fix: use shouldTrace guard for Node 18 compatibility

Node 18 backported TracingChannel but without the aggregated
`hasSubscribers` getter (it returns `undefined` instead of a boolean).
Raw truthiness checks treat `undefined` as "no subscribers" which
silently disables tracing on Node 18.

Replace all `channel.hasSubscribers` guards with `shouldTrace(channel)`
which checks `hasSubscribers !== false` — treating `undefined` (Node 18)
as "might have subscribers, trace unconditionally" and `false` (Node 20+)
as "definitely no subscribers, skip".

Also removes the now-unnecessary test skip logic since TracingChannel
does exist on Node 18.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: logaretm

packages/pg-pool/diagnostics.js

@@ -24,4 +24,12 @@ try {
   // diagnostics_channel not available (non-Node environment)
 }
 
-module.exports = { poolConnectChannel, poolReleaseChannel, poolRemoveChannel }
+// Check explicitly for `false` rather than truthiness because the aggregated
+// `hasSubscribers` getter on TracingChannel is `undefined` on Node 18 (which
+// backported TracingChannel but not the getter). When `undefined`, we assume
+// there may be subscribers and trace unconditionally.
+function shouldTrace(channel) {
+  return channel.hasSubscribers !== false
+}
+
+module.exports = { poolConnectChannel, poolReleaseChannel, poolRemoveChannel, shouldTrace }

packages/pg-pool/index.js

@@ -1,6 +1,6 @@
 'use strict'
 const EventEmitter = require('events').EventEmitter
-const { poolConnectChannel, poolReleaseChannel, poolRemoveChannel } = require('./diagnostics')
+const { poolConnectChannel, poolReleaseChannel, poolRemoveChannel, shouldTrace } = require('./diagnostics')
 
 const NOOP = function () {}
 
@@ -179,7 +179,7 @@ class Pool extends EventEmitter {
 
     this._clients = this._clients.filter((c) => c !== client)
     const context = this
-    if (poolRemoveChannel.hasSubscribers) {
+    if (shouldTrace(poolRemoveChannel)) {
       poolRemoveChannel.publish({ client: { processID: client.processID } })
     }
 
@@ -201,7 +201,7 @@ class Pool extends EventEmitter {
     const response = promisify(this.Promise, cb)
     const result = response.result
 
-    if (poolConnectChannel.hasSubscribers) {
+    if (shouldTrace(poolConnectChannel)) {
       const context = {
         pool: {
           totalCount: this.totalCount,
@@ -418,7 +418,7 @@ class Pool extends EventEmitter {
 
     this.emit('release', err, client)
 
-    if (poolReleaseChannel.hasSubscribers) {
+    if (shouldTrace(poolReleaseChannel)) {
       poolReleaseChannel.publish({ client: { processID: client.processID }, error: err || undefined })
     }
 

packages/pg-pool/test/diagnostics.js

@@ -7,8 +7,6 @@ const it = require('mocha').it
 const dc = require('diagnostics_channel')
 const Pool = require('../')
 
-const hasTracingChannel = typeof dc.tracingChannel === 'function'
-
 function mockClient(methods) {
   return function () {
     const client = new EventEmitter()
@@ -25,7 +23,7 @@ function mockClient(methods) {
 
 describe('diagnostics channels', function () {
   describe('pg:pool:connect', function () {
-    ;(hasTracingChannel ? it : it.skip)('publishes start event when connect is called', function (done) {
+    it('publishes start event when connect is called', function (done) {
       const pool = new Pool({
         Client: mockClient({
           connect: function (cb) {
@@ -62,7 +60,7 @@ describe('diagnostics channels', function () {
         })
       })
     })
-    ;(hasTracingChannel ? it : it.skip)('enriches context with client info on asyncEnd', function (done) {
+    it('enriches context with client info on asyncEnd', function (done) {
       const pool = new Pool({
         Client: mockClient({
           connect: function (cb) {

packages/pg/lib/client.js

@@ -9,7 +9,7 @@ const Query = require('./query')
 const defaults = require('./defaults')
 const Connection = require('./connection')
 const crypto = require('./crypto/utils')
-const { queryChannel, connectionChannel } = require('./diagnostics')
+const { queryChannel, connectionChannel, shouldTrace } = require('./diagnostics')
 
