test: import CWNG regression tests for #1074 (cwasync no-active-document guards)

CWA merged PR #1074 (@SethMilliken) with just the code change in main.lua.
CWNG's backport (fork PR #266, commit 31bdd5d) added 5 pattern-pin tests
that verify the hasActiveDocument() guard, statusTextIfActionUnavailable()
helper, and auto-sync early-return against the Lua source.

Imported verbatim from CWNG.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: crocodilestick

tests/unit/test_kosync_plugin_no_active_document_handling.py

@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+"""Regression coverage for the cwasync no-active-document guards (CWA #1074).
+
+Backport of CWA #1074 by @SethMilliken. Prior behavior: the Push / Pull
+menu entries and the auto-sync toggle stayed enabled whenever a password
+was set, even when opened from the file browser with no document loaded.
+Tapping them dereferenced `self.ui.document` and crashed the plugin.
+
+The fix:
+
+* Adds `hasActiveDocument()` (returns true only when `self.ui.document`
+  is set) and uses it in the `enabled_func` of the Push / Pull menu items
+  alongside the existing password check.
+* Adds `statusTextIfActionUnavailable()` which appends a parenthetical
+  reason — `(Password Not Set)` or `(No Active Document)` — to the menu
+  label so users see *why* the entry is greyed out.
+* Early-returns from the auto-sync toggle handler when no document is
+  open, so flipping the switch from the file browser is a no-op rather
+  than a crash.
+
+The plugin itself is Lua and we don't run a Lua test runner in CI, so
+these tests pattern-pin the load-bearing call sites against `main.lua`.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+pytestmark = pytest.mark.unit
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+MAIN_LUA = REPO_ROOT / "koreader" / "plugins" / "cwasync.koplugin" / "main.lua"
+
+
+def _read() -> str:
+    assert MAIN_LUA.exists(), f"missing file: {MAIN_LUA}"
+    return MAIN_LUA.read_text(encoding="utf-8")
+
+
+def test_has_active_document_helper_defined():
+    body = _read()
+    assert "function CWASync:hasActiveDocument()" in body, (
+        "main.lua must define CWASync:hasActiveDocument() (CWA #1074)"
+    )
+    assert "(self.ui and self.ui.document) ~= nil" in body, (
+        "hasActiveDocument must check both self.ui and self.ui.document — "
+        "the file-browser entry point has self.ui but no document"
+    )
+
+
+def test_status_text_helper_defined():
+    body = _read()
+    assert "function CWASync:statusTextIfActionUnavailable()" in body, (
+        "main.lua must define CWASync:statusTextIfActionUnavailable() (CWA #1074)"
+    )
+    assert '_(" (Password Not Set)")' in body, (
+        "statusTextIfActionUnavailable must surface the missing-password reason"
+    )
+    assert '_(" (No Active Document)")' in body, (
+        "statusTextIfActionUnavailable must surface the no-active-document reason"
+    )
+
+
+def test_push_menu_uses_status_text_and_active_document_guard():
+    body = _read()
+    assert (
+        '_("Push progress from this device now") .. self:statusTextIfActionUnavailable()'
+        in body
+    ), "Push menu entry must append statusTextIfActionUnavailable() (CWA #1074)"
+    # The enabled_func now combines the password check with hasActiveDocument().
+    # We pin the exact predicate so a future edit that drops either side trips
+    # this test.
+    assert (
+        "return self.settings.password ~= nil and self:hasActiveDocument()"
+        in body
+    ), "Push/Pull enabled_func must AND password presence with hasActiveDocument()"
+
+
+def test_pull_menu_uses_status_text():
+    body = _read()
+    assert (
+        '_("Pull progress from other devices now") .. self:statusTextIfActionUnavailable()'
+        in body
+    ), "Pull menu entry must append statusTextIfActionUnavailable() (CWA #1074)"
+
+
+def test_auto_sync_toggle_early_returns_when_no_active_document():
+    body = _read()
+    # The auto-sync toggle handler now bails out before scheduling tasks if no
+    # document is open. Pin the exact guard so a refactor doesn't quietly drop
+    # the early return and revive the original crash path.
+    assert "if not(self:hasActiveDocument()) then\n                        return" in body, (
+        "auto-sync toggle must early-return when hasActiveDocument() is false (CWA #1074)"
+    )