Always generate QML cache files in the cache directory, never in sources

This patch eliminates the annoying behavior of the QML compiler that .qmlc cache
files are stored alongside the sources. When cache files are generated at
run-time, then they are always stored in the application's local cache directory
defined by QStandardPaths::CacheLocation (qmlcache subfolder). The application's
uninstaller is responsible for cleaning up the cache directory during removal.

If explicitly precompiled QML files exist at the source location, then they are
loaded from there and no cache file is being generated.

Storing cache files in the source directory is as problematic as an in-tree
build. The cache files pollute the source directory and create unnecessary
inconvenience with version control systems.

[ChangeLog][QtQml][QQmlEngine] QML cache files are now always stored in the
application's cache directory when being generated at run-time. If precompiled
QML files exist at the source location, then they are loaded and no cache file
is being generated. The application's uninstaller is responsible for cleaning up
the cache during removal.

Task-number: QTBUG-56150
Change-Id: I5a64b7f958e782e03c71873a82cef4b07011cbf1
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

2 files changed, 19 insertions, 19 deletions

diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index e72bbe1f5e..c809d497fd 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -78,23 +78,6 @@ namespace CompiledData {
 
 static_assert(sizeof(Unit::libraryVersionHash) >= QML_COMPILE_HASH_LENGTH + 1, "Compile hash length exceeds reserved size in data structure. Please adjust and bump the format version");
 
-#if !defined(V4_BOOTSTRAP)
-static QString cacheFilePath(const QUrl &url)
-{
-    const QString localSourcePath = QQmlFile::urlToLocalFileOrQrc(url);
-    const QString localCachePath = localSourcePath + QLatin1Char('c');
-#ifndef Q_OS_ANDROID
-    if (QFile::exists(localCachePath) || QFileInfo(QFileInfo(localSourcePath).dir().absolutePath()).isWritable())
-        return localCachePath;
-#endif
-    QCryptographicHash fileNameHash(QCryptographicHash::Sha1);
-    fileNameHash.addData(localSourcePath.toUtf8());
-    QString directory = QStandardPaths::writableLocation(QStandardPaths::CacheLocation) + QLatin1String("/qmlcache/");
-    QDir::root().mkpath(directory);
-    return directory + QString::fromUtf8(fileNameHash.result().toHex()) + QLatin1Char('.') + QFileInfo(localCachePath).completeSuffix();
-}
-#endif
-
 CompilationUnit::CompilationUnit(const Unit *unitData)
 {
     data = unitData;
@@ -109,6 +92,17 @@ CompilationUnit::~CompilationUnit()
     data = nullptr;
 }
 
+QString CompilationUnit::localCacheFilePath(const QUrl &url)
+{
+    const QString localSourcePath = QQmlFile::urlToLocalFileOrQrc(url);
+    const QString cacheFileSuffix = QFileInfo(localSourcePath + QLatin1Char('c')).completeSuffix();
+    QCryptographicHash fileNameHash(QCryptographicHash::Sha1);
+    fileNameHash.addData(localSourcePath.toUtf8());
+    QString directory = QStandardPaths::writableLocation(QStandardPaths::CacheLocation) + QLatin1String("/qmlcache/");
+    QDir::root().mkpath(directory);
+    return directory + QString::fromUtf8(fileNameHash.result().toHex()) + QLatin1Char('.') + cacheFileSuffix;
+}
+
 QV4::Function *CompilationUnit::linkToEngine(ExecutionEngine *engine)
 {
     this->engine = engine;
@@ -361,7 +355,11 @@ bool CompilationUnit::loadFromDisk(const QUrl &url, const QDateTime &sourceTimeS
     const QString sourcePath = QQmlFile::urlToLocalFileOrQrc(url);
     QScopedPointer<CompilationUnitMapper> cacheFile(new CompilationUnitMapper());
 
-    CompiledData::Unit *mappedUnit = cacheFile->open(cacheFilePath(url), sourceTimeStamp, errorString);
+    QString cachePath = sourcePath + QLatin1Char('c');
+    if (!QFile::exists(cachePath))
+        cachePath = localCacheFilePath(url);
+
+    CompiledData::Unit *mappedUnit = cacheFile->open(cachePath, sourceTimeStamp, errorString);
     if (!mappedUnit)
         return false;
 
@@ -423,7 +421,7 @@ bool CompilationUnit::saveToDisk(const QUrl &unitUrl, QString *errorString)
         *errorString = QStringLiteral("File has to be a local file.");
         return false;
     }
-    const QString outputFileName = cacheFilePath(unitUrl);
+    const QString outputFileName = localCacheFilePath(unitUrl);
 #endif
 
 #if QT_CONFIG(temporaryfile)
diff --git a/src/qml/compiler/qv4compileddata_p.h b/src/qml/compiler/qv4compileddata_p.h
index bd19c1e1a8..08170e1c3b 100644
--- a/src/qml/compiler/qv4compileddata_p.h
+++ b/src/qml/compiler/qv4compileddata_p.h
@@ -1055,6 +1055,8 @@ public:
 
     bool loadFromDisk(const QUrl &url, const QDateTime &sourceTimeStamp, QString *errorString);
 
+    static QString localCacheFilePath(const QUrl &url);
+
 protected:
     void linkBackendToEngine(QV4::ExecutionEngine *engine);
 #endif // V4_BOOTSTRAP