Python: optimize venv and pip checks

Checking for the venv and pip module can take some time. Since this is
done now whenever the kits are validated this has performance
implications for multiple actions. For example showing the target
selector wizard page or opening/switching sessions.

Use a cache to reduce the number of python processes started to check
the existence of the modules, and if the module can be found store that
info in a persistent store to avoid checking it again after a restart.

Change-Id: Ib899da0e6b2da28fbee2b5baff7f923e4595260a
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

1 files changed, 47 insertions, 14 deletions

diff --git a/src/plugins/python/pythonutils.cpp b/src/plugins/python/pythonutils.cpp
index 096520dd7ec..71cbc5763d2 100644
--- a/src/plugins/python/pythonutils.cpp
+++ b/src/plugins/python/pythonutils.cpp
@@ -19,6 +19,7 @@
 
 #include <utils/algorithm.h>
 #include <utils/mimeutils.h>
+#include <utils/persistentcachestore.h>
 #include <utils/process.h>
 
 #include <QReadLocker>
@@ -169,8 +170,8 @@ PythonProject *pythonProjectForFile(const FilePath &pythonFile)
     return nullptr;
 }
 
-void createVenv(const Utils::FilePath &python,
-                const Utils::FilePath &venvPath,
+void createVenv(const FilePath &python,
+                const FilePath &venvPath,
                 const std::function<void(bool)> &callback)
 {
     QTC_ASSERT(python.isExecutableFile(), callback(false); return);
@@ -189,25 +190,57 @@ void createVenv(const Utils::FilePath &python,
     process->start();
 }
 
-bool isVenvPython(const Utils::FilePath &python)
+bool isVenvPython(const FilePath &python)
 {
     return python.parentDir().parentDir().contains("pyvenv.cfg");
 }
 
-bool venvIsUsable(const Utils::FilePath &python)
+bool venvIsUsable(const FilePath &python)
 {
-    Process process;
-    process.setCommand({python, QStringList{"-m", "venv", "-h"}});
-    process.runBlocking();
-    return process.result() == ProcessResult::FinishedWithSuccess;
+    static QHash<FilePath, bool> cache;
+    auto it = cache.find(python);
+    if (it == cache.end()) {
+        auto store = PersistentCacheStore::byKey(keyFromString("pyVenvIsUsable"));
+        if (store && store->value(keyFromString(python.toString())).toBool()) {
+            cache.insert(python, true);
+            return true;
+        }
+        Process process;
+        process.setCommand({python, QStringList{"-m", "venv", "-h"}});
+        process.runBlocking();
+        const bool usable = process.result() == ProcessResult::FinishedWithSuccess;
+        if (usable) {
+            Store newStore = store.value_or(Store{});
+            newStore.insert(keyFromString(python.toString()), true);
+            PersistentCacheStore::write(keyFromString("pyVenvIsUsable"), newStore);
+        }
+        it = cache.insert(python, usable);
+    }
+    return *it;
 }
 
-bool pipIsUsable(const Utils::FilePath &python)
+bool pipIsUsable(const FilePath &python)
 {
-    Process process;
-    process.setCommand({python, QStringList{"-m", "pip", "-V"}});
-    process.runBlocking();
-    return process.result() == ProcessResult::FinishedWithSuccess;
+    static QHash<FilePath, bool> cache;
+    auto it = cache.find(python);
+    if (it == cache.end()) {
+        auto store = PersistentCacheStore::byKey(keyFromString("pyPipIsUsable"));
+        if (store && store->value(keyFromString(python.toString())).toBool()) {
+            cache.insert(python, true);
+            return true;
+        }
+        Process process;
+        process.setCommand({python, QStringList{"-m", "pip", "-h"}});
+        process.runBlocking();
+        const bool usable = process.result() == ProcessResult::FinishedWithSuccess;
+        if (usable) {
+            Store newStore = store.value_or(Store{});
+            newStore.insert(keyFromString(python.toString()), true);
+            PersistentCacheStore::write(keyFromString("pyPipIsUsable"), newStore);
+        }
+        it = cache.insert(python, usable);
+    }
+    return *it;
 }
 
 QString pythonVersion(const FilePath &python)
@@ -225,7 +258,7 @@ QString pythonVersion(const FilePath &python)
     Process p;
     p.setCommand({python, {"--version"}});
     p.runBlocking();
-    if (p.result() == Utils::ProcessResult::FinishedWithSuccess) {
+    if (p.result() == ProcessResult::FinishedWithSuccess) {
         const QString version = p.readAllStandardOutput().trimmed();
         QWriteLocker locker(&lock);
         versionCache.insert(python, version);