QQmlLoggingCategory: Avoid unnecessary warnings from setters

Assigning same value should be a no-op, especially because such
assignments may happen without explicit user/developer intent.

For example, it can be triggered with QQmlEngine::retranslate() call on
5.15 and early 6.x branches. Since the recent optimizations to
retranslate() which now only forces to re-evaluate what's really
dependent on qsTr, it became harder, but still possible to pull it off.

Fixes: QTBUG-97717
Pick-to: 5.15 6.2
Change-Id: I60ca8e36ed98a15ea5f3c15290865cec27084fbc
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/qml/qml/qqmlloggingcategory.cpp

@@ -129,7 +129,7 @@ void QQmlLoggingCategory::componentComplete()
 {
     m_initialized = true;
     if (m_name.isNull()) {
-        qmlWarning(this) << QLatin1String("Declaring the name of the LoggingCategory is mandatory and cannot be changed later !");
+        qmlWarning(this) << QLatin1String("Declaring the name of a LoggingCategory is mandatory and cannot be changed later");
     } else {
         QScopedPointer<QLoggingCategory> category(new QLoggingCategory(m_name.constData(), QtMsgType(m_defaultLogLevel)));
         m_category.swap(category);
@@ -138,23 +138,30 @@ void QQmlLoggingCategory::componentComplete()
 
 void QQmlLoggingCategory::setDefaultLogLevel(DefaultLogLevel defaultLogLevel)
 {
+    if (m_defaultLogLevel == defaultLogLevel)
+        return;
+
     if (m_initialized) {
-        qmlWarning(this) << QLatin1String("The defaultLogLevel of a LoggingCategory cannot be changed after the Item is created");
+        qmlWarning(this) << QLatin1String("The defaultLogLevel of a LoggingCategory cannot be changed after the component is completed");
         return;
     }
 
     m_defaultLogLevel = defaultLogLevel;
 }
 
-
 void QQmlLoggingCategory::setName(const QString &name)
 {
+    const QByteArray newName = name.toUtf8();
+
+    if (m_name == newName)
+        return;
+
     if (m_initialized) {
-        qmlWarning(this) << QLatin1String("The name of a LoggingCategory cannot be changed after the Item is created");
+        qmlWarning(this) << QLatin1String("The name of a LoggingCategory cannot be changed after the component is completed");
         return;
     }
 
-    m_name = name.toUtf8();
+    m_name = newName;
 }
 
 #include "moc_qqmlloggingcategory_p.cpp"

tests/auto/qml/qqmlconsole/data/assert.qml

@@ -29,21 +29,22 @@
 import QtQuick 2.0
 
 QtObject {
-    property int q:1
+    property int q: 1
+
     function assertFail() {
-        console.assert(0, "This will fail too")
+        console.assert(0, "This will fail too");
     }
 
     Component.onCompleted: {
-        var x = 12;
+        const x = 12;
         console.assert(x == 12, "This will pass");
         try {
-        console.assert(x < 12, "This will fail");
+            console.assert(x < 12, "This will fail");
         } catch (e) {
             console.log(e);
         }
-        console.assert("x < 12", "This will pass too")
+        console.assert("x < 12", "This will pass too");
         assertFail();
-        console.assert(1)
+        console.assert(1);
     }
 }

tests/auto/qml/qqmlconsole/data/categorized_logging.qml

@@ -40,7 +40,7 @@
 import QtQuick 2.12
 
 Item {
-    id:root
+    id: root
 
     LoggingCategory {
         id: testCategory
@@ -69,8 +69,11 @@ Item {
         console.warn(testCategoryStartingFromWarning, "console.warn");
         console.error(testCategoryStartingFromWarning, "console.error");
 
-        testCategory.name = "qt.test2";
+        testCategory.name = "qt.test"; // should be silent
-        testCategory.defaultLogLevel = LoggingCategory.Debug;
+        testCategoryStartingFromWarning.name = "qt.test.other"; // should issue a warning
+
+        testCategory.defaultLogLevel = LoggingCategory.Debug; // should be silent
+        testCategoryStartingFromWarning.defaultLogLevel = LoggingCategory.Debug; // should issue a warning
 
         console.error(emptyCategory, "console.error");
     }

tests/auto/qml/qqmlconsole/data/exception.qml

@@ -30,12 +30,12 @@ import QtQuick 2.0
 
 QtObject {
     function exceptionFail() {
-        console.exception("Exception 2")
+        console.exception("Exception 2");
     }
 
