QFileInfo: harmonize QFileInfo() and QFileInfo("")

If a QFileInfo was constructed with an empty path, which could happen
with QFileInfo(QFile()) or via QDir, etc., then it would issue system
calls to empty paths and could even produce warnings. This commit makes
am empty path name be the same as a default-constructed QFileInfo and
corrects the use if 0 for ownerId and groupId to match the
documentation.

[ChangeLog][Important Behavior Changes] QFileInfo on empty strings now
behaves like the default-constructed QFileInfo. Notably, path() will now
be the empty string too, instead of ".", which means absoluteFilePath()
is no longer the current working directory.

Change-Id: I8d96dea9955d4c749b99fffd14ce34968b1d9bbf
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 70 insertions, 123 deletions

diff --git a/src/corelib/io/qfileinfo.cpp b/src/corelib/io/qfileinfo.cpp
index 104a171e99..235e391aa0 100644
--- a/src/corelib/io/qfileinfo.cpp
+++ b/src/corelib/io/qfileinfo.cpp
@@ -591,9 +591,6 @@ QString QFileInfo::absolutePath() const
 
     if (d->isDefaultConstructed) {
         return QLatin1String("");
-    } else if (d->fileEntry.isEmpty()) {
-        qWarning("QFileInfo::absolutePath: Constructed with empty filename");
-        return QLatin1String("");
     }
     return d->getFileName(QAbstractFileEngine::AbsolutePathName);
 }
@@ -913,14 +910,10 @@ QDir QFileInfo::absoluteDir() const
 bool QFileInfo::isReadable() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::UserReadPermission))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::UserReadPermission);
-        return (d->metaData.permissions() & QFile::ReadUser) != 0;
-    }
-    return d->getFileFlags(QAbstractFileEngine::ReadUserPerm);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::UserReadPermission,
+                [d]() { return (d->metaData.permissions() & QFile::ReadUser) != 0; },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::ReadUserPerm); });
 }
 
 /*!
@@ -934,14 +927,10 @@ bool QFileInfo::isReadable() const
 bool QFileInfo::isWritable() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::UserWritePermission))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::UserWritePermission);
-        return (d->metaData.permissions() & QFile::WriteUser) != 0;
-    }
-    return d->getFileFlags(QAbstractFileEngine::WriteUserPerm);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::UserWritePermission,
+                [d]() { return (d->metaData.permissions() & QFile::WriteUser) != 0; },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::WriteUserPerm); });
 }
 
 /*!
@@ -952,14 +941,10 @@ bool QFileInfo::isWritable() const
 bool QFileInfo::isExecutable() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::UserExecutePermission))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::UserExecutePermission);
-        return (d->metaData.permissions() & QFile::ExeUser) != 0;
-    }
-    return d->getFileFlags(QAbstractFileEngine::ExeUserPerm);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::UserExecutePermission,
+                [d]() { return (d->metaData.permissions() & QFile::ExeUser) != 0; },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::ExeUserPerm); });
 }
 
 /*!
@@ -971,14 +956,10 @@ bool QFileInfo::isExecutable() const
 bool QFileInfo::isHidden() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::HiddenAttribute))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::HiddenAttribute);
-        return d->metaData.isHidden();
-    }
-    return d->getFileFlags(QAbstractFileEngine::HiddenFlag);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::HiddenAttribute,
+                [d]() { return d->metaData.isHidden(); },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::HiddenFlag); });
 }
 
 /*!
@@ -1014,14 +995,10 @@ bool QFileInfo::isNativePath() const
 bool QFileInfo::isFile() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::FileType))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::FileType);
-        return d->metaData.isFile();
-    }
-    return d->getFileFlags(QAbstractFileEngine::FileType);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::FileType,
+                [d]() { return d->metaData.isFile(); },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::FileType); });
 }
 
 /*!
@@ -1033,14 +1010,10 @@ bool QFileInfo::isFile() const
 bool QFileInfo::isDir() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::DirectoryType))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::DirectoryType);
-        return d->metaData.isDirectory();
-    }
-    return d->getFileFlags(QAbstractFileEngine::DirectoryType);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::DirectoryType,
+                [d]() { return d->metaData.isDirectory(); },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::DirectoryType); });
 }
 
 
@@ -1054,14 +1027,10 @@ bool QFileInfo::isDir() const
 bool QFileInfo::isBundle() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::BundleType))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::BundleType);
-        return d->metaData.isBundle();
-    }
-    return d->getFileFlags(QAbstractFileEngine::BundleType);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::BundleType,
+                [d]() { return d->metaData.isBundle(); },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::BundleType); });
 }
 
 /*!
@@ -1084,14 +1053,10 @@ bool QFileInfo::isBundle() const
 bool QFileInfo::isSymLink() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::LegacyLinkType))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::LegacyLinkType);
-        return d->metaData.isLegacyLink();
-    }
-    return d->getFileFlags(QAbstractFileEngine::LinkType);
+    return d->checkAttribute<bool>(
+                QFileSystemMetaData::LegacyLinkType,
+                [d]() { return d->metaData.isLegacyLink(); },
+                [d]() { return d->getFileFlags(QAbstractFileEngine::LinkType); });
 }
 
