moc: Add warnings when resolving and opening includes fails

Previously, only cryptic warnings:

QFSFileEngine::open: No file name specified

occurred.

Task-number: QTBUG-55014
Change-Id: Ic99614eb58c605ed6e1b86d3d4b8f527c5b9244c
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

2 files changed, 23 insertions, 5 deletions

diff --git a/src/tools/moc/main.cpp b/src/tools/moc/main.cpp
index 0a10aef989..55cf7ed872 100644
--- a/src/tools/moc/main.cpp
+++ b/src/tools/moc/main.cpp
@@ -457,11 +457,22 @@ int runMoc(int argc, char **argv)
     const auto includeFiles = parser.values(includeOption);
     for (const QString &includeName : includeFiles) {
         QByteArray rawName = pp.resolveInclude(QFile::encodeName(includeName), moc.filename);
-        QFile f(QFile::decodeName(rawName));
-        if (f.open(QIODevice::ReadOnly)) {
-            moc.symbols += Symbol(0, MOC_INCLUDE_BEGIN, rawName);
-            moc.symbols += pp.preprocessed(rawName, &f);
-            moc.symbols += Symbol(0, MOC_INCLUDE_END, rawName);
+        if (rawName.isEmpty()) {
+            fprintf(stderr, "Warning: Failed to resolve include \"%s\" for moc file %s\n",
+                    includeName.toLocal8Bit().constData(),
+                    moc.filename.isEmpty() ? "<standard input>" : moc.filename.constData());
+        } else {
+            QFile f(QFile::decodeName(rawName));
+            if (f.open(QIODevice::ReadOnly)) {
+                moc.symbols += Symbol(0, MOC_INCLUDE_BEGIN, rawName);
+                moc.symbols += pp.preprocessed(rawName, &f);
+                moc.symbols += Symbol(0, MOC_INCLUDE_END, rawName);
+            } else {
+                fprintf(stderr, "Warning: Cannot open %s included by moc file %s: %s\n",
+                        rawName.constData(),
+                        moc.filename.isEmpty() ? "<standard input>" : moc.filename.constData(),
+                        f.errorString().toLocal8Bit().constData());
+            }
         }
     }
     moc.symbols += pp.preprocessed(moc.filename, &in);
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index d9a0a6ad60..94df29f539 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -2027,6 +2027,13 @@ void tst_Moc::warnings_data()
         << 1
         << QString("IGNORE_ALL_STDOUT")
         << QString(":-1: Error: Unexpected character in macro argument list.");
+
+    QTest::newRow("Missing header warning")
+        << QByteArray("class X : public QObject { Q_OBJECT };")
+        << (QStringList() << QStringLiteral("--include") << QStringLiteral("doesnotexist.h"))
+        << 0
+        << QString("IGNORE_ALL_STDOUT")
+        << QStringLiteral("Warning: Failed to resolve include \"doesnotexist.h\" for moc file <standard input>");
 }
 
 void tst_Moc::warnings()