Get current context from docker config

Signed-off-by: Anca Iordache <anca.iordache@docker.com>

docker/context/api.py

@@ -2,7 +2,9 @@
 import os
 
 from docker import errors
-from docker.context.config import METADATA_DIR, METAFILE
+from docker.context.config import (
+    METADATA_DIR, METAFILE, get_current_context_name
+)
 from docker.context import Context
 
 
@@ -93,6 +95,16 @@ def contexts(cls):
             contexts.append(Context.load_context(name))
         return contexts
 
+    @classmethod
+    def get_current_context(cls):
+        """Context list.
+        Returns:
+            (Context): current context object.
+        """
+        # get current context from docker config
+        name = get_current_context_name()
+        return ContextAPI.get_context(name)
+
     @classmethod
     def remove_context(cls, name):
         """Remove a context. Similar to the ``docker context rm`` command.
@@ -132,10 +144,6 @@ def get_context(cls, name="default"):
         Args:
             name (str): The name of the context
 
-        Raises:
-            :py:class:`docker.errors.MissingContextParameter`
-                If a context name is not provided.
-
         Example:
 
         >>> from docker.context import ContextAPI
@@ -154,9 +162,7 @@ def get_context(cls, name="default"):
             }
         }
         """
-        if not name:
-            raise errors.MissingContextParameter("name")
-        if name == "default":
+        if not name or name == "default":
             return ContextAPI.DEFAULT_CONTEXT
         # load the context to check if it already exists
         ctx = Context.load_context(name)

docker/context/config.py

@@ -1,4 +1,5 @@
 import os
+import json
 import hashlib
 from .. import utils
 
@@ -9,6 +10,13 @@
 METAFILE = "meta.json"
 
 
+def get_current_context_name():
+    docker_config = utils.find_docker_config_file()
+    if docker_config:
+        return json.load(docker_config).get("currentContext")
+    return None
+
+
 def get_context_id(name):
     return hashlib.sha256(name.encode('utf-8')).hexdigest()
 

tests/integration/context_api_test.py

@@ -10,9 +10,15 @@
 class ContextLifecycleTest(BaseAPIIntegrationTest):
     def test_lifecycle(self):
         # check there is no context 'test'
+        ctx = ContextAPI.get_context()
+        assert ctx is not None and ctx.Name is "default"
+
         ctx = ContextAPI.get_context("test")
         assert ctx is None
 
+        ctx = ContextAPI.get_current_context()
+        assert ctx is not None
+
         success = False
         dirpath = tempfile.mkdtemp()
         ca = tempfile.NamedTemporaryFile(

tests/unit/context_test.py

@@ -39,6 +39,10 @@ def test_default_in_context_list(self):
                 found = True
         assert found is True
 
+    def test_get_current_context(self):
+        ctx = ContextAPI.get_current_context()
+        assert ctx is not None
+
     def test_context_inspect_without_params(self):
         ctx = ContextAPI.inspect_context()
         assert ctx["Name"] == "default"