Connection config provider

lib/client.js

@@ -15,6 +15,7 @@ const TableBuilder = require('./schema/tablebuilder');
 const TableCompiler = require('./schema/tablecompiler');
 const ColumnBuilder = require('./schema/columnbuilder');
 const ColumnCompiler = require('./schema/columncompiler');
+const Connection = require('./connection');
 
 const { Pool, TimeoutError } = require('tarn');
 const inherits = require('inherits');
@@ -53,8 +54,12 @@ function Client(config = {}) {
   if (config.version) {
     this.version = config.version;
   }
-
-  this.connectionSettings = cloneDeep(config.connection || {});
+  // if the type of connection settings is a function, pass it to the next layer
+  if (typeof config.connection === 'function') {
+    this.connectionSettings = config.connection;
+  } else {
+    this.connectionSettings = cloneDeep(config.connection || {});
+  }
   if (this.driverName && config.connection) {
     this.initializeDriver();
     if (!config.pool || (config.pool && config.pool.max !== 0)) {
@@ -122,6 +127,10 @@ Object.assign(Client.prototype, {
     return new Ref(this, ...arguments);
   },
 
+  connection() {
+    return new Connection(this);
+  },
+
   _formatQuery(sql, bindings, timeZone) {
     bindings = bindings == null ? [] : [].concat(bindings);
     let index = 0;

lib/connection.js

@@ -0,0 +1,18 @@
+class Connection {
+  constructor(client) {
+    this.client = client;
+    this.resolvedConnectionSettings = null;
+  }
+
+  async resolveConnectionConfig() {
+    if (typeof this.client.connectionSettings === 'function') {
+      // if the config is a function, execute the function and resolve the connection settings
+      if (!this.resolvedConnectionSettings) {
+        this.resolvedConnectionSettings = await this.client.connectionSettings();
+        this.client.connectionSettings = this.resolvedConnectionSettings;
+      }
+    }
+  }
+}
+
+module.exports = Connection;

lib/dialects/postgres/index.js

@@ -21,6 +21,7 @@ function Client_PG(config) {
     this.searchPath = config.searchPath;
   }
 }
+
 inherits(Client_PG, Client);
 
 Object.assign(Client_PG.prototype, {
@@ -105,7 +106,8 @@ Object.assign(Client_PG.prototype, {
   // connection needs to be added to the pool.
   acquireRawConnection() {
     const client = this;
-    return new Bluebird(function(resolver, rejecter) {
+    return new Bluebird(async function(resolver, rejecter) {
+      await client.connection().resolveConnectionConfig();
       const connection = new client.driver.Client(client.connectionSettings);
       connection.connect(function(err, connection) {
         if (err) {