fix: gracefully handle missing diagChannel.tracingChannel on Node < 18.19

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [macOS-latest, windows-latest, ubuntu-latest]
-        node-version: [18, 20, 22]
+        node-version: [18, '18.18', 20, 22]
         exclude:
           - os: windows-latest
             node-version: 22

lib/tools.js

@@ -28,7 +28,19 @@ const {
 const { isMainThread } = require('worker_threads')
 const transport = require('./transport')
 
-const asJsonChan = diagChan.tracingChannel('pino_asJson')
+let asJsonChan
+// Node >= 18.19 supports diagnostics_channel.tracingChannel
+if (typeof diagChan.tracingChannel === 'function') {
+  asJsonChan = diagChan.tracingChannel('pino_asJson')
+} else {
+  // Older Node 18.x (e.g. 18.18), provided a no-op fallback
+  asJsonChan = {
+    hasSubscribers: false,
+    traceSync (fn, store, thisArg, ...args) {
+      return fn.call(thisArg, ...args)
+    }
+  }
+}
 
 function noop () {
 }

test/diagnostics.test.js

@@ -13,6 +13,9 @@ const { pid } = process
 const AS_JSON_START = 'tracing:pino_asJson:start'
 const AS_JSON_END = 'tracing:pino_asJson:end'
 
+// Skip tests if diagnostics_channel.tracingChannel is not available (Node < 18.19)
+const skip = typeof diagChan.tracingChannel !== 'function'
+
 test.beforeEach(ctx => {
   ctx.pino = {
     ts: 1757512800000, // 2025-09-10T10:00:00.000-05:00
@@ -33,7 +36,7 @@ test.afterEach(ctx => {
   Date.now = ctx.pino.now
 })
 
-test('asJson emits events', async (t) => {
+test('asJson emits events', { skip }, async (t) => {
   const plan = tspl(t, { plan: 8 })
   const { dest } = t.pino
   const logger = pino({}, dest)
@@ -74,7 +77,7 @@ test('asJson emits events', async (t) => {
   }
 })
 
-test('asJson context is not lost', async (t) => {
+test('asJson context is not lost', { skip }, async (t) => {
   const plan = tspl(t, { plan: 2 })
   const { dest } = t.pino
   const logger = pino({}, dest)