Improve std::tuple handling in tests

Currently when doing comparison with std::tuple the fallback toString
method is called which returns a Q_NULLPTR thus not allowing proper
diagnostic of the values that triggered an error. This patch
adds support for std::tuple to improve the tests output readability.

[ChangeLog][QtTest][QCOMPARE] Now outputs contents of std::tuple on
failure.

Change-Id: I046a55e2ce44c3f7728d51e4745120d38aa5e007
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 51 insertions, 0 deletions

diff --git a/src/testlib/qtest.h b/src/testlib/qtest.h
index 1cb6a91d33..927b68bd27 100644
--- a/src/testlib/qtest.h
+++ b/src/testlib/qtest.h
@@ -59,6 +59,8 @@
 #include <QtCore/qsize.h>
 #include <QtCore/qrect.h>
 
+#include <memory>
+
 QT_BEGIN_NAMESPACE
 
 
@@ -215,6 +217,25 @@ inline char *toString(const std::pair<T1, T2> &pair)
     return toString(QString::asprintf("std::pair(%s,%s)", first.data(), second.data()));
 }
 
+template <typename Tuple, int... I>
+inline char *toString(const Tuple & tuple, QtPrivate::IndexesList<I...>) {
+    using UP = std::unique_ptr<char[]>;
+    // Generate a table of N + 1 elements where N is the number of
+    // elements in the tuple.
+    // The last element is needed to support the empty tuple use case.
+    const UP data[] = {
+        UP(toString(std::get<I>(tuple)))..., UP{}
+    };
+    return formatString("std::tuple(", ")", sizeof...(I), data[I].get()...);
+}
+
+template <class... Types>
+inline char *toString(const std::tuple<Types...> &tuple)
+{
+    static const std::size_t params_count = sizeof...(Types);
+    return toString(tuple, typename QtPrivate::Indexes<params_count>::Value());
+}
+
 inline char *toString(std::nullptr_t)
 {
     return toString(QLatin1String("nullptr"));
diff --git a/src/testlib/qtestcase.cpp b/src/testlib/qtestcase.cpp
index 0866176b6b..469c423109 100644
--- a/src/testlib/qtestcase.cpp
+++ b/src/testlib/qtestcase.cpp
@@ -1147,6 +1147,31 @@ void *fetchData(QTestData *data, const char *tagName, int typeId)
 }
 
 /*!
+ * \internal
+ */
+char *formatString(const char *prefix, const char *suffix, size_t numArguments, ...)
+{
+    va_list ap;
+    va_start(ap, numArguments);
+
+    QByteArray arguments;
+    arguments += prefix;
+
+    if (numArguments > 0) {
+        arguments += va_arg(ap, const char *);
+
+        for (size_t i = 1; i < numArguments; ++i) {
+            arguments += ", ";
+            arguments += va_arg(ap, const char *);
+        }
+    }
+
+    va_end(ap);
+    arguments += suffix;
+    return qstrdup(arguments.constData());
+}
+
+/*!
   \fn char* QTest::toHexRepresentation(const char *ba, int length)
 
   Returns a pointer to a string that is the string \a ba represented
diff --git a/src/testlib/qtestcase.h b/src/testlib/qtestcase.h
index 4bf816a850..f6891dc941 100644
--- a/src/testlib/qtestcase.h
+++ b/src/testlib/qtestcase.h
@@ -283,6 +283,9 @@ namespace QTest
     template <typename T1, typename T2>
     inline char *toString(const std::pair<T1, T2> &pair);
 
+    template <class... Types>
+    inline char *toString(const std::tuple<Types...> &tuple);
+
     Q_TESTLIB_EXPORT char *toHexRepresentation(const char *ba, int length);
     Q_TESTLIB_EXPORT char *toPrettyCString(const char *unicode, int length);
     Q_TESTLIB_EXPORT char *toPrettyUnicode(QStringView string);
@@ -388,6 +391,8 @@ namespace QTest
     Q_TESTLIB_EXPORT bool compare_string_helper(const char *t1, const char *t2, const char *actual,
                                       const char *expected, const char *file, int line);
 
+    Q_TESTLIB_EXPORT char *formatString(const char *prefix, const char *suffix, size_t numArguments, ...);
+
 #ifndef Q_QDOC
     QTEST_COMPARE_DECL(short)
     QTEST_COMPARE_DECL(ushort)