Add port command

index.d.ts

@@ -18,6 +18,7 @@ declare module "docker-compose" {
     buildOne(service:String, options: IDockerComposeOptions): Promise<IDockerComposeResult>;
     ps(options: IDockerComposeOptions): Promise<IDockerComposeResult>;
     push(options: IDockerComposePushOptions): Promise<IDockerComposeResult>;
+    port(service:String, containerPort:String|Number, options: IDockerComposeOptions): Promise<IDockerComposeResult>;
   }
 
   interface IDockerComposeOptions {

index.js

@@ -359,6 +359,21 @@ const logs = function (service, options) {
   return execCompose('logs', args, options);
 };
 
+/**
+ * @param {string} service
+ * @param {string|number} containerPort
+ * @param {object} options
+ * @param {string} options.cwd
+ * @param {boolean} [options.log]
+ * @param {?(string|string[])} [options.config]
+ * @param {?object} [options.env]
+ * @param {?(string[]|Array<string|string[]>)} [options.composeOptions]
+ */
+const port = function(service, containerPort, options) {
+  const args = [service, containerPort]
+  return execCompose('port', args, options)
+};
+
 module.exports = {
   upAll,
   upMany,
@@ -378,4 +393,5 @@ module.exports = {
   buildOne,
   ps,
   push,
+  port,
 };

test/docker-compose-2.yml

@@ -3,4 +3,6 @@ version: '2'
 services: 
   db:
     image: mongo:3.4
-    container_name: compose_test_mongodb_2
+    container_name: compose_test_mongodb_2
+    ports:
+      - "5432"

test/index.js

@@ -321,3 +321,15 @@ test('logs does follow service logs', async assert => {
   assert.true(await isContainerRunning('/compose_test_mongodb'));
   assert.end();
 });
+
+test('returns the port for a started service', async assert => {
+  const config = {
+    cwd: path.join(__dirname),
+    config: './docker-compose-2.yml'
+  }
+  await compose.upAll(config);
+  const port = await compose.port('db', 5432, config);
+
+  assert.true(port.out.match(/.*:[0-9]{1,5}/));
+  assert.end();
+})