Better error reporting when failing to open settings database

Mention the filename and the driver error text (though this last thing
doesn't seem that useful). Also, don't spam with failures afterwards
when the database failed to open.

src/plugins/coreplugin/settingsdatabase.cpp

@@ -31,6 +31,7 @@
 
 #include <QtCore/QMap>
 #include <QtSql/QSqlDatabase>
+#include <QtSql/QSqlError>
 #include <QtSql/QSqlQuery>
 #include <QDebug>
 
@@ -101,16 +102,18 @@ SettingsDatabase::SettingsDatabase(const QString &path,
 
     d->m_db = QSqlDatabase::addDatabase("QSQLITE", QLatin1String("settings"));
     d->m_db.setDatabaseName(fileName);
-    if (!d->m_db.open())
+    if (!d->m_db.open()) {
-        qWarning() << "Warning: Failed to open settings database!";
+        qWarning().nospace() << "Warning: Failed to open settings database at " << fileName << " ("
-
+                             << d->m_db.lastError().driverText() << ")";
+    } else {
         // Create the settings table if it doesn't exist yet
         QSqlQuery query(d->m_db);
         query.prepare(QLatin1String("CREATE TABLE IF NOT EXISTS settings ("
                                     "key PRIMARY KEY ON CONFLICT REPLACE, "
                                     "value)"));
-    if (d->m_db.isOpen() && !query.exec())
+        if (!query.exec())
-        qWarning() << "Warning: Failed to prepare settings database!";
+            qWarning().nospace() << "Warning: Failed to prepare settings database! ("
+                                 << query.lastError().driverText() << ")";
 
         // Retrieve all available keys (values are retrieved lazily)
         if (query.exec(QLatin1String("SELECT key FROM settings"))) {
@@ -118,6 +121,7 @@ SettingsDatabase::SettingsDatabase(const QString &path,
                 d->m_settings.insert(query.value(0).toString(), QVariant());
             }
         }
+    }
 }
 
 SettingsDatabase::~SettingsDatabase()
@@ -135,6 +139,9 @@ void SettingsDatabase::setValue(const QString &key, const QVariant &value)
     // Add to cache
     d->m_settings.insert(effectiveKey, value);
 
+    if (!d->m_db.isOpen())
+        return;
+
     // Instant apply (TODO: Delay writing out settings)
     QSqlQuery query(d->m_db);
     query.prepare(QLatin1String("INSERT INTO settings VALUES (?, ?)"));
@@ -154,7 +161,7 @@ QVariant SettingsDatabase::value(const QString &key, const QVariant &defaultValu
     SettingsMap::const_iterator i = d->m_settings.constFind(effectiveKey);
     if (i != d->m_settings.constEnd() && i.value().isValid()) {
         value = i.value();
-    } else {
+    } else if (d->m_db.isOpen()) {
         // Try to read the value from the database
         QSqlQuery query(d->m_db);
         query.prepare(QLatin1String("SELECT value FROM settings WHERE key = ?"));
@@ -183,13 +190,6 @@ void SettingsDatabase::remove(const QString &key)
 {
     const QString effectiveKey = d->effectiveKey(key);
 
-    // Delete keys from the database
-    QSqlQuery query(d->m_db);
-    query.prepare(QLatin1String("DELETE FROM settings WHERE key = ? OR key LIKE ?"));
-    query.addBindValue(effectiveKey);
-    query.addBindValue(effectiveKey + QLatin1String("/%"));
-    query.exec();
-
     // Remove keys from the cache
     foreach (const QString &k, d->m_settings.keys()) {
         // Either it's an exact match, or it matches up to a /
@@ -200,6 +200,16 @@ void SettingsDatabase::remove(const QString &key)
             d->m_settings.remove(k);
         }
     }
+
+    if (!d->m_db.isOpen())
+        return;
+
+    // Delete keys from the database
+    QSqlQuery query(d->m_db);
+    query.prepare(QLatin1String("DELETE FROM settings WHERE key = ? OR key LIKE ?"));
+    query.addBindValue(effectiveKey);
+    query.addBindValue(effectiveKey + QLatin1String("/%"));
+    query.exec();
 }
 
 void SettingsDatabase::beginGroup(const QString &prefix)