     Component.onCompleted: {
         try {
-            console.exception("Exception 1")
+            console.exception("Exception 1");
         } catch (e) {
             console.log(e);
         }

tests/auto/qml/qqmlconsole/data/logging.qml

@@ -30,7 +30,8 @@
 import QtQuick 2.0
 
 QtObject {
-    id:root
+    id: root
+
     required property var customObject
     required property var stringListProperty
 
@@ -49,14 +50,14 @@ QtObject {
         consoleCount();
         consoleCount();
 
-        var a = [1, 2];
+        const a = [1, 2];
-        var b = {a: "hello", d: 1 };
+        const b = { a: "hello", d: 1 };
-        b.toString = function() { return JSON.stringify(b) }
+        b.toString = function() { return JSON.stringify(b); }
-        var c
+        let c;
-        var d = 12;
+        const d = 12;
-        var e = function() { return 5;};
+        const e = function() { return 5; };
-        var f = true;
+        const f = true;
-        var g = {toString: function() { throw new Error('toString'); }};
+        const g = { toString: function() { throw new Error('toString'); } };
 
         console.log(a);
         console.log(b);
@@ -79,6 +80,6 @@ QtObject {
             return;
         }
 
-        throw ("console.log(exception) should have raised an exception");
+        throw "console.log(exception) should have raised an exception";
     }
 }

tests/auto/qml/qqmlconsole/tst_qqmlconsole.cpp

@@ -133,18 +133,27 @@ void tst_qqmlconsole::categorized_logging()
     QVERIFY(messageHandler.messages().contains("qt.test.warning: console.error"));
 
     QString emptyCategory = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(56).arg(5) +
-                            "QML LoggingCategory: Declaring the name of the LoggingCategory is mandatory and cannot be changed later !";
+                            "QML LoggingCategory: Declaring the name of a LoggingCategory is mandatory and cannot be changed later";
     QVERIFY(messageHandler.messages().contains(emptyCategory));
 
-    QString changedCategory = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(45).arg(5) +
+
-                            "QML LoggingCategory: The name of a LoggingCategory cannot be changed after the Item is created";
+    QString notChangedCategory = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(45).arg(5) +
+                            "QML LoggingCategory: The name of a LoggingCategory cannot be changed after the component is completed";
+    QVERIFY(!messageHandler.messages().contains(notChangedCategory));
+    QString changedCategory = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(50).arg(5) +
+                            "QML LoggingCategory: The name of a LoggingCategory cannot be changed after the component is completed";
     QVERIFY(messageHandler.messages().contains(changedCategory));
 
-    QString changedDefaultLogLevel = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(45).arg(5) +
+
-                            "QML LoggingCategory: The defaultLogLevel of a LoggingCategory cannot be changed after the Item is created";
+    QString notChangedDefaultLogLevel = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(45).arg(5) +
+                            "QML LoggingCategory: The defaultLogLevel of a LoggingCategory cannot be changed after the component is completed";
+    QVERIFY(!messageHandler.messages().contains(notChangedDefaultLogLevel));
+    QString changedDefaultLogLevel = "default: " + QString::fromLatin1("%1:%2:%3: ").arg(testUrl.toString()).arg(50).arg(5) +
+                            "QML LoggingCategory: The defaultLogLevel of a LoggingCategory cannot be changed after the component is completed";
     QVERIFY(messageHandler.messages().contains(changedDefaultLogLevel));
 
-    QString useEmptyCategory = "default: " + QString::fromLatin1("%1:%2: ").arg(testUrl.toString()).arg(75) +
+
+    QString useEmptyCategory = "default: " + QString::fromLatin1("%1:%2: ").arg(testUrl.toString()).arg(78) +
                             "Error: A QmlLoggingCatgory was provided without a valid name";
     QVERIFY(messageHandler.messages().contains(useEmptyCategory));
 
@@ -190,13 +199,13 @@ void tst_qqmlconsole::testAssert()
     QString assert1 = "This will fail\n"
             + QString::fromLatin1("expression for onCompleted (%1:%2)")
                       .arg(testUrl.toString())
-                      .arg(41);
+                      .arg(42);
 
     QString assert2 = "This will fail too\n"
-            + QString::fromLatin1("assertFail (%1:%2)\n").arg(testUrl.toString()).arg(34)
+            + QString::fromLatin1("assertFail (%1:%2)\n").arg(testUrl.toString()).arg(35)
             + QString::fromLatin1("expression for onCompleted (%1:%2)")
                       .arg(testUrl.toString())
-                      .arg(46);
+                      .arg(47);
 
     QTest::ignoreMessage(QtCriticalMsg, qPrintable(assert1));
     QTest::ignoreMessage(QtCriticalMsg, qPrintable(assert2));