Add YAML param files support

.changes/next-release/enhancement-file-64839.json

@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "file",
+  "description": "Add support for YAML input files with ``yaml"
+}

awscli/paramfile.py

@@ -10,10 +10,14 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
 # ANY KIND, either express or implied. See the License for the specific
 # language governing permissions and limitations under the License.
+import json
 import logging
 import os
 import copy
 
+import ruamel
+from ruamel.yaml import YAML
+
 from awscli.compat import six
 
 from awscli.compat import compat_open
@@ -79,22 +83,55 @@ def get_paramfile(path, cases):
     return data
 
 
-def get_file(prefix, path, mode):
-    file_path = os.path.expandvars(os.path.expanduser(path[len(prefix):]))
-    try:
-        with compat_open(file_path, mode) as f:
-            return f.read()
-    except UnicodeDecodeError:
-        raise ResourceLoadingError(
-            'Unable to load paramfile (%s), text contents could '
-            'not be decoded.  If this is a binary file, please use the '
-            'fileb:// prefix instead of the file:// prefix.' % file_path)
-    except (OSError, IOError) as e:
-        raise ResourceLoadingError('Unable to load paramfile %s: %s' % (
-            path, e))
+class FileLoader:
+
+    def __call__(self, prefix, path, mode):
+        return getattr(self, '_get_%s' % mode)(prefix, path)
+
+    def _get_r(self, prefix, path):
+        return self._get_file(prefix, path, 'r')
+
+    def _get_rb(self, prefix, path):
+        return self._get_file(prefix, path, 'rb')
+
+    def _get_yaml(self, prefix, path):
+        file_path = os.path.expandvars(os.path.expanduser(path[len(prefix):]))
+        yaml = YAML(typ='safe')
+        yaml.constructor.add_constructor(
+            'tag:yaml.org,2002:binary', self._load_binary
+        )
+        try:
+            with compat_open(file_path, 'r') as f:
+                return json.dumps(yaml.load(f))
+        except ruamel.yaml.scanner.ScannerError:
+            raise ResourceLoadingError(
+                'Unable to load paramfile (%s), it is not a valid YAML '
+                'file' % file_path)
+        except (OSError, IOError) as e:
+            raise ResourceLoadingError('Unable to load paramfile %s: %s' % (
+                path, e))
+
+    def _get_file(self, prefix, path, mode):
+        file_path = os.path.expandvars(os.path.expanduser(path[len(prefix):]))
+        try:
+            with compat_open(file_path, mode) as f:
+                return f.read()
+        except UnicodeDecodeError:
+            raise ResourceLoadingError(
+                'Unable to load paramfile (%s), text contents could '
+                'not be decoded.  If this is a binary file, please use the '
+                'fileb:// prefix instead of the file:// prefix.' % file_path)
+        except (OSError, IOError) as e:
+            raise ResourceLoadingError('Unable to load paramfile %s: %s' % (
+                path, e))
+
+    def _load_binary(self, loader, node):
+        # stringify the binary value
+        return node.value
 
 
 LOCAL_PREFIX_MAP = {
-    'file://': (get_file, {'mode': 'r'}),
-    'fileb://': (get_file, {'mode': 'rb'}),
+    'file://': (FileLoader(), {'mode': 'r'}),
+    'fileb://': (FileLoader(), {'mode': 'rb'}),
+    'yaml://': (FileLoader(), {'mode': 'yaml'}),
 }

tests/functional/test_paramfile.py

@@ -69,6 +69,22 @@ def test_does_use_fileb_prefix(self):
             expected_param=b'file content'
         )
 
+    def test_does_use_yaml_prefix(self):
+        path = self.files.create_file('foobar.yaml', '- key: value')
+        param = 'yaml://%s' % path
+        self.assert_param_expansion_is_correct(
+            provided_param=param,
+            expected_param='[{"key": "value"}]'
+        )
+
+    def test_does_use_yaml_binary_data(self):
+        path = self.files.create_file('foobar.yaml', '{key: !!binary "4pyT"}')
+        param = 'yaml://%s' % path
+        self.assert_param_expansion_is_correct(
+            provided_param=param,
+            expected_param='{"key": "4pyT"}'
+        )
+
 
 class TestCLIUseEncodingFromEnv(BaseTestCLIFollowParamFile):
 

tests/unit/test_paramfile.py

@@ -48,6 +48,22 @@ def test_binary_file(self):
         self.assertEqual(data, b'This is a test')
         self.assertIsInstance(data, six.binary_type)
 
+    def test_yaml_file(self):
+        contents = '- key: value'
+        filename = self.files.create_file('foo', contents)
+        prefixed_filename = 'yaml://' + filename
+        data = self.get_paramfile(prefixed_filename)
+        self.assertEqual(data, '[{"key": "value"}]')
+        self.assertIsInstance(data, six.string_types)
+
+    def test_invalid_yaml_file(self):
+        contents = '- - "key -value'
+        filename = self.files.create_file('foo', contents)
+        prefixed_filename = 'yaml://' + filename
+        with self.assertRaises(ResourceLoadingError) as e:
+            self.get_paramfile(prefixed_filename)
+
+
     @skip_if_windows('Binary content error only occurs '
                      'on non-Windows platforms.')
     def test_cannot_load_text_file(self):
@@ -61,6 +77,10 @@ def test_file_does_not_exist_raises_error(self):
         with self.assertRaises(ResourceLoadingError):
             self.get_paramfile('file://file/does/not/existsasdf.txt')
 
+    def test_yaml_file_does_not_exist_raises_error(self):
+        with self.assertRaises(ResourceLoadingError):
+            self.get_paramfile('yaml://file/does/not/existsasdf.yaml')
+
     def test_no_match_uris_returns_none(self):
         self.assertIsNone(self.get_paramfile('foobar://somewhere.bar'))