Make config validation error messages more consistent.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

compose/config/validation.py

@@ -111,30 +111,29 @@ def validate_config_section(filename, config, section):
     """
     if not isinstance(config, dict):
         raise ConfigurationError(
-            "In file '{filename}' {section} must be a mapping, not "
+            "In file '{filename}', {section} must be a mapping, not "
-            "'{type}'.".format(
+            "{type}.".format(
                 filename=filename,
                 section=section,
-                type=python_type_to_yaml_type(config)))
+                type=anglicize_json_type(python_type_to_yaml_type(config))))
 
     for key, value in config.items():
         if not isinstance(key, six.string_types):
             raise ConfigurationError(
-                "In file '{filename}' {section} name {name} needs to be a "
+                "In file '{filename}', the {section} name {name} must be a "
-                "string, eg '{name}'".format(
+                "quoted string, i.e. '{name}'.".format(
                     filename=filename,
                     section=section,
                     name=key))
 
         if not isinstance(value, (dict, type(None))):
             raise ConfigurationError(
-                "In file '{filename}' {section} '{name}' is the wrong type. "
+                "In file '{filename}', {section} '{name}' must be a mapping not "
-                "It should be a mapping of configuration options, it is a "
+                "{type}.".format(
-                "'{type}'.".format(
                     filename=filename,
                     section=section,
                     name=key,
-                    type=python_type_to_yaml_type(value)))
+                    type=anglicize_json_type(python_type_to_yaml_type(value))))
 
 
 def validate_top_level_object(config_file):
@@ -203,10 +202,10 @@ def get_unsupported_config_msg(path, error_key):
     return msg
 
 
-def anglicize_validator(validator):
+def anglicize_json_type(json_type):
-    if validator in ["array", "object"]:
+    if json_type.startswith(('a', 'e', 'i', 'o', 'u')):
-        return 'an ' + validator
+        return 'an ' + json_type
-    return 'a ' + validator
+    return 'a ' + json_type
 
 
 def is_service_dict_schema(schema_id):
@@ -314,14 +313,14 @@ def _parse_valid_types_from_validator(validator):
     a valid type. Parse the valid types and prefix with the correct article.
     """
     if not isinstance(validator, list):
-        return anglicize_validator(validator)
+        return anglicize_json_type(validator)
 
     if len(validator) == 1:
-        return anglicize_validator(validator[0])
+        return anglicize_json_type(validator[0])
 
     return "{}, or {}".format(
-        ", ".join([anglicize_validator(validator[0])] + validator[1:-1]),
+        ", ".join([anglicize_json_type(validator[0])] + validator[1:-1]),
-        anglicize_validator(validator[-1]))
+        anglicize_json_type(validator[-1]))
 
 
 def _parse_oneof_validator(error):

docs/compose-file.md

@@ -477,7 +477,7 @@ Networks to join, referencing entries under the
 
 #### aliases
 
-Aliases (alternative hostnames) for this service on the network. Other containers on the same network can use either the service name or this alias to connect to one of the service's containers.  
+Aliases (alternative hostnames) for this service on the network. Other containers on the same network can use either the service name or this alias to connect to one of the service's containers.
 
 Since `aliases` is network-scoped, the same service can have different aliases on different networks.
 

tests/acceptance/cli_test.py

@@ -159,7 +159,7 @@ class CLITestCase(DockerClientTestCase):
             '-f', 'tests/fixtures/invalid-composefile/invalid.yml',
             'config', '-q'
         ], returncode=1)
-        assert "'notaservice' is the wrong type" in result.stderr
+        assert "'notaservice' must be a mapping" in result.stderr
 
     # TODO: this shouldn't be v2-dependent
     @v2_only()

tests/unit/config/config_test.py

@@ -268,7 +268,7 @@ class ConfigTest(unittest.TestCase):
         })
         with pytest.raises(ConfigurationError) as exc:
             config.load(config_details)
-        assert "volume must be a mapping, not 'array'" in exc.exconly()
+        assert "volume must be a mapping, not an array" in exc.exconly()
 
     def test_networks_invalid_type_list(self):
         config_details = build_config_details({
@@ -280,7 +280,7 @@ class ConfigTest(unittest.TestCase):
         })
         with pytest.raises(ConfigurationError) as exc:
             config.load(config_details)
-        assert "network must be a mapping, not 'array'" in exc.exconly()
+        assert "network must be a mapping, not an array" in exc.exconly()
 
     def test_load_service_with_name_version(self):
         with mock.patch('compose.config.config.log') as mock_logging:
@@ -392,8 +392,7 @@ class ConfigTest(unittest.TestCase):
             'filename.yml')
         with pytest.raises(ConfigurationError) as exc:
             config.load(config_details)
-        error_msg = "service 'web' is the wrong type"
+        assert "service 'web' must be a mapping not a string." in exc.exconly()
-        assert error_msg in exc.exconly()
 
     def test_config_integer_service_name_raise_validation_error(self):
         with pytest.raises(ConfigurationError) as excinfo:
@@ -405,8 +404,10 @@ class ConfigTest(unittest.TestCase):
                 )
             )
 
-        assert "In file 'filename.yml' service name 1 needs to be a string, eg '1'" \
+        assert (
-            in excinfo.exconly()
+            "In file 'filename.yml', the service name 1 must be a quoted string, i.e. '1'" in
+            excinfo.exconly()
+        )
 
     def test_config_integer_service_name_raise_validation_error_v2(self):
         with pytest.raises(ConfigurationError) as excinfo:
@@ -421,8 +422,10 @@ class ConfigTest(unittest.TestCase):
                 )
             )
 
-        assert "In file 'filename.yml' service name 1 needs to be a string, eg '1'" \
+        assert (
-            in excinfo.exconly()
+            "In file 'filename.yml', the service name 1 must be a quoted string, i.e. '1'." in
+            excinfo.exconly()
+        )
 
     def test_load_with_multiple_files_v1(self):
         base_file = config.ConfigFile(
@@ -556,7 +559,7 @@ class ConfigTest(unittest.TestCase):
 
         with pytest.raises(ConfigurationError) as exc:
             config.load(details)
-        assert "service 'bogus' is the wrong type" in exc.exconly()
+        assert "service 'bogus' must be a mapping not a string." in exc.exconly()
         assert "In file 'override.yaml'" in exc.exconly()
 
     def test_load_sorts_in_dependency_order(self):