QDir: change qt_normalizePathSegments to preserve trailing '/'s

... for local URLs too.

For example normalizing "/Users/sam/troll/qt4.0/.." by following the
alogrithm at https://www.ietf.org/rfc/rfc3986.html#section-5.2.4:
- replace "/.." with a "/" in the input buffer, then remove the previous
  path segment from the output buffer up to, and including, the
  previous "/"
- next iteration will find the input buffer starting with a "/" which
  is moved to the output buffer; the final result would be:
  "/Users/sam/troll/"

Remove the KeepLocalTrailingSlash enumerator, it's become redundant with
this change.

De-duplicate a row in tst_QDir.

[ChangeLog][Important Behavior Change] Aligned how QDir and QUrl
normalize paths with respect to preserving a trailing slash. That is,
QDir::cleanPath("/b/.") and
QUrl("file:///b/.).toString(QUrl::NormalizePathSegments) will return
"/b/" and "file:///b/" respectively. For more details see:
https://www.ietf.org/rfc/rfc3986.html#section-5.2.4

Task-number: QTBUG-128940
Change-Id: Id5a4bdab14e7312a60b1b54de07e5d9f3e8aa40a
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qdir.cpp

@@ -2223,16 +2223,12 @@ bool QDir::match(const QString &filter, const QString &fileName)
        "a/b/" and "a/b//../.." becomes "a/"), which matches the behavior
        observed in web browsers.
 
-    However, QUrl also uses local path mode for local URLs; with one exception:
+    As a Qt extension, for local URLs we treat multiple slashes as one slash.
-    Even in local mode we leave one trailing slash for paths ending in "/." if
-    the KeepLocalTrailingSlash flag is given. This reflects how QUrl needs to
-    treat local URLs due to compatibility constraints.
 */
 bool qt_normalizePathSegments(QString *path, QDirPrivate::PathNormalizations flags)
 {
     const bool allowUncPaths = flags.testAnyFlag(QDirPrivate::AllowUncPaths);
     const bool isRemote = flags.testAnyFlag(QDirPrivate::RemotePath);
-    const bool keepLocalTrailingSlash = flags.testAnyFlags(QDirPrivate::KeepLocalTrailingSlash);
     const qsizetype prefixLength = rootLength(*path, allowUncPaths);
 
     // RFC 3986 says: "The input buffer is initialized with the now-appended
@@ -2343,27 +2339,12 @@ bool qt_normalizePathSegments(QString *path, QDirPrivate::PathNormalizations fla
             ++in;       // the one dot
         }
 
-        if (out > start) {
+        // Not at 'end' yet, prepare for the next loop iteration by backtracking one slash.
-            // Always backtrack one slash
+        // E.g.: /a/b/../c    >>> /a/b/../c
-            if (out[-1] == u'/' && in != end)
+        //          ^out            ^out
+        // the next iteration will copy '/c' to the output buffer >>> /a/c
+        if (in != end && out > start && out[-1] == u'/')
             --out;
-
-            if (!isRemote) {
-                bool removedAnySlashes = false;
-
-                // Backtrack all slashes ...
-                while (out > start && out[-1] == u'/') {
-                    --out;
-                    removedAnySlashes = true;
-                }
-
-                // ... except a trailing one if it exists and flag given
-                if (removedAnySlashes && keepLocalTrailingSlash && out > start) {
-                    ++out;
-                    break;
-                }
-            }
-        }
         if (out == start) {
             // We've reached the root. Make sure we don't turn a relative path
             // to absolute or, in the case of local paths that are already

src/corelib/io/qdir_p.h

@@ -31,7 +31,6 @@ public:
         DefaultNormalization = 0x00,
         AllowUncPaths = 0x01,
         RemotePath = 0x02,
-        KeepLocalTrailingSlash = 0x04,
     };
     Q_DECLARE_FLAGS(PathNormalizations, PathNormalization)
     Q_FLAGS(PathNormalizations)

src/corelib/io/qurl.cpp

@@ -913,7 +913,7 @@ inline void QUrlPrivate::appendPath(QString &appendTo, QUrl::FormattingOptions o
     if (options & QUrl::NormalizePathSegments) {
         qt_normalizePathSegments(
                 &thePath,
-                isLocalFile() ? QDirPrivate::KeepLocalTrailingSlash : QDirPrivate::RemotePath);
+                isLocalFile() ? QDirPrivate::DefaultNormalization : QDirPrivate::RemotePath);
     }
 
     QStringView thePathView(thePath);
@@ -2716,7 +2716,7 @@ QUrl QUrl::resolved(const QUrl &relative) const
 
     qt_normalizePathSegments(
             &t.d->path,
-            isLocalFile() ? QDirPrivate::KeepLocalTrailingSlash : QDirPrivate::RemotePath);
+            isLocalFile() ? QDirPrivate::DefaultNormalization : QDirPrivate::RemotePath);
     if (!t.d->hasAuthority())
         fixupNonAuthorityPath(&t.d->path);
 