 /*!
@@ -1103,7 +1068,7 @@ bool QFileInfo::isRoot() const
 {
     Q_D(const QFileInfo);
     if (d->isDefaultConstructed)
-        return true;
+        return false;
     if (d->fileEngine == 0) {
         if (d->fileEntry.isRoot()) {
 #if defined(Q_OS_WIN) && !defined(Q_OS_WINRT)
@@ -1179,14 +1144,10 @@ QString QFileInfo::owner() const
 uint QFileInfo::ownerId() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return 0;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::UserId))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::UserId);
-        return d->metaData.userId();
-    }
-    return d->fileEngine->ownerId(QAbstractFileEngine::OwnerUser);
+    return d->checkAttribute(uint(-2),
+                QFileSystemMetaData::UserId,
+                [d]() { return d->metaData.userId(); },
+                [d]() { return d->fileEngine->ownerId(QAbstractFileEngine::OwnerUser); });
 }
 
 /*!
@@ -1218,14 +1179,10 @@ QString QFileInfo::group() const
 uint QFileInfo::groupId() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return 0;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::GroupId))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::GroupId);
-        return d->metaData.groupId();
-    }
-    return d->fileEngine->ownerId(QAbstractFileEngine::OwnerGroup);
+    return d->checkAttribute(uint(-2),
+                QFileSystemMetaData::GroupId,
+                [d]() { return d->metaData.groupId(); },
+                [d]() { return d->fileEngine->ownerId(QAbstractFileEngine::OwnerGroup); });
 }
 
 /*!
@@ -1247,16 +1204,15 @@ uint QFileInfo::groupId() const
 bool QFileInfo::permission(QFile::Permissions permissions) const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return false;
-    if (d->fileEngine == 0) {
-        // the QFileSystemMetaData::MetaDataFlag and QFile::Permissions overlap, so just static cast.
-        QFileSystemMetaData::MetaDataFlag permissionFlags = static_cast<QFileSystemMetaData::MetaDataFlag>((int)permissions);
-        if (!d->cache_enabled || !d->metaData.hasFlags(permissionFlags))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, permissionFlags);
-        return (d->metaData.permissions() & permissions) == permissions;
-    }
-    return d->getFileFlags(QAbstractFileEngine::FileFlags((int)permissions)) == (uint)permissions;
+    // the QFileSystemMetaData::MetaDataFlag and QFile::Permissions overlap, so just cast.
+    auto fseFlags = QFileSystemMetaData::MetaDataFlag(int(permissions));
+    auto feFlags = QAbstractFileEngine::FileFlags(int(permissions));
+    return d->checkAttribute<bool>(
+                fseFlags,
+                [=]() { return (d->metaData.permissions() & permissions) == permissions; },
+        [=]() {
+            return d->getFileFlags(feFlags) == uint(permissions);
+        });
 }
 
 /*!
@@ -1269,14 +1225,12 @@ bool QFileInfo::permission(QFile::Permissions permissions) const
 QFile::Permissions QFileInfo::permissions() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return 0;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::Permissions))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::Permissions);
-        return d->metaData.permissions();
-    }
-    return QFile::Permissions(d->getFileFlags(QAbstractFileEngine::PermsMask) & QAbstractFileEngine::PermsMask);
+    return d->checkAttribute<QFile::Permissions>(
+                QFileSystemMetaData::Permissions,
+                [d]() { return d->metaData.permissions(); },
+        [d]() {
+            return QFile::Permissions(d->getFileFlags(QAbstractFileEngine::PermsMask) & QAbstractFileEngine::PermsMask);
+        });
 }
 
 
@@ -1289,18 +1243,16 @@ QFile::Permissions QFileInfo::permissions() const
 qint64 QFileInfo::size() const
 {
     Q_D(const QFileInfo);
-    if (d->isDefaultConstructed)
-        return 0;
-    if (d->fileEngine == 0) {
-        if (!d->cache_enabled || !d->metaData.hasFlags(QFileSystemMetaData::SizeAttribute))
-            QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, QFileSystemMetaData::SizeAttribute);
-        return d->metaData.size();
-    }
-    if (!d->getCachedFlag(QFileInfoPrivate::CachedSize)) {
-        d->setCachedFlag(QFileInfoPrivate::CachedSize);
-        d->fileSize = d->fileEngine->size();
-    }
-    return d->fileSize;
+    return d->checkAttribute<qint64>(
+                QFileSystemMetaData::SizeAttribute,
+                [d]() { return d->metaData.size(); },
+        [d]() {
+            if (!d->getCachedFlag(QFileInfoPrivate::CachedSize)) {
+                d->setCachedFlag(QFileInfoPrivate::CachedSize);
+                d->fileSize = d->fileEngine->size();
+            }
+            return d->fileSize;
+        });
 }
 
 #if QT_DEPRECATED_SINCE(5, 10)
@@ -1394,11 +1346,6 @@ QDateTime QFileInfo::fileTime(QFile::FileTime time) const
 
     Q_D(const QFileInfo);
     auto fetime = QAbstractFileEngine::FileTime(time);
-    if (d->isDefaultConstructed)
-        return QDateTime();
-    if (d->fileEngine)
-        return d->getFileTime(fetime).toLocalTime();
-
     QFileSystemMetaData::MetaDataFlags flag;
     switch (time) {
     case QFile::FileAccessTime:
@@ -1415,10 +1362,10 @@ QDateTime QFileInfo::fileTime(QFile::FileTime time) const
         break;
     }
 
-    if (!d->cache_enabled || !d->metaData.hasFlags(flag))
-        if (!QFileSystemEngine::fillMetaData(d->fileEntry, d->metaData, flag))
-            return QDateTime();
-    return d->metaData.fileTime(fetime).toLocalTime();
+    return d->checkAttribute<QDateTime>(
+                flag,
+                [=]() { return d->metaData.fileTime(fetime).toLocalTime(); },
+                [=]() { return d->getFileTime(fetime).toLocalTime(); });
 }
 
 /*!