fix(pg): keep the connection error as the cause of the "not queryable" error

packages/pg/lib/client.js

@@ -81,6 +81,7 @@ class Client extends EventEmitter {
     this._connected = false
     this._connectionError = false
     this._queryable = true
+    this._unqueryableReason = null
     this._activeQuery = null
     this._txStatus = null
 
@@ -418,6 +419,7 @@ class Client extends EventEmitter {
       return this._handleErrorWhileConnecting(err)
     }
     this._queryable = false
+    this._unqueryableReason = this._unqueryableReason || err
     this._errorAllQueries(err)
     this.emit('error', err)
   }
@@ -764,7 +766,12 @@ class Client extends EventEmitter {
 
     if (!this._queryable) {
       process.nextTick(() => {
-        query.handleError(new Error('Client has encountered a connection error and is not queryable'), this.connection)
+        query.handleError(
+          new Error('Client has encountered a connection error and is not queryable', {
+            cause: this._unqueryableReason,
+          }),
+          this.connection
+        )
       })
       return result
     }

packages/pg/lib/native/client.js

@@ -36,6 +36,7 @@ const Client = (module.exports = function (config) {
   this._connecting = false
   this._connected = false
   this._queryable = true
+  this._unqueryableReason = null
   this.pipeline = Boolean(config.pipeline)
   this._pipelineInFlight = false
 
@@ -110,6 +111,7 @@ Client.prototype._connect = function (cb) {
       // handle connection errors from the native layer
       self.native.on('error', function (err) {
         self._queryable = false
+        self._unqueryableReason = self._unqueryableReason || err
         self._errorAllQueries(err)
         self.emit('error', err)
       })
@@ -223,7 +225,11 @@ Client.prototype.query = function (config, values, callback) {
   if (!this._queryable) {
     query.native = this.native
     process.nextTick(() => {
-      query.handleError(new Error('Client has encountered a connection error and is not queryable'))
+      query.handleError(
+        new Error('Client has encountered a connection error and is not queryable', {
+          cause: this._unqueryableReason,
+        })
+      )
     })
     return result
   }
@@ -358,6 +364,7 @@ Client.prototype._pulsePipelinedQueryQueue = function () {
       // for the life of the process.
       self._connected = false
       self._queryable = false
+      self._unqueryableReason = self._unqueryableReason || err
       for (let i = 0; i < nativeQueries.length; i++) {
         const q = nativeQueries[i]
         q.native = self.native

packages/pg/test/integration/gh-issues/3852-tests.js

@@ -0,0 +1,28 @@
+'use strict'
+const helper = require('../test-helper')
+const assert = require('assert')
+const suite = new helper.Suite()
+
+// libpq does not report a FATAL error while no query is running
+if (helper.args.native) {
+  return
+}
+
+suite.test('not queryable error has the idle-in-transaction timeout as cause', async () => {
+  const client = new helper.pg.Client(helper.config)
+  const errors = []
+  client.on('error', (err) => errors.push(err))
+  const ended = new Promise((resolve) => client.once('end', resolve))
+  await client.connect()
+  await client.query("SET idle_in_transaction_session_timeout = '100ms'")
+  await client.query('BEGIN')
+  await ended
+
+  const timeoutError = errors[0]
+  assert.equal(timeoutError.code, '25P03')
+  await assert.rejects(client.query('SELECT 1'), (err) => {
+    assert.equal(err.message, 'Client has encountered a connection error and is not queryable')
+    assert.strictEqual(err.cause, timeoutError)
+    return true
+  })
+})

packages/pg/test/native/unqueryable-error-cause-tests.js

@@ -0,0 +1,23 @@
+'use strict'
+const helper = require('./../test-helper')
+const Client = require('./../../lib/native')
+const suite = new helper.Suite()
+const assert = require('assert')
+
+suite.test('not queryable error keeps the error that made the client unqueryable as cause', async function () {
+  const client = new Client(helper.config)
+  await client.connect()
+
+  const connectionError = new Error('server closed the connection unexpectedly')
+  client.on('error', function (err) {
+    assert.strictEqual(err, connectionError)
+  })
+  client.native.emit('error', connectionError)
+
+  await assert.rejects(client.query('SELECT 1'), function (err) {
+    assert.equal(err.message, 'Client has encountered a connection error and is not queryable')
+    assert.strictEqual(err.cause, connectionError)
+    return true
+  })
+  await client.end()
+})

packages/pg/test/unit/client/unqueryable-error-cause-tests.js

@@ -0,0 +1,26 @@
+'use strict'
+const helper = require('./test-helper')
+const assert = require('assert')
+const suite = new helper.Suite()
+const test = suite.test.bind(suite)
+
+test('not queryable error keeps the error that made the client unqueryable as cause', function (done) {
+  const client = helper.client()
+  client.connection.emit('readyForQuery')
+
+  const fatal = new Error('terminating connection due to idle-in-transaction timeout')
+  fatal.severity = 'FATAL'
+  fatal.code = '25P03'
+
+  client.on('error', function (err) {
+    assert.strictEqual(err, fatal)
+  })
+  client.connection.emit('errorMessage', fatal)
+
+  client.query('SELECT 1', function (err) {
+    assert.equal(err.message, 'Client has encountered a connection error and is not queryable')
+    assert.strictEqual(err.cause, fatal)
+    assert.equal(err.cause.code, '25P03')
+    done()
+  })
+})