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

@@ -1384,8 +1384,14 @@ void tst_QDir::normalizePathSegments_data()
     QTest::addColumn<UncHandling>("uncHandling");
     QTest::addColumn<QString>("expected");
 
-    QTest::newRow("data0") << "/Users/sam/troll/qt4.0//.." << HandleUnc << "/Users/sam/troll";
+    QTest::newRow("data0") << "/Users/sam/troll/qt4.0//.." << HandleUnc << "/Users/sam/troll/";
-    QTest::newRow("data1") << "/Users/sam////troll/qt4.0//.." << HandleUnc << "/Users/sam/troll";
+    QTest::newRow("data1") << "/Users/sam////troll/qt4.0//.." << HandleUnc << "/Users/sam/troll/";
+    QTest::newRow("data53") <<"/b//." << HandleUnc << "/b/";
+    QTest::newRow("data54") <<"/b//./" << HandleUnc << "/b/";
+    QTest::newRow("data55") <<"/b/." << HandleUnc << "/b/";
+    QTest::newRow("data56") <<"/b/./" << HandleUnc << "/b/";
+    QTest::newRow("data57") <<"/b" << HandleUnc << "/b";
+
     QTest::newRow("data2") << "/" << HandleUnc << "/";
     QTest::newRow("data3") << "//" << HandleUnc << "//";
     QTest::newRow("data4") << "//" << IgnoreUnc << "/";
@@ -1426,12 +1432,11 @@ void tst_QDir::normalizePathSegments_data()
     QTest::newRow("data34") << "c://foo" << HandleUnc << "c:/foo";
     QTest::newRow("data35") << "c:" << HandleUnc << "c:";
     QTest::newRow("data36") << "c:foo/bar" << IgnoreUnc << "c:foo/bar";
-#if defined Q_OS_WIN
     QTest::newRow("data37") << "c:/." << HandleUnc << "c:/";
+#if defined Q_OS_WIN
     QTest::newRow("data38") << "c:/.." << HandleUnc << "c:/..";
     QTest::newRow("data39") << "c:/../" << HandleUnc << "c:/../";
 #else
-    QTest::newRow("data37") << "c:/." << HandleUnc << "c:";
     QTest::newRow("data38") << "c:/.." << HandleUnc << ".";
     QTest::newRow("data39") << "c:/../" << HandleUnc << ".";
 #endif
@@ -1439,9 +1444,9 @@ void tst_QDir::normalizePathSegments_data()
     QTest::newRow("data41") << "foo/../foo/.." << HandleUnc << ".";
     QTest::newRow("data42") << "foo/../foo/../.." << HandleUnc << "..";
     QTest::newRow("data43") << "..foo.bar/foo" << HandleUnc << "..foo.bar/foo";
-    QTest::newRow("data44") << ".foo./bar/.." << HandleUnc << ".foo.";
+    QTest::newRow("data44") << ".foo./bar/.." << HandleUnc << ".foo./";
     QTest::newRow("data45") << "foo/..bar.." << HandleUnc << "foo/..bar..";
-    QTest::newRow("data46") << "foo/.bar./.." << HandleUnc << "foo";
+    QTest::newRow("data46") << "foo/.bar./.." << HandleUnc << "foo/";
     QTest::newRow("data47") << "//foo//bar" << HandleUnc << "//foo/bar";
     QTest::newRow("data48") << "..." << HandleUnc << "...";
     QTest::newRow("data49") << "foo/.../bar" << HandleUnc << "foo/.../bar";

tests/auto/corelib/io/qurl/tst_qurl.cpp

@@ -1487,6 +1487,11 @@ void tst_QUrl::fromLocalFileNormalize_data()
 
     QTest::newRow("absolute-path") << QString::fromLatin1("/a.txt") << QString::fromLatin1("file:///a.txt") << QString::fromLatin1("file:///a.txt");
     QTest::newRow("relative-path") << QString::fromLatin1("a.txt") << QString::fromLatin1("file:a.txt") << QString::fromLatin1("file:a.txt");
+
+    QTest::newRow("absolute-path-trailing-slash") << u"/b/"_s << u"file:///b/"_s << u"file:///b/"_s;
+    QTest::newRow("absolute-path-no-trailing-slash") << u"/b"_s << u"file:///b"_s << u"file:///b"_s;
+    QTest::newRow("absolute-path-2-trailing-slashes") << u"/b//"_s << u"file:///b//"_s << u"file:///b/"_s;
+
     QTest::newRow("percent") << QString::fromLatin1("/a%.txt") << QString::fromLatin1("file:///a%25.txt")
                              << QString::fromLatin1("file:///a%25.txt");
     QTest::newRow("percent25") << QString::fromLatin1("/a%25.txt") << QString::fromLatin1("file:///a%2525.txt")