Add docker build --pull command.

Author: glogiotatidis

compose/cli/main.py

@@ -119,9 +119,11 @@ def build(self, project, options):
 
         Options:
             --no-cache  Do not use cache when building the image.
+            --pull      Always attempt to pull a newer version of the image
         """
         no_cache = bool(options.get('--no-cache', False))
-        project.build(service_names=options['SERVICE'], no_cache=no_cache)
+        pull = bool(options.get('--pull', False))
+        project.build(service_names=options['SERVICE'], no_cache=no_cache, pull=pull)
 
     def help(self, project, options):
         """

compose/project.py

@@ -198,10 +198,10 @@ def restart(self, service_names=None, **options):
         for service in self.get_services(service_names):
             service.restart(**options)
 
-    def build(self, service_names=None, no_cache=False):
+    def build(self, service_names=None, no_cache=False, pull=False):
         for service in self.get_services(service_names):
             if service.can_be_built():
-                service.build(no_cache)
+                service.build(no_cache, pull)
             else:
                 log.info('%s uses an image, skipping' % service.name)
 

compose/service.py

@@ -633,7 +633,7 @@ def _get_container_host_config(self, override_options, one_off=False):
             security_opt=security_opt
         )
 
-    def build(self, no_cache=False):
+    def build(self, no_cache=False, pull=False):
         log.info('Building %s...' % self.name)
 
         path = six.binary_type(self.options['build'])
@@ -644,6 +644,7 @@ def build(self, no_cache=False):
             stream=True,
             rm=True,
             nocache=no_cache,
+            pull=pull,
             dockerfile=self.options.get('dockerfile', None),
         )
 

tests/integration/cli_test.py

@@ -99,6 +99,22 @@ def test_build_no_cache(self, mock_stdout):
         output = mock_stdout.getvalue()
         self.assertNotIn(cache_indicator, output)
 
+    @patch('sys.stdout', new_callable=StringIO)
+    def test_build_pull(self, mock_stdout):
+        self.command.base_dir = 'tests/fixtures/simple-dockerfile'
+        self.command.dispatch(['build', 'simple'], None)
+
+        mock_stdout.truncate(0)
+        cache_indicator = 'latest: Pulling from busybox'
+        self.command.dispatch(['build', 'simple'], None)
+        output = mock_stdout.getvalue()
+        self.assertNotIn(cache_indicator, output)
+
+        mock_stdout.truncate(0)
+        self.command.dispatch(['build', '--pull', 'simple'], None)
+        output = mock_stdout.getvalue()
+        self.assertIn(cache_indicator, output)
+
     def test_up(self):
         self.command.dispatch(['up', '-d'], None)
         service = self.project.get_service('simple')