ProjectExplorer: run vcvars bat in parallel

Instead of collecting the environment differences for all
MsvcToolChain when needed, start an async job at object construction.

This reduces the blocking startup time depending on the Toolchain count
up to 8 seconds.

Change-Id: Ie004956f290d7555f88226c7f4d9f7eb37ec2261
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/projectexplorer/msvctoolchain.cpp

@@ -27,15 +27,17 @@
 
 #include "msvcparser.h"
 #include "projectexplorerconstants.h"
+#include "toolchainmanager.h"
 
 #include <utils/algorithm.h>
+#include <utils/hostosinfo.h>
+#include <utils/optional.h>
+#include <utils/qtcassert.h>
 #include <utils/qtcfallthrough.h>
 #include <utils/synchronousprocess.h>
-#include <utils/winutils.h>
-#include <utils/qtcassert.h>
-#include <utils/hostosinfo.h>
+#include <utils/runextensions.h>
 #include <utils/temporarydirectory.h>
-#include <utils/optional.h>
+#include <utils/winutils.h>
 
 #include <QDir>
 #include <QFileInfo>
@@ -520,13 +522,14 @@ static QString winExpandDelayedEnvReferences(QString in, const Utils::Environmen
     return in;
 }
 
-QList<Utils::EnvironmentItem> MsvcToolChain::environmentModifications() const
+void MsvcToolChain::environmentModifications(QFutureInterface<QList<Utils::EnvironmentItem>> &future,
+                                             QString vcvarsBat, QString varsBatArg)
 {
     const Utils::Environment inEnv = Utils::Environment::systemEnvironment();
     Utils::Environment outEnv;
     QMap<QString, QString> envPairs;
-    if (!generateEnvironmentSettings(inEnv, m_vcvarsBat, m_varsBatArg, envPairs))
-        return QList<Utils::EnvironmentItem>();
+    if (!generateEnvironmentSettings(inEnv, vcvarsBat, varsBatArg, envPairs))
+        return;
 
     // Now loop through and process them
     for (auto envIter = envPairs.cbegin(), eend = envPairs.cend(); envIter != eend; ++envIter) {
@@ -552,13 +555,21 @@ QList<Utils::EnvironmentItem> MsvcToolChain::environmentModifications() const
         }
     }
 
-    return diff;
+    future.reportResult(diff);
+}
+
+void MsvcToolChain::initEnvModWatcher(const QFuture<QList<Utils::EnvironmentItem> > &future)
+{
+    QObject::connect(&m_envModWatcher, &QFutureWatcherBase::resultReadyAt, [&]() {
+        m_environmentModifications = m_envModWatcher.result();
+    });
+    m_envModWatcher.setFuture(future);
 }
 
 Utils::Environment MsvcToolChain::readEnvironmentSetting(const Utils::Environment& env) const
 {
-    if (m_environmentModifications.isEmpty())
-        m_environmentModifications = environmentModifications();
+    if (m_environmentModifications.isEmpty() && m_envModWatcher.isRunning())
+        m_envModWatcher.waitForFinished();
     Utils::Environment result = env;
     result.modify(m_environmentModifications);
     return result;
@@ -574,11 +585,26 @@ MsvcToolChain::MsvcToolChain(const QString &name, const Abi &abi,
     MsvcToolChain(Constants::MSVC_TOOLCHAIN_TYPEID, name, abi, varsBat, varsBatArg, l, d)
 { }
 
+MsvcToolChain::MsvcToolChain(const MsvcToolChain &other)
+    : AbstractMsvcToolChain(other.typeId(), other.language(), other.detection(), other.targetAbi(), other.varsBat())
+    , m_environmentModifications(other.m_environmentModifications)
+    , m_varsBatArg(other.m_varsBatArg)
+{
+    if (!other.m_envModWatcher.isRunning())
+        initEnvModWatcher(other.m_envModWatcher.future());
+
+    setDisplayName(other.displayName());
+}
+
 MsvcToolChain::MsvcToolChain(Core::Id typeId, const QString &name, const Abi &abi,
                              const QString &varsBat, const QString &varsBatArg, Core::Id l,
-                             Detection d) : AbstractMsvcToolChain(typeId, l, d, abi, varsBat),
-    m_varsBatArg(varsBatArg)
+                             Detection d)
+    : AbstractMsvcToolChain(typeId, l, d, abi, varsBat)
+    , m_varsBatArg(varsBatArg)
 {
+    initEnvModWatcher(Utils::runAsync(&MsvcToolChain::environmentModifications,
+                                      varsBat, varsBatArg));
+
     Q_ASSERT(!name.isEmpty());
 
     setDisplayName(name);

src/plugins/projectexplorer/msvctoolchain.h

@@ -29,6 +29,8 @@
 #include "abi.h"
 #include "toolchainconfigwidget.h"
 
+#include <QFutureWatcher>
+
 QT_FORWARD_DECLARE_CLASS(QLabel)
 QT_FORWARD_DECLARE_CLASS(QVersionNumber)
 
@@ -57,6 +59,7 @@ public:
     explicit MsvcToolChain(const QString &name, const Abi &abi,
                            const QString &varsBat, const QString &varsBatArg,
                            Core::Id l, Detection d = ManualDetection);
+    MsvcToolChain(const MsvcToolChain &other);
     MsvcToolChain();
 
     Utils::FileNameList suggestedMkspecList() const override;
@@ -86,9 +89,12 @@ protected:
                                 const Utils::Environment &env) const override;
 
 private:
-    QList<Utils::EnvironmentItem> environmentModifications() const;
+    static void environmentModifications(QFutureInterface<QList<Utils::EnvironmentItem> > &future,
+                                         QString vcvarsBat, QString varsBatArg);
+    void initEnvModWatcher(const QFuture<QList<Utils::EnvironmentItem>> &future);
 
     mutable QList<Utils::EnvironmentItem> m_environmentModifications;
+    mutable QFutureWatcher<QList<Utils::EnvironmentItem>> m_envModWatcher;
 
     QString m_varsBatArg; // Argument
 };