Always include error name and message in stack

lib/log.js

@@ -54,6 +54,21 @@ function isCauseProperty(key) {
   return key !== 'name' && key !== 'message' && key !== 'stack';
 }
 
+/**
+ * @param {string | Error | LogError} error
+ * @returns {string}
+ */
+function stack(error) {
+  if (typeof error === 'string') {
+    return error;
+  }
+  const msg = error.name && error.message
+    ? `${error.name}: ${error.message}`
+    : error.name || String(error);
+  const s = error.stack;
+  return !s ? msg : s.indexOf(msg) === 0 ? s : `${msg}\n${s}`;
+}
+
 /**
  * @param {LogEntry} entry
  * @param {LogError} error
@@ -73,9 +88,9 @@ function addError(entry, error) {
       }, {});
     }
   }
-  entry.stack = error.stack || String(error);
+  entry.stack = stack(error);
   if (cause) {
-    entry.cause = cause.stack || String(cause);
+    entry.cause = stack(cause);
   }
 }
 
@@ -117,11 +132,7 @@ function write(ns, base_data, topic, msg, data, error) {
     } else {
       entry.data = base_data ? Object.assign({}, base_data, data) : data;
       if (error) {
-        if (typeof error === 'string') {
-          entry.stack = error;
-        } else {
-          addError(entry, /** @type {LogError} */ (error));
-        }
+        addError(entry, /** @type {LogError} */ (error));
       }
     }
   } else if (base_data) {

test/log-test.js

@@ -56,7 +56,16 @@ describe('logger', () => {
       + '"data":{"the":"things"}}\n');
   });
 
-  it('logs error', () => {
+  it('logs error without message', () => {
+    const error = new Error();
+
+    log.error('Oups', error);
+
+    assert.equals(out, '{"ts":123,"ns":"test","topic":"error","msg":"Oups",'
+      + `"stack":${JSON.stringify(error.stack)}}\n`);
+  });
+
+  it('logs error with message', () => {
     const error = new Error('Ouch!');
 
     log.error('Oups', error);
@@ -224,11 +233,46 @@ describe('logger', () => {
       + '"data":{"name":"a","message":"b"}}\n');
   });
 
-  it('logs message with error-like object { name, message, stack }', () => {
-    log.error({ name: 'SomeError', message: 'b', stack: 'Some issue' });
+  it('logs error-like object { name, message, stack } with error in stack', () => {
+    const error = {
+      name: 'SyntaxError',
+      message: 'Ouch!',
+      stack: 'SyntaxError: Ouch!\n  at xyz:123'
+    };
+
+    log.error(error);
+
+    assert.equals(out, '{"ts":123,"ns":"test","topic":"error",'
+      + `"stack":"SyntaxError: Ouch!\\n  at xyz:123"}\n`);
+  });
+
+  it('logs error-like object { name, message }', () => {
+    const error = { name: 'SyntaxError', message: 'Ouch!' };
+
+    log.error('Test', {}, error);
+
+    assert.equals(out, '{"ts":123,"ns":"test","topic":"error","msg":"Test",'
+      + `"data":{},"stack":"SyntaxError: Ouch!"}\n`);
+  });
+
+  it('logs error-like object { name, message, stack } without error in stack', () => {
+    const error = { name: 'SyntaxError', message: 'Ouch!', stack: '  at xyz:123' };
+
+    log.error(error);
+
+    assert.equals(out, '{"ts":123,"ns":"test","topic":"error",'
+      + `"stack":"SyntaxError: Ouch!\\n  at xyz:123"}\n`);
+  });
+
+  it('logs error-like cause { name, message, stack }', () => {
+    const error = new Error('Ouch!');
+    error.cause = { name: 'SyntaxError', message: 'Cause', stack: '  at xyz:123' };
+
+    log.error(error);
 
     assert.equals(out, '{"ts":123,"ns":"test","topic":"error",'
-      + '"stack":"Some issue"}\n');
+      + `"stack":${JSON.stringify(error.stack)},`
+      + `"cause":"SyntaxError: Cause\\n  at xyz:123"}\n`);
   });
 
   it('logs data and error object', () => {