 const activeQueryDeprecationNotice = nodeUtils.deprecate(
   () => {},
@@ -208,7 +208,7 @@ class Client extends EventEmitter {
 
   connect(callback) {
     if (callback) {
-      if (connectionChannel.hasSubscribers) {
+      if (shouldTrace(connectionChannel)) {
         const context = {
           connection: { database: this.database, host: this.host, port: this.port, user: this.user, ssl: !!this.ssl },
         }
@@ -227,7 +227,7 @@ class Client extends EventEmitter {
         })
       })
 
-    if (connectionChannel.hasSubscribers) {
+    if (shouldTrace(connectionChannel)) {
       const context = {
         connection: { database: this.database, host: this.host, port: this.port, user: this.user, ssl: !!this.ssl },
       }
@@ -708,7 +708,7 @@ class Client extends EventEmitter {
       this._pulseQueryQueue()
     }
 
-    if (queryChannel.hasSubscribers) {
+    if (shouldTrace(queryChannel)) {
       const context = {
         query: { text: query.text, name: query.name, rowMode: query._rowMode },
         client: {

packages/pg/lib/diagnostics.js

@@ -20,4 +20,12 @@ try {
   // diagnostics_channel not available (non-Node environment)
 }
 
-module.exports = { queryChannel, connectionChannel }
+// Check explicitly for `false` rather than truthiness because the aggregated
+// `hasSubscribers` getter on TracingChannel is `undefined` on Node 18 (which
+// backported TracingChannel but not the getter). When `undefined`, we assume
+// there may be subscribers and trace unconditionally.
+function shouldTrace(channel) {
+  return channel.hasSubscribers !== false
+}
+
+module.exports = { queryChannel, connectionChannel, shouldTrace }

packages/pg/test/unit/client/diagnostics-tests.js

@@ -3,15 +3,11 @@ const helper = require('./test-helper')
 const assert = require('assert')
 const dc = require('diagnostics_channel')
 
-const hasTracingChannel = typeof dc.tracingChannel === 'function'
-
 const suite = new helper.Suite()
 const test = suite.test.bind(suite)
-// pass undefined as callback to skip when TracingChannel is unavailable
-const testTracing = (name, cb) => test(name, hasTracingChannel ? cb : undefined)
 
-testTracing('query diagnostics channel', function () {
-  testTracing('publishes start and asyncEnd on successful query', function (done) {
+test('query diagnostics channel', function () {
+  test('publishes start and asyncEnd on successful query', function (done) {
     const client = helper.client()
     client.connection.emit('readyForQuery')
 
@@ -54,7 +50,7 @@ testTracing('query diagnostics channel', function () {
     client.connection.emit('readyForQuery')
   })
 
-  testTracing('publishes error on failed query', function (done) {
+  test('publishes error on failed query', function (done) {
     const client = helper.client()
     client.connection.emit('readyForQuery')
 
@@ -91,7 +87,7 @@ testTracing('query diagnostics channel', function () {
     })
   })
 
-  testTracing('query context includes client info', function (done) {
+  test('query context includes client info', function (done) {
     const client = helper.client({ database: 'testdb', host: 'localhost', port: 5432, user: 'testuser' })
     client.connection.emit('readyForQuery')
 
@@ -124,7 +120,7 @@ testTracing('query diagnostics channel', function () {
     client.connection.emit('readyForQuery')
   })
 
-  testTracing('promise query publishes diagnostics', function (done) {
+  test('promise query publishes diagnostics', function (done) {
     const client = helper.client()
     client.connection.emit('readyForQuery')
 
@@ -158,8 +154,8 @@ testTracing('query diagnostics channel', function () {
   })
 })
 
-testTracing('connection diagnostics channel', function () {
-  testTracing('publishes start on connect with callback', function (done) {
+test('connection diagnostics channel', function () {
+  test('publishes start on connect with callback', function (done) {
     const Connection = require('../../../lib/connection')
     const { Client } = helper