()) creates info with error cause`, function (done) {
+        const errCause = new Error("error cause");
+        const err = new Error('test', { cause: errCause });
+        const logger = helpers.createLogger(function (info) {
+          assume(info).instanceOf(Error);
+          assume(info).equals(err);
+          assume(info.cause).equals(errCause)
+          done();
+        });
+
+        logger.log('info', err);
+      });
     });
   });
 });