feat(config): add the trash query generator

Adds trash as a fifth built-in query filter beside Unread, Inbox,
Important and Sent, composing per-account exactly as Sent does:
Config::resolvedQuery() asks each account for its own trashQuery()
rather than wrapping the all-accounts union, and an account with no
trash folder resolves to matchNothingQuery() rather than "match
everything".

Also gives the Trash button a toolbar icon (user-trash) and a trash
key to the mainwindow fixture that asserts every filter button carries
one; without it the button is skipped from the row entirely (no
account configured a trash folder), and the existing icon test found
no button to check.

2 files changed, 66 insertions, 5 deletions

diff --git a/tests/test_config.cpp b/tests/test_config.cpp
index 10dcf68..ea5c363 100644
--- a/tests/test_config.cpp
+++ b/tests/test_config.cpp
@@ -119,6 +119,8 @@ private slots:
     void anAccountCarriesItsTrashFolder();
     void aBracketedTrashFolderIsQuoted();
     void anAccountWithoutATrashFolderWarns();
+    void theTrashFilterComposesPerAccount();
+    void theTrashFilterMatchesNothingWithoutAFolder();
 };
 
 static QString writeIni(const QTemporaryDir &dir, const QString &body)
@@ -1009,6 +1011,54 @@ void TestConfig::anAccountWithoutATrashFolderWarns()
     QVERIFY(joined.contains(QStringLiteral("trash")));
 }
 
+void TestConfig::theTrashFilterComposesPerAccount()
+{
+    // Two accounts, one with a plain folder and one nested under a bracketed
+    // parent, since the real setup has both shapes.
+    QTemporaryDir dir;
+    Config config;
+    config.load(writeIni(dir, QStringLiteral(
+        "[account.work]\n"
+        "maildir=work\n"
+        "trash=Trash\n"
+        "\n"
+        "[account.personal]\n"
+        "maildir=personal\n"
+        "trash=[Provider]/Cestino\n")));
+
+    const SavedQuery trash = Config::builtinFilter(QStringLiteral("trash"));
+    QVERIFY(trash.isGenerated());
+
+    // All accounts: the union, never a bare path that would match one account.
+    const QString all = config.resolvedQuery(trash, QString());
+    QVERIFY(all.contains(QStringLiteral("path:\"work/Trash/**\"")));
+    QVERIFY(all.contains(
+        QStringLiteral("path:\"personal/[Provider]/Cestino/**\"")));
+
+    // One account: that account's OWN query. Asserting on the STRING, not on a
+    // row count: the all-accounts query wrapped in this account's path returns
+    // exactly the right rows, because path: is hierarchical, so a count passes
+    // against the wrong thing. Config::resolvedQuery documents this trap.
+    const QString scoped = config.resolvedQuery(trash, QStringLiteral("work"));
+    QCOMPARE(scoped, QStringLiteral("path:\"work/Trash/**\""));
+    QVERIFY(!scoped.contains(QStringLiteral("personal")));
+}
+
+void TestConfig::theTrashFilterMatchesNothingWithoutAFolder()
+{
+    // An empty query means "match everything" to notmuch, so a filter with
+    // nothing to match must say so explicitly. A button labelled Trash that
+    // showed the whole Maildir is the failure this prevents.
+    QTemporaryDir dir;
+    Config config;
+    config.load(writeIni(dir, QStringLiteral(
+        "[account.work]\n"
+        "maildir=work\n")));
+
+    const SavedQuery trash = Config::builtinFilter(QStringLiteral("trash"));
+    QCOMPARE(config.resolvedQuery(trash, QString()), Config::matchNothingQuery());
+}
+
 void TestConfig::sentQueryComposesWithScopedQuery()
 {
     // A Sent view under one account must not show another account's sent mail.
@@ -1432,7 +1482,7 @@ void TestConfig::everyBuiltinFilterIsAKnownGenerator()
     Config config;
     const QList<SavedQuery> filters = config.builtinFilters();
 
-    QCOMPARE(filters.size(), 4);
+    QCOMPARE(filters.size(), 5);
 
     QStringList names;
     for (const SavedQuery &filter : filters) {
@@ -1453,7 +1503,8 @@ void TestConfig::everyBuiltinFilterIsAKnownGenerator()
     QCOMPARE(names, (QStringList{ QStringLiteral("Unread"),
                                   QStringLiteral("Inbox"),
                                   QStringLiteral("Important"),
-                                  QStringLiteral("Sent") }));
+                                  QStringLiteral("Sent"),
+                                  QStringLiteral("Trash") }));
 }
 
 void TestConfig::aFilterAcrossAllAccountsIsTheUnscopedQuery()
diff --git a/tests/test_mainwindow.cpp b/tests/test_mainwindow.cpp
index b188ef4..7316689 100644
--- a/tests/test_mainwindow.cpp
+++ b/tests/test_mainwindow.cpp
@@ -7922,10 +7922,20 @@ void TestMainWindow::everyBuiltinFilterButtonCarriesAnIconAndItsText()
     // which is the same argument the Save button records.
     QTemporaryDir dir;
     QVERIFY(dir.isValid());
-    Config config;
-    config.load(writeSentConfig(dir, {
+    const QString path = writeSentConfig(dir, {
         {QStringLiteral("work"), QStringLiteral("Sent")},
-    }));
+    });
+    // A trash key too, or the Trash filter finds nothing and is skipped from
+    // the row entirely (item 103), leaving no trashButton for this loop to
+    // find.
+    {
+        QSettings s(path, QSettings::IniFormat);
+        s.beginGroup(QStringLiteral("account.work"));
+        s.setValue(QStringLiteral("trash"), QStringLiteral("Trash"));
+        s.endGroup();
+    }
+    Config config;
+    config.load(path);
 
     MainWindow window(config);