QTestlib/selftests: Refactor the code printing output differences

Use qInfo() instead of qDebug() in case QDebug is turned off.

If the 'diff' tool is available, write the output to temporary files and
run diff on it. Otherwise, print the lines as was before, but onto one
stream to avoid indentation by the testlib handler.

Change-Id: Ib5a5dfb66ce481b493b85b915aa8c785ecb6b387
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 73 insertions, 8 deletions

diff --git a/tests/auto/testlib/selftests/tst_selftests.cpp b/tests/auto/testlib/selftests/tst_selftests.cpp
index 3f11ea50b6..2ef7258d81 100644
--- a/tests/auto/testlib/selftests/tst_selftests.cpp
+++ b/tests/auto/testlib/selftests/tst_selftests.cpp
@@ -28,10 +28,18 @@
 ****************************************************************************/
 
 #include <QtCore/QCoreApplication>
+
+#if QT_CONFIG(temporaryfile) && QT_CONFIG(process)
+#  define USE_DIFF
+#endif
 #include <QtCore/QXmlStreamReader>
 #include <QtCore/QFileInfo>
 #include <QtCore/QDir>
 #include <QtCore/QTemporaryDir>
+#ifdef USE_DIFF
+#  include <QtCore/QTemporaryFile>
+#  include <QtCore/QStandardPaths>
+#endif
 #include <QtTest/QtTest>
 
 #include <private/cycle_p.h>
@@ -175,6 +183,70 @@ static QList<QByteArray> expectedResult(const QString &fileName)
     return splitLines(file.readAll());
 }
 
+// Helpers for running the 'diff' tool in case comparison fails
+#ifdef USE_DIFF
+static inline void writeLines(QIODevice &d, const QByteArrayList &lines)
+{
+    for (const QByteArray &l : lines) {
+        d.write(l);
+        d.write("\n");
+    }
+}
+#endif // USE_DIFF
+
+static QByteArray runDiff(const QByteArrayList &expected, const QByteArrayList &actual)
+{
+    QByteArray result;
+#ifdef USE_DIFF
+#  ifndef Q_OS_WIN
+    const QString diff = QStandardPaths::findExecutable("diff");
+#  else
+    const QString diff = QStandardPaths::findExecutable("diff.exe");
+#  endif
+    if (diff.isEmpty())
+        return result;
+    QTemporaryFile expectedFile;
+    if (!expectedFile.open())
+        return result;
+    writeLines(expectedFile, expected);
+    expectedFile.close();
+    QTemporaryFile actualFile;
+    if (!actualFile.open())
+        return result;
+    writeLines(actualFile, actual);
+    actualFile.close();
+    QProcess diffProcess;
+    diffProcess.start(diff, {QLatin1String("-u"), expectedFile.fileName(), actualFile.fileName()});
+    if (!diffProcess.waitForStarted())
+        return result;
+    if (diffProcess.waitForFinished())
+        result = diffProcess.readAllStandardOutput();
+    else
+        diffProcess.kill();
+#endif // USE_DIFF
+    return result;
+}
+
+// Print the difference preferably using 'diff', else just print lines
+static void printDifference(const QByteArrayList &expected, const QByteArrayList &actual)
+{
+    QDebug info = qInfo();
+    info.noquote();
+    info.nospace();
+    const QByteArray diff = runDiff(expected, actual);
+    if (diff.isEmpty()) {
+        info << "<<<<<<\n";
+        for (const QByteArray &line : actual)
+            info << line << '\n';
+        info << "======\n";
+        for (const QByteArray &line : expected)
+            info << line << '\n';
+        info << ">>>>>>\n";
+    } else {
+        info << diff;
+    }
+}
+
 // Each test is run with a set of one or more test output loggers.
 // This struct holds information about one such test.
 struct LoggerSet
@@ -728,14 +800,7 @@ void tst_Selftests::doRunSubTest(QString const& subdir, QStringList const& logge
             }
         } else {
             if (res.count() != exp.count()) {
-                qDebug() << "<<<<<<";
-                foreach (const QByteArray &line, res)
-                    qDebug() << line;
-                qDebug() << "======";
-                foreach (const QByteArray &line, exp)
-                    qDebug() << line;
-                qDebug() << ">>>>>>";
-
+                printDifference(exp, res);
                 QVERIFY2(res.count() == exp.count(),
                      qPrintable(QString::fromLatin1("Mismatch in line count: %1 != %2 (%3, %4).")
                                 .arg(res.count()).arg(exp.count()).arg(loggers.at(n), expectedFileName)));