fix: handle a missing pardus-xfce-settings without crashing or discarding user config

src/DatetimeManager.py

@@ -8,17 +8,41 @@
 PLUGIN_RC_FILE_PATH = f"{HOME_PATH}/.config/xfce4/panel/datetime-8.rc"
 ETC_XDG_DATETIME_PATH = "/etc/xdg/pardus/xfce4/panel/datetime-8.rc"
 
-# Copy the default config file if not exists:
-if not os.path.exists(PLUGIN_RC_FILE_PATH):
+def defaults_available():
+    """Whether the packaged default plugin configuration is present.
+
+    It comes from pardus-xfce-settings, which is not a declared dependency of
+    this library, so it can legitimately be missing.
+    """
+    return os.path.exists(ETC_XDG_DATETIME_PATH)
+
+
+def _seed_config_file():
+    """Copy the packaged defaults into the user's config, if there is anything
+    to copy. Missing defaults are not an error here: the plugin settings simply
+    start out empty."""
+    if os.path.exists(PLUGIN_RC_FILE_PATH) or not defaults_available():
+        return
+
     # Create directories if not exists
     os.makedirs(PLUGIN_RC_FILE_DIRECTORY, exist_ok=True)
 
     shutil.copyfile(ETC_XDG_DATETIME_PATH, PLUGIN_RC_FILE_PATH)
 
-# Read config file
-config_file_data = ""
-with open(PLUGIN_RC_FILE_PATH, "r") as file:
-    config_file_data = file.read()
+
+def _read_config_file():
+    try:
+        with open(PLUGIN_RC_FILE_PATH, "r") as file:
+            return file.read()
+    except FileNotFoundError:
+        return ""
+
+
+# Seed and read the config file. Neither step may raise: this module is
+# imported at application start-up, so a failure here takes down the whole UI
+# before it is shown.
+_seed_config_file()
+config_file_data = _read_config_file()
 
 
 def get(key):
@@ -63,9 +87,23 @@ def save_file():
 
 
 def restore_default_settings():
-    os.remove(PLUGIN_RC_FILE_PATH)
+    global config_file_data
+
+    if not defaults_available():
+        raise FileNotFoundError(
+            f"Default datetime plugin configuration not found at "
+            f"{ETC_XDG_DATETIME_PATH}. Is pardus-xfce-settings installed?"
+        )
+
+    # copyfile overwrites, so there is no need to remove the current file
+    # first - and removing it first would leave the user with nothing if the
+    # copy went on to fail.
     shutil.copyfile(ETC_XDG_DATETIME_PATH, PLUGIN_RC_FILE_PATH)
 
+    # Drop the stale in-memory copy, otherwise the next save_file() would write
+    # the pre-restore configuration back out.
+    config_file_data = _read_config_file()
+
 
 def set_panel_clock(key, value):
     subprocess.call(

src/PanelManager.py

@@ -1,3 +1,5 @@
+import os
+import shutil
 import subprocess
 
 import gi
@@ -89,14 +91,59 @@ def set_startup_icon(path):
     xfce4_panel.set_string(f"{whisker_plugin}/button-icon", path)
 
 
+DEFAULT_PANEL_DIR = "/etc/xdg/pardus/xfce4/panel"
+DEFAULT_PANEL_XML = (
+    "/etc/xdg/pardus/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml"
+)
+
+
+def defaults_available():
+    """Whether the packaged default panel configuration is present.
+
+    These files come from pardus-xfce-settings, which is not a declared
+    dependency of this library. Restoring without them would delete the user's
+    configuration and put nothing back.
+    """
+    return os.path.isdir(DEFAULT_PANEL_DIR) and os.path.isfile(DEFAULT_PANEL_XML)
+
+
 def restore_default_settings():
+    """Replace the user's panel configuration with the packaged defaults.
+
+    Raises FileNotFoundError if the defaults are missing, before touching
+    anything the user owns.
+    """
+    if not defaults_available():
+        raise FileNotFoundError(
+            "Default panel configuration not found under /etc/xdg/pardus/xfce4. "
+            "Is pardus-xfce-settings installed?"
+        )
+
+    panel_dir = os.path.expanduser("~/.config/xfce4/panel")
+    xml_path = os.path.expanduser(
+        "~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml"
+    )
+
+    # The current configuration is about to be removed and cannot be
+    # reconstructed, so keep a copy next to it.
+    backup_dir = f"{panel_dir}.bak"
+    if os.path.isdir(panel_dir):
+        shutil.rmtree(backup_dir, ignore_errors=True)
+        shutil.copytree(panel_dir, backup_dir, symlinks=True)
+    if os.path.isfile(xml_path):
+        shutil.copy2(xml_path, f"{xml_path}.bak")
+
     xfce4_panel.reset_property("/", True)
+
+    # Chained with && so that a failure stops the sequence instead of carrying
+    # on to the next step; check=True surfaces it to the caller.
     subprocess.run(
-        """xfce4-panel --quit;
-        pkill xfconfd;
-        rm -rf ~/.config/xfce4/panel/* ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml;
-        cp -R /etc/xdg/pardus/xfce4/panel/* ~/.config/xfce4/panel/;
-        cp /etc/xdg/pardus/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml ~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml;
-        (xfce4-panel &)""",
+        "xfce4-panel --quit; "
+        "pkill xfconfd; "
+        f'rm -rf "{panel_dir}"/* "{xml_path}" && '
+        f'cp -R "{DEFAULT_PANEL_DIR}"/* "{panel_dir}/" && '
+        f'cp "{DEFAULT_PANEL_XML}" "{xml_path}" && '
+        "(xfce4-panel &)",
         shell=True,
+        check=True,
     )