fix: ensure a 'message' field when no message in pino log statement (#64)

Author: trentm

loggers/pino/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- Set the "message" to the empty string for logger calls that provide no
+  message, e.g. `log.info({foo: 'bar'})`. In this case pino will not add a
+  message field, which breaks ecs-logging spec.
+
 - Fix handling when the [`base`](https://getpino.io/#/docs/api?id=base-object)
   option is used to the pino constructor.
 

loggers/pino/index.js

@@ -213,6 +213,12 @@ function createEcsPinoOptions (opts) {
           }
         }
 
+        // If no message (https://getpino.io/#/docs/api?id=message-string) is
+        // given in the log statement, then pino will not emit a message field.
+        // However, the ecs-logging spec requires a message field, so we set
+        // a fallback empty string.
+        ecsObj.message = ''
+
         return ecsObj
       }
     }

loggers/pino/test/basic.test.js

@@ -131,6 +131,21 @@ test('ecsPinoFormat cases', suite => {
         ecs: { version: ecsVersion },
         message: 'hi'
       }
+    },
+    {
+      name: 'no message in log call should result in empty string message',
+      pinoOpts: ecsFormat(),
+      loggingFn: (log) => {
+        log.info({ foo: 'bar' })
+      },
+      rec: {
+        'log.level': 'info',
+        ecs: { version: ecsVersion },
+        process: { pid: process.pid },
+        host: { hostname: os.hostname },
+        foo: 'bar',
+        message: ''
+      }
     }
   ]