Merge fixes for QDir::operator==

There were two fixes in 4.8 which each fixed a part of the problem.
Comparing canonical paths is more correct, but is only possible where
both directories exist. If neither directory exists, then compare
absolute paths instead.
Changed a regression test, because /tmp is a symbolic link on MacOS.
I.E. "/tmp/.." is canonically "/private" and not "/" as expected.

Task-Number: QTBUG-20495
Reviewed-By: joao
(cherry-picked from ad35d25e78c8252a72108a4ba931934047c4707e)

Change-Id: Ia4986e8337f0e512e1a3398a5a4dd36e62680b9c
Reviewed-on: http://codereview.qt-project.org/5813
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Shane Kearns <shane.kearns@accenture.com>

src/corelib/io/qdir.cpp

@@ -1600,8 +1600,23 @@ bool QDir::operator==(const QDir &dir) const
        && d->sort == other->sort
        && d->nameFilters == other->nameFilters) {
 
-        // Fallback to expensive canonical path computation
-        return canonicalPath().compare(dir.canonicalPath(), sensitive) == 0;
+        // Assume directories are the same if path is the same
+        if (d->dirEntry.filePath() == other->dirEntry.filePath())
+            return true;
+
+        if (exists()) {
+            if (!dir.exists())
+                return false; //can't be equal if only one exists
+            // Both exist, fallback to expensive canonical path computation
+            return canonicalPath().compare(dir.canonicalPath(), sensitive) == 0;
+        } else {
+            if (dir.exists())
+                return false; //can't be equal if only one exists
+            // Neither exists, compare absolute paths rather than canonical (which would be empty strings)
+            d->resolveAbsoluteEntry();
+            other->resolveAbsoluteEntry();
+            return d->absoluteDirEntry.filePath().compare(other->absoluteDirEntry.filePath(), sensitive) == 0;
+        }
     }
     return false;
 }

src/corelib/io/qfileinfo.cpp

@@ -403,6 +403,11 @@ bool QFileInfo::operator==(const QFileInfo &fileinfo) const
         return true;
     if (d->isDefaultConstructed || fileinfo.d_ptr->isDefaultConstructed)
         return false;
+
+    // Assume files are the same if path is the same
+    if (d->fileEntry.filePath() == fileinfo.d_ptr->fileEntry.filePath())
+        return true;
+
     Qt::CaseSensitivity sensitive;
     if (d->fileEngine == 0 || fileinfo.d_ptr->fileEngine == 0) {
         if (d->fileEngine != fileinfo.d_ptr->fileEngine) // one is native, the other is a custom file-engine

tests/auto/corelib/io/qdir/tst_qdir.cpp

@@ -1776,10 +1776,30 @@ void tst_QDir::equalityOperator_data()
         << "." << "*.cpp" << int(QDir::Name) << int(QDir::Files)
         << true;
 
-    QTest::newRow("QTBUG-20495-root") << QDir::rootPath() + "tmp/.." << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+    //need a path in the root directory that is unlikely to be a symbolic link.
+#if defined (Q_OS_WIN)
+    QString pathinroot("c:/windows/..");
+#elif defined (Q_OS_SYMBIAN)
+    QString pathinroot("c:/data/..");
+#else
+    QString pathinroot("/sbin/..");
+#endif
+    QTest::newRow("QTBUG-20495-root") << pathinroot << "*.cpp" << int(QDir::Name) << int(QDir::Files)
         << QDir::rootPath() << "*.cpp" << int(QDir::Name) << int(QDir::Files)
         << true;
 
+    QTest::newRow("slashdot") << QDir::rootPath() + "." << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << QDir::rootPath() << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << true;
+
+    QTest::newRow("slashdotslash") << QDir::rootPath() + "./" << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << QDir::rootPath() << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << true;
+
+    QTest::newRow("nonexistantpaths") << "dir-that-dont-exist" << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << "another-dir-that-dont-exist" << "*.cpp" << int(QDir::Name) << int(QDir::Files)
+        << false;
+
     QTest::newRow("diff-filters") << SRCDIR << "*.cpp" << int(QDir::Name) << int(QDir::Files)
         << SRCDIR << "*.cpp" << int(QDir::Name) << int(QDir::Dirs)
         << false;