CMake: Allow contents of resources to be replaced by empty files

This makes it possible to process QML files using qmlcachegen, and
retain the file nodes in the resource file system, but remove their
actual content from the binary. To do so, you need to mark your files
with the QT_DISCARD_FILE_CONTENTS source file property.

Fixes: QTBUG-87676
Fixes: QTBUG-103481
Fixes: QTBUG-102024
Fixes: QTBUG-102785
Change-Id: I93d5a2bfca1739ff1e0f74c8082eb8aa451b9815
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
Reviewed-by: hjk <hjk@qt.io>

2 files changed, 36 insertions, 10 deletions

diff --git a/src/tools/rcc/rcc.cpp b/src/tools/rcc/rcc.cpp
index a87f15de33..3b5166a70e 100644
--- a/src/tools/rcc/rcc.cpp
+++ b/src/tools/rcc/rcc.cpp
@@ -82,7 +82,8 @@ public:
                 RCCResourceLibrary::CompressionAlgorithm compressAlgo = RCCResourceLibrary::CompressionAlgorithm::Best,
                 int compressLevel = CONSTANT_COMPRESSLEVEL_DEFAULT,
                 int compressThreshold = CONSTANT_COMPRESSTHRESHOLD_DEFAULT,
-                bool noZstd = false);
+                bool noZstd = false,
+                bool isEmpty = false);
     ~RCCFileInfo();
 
     QString resourceName() const;
@@ -107,12 +108,13 @@ public:
     qint64 m_dataOffset;
     qint64 m_childOffset;
     bool m_noZstd;
+    bool m_isEmpty;
 };
 
 RCCFileInfo::RCCFileInfo(const QString &name, const QFileInfo &fileInfo,
     QLocale::Language language, QLocale::Territory territory, uint flags,
     RCCResourceLibrary::CompressionAlgorithm compressAlgo, int compressLevel, int compressThreshold,
-    bool noZstd)
+    bool noZstd, bool isEmpty)
 {
     m_name = name;
     m_fileInfo = fileInfo;
@@ -127,6 +129,7 @@ RCCFileInfo::RCCFileInfo(const QString &name, const QFileInfo &fileInfo,
     m_compressLevel = compressLevel;
     m_compressThreshold = compressThreshold;
     m_noZstd = noZstd;
+    m_isEmpty = isEmpty;
 }
 
 RCCFileInfo::~RCCFileInfo()
@@ -225,14 +228,18 @@ qint64 RCCFileInfo::writeDataBlob(RCCResourceLibrary &lib, qint64 offset,
 
     //capture the offset
     m_dataOffset = offset;
+    QByteArray data;
 
-    //find the data to be written
-    QFile file(m_fileInfo.absoluteFilePath());
-    if (!file.open(QFile::ReadOnly)) {
-        *errorMessage = msgOpenReadFailed(m_fileInfo.absoluteFilePath(), file.errorString());
-        return 0;
+    if (!m_isEmpty) {
+        //find the data to be written
+        QFile file(m_fileInfo.absoluteFilePath());
+        if (!file.open(QFile::ReadOnly)) {
+            *errorMessage = msgOpenReadFailed(m_fileInfo.absoluteFilePath(), file.errorString());
+            return 0;
+        }
+
+        data = file.readAll();
     }
-    QByteArray data = file.readAll();
 
     // Check if compression is useful for this file
     if (data.size() != 0) {
@@ -420,6 +427,7 @@ RCCResourceLibrary::Strings::Strings() :
    ATTRIBUTE_LANG("lang"_L1),
    ATTRIBUTE_PREFIX("prefix"_L1),
    ATTRIBUTE_ALIAS("alias"_L1),
+   ATTRIBUTE_EMPTY("empty"_L1),
    ATTRIBUTE_THRESHOLD("threshold"_L1),
    ATTRIBUTE_COMPRESS("compress"_L1),
    ATTRIBUTE_COMPRESSALGO(QStringLiteral("compression-algorithm"))
@@ -464,6 +472,17 @@ enum RCCXmlTag {
 };
 Q_DECLARE_TYPEINFO(RCCXmlTag, Q_PRIMITIVE_TYPE);
 
+static bool parseBoolean(QStringView value, QString *errorMsg)
+{
+    if (value.compare("true"_L1, Qt::CaseInsensitive) == 0)
+        return true;
+    if (value.compare("false"_L1, Qt::CaseInsensitive) == 0)
+        return false;
+
+    *errorMsg = QString::fromLatin1("Invalid value for boolean attribute: '%1'").arg(value);
+    return false;
+}
+
 bool RCCResourceLibrary::interpretResourceFile(QIODevice *inputDevice,
     const QString &fname, QString currentPath, bool listMode)
 {
@@ -479,6 +498,7 @@ bool RCCResourceLibrary::interpretResourceFile(QIODevice *inputDevice,
     QLocale::Language language = QLocale::c().language();
     QLocale::Territory territory = QLocale::c().territory();
     QString alias;
+    bool empty = false;
     auto compressAlgo = m_compressionAlgo;
     int compressLevel = m_compressLevel;
     int compressThreshold = m_compressThreshold;
@@ -538,6 +558,11 @@ bool RCCResourceLibrary::interpretResourceFile(QIODevice *inputDevice,
                     compressThreshold = m_compressThreshold;
 
                     QString errorString;
+                    if (attributes.hasAttribute(m_strings.ATTRIBUTE_EMPTY))
+                        empty = parseBoolean(attributes.value(m_strings.ATTRIBUTE_EMPTY), &errorString);
+                    else
+                        empty = false;
+
                     if (attributes.hasAttribute(m_strings.ATTRIBUTE_COMPRESSALGO))
                         compressAlgo = parseCompressionAlgorithm(attributes.value(m_strings.ATTRIBUTE_COMPRESSALGO), &errorString);
                     if (errorString.isEmpty() && attributes.hasAttribute(m_strings.ATTRIBUTE_COMPRESS)) {
@@ -628,7 +653,7 @@ bool RCCResourceLibrary::interpretResourceFile(QIODevice *inputDevice,
                                                     child.isDir() ? RCCFileInfo::Directory
                                                                   : RCCFileInfo::NoFlags,
                                                     compressAlgo, compressLevel, compressThreshold,
-                                                    m_noZstd));
+                                                    m_noZstd, empty));
                         if (!arc)
                             m_failedResources.push_back(child.fileName());
                     }
@@ -643,7 +668,7 @@ bool RCCResourceLibrary::interpretResourceFile(QIODevice *inputDevice,
                                             compressAlgo,
                                             compressLevel,
                                             compressThreshold,
-                                            m_noZstd)
+                                            m_noZstd, empty)
                                 );
                     if (!arc)
                         m_failedResources.push_back(absFileName);
diff --git a/src/tools/rcc/rcc.h b/src/tools/rcc/rcc.h
index fe0e0989df..78d7600492 100644
--- a/src/tools/rcc/rcc.h
+++ b/src/tools/rcc/rcc.h
@@ -96,6 +96,7 @@ private:
         const QString ATTRIBUTE_LANG;
         const QString ATTRIBUTE_PREFIX;
         const QString ATTRIBUTE_ALIAS;
+        const QString ATTRIBUTE_EMPTY;
         const QString ATTRIBUTE_THRESHOLD;
         const QString ATTRIBUTE_COMPRESS;
         const QString ATTRIBUTE_COMPRESSALGO;