fix(context): use default config dir when config.json is missing

docker/context/config.py

@@ -4,11 +4,23 @@
 
 from docker import utils
 from docker.constants import DEFAULT_UNIX_SOCKET, IS_WINDOWS_PLATFORM
-from docker.utils.config import find_config_file
+from docker.utils.config import (
+    DOCKER_CONFIG_FILENAME,
+    config_path_from_environment,
+    find_config_file,
+    home_dir,
+)
 
 METAFILE = "meta.json"
 
 
+def _default_docker_config_path():
+    return (
+        config_path_from_environment()
+        or os.path.join(home_dir(), DOCKER_CONFIG_FILENAME)
+    )
+
+
 def get_current_context_name():
     name = "default"
     docker_cfg_path = find_config_file()
@@ -24,9 +36,9 @@ def get_current_context_name():
 def write_context_name_to_docker_config(name=None):
     if name == 'default':
         name = None
-    docker_cfg_path = find_config_file()
+    docker_cfg_path = find_config_file() or _default_docker_config_path()
     config = {}
-    if docker_cfg_path:
+    if os.path.exists(docker_cfg_path):
         try:
             with open(docker_cfg_path) as f:
                 config = json.load(f)
@@ -40,6 +52,7 @@ def write_context_name_to_docker_config(name=None):
     else:
         return
     try:
+        os.makedirs(os.path.dirname(docker_cfg_path), exist_ok=True)
         with open(docker_cfg_path, "w") as f:
             json.dump(config, f, indent=4)
     except Exception as e:
@@ -51,7 +64,10 @@ def get_context_id(name):
 
 
 def get_context_dir():
-    return os.path.join(os.path.dirname(find_config_file() or ""), "contexts")
+    return os.path.join(
+        os.path.dirname(find_config_file() or _default_docker_config_path()),
+        "contexts",
+    )
 
 
 def get_meta_dir(name=None):

tests/unit/context_test.py

@@ -1,10 +1,15 @@
+import json
+import os
+import tempfile
 import unittest
+from unittest import mock
 
 import pytest
 
 import docker
 from docker.constants import DEFAULT_NPIPE, DEFAULT_UNIX_SOCKET, IS_WINDOWS_PLATFORM
 from docker.context import Context, ContextAPI
+from docker.context.config import get_context_dir, get_meta_dir, get_tls_dir
 
 
 class BaseContextTest(unittest.TestCase):
@@ -49,3 +54,37 @@ def test_context_inspect_without_params(self):
             DEFAULT_NPIPE,
             DEFAULT_UNIX_SOCKET[5:],
         )
+
+
+@pytest.mark.skipif(IS_WINDOWS_PLATFORM, reason='POSIX-specific HOME handling')
+def test_context_paths_use_default_docker_config_dir_when_config_missing():
+    with tempfile.TemporaryDirectory() as home:
+        with mock.patch.dict(os.environ, {'HOME': home}, clear=False):
+            assert get_context_dir() == os.path.join(home, '.docker', 'contexts')
+            assert get_meta_dir('demo').startswith(
+                os.path.join(home, '.docker', 'contexts', 'meta')
+            )
+            assert get_tls_dir('demo').startswith(
+                os.path.join(home, '.docker', 'contexts', 'tls')
+            )
+
+
+@pytest.mark.skipif(IS_WINDOWS_PLATFORM, reason='POSIX-specific HOME handling')
+def test_set_current_context_creates_config_in_default_docker_dir():
+    with tempfile.TemporaryDirectory() as home, tempfile.TemporaryDirectory() as cwd:
+        with mock.patch.dict(os.environ, {'HOME': home}, clear=False):
+            old_cwd = os.getcwd()
+            try:
+                os.chdir(cwd)
+                ctx = ContextAPI.create_context('demo')
+                ContextAPI.set_current_context('demo')
+            finally:
+                os.chdir(old_cwd)
+
+        config_path = os.path.join(home, '.docker', 'config.json')
+        with open(config_path) as f:
+            config = json.load(f)
+
+        assert config["currentContext"] == 'demo'
+        assert ctx.meta_path.startswith(os.path.join(home, '.docker', 'contexts'))
+        assert not os.path.exists(os.path.join(cwd, 'contexts'))