Avoid requiring jupyter_config.py in to be in CYLC_SITE_CONF_PATH/uis…

…erver

Remove the need for the uiserver subdirectory.
Ensure that user is warned if file at CYLC_SITE_CONF_PATH is
* Unreadable
* Non-existent

changes.d/594.fix

@@ -0,0 +1 @@
+Avoid requiring jupyter_config.py in to be in uiserver subdirectory when using CYLC_SITE_CONF_PATH

cylc/uiserver/config_util.py

@@ -30,7 +30,8 @@
 )
 
 # base configuration - always used
-DEFAULT_CONF_PATH: Path = Path(uis_pkg).parent / 'jupyter_config.py'
+CONF_FILE_NAME = 'jupyter_config.py'
+DEFAULT_CONF_PATH: Path = Path(uis_pkg).parent / CONF_FILE_NAME
 UISERVER_DIR = 'uiserver'
 # UIS configuration dirs
 SITE_CONF_ROOT: Path = Path(

cylc/uiserver/jupyterhub_config.py

@@ -25,8 +25,8 @@
 from pathlib import Path
 
 from cylc.uiserver.config_util import (
+    CONF_FILE_NAME,
     DEFAULT_CONF_PATH,
-    UISERVER_DIR,
     USER_CONF_ROOT,
     SITE_CONF_ROOT,
     get_conf_dir_hierarchy
@@ -46,10 +46,8 @@ def _load(path):
 def load() -> None:
     """Load the relevant UIS/Hub configuration files."""
     if os.getenv('CYLC_SITE_CONF_PATH'):
-        site_conf_path: Path = Path(
-            os.environ['CYLC_SITE_CONF_PATH'],
-            UISERVER_DIR
-        )
+        site_conf_path: Path = check_cylc_site_conf_path(
+            Path(os.environ['CYLC_SITE_CONF_PATH']))
     else:
         site_conf_path = SITE_CONF_ROOT
     base_config_paths = [site_conf_path, USER_CONF_ROOT]
@@ -61,6 +59,24 @@ def load() -> None:
         _load(Path(path))
 
 
+def check_cylc_site_conf_path(path_: Path) -> Path:
+    """Check path set by CYLC_SITE_CONF_PATH
+
+    1. Path exists and has a file.
+    2. File is readable.
+    """
+    conf_file_path = (path_ / CONF_FILE_NAME)
+    if not conf_file_path.is_file():
+        LOG.warning(
+            f'Config path {path_} set by'
+            ' "CYLC_SITE_CONF_PATH" does not exist or.'
+            ' does not have a jupyter_config.py file.')
+    elif not os.access(conf_file_path, os.R_OK):
+        LOG.error(f'Unable to read config file at {path_}')
+        return SITE_CONF_ROOT
+    return path_
+
+
 hub_version = os.environ.get('CYLC_HUB_VERSION')
 if hub_version:
     # auto-load the config (jupyterhub requirement)

cylc/uiserver/tests/test_config.py

@@ -77,8 +77,8 @@ def test_cylc_site_conf_path(clear_env, capload, monkeypatch):
     load()
     assert capload == [
         SYS_CONF,
-        Path('elephant/uiserver/jupyter_config.py'),
-        Path('elephant/uiserver/0/jupyter_config.py'),
+        Path('elephant/jupyter_config.py'),
+        Path('elephant/0/jupyter_config.py'),
         Path(USER_CONF / 'jupyter_config.py'),
         Path(USER_CONF / '0/jupyter_config.py')
     ]

cylc/uiserver/tests/test_jupyterhub_config.py

@@ -0,0 +1,39 @@
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""Tests for jupyterhub_config module."""
+
+from cylc.uiserver.jupyterhub_config import check_cylc_site_conf_path
+from cylc.uiserver.config_util import CONF_FILE_NAME, SITE_CONF_ROOT
+
+
+def test_cylc_site_conf_path_ok(tmp_path, caplog):
+    """Method passes valid file without comment"""
+    (tmp_path / CONF_FILE_NAME).touch()
+    assert check_cylc_site_conf_path(tmp_path) == tmp_path
+    assert caplog.messages == []
+
+
+def test_cylc_site_conf_path_unreadable(tmp_path, caplog):
+    """Method logs error because file exists but is unreadable."""
+    (tmp_path / CONF_FILE_NAME).touch()
+    (tmp_path / CONF_FILE_NAME).chmod(0)
+    assert check_cylc_site_conf_path(tmp_path) == SITE_CONF_ROOT
+    assert caplog.messages[0].startswith('Unable to read config file at')
+
+
+def test_cylc_site_conf_path_empty(tmp_path, caplog):
+    """Method logs error because file does not exist."""
+    assert check_cylc_site_conf_path(tmp_path) == tmp_path
+    assert 'does not exist' in caplog.messages[0]