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.

6 files changed, 104 insertions, 6 deletions

diff --git a/src/config.cpp b/src/config.cpp
index 8294e4b..1799ac6 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -60,7 +60,8 @@ constexpr int kQueriesFormatVersion = 1;
 const QStringList kQueryGenerators = { QStringLiteral("unread"),
                                        QStringLiteral("inbox"),
                                        QStringLiteral("flagged"),
-                                       QStringLiteral("sent") };
+                                       QStringLiteral("sent"),
+                                       QStringLiteral("trash") };
 
 /// The tag a generator matches, for the three filters that are a plain tag
 /// query. Empty for "sent", which composes from each account's folder instead
@@ -152,6 +153,11 @@ QString Config::allDraftsQuery() const
     return joinAccountQueries(m_accounts, &Account::draftsQuery);
 }
 
+QString Config::allTrashQuery() const
+{
+    return joinAccountQueries(m_accounts, &Account::trashQuery);
+}
+
 QString Config::defaultPath()
 {
     const QString base =
@@ -737,6 +743,8 @@ QString Config::resolvedQuery(const SavedQuery &query) const
     if (query.isGenerated()) {
         if (query.generated == QStringLiteral("sent"))
             return allSentQuery();
+        if (query.generated == QStringLiteral("trash"))
+            return allTrashQuery();
         // An unknown generator was reported on load. Empty rather than the
         // bare stored query, which for a generated entry is empty anyway and
         // would otherwise run as "match everything".
@@ -809,6 +817,11 @@ SavedQuery Config::builtinFilter(const QString &generator)
         // thread would fold the user's sent message back into the conversation
         // it belongs to, which is item 63's finding.
         filter.flat = true;
+    } else if (generator == QStringLiteral("trash")) {
+        filter.name = tr("Trash");
+        // NOT flat, unlike Sent. A deleted message still belongs to its
+        // conversation, and folding it back is what Sent had to avoid rather
+        // than something every folder filter wants.
     }
 
     return filter;
@@ -833,6 +846,10 @@ QString Config::resolvedQuery(const SavedQuery &query,
             const QString all = allSentQuery();
             return all.isEmpty() ? matchNothingQuery() : all;
         }
+        if (query.generated == QStringLiteral("trash")) {
+            const QString all = allTrashQuery();
+            return all.isEmpty() ? matchNothingQuery() : all;
+        }
         return QStringLiteral("tag:%1").arg(generatorTag(query.generated));
     }
 
@@ -853,6 +870,14 @@ QString Config::resolvedQuery(const SavedQuery &query,
         return sent.isEmpty() ? matchNothingQuery() : sent;
     }
 
+    if (query.generated == QStringLiteral("trash")) {
+        // The account's OWN trash query, for the reason spelled out above the
+        // sent case: wrapping the all-accounts query in this account's path
+        // works by accident of path: being hierarchical.
+        const QString trash = scope.trashQuery();
+        return trash.isEmpty() ? matchNothingQuery() : trash;
+    }
+
     // A tag filter carries no path of its own, so scoping is exactly what
     // scopedQuery() does. Its parentheses are load-bearing: `path:... and a or
     // b` binds as `(path:... and a) or b`.
diff --git a/src/config.h b/src/config.h
index 1feeeda..f60e7cc 100644
--- a/src/config.h
+++ b/src/config.h
@@ -291,6 +291,13 @@ public:
     /// open-coded at the call site.
     QString allSentQuery() const;
 
+    /// Matches every configured account's trash, or empty when none has one.
+    ///
+    /// Joins only the NON-EMPTY trashQuery() results, for the same reason
+    /// allSentQuery() does: notmuch accepts a bare "or" without complaint and
+    /// silently answers a different question.
+    QString allTrashQuery() const;
+
     /// Matches every configured account's drafts, or empty when none has one.
     ///
     /// Joins only the NON-EMPTY draftsQuery() results, for the same reason
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 594535b..67d3ee4 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -1893,6 +1893,7 @@ void MainWindow::buildSavedQueryRow(QWidget *parent, QVBoxLayout *layout)
             { QStringLiteral("inbox"),   QStringLiteral("mail-inbox") },
             { QStringLiteral("flagged"), QStringLiteral("starred") },
             { QStringLiteral("sent"),    QStringLiteral("mail-folder-sent") },
+            { QStringLiteral("trash"),   QStringLiteral("user-trash") },
         };
         button->setIcon(
             QIcon::fromTheme(filterIcons.value(filter.generated)));
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);
 
diff --git a/translations/qtmaildir_it_IT.ts b/translations/qtmaildir_it_IT.ts
index fd51547..ef88967 100644
--- a/translations/qtmaildir_it_IT.ts
+++ b/translations/qtmaildir_it_IT.ts
@@ -95,6 +95,10 @@
         <source>Sent</source>
         <translation>Inviati</translation>
     </message>
+    <message>
+        <source>Trash</source>
+        <translation>Cestino</translation>
+    </message>
 </context>
 <context>
     <name>HtmlBuilder</name>