Remove extra s from --add-host

linting...
six.string_types
list-of-strings in examples
disallow extra_hosts support for list-of-dicts
A more thorough sets of tests for extra_hosts
Provide better examples
As per @aanand's [comment](https://github.com/docker/compose/pull/1158/files#r28326312)

  I think it'd be better to check `if not isinstance(extra_hosts_line,
  six.string_types)` and raise an error saying `extra_hosts_config must be
  either a list of strings or a string->string mapping`. We shouldn't need
  to do anything special with the list-of-dicts case.
order result to work with assert
use set() instead of sort()

Signed-off-by: CJ <[email protected]>

compose/service.py

@@ -626,20 +626,25 @@ def split_port(port):
 
 
 def build_extra_hosts(extra_hosts_config):
-    if extra_hosts_config is None:
-        return None
-
-    if isinstance(extra_hosts_config, basestring):
-        extra_hosts_config = [extra_hosts_config]
-
-    extra_hosts_dict = {}
-    for extra_hosts_line in extra_hosts_config:
-        if isinstance(extra_hosts_line, dict):
-            # already interpreted as a dict (depends on pyyaml version)
-            extra_hosts_dict.update(extra_hosts_line)
-        else:
-            # not already interpreted as a dict
+    if not extra_hosts_config:
+        return {}
+
+    if isinstance(extra_hosts_config, list):
+        extra_hosts_dict = {}
+        for extra_hosts_line in extra_hosts_config:
+            if not isinstance(extra_hosts_line, six.string_types):
+                raise ConfigError(
+                    "extra_hosts_config \"%s\" must be either a list of strings or a string->string mapping," %
+                    extra_hosts_config
+                )
             host, ip = extra_hosts_line.split(':')
             extra_hosts_dict.update({host.strip(): ip.strip()})
+        extra_hosts_config = extra_hosts_dict
+
+    if isinstance(extra_hosts_config, dict):
+        return extra_hosts_config
 
-    return extra_hosts_dict
+    raise ConfigError(
+        "extra_hosts_config \"%s\" must be either a list of strings or a string->string mapping," %
+        extra_hosts_config
+    )

docs/yml.md

@@ -89,19 +89,19 @@ external_links:
 
 ### extra_hosts
 
-Add hostname mappings. Use the same values as the docker client `--add-hosts` parameter.
+Add hostname mappings. Use the same values as the docker client `--add-host` parameter.
 
 ```
 extra_hosts:
- - docker: 162.242.195.82
- - fig: 50.31.209.229
+ - "somehost:162.242.195.82"
+ - "otherhost:50.31.209.229"
 ```
 
 An entry with the ip address and hostname will be created in `/etc/hosts` inside containers for this service, e.g:
 
 ```
-162.242.195.82  docker
-50.31.209.229   fig
+162.242.195.82  somehost
+50.31.209.229   otherhost
 ```
 
 ### ports

tests/integration/service_test.py

@@ -5,8 +5,11 @@ from os import path
 import mock
 
 from compose import Service
-from compose.service import CannotBeScaledError
-from compose.service import build_extra_hosts
+from compose.service import (
+    CannotBeScaledError,
+    build_extra_hosts,
+    ConfigError,
+)
 from compose.container import Container
 from docker.errors import APIError
 from .testcases import DockerClientTestCase
@@ -110,39 +113,59 @@ class ServiceTest(DockerClientTestCase):
 
     def test_build_extra_hosts(self):
         # string
-        self.assertEqual(build_extra_hosts("www.example.com: 192.168.0.17"),
-                         {'www.example.com': '192.168.0.17'})
+        self.assertRaises(ConfigError, lambda: build_extra_hosts("www.example.com: 192.168.0.17"))
 
         # list of strings
         self.assertEqual(build_extra_hosts(
-                          ["www.example.com: 192.168.0.17"]),
-                         {'www.example.com': '192.168.0.17'})
+            ["www.example.com:192.168.0.17"]),
+            {'www.example.com': '192.168.0.17'})
         self.assertEqual(build_extra_hosts(
-                          ["www.example.com: 192.168.0.17",
-                           "api.example.com: 192.168.0.18"]),
-                         {'www.example.com': '192.168.0.17',
-                          'api.example.com': '192.168.0.18'})
+            ["www.example.com: 192.168.0.17"]),
+            {'www.example.com': '192.168.0.17'})
+        self.assertEqual(build_extra_hosts(
+            ["www.example.com: 192.168.0.17",
+             "static.example.com:192.168.0.19",
+             "api.example.com: 192.168.0.18"]),
+            {'www.example.com': '192.168.0.17',
+             'static.example.com': '192.168.0.19',
+             'api.example.com': '192.168.0.18'})
+
         # list of dictionaries
+        self.assertRaises(ConfigError, lambda: build_extra_hosts(
+            [{'www.example.com': '192.168.0.17'},
+             {'api.example.com': '192.168.0.18'}]))
+
+        # dictionaries
         self.assertEqual(build_extra_hosts(
-                          [{'www.example.com': '192.168.0.17'},
-                           {'api.example.com': '192.168.0.18'}
-                          ]),
-                          {'www.example.com': '192.168.0.17',
-                           'api.example.com': '192.168.0.18'})
+            {'www.example.com': '192.168.0.17',
+             'api.example.com': '192.168.0.18'}),
+            {'www.example.com': '192.168.0.17',
+             'api.example.com': '192.168.0.18'})
 
     def test_create_container_with_extra_hosts_list(self):
-        extra_hosts = ['docker:162.242.195.82', 'fig:50.31.209.229']
+        extra_hosts = ['somehost:162.242.195.82', 'otherhost:50.31.209.229']
         service = self.create_service('db', extra_hosts=extra_hosts)
         container = service.create_container()
         service.start_container(container)
-        self.assertEqual(container.get('HostConfig.ExtraHosts'), extra_hosts)
+        self.assertEqual(set(container.get('HostConfig.ExtraHosts')), set(extra_hosts))
 
     def test_create_container_with_extra_hosts_string(self):
-        extra_hosts = 'docker:162.242.195.82'
+        extra_hosts = 'somehost:162.242.195.82'
+        service = self.create_service('db', extra_hosts=extra_hosts)
+        self.assertRaises(ConfigError, lambda: service.create_container())
+
+    def test_create_container_with_extra_hosts_list_of_dicts(self):
+        extra_hosts = [{'somehost': '162.242.195.82'}, {'otherhost': '50.31.209.229'}]
+        service = self.create_service('db', extra_hosts=extra_hosts)
+        self.assertRaises(ConfigError, lambda: service.create_container())
+
+    def test_create_container_with_extra_hosts_dicts(self):
+        extra_hosts = {'somehost': '162.242.195.82', 'otherhost': '50.31.209.229'}
+        extra_hosts_list = ['somehost:162.242.195.82', 'otherhost:50.31.209.229']
         service = self.create_service('db', extra_hosts=extra_hosts)
         container = service.create_container()
         service.start_container(container)
-        self.assertEqual(container.get('HostConfig.ExtraHosts'), [extra_hosts])
+        self.assertEqual(set(container.get('HostConfig.ExtraHosts')), set(extra_hosts_list))
 
     def test_create_container_with_specified_volume(self):
         host_path = '/tmp/host-path'