fix: Fixed handling of Pino merging object

lib/instrumentation/pino/pino.js

@@ -131,7 +131,15 @@ function reformatLogLine({ logLine, msg, agent, chindings = '', level, logger })
     delete metadata.hostname
   }
 
-  const agentMeta = Object.assign({}, { timestamp: Date.now(), message: msg }, metadata)
+  const agentMeta = Object.assign({}, { timestamp: Date.now() }, metadata)
+  // eslint-disable-next-line eqeqeq
+  if (msg != undefined) {
+    // The spec lists `message` as "MUST" under the required column, but then
+    // details that it "MUST be omitted" if the value is "empty". Additionally,
+    // if someone has logged only a merging object, and that object contains a
+    // message key, we do not want to overwrite their value. See issue 2595.
+    agentMeta.message = msg
+  }
 
   /**
    * A function that gets executed in `_toPayloadSync` of log aggregator.

test/versioned/pino/issue-2595.test.js

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2024 New Relic Corporation. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert')
+const { Writable } = require('node:stream')
+
+const helper = require('../../lib/agent_helper')
+
+test('does not strip message property', (t, end) => {
+  const logs = []
+  const dest = new Writable({
+    write(chunk, encoding, callback) {
+      logs.push(JSON.parse(chunk.toString()))
+      callback()
+    }
+  })
+  const agent = helper.instrumentMockedAgent({
+    application_logging: {
+      forwarding: { enabled: true }
+    }
+  })
+  const pinoHttp = require('pino-http')
+  const { logger } = pinoHttp({ level: 'info' }, dest)
+
+  helper.runInTransaction(agent, (tx) => {
+    logger.info({ message: 'keep me', message2: 'me too' })
+
+    tx.end()
+
+    const agentLogs = agent.logs.getEvents()
+    assert.equal(agentLogs.length, 1, 'aggregator should have recorded log')
+    assert.equal(logs.length, 1, 'stream should have recorded one log')
+
+    // Verify the destination stream log has the expected properties.
+    const expectedLog = logs[0]
+    assert.equal(expectedLog.message, 'keep me')
+    assert.equal(expectedLog.message2, 'me too')
+
+    const foundLog = agentLogs[0]()
+
+    // The forwarded log should have all of the extra keys that were logged to
+    // the destination stream by Pino.
+    const expectedKeys = Object.keys(expectedLog).filter(
+      (k) => ['level', 'time', 'pid', 'hostname'].includes(k) === false // Omit baseline Pino keys.
+    )
+    for (const key of expectedKeys) {
+      assert.equal(Object.hasOwn(foundLog, key), true, `forwarded log should have key "${key}"`)
+      assert.equal(
+        foundLog[key],
+        expectedLog[key],
+        `"${key}" key should have same value as original log`
+      )
+    }
+
+    end()
+  })
+})

test/versioned/pino/package.json

@@ -16,6 +16,19 @@
       "files": [
         "pino.tap.js"
       ]
+    },
+
+    {
+      "engines": {
+        "node": ">=18"
+      },
+      "dependencies": {
+        "pino": ">=7.0.0",
+        "pino-http": ">=10.3.0"
+      },
+      "files": [
+        "issue-2595.test.js"
+      ]
     }
   ]
 }