feat: write calendar files atomically, refusing stale ones

2 files changed, 125 insertions, 0 deletions

diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 6df7112..6be4a22 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -74,6 +74,7 @@ target_compile_definitions(test_contactstore PRIVATE
     FIXTURE_DIR="${CMAKE_CURRENT_SOURCE_DIR}/fixtures")
 add_qtmaildir_test(repeatrule)
 add_qtmaildir_test(calendarstore)
+add_qtmaildir_test(calendarwriter)
 add_qtmaildir_test(signatures)
 add_qtmaildir_test(busyindicator)
 add_qtmaildir_test(tagstrip)
diff --git a/tests/test_calendarwriter.cpp b/tests/test_calendarwriter.cpp
new file mode 100644
index 0000000..1989d0e
--- /dev/null
+++ b/tests/test_calendarwriter.cpp
@@ -0,0 +1,124 @@
+/*
+ * qtmaildir - a Qt6 mail client for notmuch-indexed Maildirs
+ * Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <QtTest>
+#include <QDir>
+#include <QFile>
+#include <QTemporaryDir>
+
+#include "calendarwriter.h"
+
+namespace {
+
+QByteArray read(const QString &path)
+{
+    QFile f(path);
+    return f.open(QIODevice::ReadOnly) ? f.readAll() : QByteArray();
+}
+
+} // namespace
+
+class TestCalendarWriter : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void createsAFileThatDidNotExist();
+    void refusesToCreateOverAnExistingFile();
+    void replacesWhenTheFileIsWhatWasExpected();
+    void refusesWhenTheFileChangedUnderneath();
+    void deletes();
+    void leavesNoTemporaryFileBehind();
+};
+
+void TestCalendarWriter::createsAFileThatDidNotExist()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QString error;
+    QCOMPARE(CalendarWriter::replace(path, std::nullopt, QByteArray("new"), &error),
+             CalendarWriter::Result::Ok);
+    QCOMPARE(read(path), QByteArray("new"));
+}
+
+void TestCalendarWriter::refusesToCreateOverAnExistingFile()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QFile f(path);
+    QVERIFY(f.open(QIODevice::WriteOnly));
+    f.write("synced in meanwhile");
+    f.close();
+    QString error;
+    QCOMPARE(CalendarWriter::replace(path, std::nullopt, QByteArray("new"), &error),
+             CalendarWriter::Result::Stale);
+    QCOMPARE(read(path), QByteArray("synced in meanwhile"));
+}
+
+void TestCalendarWriter::replacesWhenTheFileIsWhatWasExpected()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QString error;
+    CalendarWriter::replace(path, std::nullopt, QByteArray("one"), &error);
+    QCOMPARE(CalendarWriter::replace(path, QByteArray("one"), QByteArray("two"), &error),
+             CalendarWriter::Result::Ok);
+    QCOMPARE(read(path), QByteArray("two"));
+}
+
+void TestCalendarWriter::refusesWhenTheFileChangedUnderneath()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QString error;
+    CalendarWriter::replace(path, std::nullopt, QByteArray("synced"), &error);
+    // The caller loaded "one"; a sync wrote "synced" since. Nothing is clobbered.
+    QCOMPARE(CalendarWriter::replace(path, QByteArray("one"), QByteArray("two"), &error),
+             CalendarWriter::Result::Stale);
+    QCOMPARE(read(path), QByteArray("synced"));
+    // Also stale: expecting a file that a sync has removed.
+    QFile::remove(path);
+    QCOMPARE(CalendarWriter::replace(path, QByteArray("synced"), QByteArray("two"), &error),
+             CalendarWriter::Result::Stale);
+    QVERIFY(!QFile::exists(path));
+}
+
+void TestCalendarWriter::deletes()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QString error;
+    CalendarWriter::replace(path, std::nullopt, QByteArray("one"), &error);
+    QCOMPARE(CalendarWriter::replace(path, QByteArray("one"), std::nullopt, &error),
+             CalendarWriter::Result::Ok);
+    QVERIFY(!QFile::exists(path));
+}
+
+void TestCalendarWriter::leavesNoTemporaryFileBehind()
+{
+    QTemporaryDir dir;
+    const QString path = dir.filePath(QStringLiteral("a.ics"));
+    QString error;
+    CalendarWriter::replace(path, std::nullopt, QByteArray("one"), &error);
+    CalendarWriter::replace(path, QByteArray("one"), QByteArray("two"), &error);
+    QCOMPARE(QDir(dir.path()).entryList(QDir::Files | QDir::Hidden),
+             QStringList{ QStringLiteral("a.ics") });
+}
+
+QTEST_MAIN(TestCalendarWriter)
+#include "test_calendarwriter.moc"