Fix IndexError at startup when all view plugins are hidden

gramps/gui/test/viewmanager_test.py

@@ -0,0 +1,68 @@
+#
+# Gramps - a GTK+/GNOME based genealogy program
+#
+# Copyright (C) 2026       The Gramps project
+#
+# 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 2 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 <https://www.gnu.org/licenses/>.
+#
+
+"""Unittest for gramps.gui.viewmanagerutils.views_to_show.
+
+Regression test for bug 8796: hiding **every** view plugin in the Plugin
+Manager makes Gramps crash at startup with
+``IndexError: list assignment index out of range``.
+
+Root cause: with no view plugins available ``ViewManager.get_available_views()``
+returns ``[]``, so ``views_to_show([])`` used to yield ``(0, 0, [])`` -- claiming
+category 0 exists.  ``ViewManager.init_interface`` then called
+``goto_page(0, 0)``, whose ``self.current_views[cat_num] = view_num`` indexed the
+empty ``current_views`` list and raised.
+
+This test drives the **production** ``views_to_show`` -- the exact function
+``viewmanager.init_interface`` calls (``viewmanager`` re-imports it from
+``viewmanagerutils``) -- not a re-implementation.  ``viewmanagerutils`` carries no
+``gi`` / GTK import, so the genuine production decision logic is exercised here
+under the headless test runner without launching the GTK ``ViewManager``.
+
+The fix makes ``views_to_show`` total over the empty view set: it reports "no
+category" (``current_cat is None``) so ``init_interface`` leaves the interface
+with no active page instead of navigating into the empty set.
+"""
+
+import unittest
+
+from ..viewmanagerutils import views_to_show
+
+
+class TestViewsToShowEmpty(unittest.TestCase):
+    """views_to_show must be total over zero available views (bug 8796)."""
+
+    def test_empty_views_reports_no_category(self):
+        """views_to_show([]) reports no category instead of collapsing to (0, 0, []).
+
+        Pre-fix this returns ``(0, 0, [])``; the caller then ran
+        ``goto_page(0, 0)`` -> ``self.current_views[0] = 0`` on an empty list and
+        raised ``IndexError: list assignment index out of range`` at startup.
+        Post-fix it returns ``(None, None, [])`` so ``init_interface`` skips
+        navigation and the app opens with no active page.
+        """
+        self.assertEqual(views_to_show([], use_last=False), (None, None, []))
+
+    def test_empty_views_use_last(self):
+        """The empty-view set is total under use_last=True as well."""
+        self.assertEqual(views_to_show([], use_last=True), (None, None, []))
+
+
+if __name__ == "__main__":
+    unittest.main()

gramps/gui/viewmanager.py

@@ -77,6 +77,7 @@
 from .plug.report import report, BookSelector
 from .utils import AvailableUpdates, Popup
 from .pluginmanager import GuiPluginManager
+from .viewmanagerutils import views_to_show
 from gramps.gen.relationship import get_relationship_calculator
 from .displaystate import DisplayState, RecentDocsMenu
 from gramps.gen.const import (
@@ -637,12 +638,19 @@ def init_interface(self):
         Initialize the interface.
         """
         self.views = self.get_available_views()
-        defaults = views_to_show(self.views, config.get("preferences.use-last-view"))
-        self.current_views = defaults[2]
+        current_cat, current_cat_view, self.current_views = views_to_show(
+            self.views, config.get("preferences.use-last-view")
+        )
 
         self.navigator.load_plugins(self.dbstate, self.uistate)
 
-        self.goto_page(defaults[0], defaults[1])
+        if current_cat is not None:
+            # bug 8796: only navigate when there is a view to show.  With every
+            # view plugin hidden get_available_views() returns [], views_to_show()
+            # then reports no category (current_cat is None), and the interface is
+            # left with no active page instead of navigating into the empty view
+            # set (which raised 'IndexError: list assignment index out of range').
+            self.goto_page(current_cat, current_cat_view)
 
         self.uimanager.set_actions_sensitive(self.fileactions, False)
         self.__build_tools_menu(self._pmgr.get_reg_tools())
@@ -1043,6 +1051,15 @@ def __change_page(self, page_num):
         """
         self.__disconnect_previous_page()
 
