Improve tst_uic.

- Make the version regexp a member variable, avoiding repeated
  construction.
- Use QVERIFY2() with error message for opening files.
- On failure, try to locate the standard diff tool and produce
  diff output for comparison, which should make for example
  copyright header changes much easier.

Task-number: QTBUG-44406
Change-Id: Ic759899c1da3394e3eb0cee7b1c722f0945714d3
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

tests/auto/tools/uic/tst_uic.cpp

@@ -39,6 +39,7 @@
 #include <QtCore/QByteArray>
 #include <QtCore/QLibraryInfo>
 #include <QtCore/QTemporaryDir>
+#include <QtCore/QStandardPaths>
 
 class tst_uic : public QObject
 {
@@ -67,10 +68,12 @@ private:
     const QString m_command;
     QString m_baseline;
     QTemporaryDir m_generated;
+    QRegExp m_versionRegexp;
 };
 
 tst_uic::tst_uic()
     : m_command(QLibraryInfo::location(QLibraryInfo::BinariesPath) + QLatin1String("/uic"))
+    , m_versionRegexp(QLatin1String("Created by: Qt User Interface Compiler version [.\\d]{5,5}"))
 {
 }
 
@@ -83,6 +86,7 @@ static QByteArray msgProcessStartFailed(const QString &command, const QString &w
 
 void tst_uic::initTestCase()
 {
+    QVERIFY(m_versionRegexp.isValid());
     m_baseline = QFINDTESTDATA("baseline");
     QVERIFY2(!m_baseline.isEmpty(), "Could not find 'baseline'.");
     QProcess process;
@@ -171,6 +175,37 @@ void tst_uic::run_data() const
     }
 }
 
+// Helpers to generate a diff using the standard diff tool if present for failures.
+static inline QString diffBinary()
+{
+    QString binary = QLatin1String("diff");
+#ifdef Q_OS_WIN
+    binary += QLatin1String(".exe");
+#endif
+    return QStandardPaths::findExecutable(binary);
+}
+
+static QString generateDiff(const QString &originalFile, const QString &generatedFile)
+{
+    static const QString diff = diffBinary();
+    if (diff.isEmpty())
+        return QString();
+    const QStringList args = QStringList() << QLatin1String("-u")
+        << QDir::toNativeSeparators(originalFile)
+        << QDir::toNativeSeparators(generatedFile);
+    QProcess diffProcess;
+    diffProcess.start(diff, args);
+    return diffProcess.waitForStarted() && diffProcess.waitForFinished()
+        ? QString::fromLocal8Bit(diffProcess.readAllStandardOutput()) : QString();
+}
+
+static QByteArray msgCannotReadFile(const QFile &file)
+{
+    const QString result = QLatin1String("Could not read file: ")
+        + QDir::toNativeSeparators(file.fileName())
+        + QLatin1String(": ") + file.errorString();
+    return result.toLocal8Bit();
+}
 
 void tst_uic::compare()
 {
@@ -180,23 +215,23 @@ void tst_uic::compare()
     QFile orgFile(originalFile);
     QFile genFile(generatedFile);
 
-    if (!orgFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
+    QVERIFY2(orgFile.open(QIODevice::ReadOnly | QIODevice::Text), msgCannotReadFile(orgFile));
-        QString err(QLatin1String("Could not read file: %1..."));
+
-        QFAIL(err.arg(orgFile.fileName()).toUtf8());
+    QVERIFY2(genFile.open(QIODevice::ReadOnly | QIODevice::Text), msgCannotReadFile(genFile));
+
+    QString originalFileContents = orgFile.readAll();
+    originalFileContents.replace(m_versionRegexp, QString());
+
+    QString generatedFileContents = genFile.readAll();
+    generatedFileContents.replace(m_versionRegexp, QString());
+
+    if (generatedFileContents != originalFileContents) {
+        const QString diff = generateDiff(originalFile, generatedFile);
+        if (!diff.isEmpty())
+             qWarning().noquote().nospace() << "Difference:\n" << diff;
     }
 
-    if (!genFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
+    QCOMPARE(generatedFileContents, originalFileContents);
-        QString err(QLatin1String("Could not read file: %1..."));
-        QFAIL(err.arg(genFile.fileName()).toUtf8());
-    }
-
-    originalFile = orgFile.readAll();
-    originalFile.replace(QRegExp(QLatin1String("Created by: Qt User Interface Compiler version [.\\d]{5,5}")), "");
-
-    generatedFile = genFile.readAll();
-    generatedFile.replace(QRegExp(QLatin1String("Created by: Qt User Interface Compiler version [.\\d]{5,5}")), "");
-
-    QCOMPARE(generatedFile, originalFile);
 }
 
 void tst_uic::compare_data() const
@@ -240,28 +275,31 @@ void tst_uic::runTranslation()
 
 void tst_uic::runCompare()
 {
-    QFile orgFile(m_baseline + QLatin1String("/translation/Dialog_without_Buttons_tr.h"));
+    const QString dialogFile = QLatin1String("/translation/Dialog_without_Buttons_tr.h");
+    const QString originalFile = m_baseline + dialogFile;
+    QFile orgFile(originalFile);
 
     QDir generated(m_generated.path());
-    QFile genFile(generated.absolutePath() + QLatin1String("/translation/Dialog_without_Buttons_tr.h"));
+    const QString generatedFile = generated.absolutePath() + dialogFile;
+    QFile genFile(generatedFile);
 
-    if (!orgFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
+    QVERIFY2(orgFile.open(QIODevice::ReadOnly | QIODevice::Text), msgCannotReadFile(orgFile));
-        QString err(QLatin1String("Could not read file: %1..."));
+
-        QFAIL(err.arg(orgFile.fileName()).toUtf8());
+    QVERIFY2(genFile.open(QIODevice::ReadOnly | QIODevice::Text), msgCannotReadFile(genFile));
+
+    QString originalFileContents = orgFile.readAll();
+    originalFileContents.replace(m_versionRegexp, QString());
+
+    QString generatedFileContents = genFile.readAll();
+    generatedFileContents.replace(m_versionRegexp, QString());
+
+    if (generatedFileContents != originalFileContents) {
+        const QString diff = generateDiff(originalFile, generatedFile);
+        if (!diff.isEmpty())
+             qWarning().noquote().nospace() << "Difference:\n" << diff;
     }
 
-    if (!genFile.open(QIODevice::ReadOnly | QIODevice::Text)) {
+    QCOMPARE(generatedFileContents, originalFileContents);
-        QString err(QLatin1String("Could not read file: %1..."));
-        QFAIL(err.arg(genFile.fileName()).toUtf8());
-    }
-
-    QString originalFile = orgFile.readAll();
-    originalFile.replace(QRegExp(QLatin1String("Created by: Qt User Interface Compiler version [.\\d]{5,5}")), "");
-
-    QString generatedFile = genFile.readAll();
-    generatedFile.replace(QRegExp(QLatin1String("Created by: Qt User Interface Compiler version [.\\d]{5,5}")), "");
-
-    QCOMPARE(generatedFile, originalFile);
 }
 
 QTEST_MAIN(tst_uic)