QMimeDatabase: Fix MIME detection issues with magics in MIME hierarchies

Assume two MIME types A and B are registered, both with the same glob
pattern, A being parent of B, A with some magic rule, and B with another
magic rule. Given a file that matches the glob pattern and the magic rule
of A, the resulting MIME type depended on the order of registration of A
and B, because it would just check if some glob matching MIME type was
also a subclass of the magic matching MIME type.

The patch prefers the the MIME type that matches by magic if that
matches by glob pattern as well (i.e. A in our example).

The "recommended checking order" of the spec does handle that case.

Task-number: QTBUG-44846
Change-Id: I2af43f6199faf9a42cd9c35d3a045441afbd6217
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: David Faure <david.faure@kdab.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/auto/corelib/mimetypes/qmimedatabase/tst_qmimedatabase.cpp b/tests/auto/corelib/mimetypes/qmimedatabase/tst_qmimedatabase.cpp
index 3144c3071c..597d51e7e0 100644
--- a/tests/auto/corelib/mimetypes/qmimedatabase/tst_qmimedatabase.cpp
+++ b/tests/auto/corelib/mimetypes/qmimedatabase/tst_qmimedatabase.cpp
@@ -52,6 +52,7 @@ static const char *const additionalMimeFiles[] = {
     "invalid-magic1.xml",
     "invalid-magic2.xml",
     "invalid-magic3.xml",
+    "magic-and-hierarchy.xml",
     0
 };
 
@@ -985,6 +986,12 @@ void tst_QMimeDatabase::installNewGlobalMimeType()
         qDebug() << objcsrc.globPatterns();
     }
 
+    const QString fooTestFile = QLatin1String(RESOURCE_PREFIX "magic-and-hierarchy.foo");
+    QCOMPARE(db.mimeTypeForFile(fooTestFile).name(), QString::fromLatin1("application/foo"));
+
+    const QString fooTestFile2 = QLatin1String(RESOURCE_PREFIX "magic-and-hierarchy2.foo");
+    QCOMPARE(db.mimeTypeForFile(fooTestFile2).name(), QString::fromLatin1("application/vnd.qnx.bar-descriptor"));
+
     // Now test removing the mimetype definitions again
     for (int i = 0; i < m_additionalMimeFileNames.size(); ++i)
         QFile::remove(destDir + m_additionalMimeFileNames.at(i));