Add support for password function to native

packages/pg/lib/connection-parameters.js

@@ -125,9 +125,25 @@ class ConnectionParameters {
   }
 
   getLibpqConnectionString(cb) {
-    var params = []
-    add(params, this, 'user')
-    add(params, this, 'password')
+    if (typeof this.password === 'function') {
+      const pw = this.password();
+      if (typeof pw === 'string') {
+        return this._getLibpqConnectionString(cb, pw)
+      }
+      pw.then((pwString) => this._getLibpqConnectionString(cb, pwString)).catch((e) => cb(e))
+      return
+    }
+    this._getLibpqConnectionString(cb);
+  }
+
+  _getLibpqConnectionString(cb, pw) {
+    var params = [];
+    add(params, this, 'user');
+    if (pw != null) {
+      params.push('password=' + quoteParamValue(pw))
+    } else {
+      add(params, this, 'password');
+    }
     add(params, this, 'port')
     add(params, this, 'application_name')
     add(params, this, 'fallback_application_name')

packages/pg/test/unit/connection-parameters/creation-tests.js

@@ -187,6 +187,30 @@ suite.testAsync('builds simple string', async function () {
   })
 })
 
+suite.testAsync('builds simple string with pw function', async function () {
+  var config = {
+    user: 'brian',
+    password: () => 'xyz',
+    port: 888,
+    host: 'localhost',
+    database: 'bam',
+  }
+  var subject = new ConnectionParameters(config)
+  const dnsHost = await getDNSHost(config.host)
+  return new Promise((resolve) => {
+    subject.getLibpqConnectionString(function (err, constring) {
+      assert(!err)
+      var parts = constring.split(' ')
+      checkForPart(parts, "user='brian'")
+      checkForPart(parts, "password='xyz'")
+      checkForPart(parts, "port='888'")
+      checkForPart(parts, `hostaddr='${dnsHost}'`)
+      checkForPart(parts, "dbname='bam'")
+      resolve()
+    })
+  })
+})
+
 suite.test('builds dns string', async function () {
   var config = {
     user: 'brian',