Python: optimize the pip and venv checks

Those checks can take an considerable amount of time. So instead of
running them the first time we want to check this info run them in the
background as soon as we have loaded the python settings.

Change-Id: I287acd2a5fd7b053873257238f7dfbaa9cf00170
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/python/pythonsettings.cpp

@@ -855,11 +855,18 @@ QString PythonSettings::pylsConfiguration()
     return settingsInstance->m_pylsConfiguration;
 }
 
+static void cacheVenvAndPipUsability(const Interpreter &interpreter)
+{
+    Utils::asyncRun(&venvIsUsable, interpreter.command);
+    Utils::asyncRun(&pipIsUsable, interpreter.command);
+}
+
 void PythonSettings::addInterpreter(const Interpreter &interpreter, bool isDefault)
 {
     if (Utils::anyOf(settingsInstance->m_interpreters, Utils::equal(&Interpreter::id, interpreter.id)))
         return;
     settingsInstance->m_interpreters.append(interpreter);
+    cacheVenvAndPipUsability(interpreter);
     if (isDefault)
         settingsInstance->m_defaultInterpreterId = interpreter.id;
     saveSettings();
@@ -1026,8 +1033,12 @@ void PythonSettings::initFromSettings(QtcSettings *settings)
     const auto [valid, outdatedInterpreters] = Utils::partition(m_interpreters, keepInterpreter);
     m_interpreters = valid;
 
-    if (!settings->value(kitsGeneratedKey, false).toBool()) {
+    const bool kitsGenerated = settings->value(kitsGeneratedKey, false).toBool();
-        for (const Interpreter &interpreter : m_interpreters) {
+    if (kitsGenerated)
+        fixupPythonKits();
+    for (const Interpreter &interpreter : std::as_const(m_interpreters)) {
+        cacheVenvAndPipUsability(interpreter);
+        if (!kitsGenerated) {
             if (interpreter.autoDetected) {
                 const FilePath &cmd = interpreter.command;
                 if (!cmd.isLocal() || cmd.parentDir().pathAppended("activate").exists())
@@ -1035,8 +1046,6 @@ void PythonSettings::initFromSettings(QtcSettings *settings)
             }
             addKitsForInterpreter(interpreter, false);
         }
-    } else {
-        fixupPythonKits();
     }
 
     for (const Interpreter &outdated : outdatedInterpreters)

src/plugins/python/pythonutils.cpp

@@ -20,6 +20,7 @@
 #include <utils/algorithm.h>
 #include <utils/mimeutils.h>
 #include <utils/qtcprocess.h>
+#include <utils/synchronizedvalue.h>
 
 #include <QReadLocker>
 
@@ -192,31 +193,37 @@ bool isVenvPython(const FilePath &python)
     return python.parentDir().parentDir().pathAppended("pyvenv.cfg").exists();
 }
 
-static bool isUsableHelper(QHash<FilePath, bool> *cache, const QString &keyString,
+static bool isUsableHelper(
-                           const QString &commandArg, const FilePath &python)
+    SynchronizedValue<QHash<FilePath, bool>> *cache,
+    const QString &commandArg,
+    const FilePath &python)
 {
-    auto it = cache->find(python);
+    std::optional<bool> result;
-    if (it == cache->end()) {
+    cache->read([&result, python](const QHash<FilePath, bool> &cache) {
-        const Key key = keyFromString(keyString);
+        if (auto it = cache.find(python); it != cache.end())
+            result = it.value();
+    });
+    if (result)
+        return *result;
+
     Process process;
     process.setCommand({python, {"-m", commandArg, "-h"}});
     process.runBlocking();
     const bool usable = process.result() == ProcessResult::FinishedWithSuccess;
-        it = cache->insert(python, usable);
+    cache->writeLocked()->insert(python, usable);
-    }
+    return usable;
-    return *it;
 }
 
 bool venvIsUsable(const FilePath &python)
 {
-    static QHash<FilePath, bool> cache;
+    static SynchronizedValue<QHash<FilePath, bool>> cache;
-    return isUsableHelper(&cache, "pyVenvIsUsable", "venv", python);
+    return isUsableHelper(&cache, "venv", python);
 }
 
 bool pipIsUsable(const FilePath &python)
 {
-    static QHash<FilePath, bool> cache;
+    static SynchronizedValue<QHash<FilePath, bool>> cache;
-    return isUsableHelper(&cache, "pyPipIsUsable", "pip", python);
+    return isUsableHelper(&cache, "pip", python);
 }
 
 QString pythonVersion(const FilePath &python)