AutoTest: Make scan thread limit customizable

Allow users to specify the tread limit used when scanning
for tests.
By default we continue to use a fourth of the available
logical CPUs.

Task-number: QTCREATORBUG-29301
Change-Id: Ic92a4d0908093c0664aa1ba924e0c17dfd0082f9
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/plugins/autotest/testcodeparser.cpp

@@ -5,6 +5,7 @@
 
 #include "autotestconstants.h"
 #include "autotesttr.h"
+#include "testsettings.h"
 #include "testtreemodel.h"
 
 #include <coreplugin/editormanager/editormanager.h>
@@ -360,7 +361,11 @@ void TestCodeParser::scanForTests(const QSet<FilePath> &filePaths,
 
     using namespace Tasking;
 
-    QList<GroupItem> tasks{parallelLimit(std::max(QThread::idealThreadCount() / 4, 1))};
+    int limit = TestSettings::instance()->scanThreadLimit();
+    if (limit == 0)
+        limit = std::max(QThread::idealThreadCount() / 4, 1);
+    qCDebug(LOG) << "Using" << limit << "threads for scan.";
+    QList<GroupItem> tasks{parallelLimit(limit)};
     for (const FilePath &file : filteredFiles) {
         const auto setup = [this, codeParsers, file](Async<TestParseResultPtr> &async) {
             async.setConcurrentCallData(parseFileForTests, codeParsers, file);

src/plugins/autotest/testsettings.cpp

@@ -28,6 +28,12 @@ TestSettings::TestSettings()
 
     setSettingsGroup(Constants::SETTINGSGROUP);
 
+    scanThreadLimit.setSettingsKey("ScanThreadLimit");
+    scanThreadLimit.setDefaultValue(0);
+    scanThreadLimit.setRange(0, QThread::idealThreadCount());
+    scanThreadLimit.setSpecialValueText("Automatic");
+    scanThreadLimit.setToolTip(Tr::tr("Number of worker threads used when scanning for tests."));
+
     timeout.setSettingsKey("Timeout");
     timeout.setDefaultValue(defaultTimeout);
     timeout.setRange(5000, 36'000'000); // 36 Mio ms = 36'000 s = 10 h

src/plugins/autotest/testsettings.h

@@ -32,6 +32,7 @@ public:
     void toSettings(QSettings *s) const;
     void fromSettings(QSettings *s);
 
+    Utils::IntegerAspect scanThreadLimit{this};
     Utils::IntegerAspect timeout{this};
     Utils::BoolAspect omitInternalMsg{this};
     Utils::BoolAspect omitRunConfigWarn{this};

src/plugins/autotest/testsettingspage.cpp

@@ -51,6 +51,8 @@ TestSettingsWidget::TestSettingsWidget()
 {
     auto timeoutLabel = new QLabel(Tr::tr("Timeout:"));
     timeoutLabel->setToolTip(Tr::tr("Timeout used when executing each test case."));
+    auto scanThreadLabel = new QLabel(Tr::tr("Scan threads:"));
+    scanThreadLabel->setToolTip("Number of worker threads used when scanning for tests.");
 
     m_frameworkTreeWidget = new QTreeWidget;
     m_frameworkTreeWidget->setRootIsDecorated(false);
@@ -83,6 +85,7 @@ TestSettingsWidget::TestSettingsWidget()
     Group generalGroup {
         title(Tr::tr("General")),
         Column {
+            Row { scanThreadLabel, s.scanThreadLimit, st },
             s.omitInternalMsg,
             s.omitRunConfigWarn,
             s.limitResultOutput,