+        if not self.pages:
+            # bug 8796: with no available views no page was ever created, so
+            # there is nothing to activate.  Reached e.g. via _post_load_newdb_gui
+            # (viewmanager.py:1221), which calls __change_page(notebook.get_current
+            # _page()) -- get_current_page() returns -1 for an empty notebook, so
+            # both self.pages[-1] and the self.pages[0] fallback below would raise
+            # IndexError.  Leave the interface with no active page.
+            return
+
         # The following is to avoid 'IndexError: list index out of range'
         # Bugs: 12304, 12429, 12623, 12695
         try:
@@ -1498,6 +1515,12 @@ def config_view(self, *obj):
         """
         Displays the configuration dialog for the active view
         """
+        if self.active_page is None:
+            # bug 8796: with no available views (every view plugin hidden) there
+            # is no active page, so the ConfigView action (viewmanager.py:528,
+            # <shift><PRIMARY>c) has nothing to configure -- do not dereference
+            # None.
+            return
         self.active_page.configure()
 
     def undo(self, *obj):
@@ -1823,36 +1846,6 @@ def make_plugin_callback(pdata, dbstate, uistate):
     return lambda x, y: run_plugin(pdata, dbstate, uistate)
 
 
-def views_to_show(views, use_last=True):
-    """
-    Determine based on preference setting which views should be shown
-    """
-    current_cat = 0
-    current_cat_view = 0
-    default_cat_views = [0] * len(views)
-    if use_last:
-        current_page_id = config.get("preferences.last-view")
-        default_page_ids = config.get("preferences.last-views")
-        found = False
-        for indexcat, cat_views in enumerate(views):
-            cat_view = 0
-            for pdata, page_def in cat_views:
-                if not found:
-                    if pdata.id == current_page_id:
-                        current_cat = indexcat
-                        current_cat_view = cat_view
-                        default_cat_views[indexcat] = cat_view
-                        found = True
-                        break
-                if pdata.id in default_page_ids:
-                    default_cat_views[indexcat] = cat_view
-                cat_view += 1
-        if not found:
-            current_cat = 0
-            current_cat_view = 0
-    return current_cat, current_cat_view, default_cat_views
-
-
 class QuickBackup(ManagedWindow):  # TODO move this class into its own module
     def __init__(self, dbstate, uistate, user):
         """

gramps/gui/viewmanagerutils.py

@@ -0,0 +1,87 @@
+#
+# Gramps - a GTK+/GNOME based genealogy program
+#
+# Copyright (C) 2005-2007  Donald N. Allingham
+# Copyright (C) 2008       Brian G. Matherly
+# Copyright (C) 2009       Benny Malengier
+# Copyright (C) 2010,2025  Nick Hall
+# Copyright (C) 2026       The Gramps project
+#
+# 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 2 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 <https://www.gnu.org/licenses/>.
+#
+
+"""
+GTK-independent helpers for :mod:`gramps.gui.viewmanager`.
+
+This module deliberately carries no ``gi`` / GTK import, so the pure
+view-selection logic it holds can be unit tested headless (see
+``gramps/gui/test/viewmanager_test.py``).  ``viewmanager`` re-imports
+``views_to_show`` from here, so production and the test exercise the *same*
+implementation rather than a parallel copy.
+"""
+
+# -------------------------------------------------------------------------
+#
+# Gramps modules
+#
+# -------------------------------------------------------------------------
+from gramps.gen.config import config
+
+
+# -------------------------------------------------------------------------
+#
+# Functions
+#
+# -------------------------------------------------------------------------
+def views_to_show(views, use_last=True):
+    """
+    Determine based on preference setting which views should be shown.
+
+    Returns a ``(current_cat, current_cat_view, default_cat_views)`` tuple.
+    When there are no views to show -- ``views`` is empty, e.g. every view
+    plugin has been hidden in the Plugin Manager -- ``current_cat`` is ``None``
+    to signal "no category to select", so the caller leaves the interface with
+    no active page instead of navigating into the empty set.
+    """
+    current_cat = 0
+    current_cat_view = 0
+    default_cat_views = [0] * len(views)
+    if not views:
+        # bug 8796: with no available views there is no category to select.
+        # Returning (0, 0, []) here claimed category 0 exists, so the caller's
+        # goto_page(0, 0) indexed an empty current_views list and raised
+        # 'IndexError: list assignment index out of range' at startup.  Signal
+        # "no view to show" with a None category instead.
+        return None, None, default_cat_views
+    if use_last:
+        current_page_id = config.get("preferences.last-view")
+        default_page_ids = config.get("preferences.last-views")
+        found = False
+        for indexcat, cat_views in enumerate(views):
+            cat_view = 0
+            for pdata, page_def in cat_views:
+                if not found:
+                    if pdata.id == current_page_id:
+                        current_cat = indexcat
+                        current_cat_view = cat_view
+                        default_cat_views[indexcat] = cat_view
+                        found = True
+                        break
+                if pdata.id in default_page_ids:
+                    default_cat_views[indexcat] = cat_view
+                cat_view += 1
+        if not found:
+            current_cat = 0
+            current_cat_view = 0
+    return current_cat, current_cat_view, default_cat_views