CppEditor: Do not use clangd < 13

We will shortly need to use a command-line option that is new in clangd
13. Rather than starting to add checks for versions that won't work as
expected anyway, we simply refuse to use clangd < 13 now.

Change-Id: I42ec679e0f58449a2593cf92b4be7ed3101fa787
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/cppeditor/cppcodemodelsettings.cpp

@@ -34,6 +34,7 @@
 
 #include <utils/algorithm.h>
 #include <utils/qtcassert.h>
+#include <utils/qtcprocess.h>
 
 #include <QSettings>
 
@@ -312,6 +313,11 @@ ClangdSettings &ClangdSettings::instance()
     return settings;
 }
 
+bool ClangdSettings::useClangd() const
+{
+    return m_data.useClangd && clangdVersion(clangdFilePath()) >= QVersionNumber(13);
+}
+
 void ClangdSettings::setDefaultClangdPath(const FilePath &filePath)
 {
     g_defaultClangdFilePath = filePath;
@@ -333,6 +339,37 @@ void ClangdSettings::setData(const Data &data)
     }
 }
 
+static QVersionNumber getClangdVersion(const FilePath &clangdFilePath)
+{
+    Utils::QtcProcess clangdProc;
+    clangdProc.setCommand({clangdFilePath, {"--version"}});
+    clangdProc.start();
+    if (!clangdProc.waitForStarted() || !clangdProc.waitForFinished())
+        return{};
+    const QString output = clangdProc.allOutput();
+    static const QString versionPrefix = "clangd version ";
+    const int prefixOffset = output.indexOf(versionPrefix);
+    if (prefixOffset == -1)
+        return {};
+    return QVersionNumber::fromString(output.mid(prefixOffset + versionPrefix.length()));
+}
+
+QVersionNumber ClangdSettings::clangdVersion(const FilePath &clangdFilePath)
+{
+    const QDateTime timeStamp = clangdFilePath.lastModified();
+    const auto it = m_versionCache.find(clangdFilePath);
+    if (it == m_versionCache.end()) {
+        const QVersionNumber version = getClangdVersion(clangdFilePath);
+        m_versionCache.insert(clangdFilePath, qMakePair(timeStamp, version));
+        return version;
+    }
+    if (it->first != timeStamp) {
+        it->first = timeStamp;
+        it->second = getClangdVersion(clangdFilePath);
+    }
+    return it->second;
+}
+
 void ClangdSettings::loadSettings()
 {
     m_data.fromMap(Core::ICore::settings()->value(clangdSettingsKey()).toMap());

src/plugins/cppeditor/cppcodemodelsettings.h

@@ -29,8 +29,12 @@
 
 #include <utils/fileutils.h>
 
+#include <QDateTime>
+#include <QHash>
 #include <QObject>
+#include <QPair>
 #include <QStringList>
+#include <QVersionNumber>
 
 QT_BEGIN_NAMESPACE
 class QSettings;
@@ -117,7 +121,7 @@ public:
     ClangdSettings(const Data &data) : m_data(data) {}
 
     static ClangdSettings &instance();
-    bool useClangd() const { return m_data.useClangd; }
+    bool useClangd() const;
 
     static void setDefaultClangdPath(const Utils::FilePath &filePath);
     Utils::FilePath clangdFilePath() const;
@@ -129,6 +133,8 @@ public:
     void setData(const Data &data);
     Data data() const { return m_data; }
 
+    static QVersionNumber clangdVersion(const Utils::FilePath &clangdFilePath);
+
 #ifdef WITH_TESTS
     static void setUseClangd(bool use);
     static void setClangdFilePath(const Utils::FilePath &filePath);
@@ -144,6 +150,7 @@ private:
     void saveSettings();
 
     Data m_data;
+    static inline QHash<Utils::FilePath, QPair<QDateTime, QVersionNumber>> m_versionCache;
 };
 
 inline bool operator==(const ClangdSettings::Data &s1, const ClangdSettings::Data &s2)

src/plugins/cppeditor/cppcodemodelsettingspage.cpp

@@ -35,7 +35,6 @@
 #include <utils/algorithm.h>
 #include <utils/infolabel.h>
 #include <utils/pathchooser.h>
-#include <utils/qtcprocess.h>
 
 #include <QFormLayout>
 #include <QSpinBox>
@@ -285,30 +284,14 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
         if (!d->clangdChooser.isValid())
             return;
         const Utils::FilePath clangdPath = d->clangdChooser.filePath();
-        Utils::QtcProcess clangdProc;
+        const QVersionNumber clangdVersion = ClangdSettings::clangdVersion(clangdPath);
-        clangdProc.setCommand({clangdPath, {"--version"}});
-        clangdProc.start();
-        if (!clangdProc.waitForStarted() || !clangdProc.waitForFinished()) {
-            labelSetter.setWarning(tr("Failed to retrieve clangd version: %1")
-                                   .arg(clangdProc.exitMessage()));
-            return;
-        }
-        const QString output = clangdProc.allOutput();
-        static const QString versionPrefix = "clangd version ";
-        const int prefixOffset = output.indexOf(versionPrefix);
-        QVersionNumber clangdVersion;
-        if (prefixOffset != -1) {
-            clangdVersion = QVersionNumber::fromString(output.mid(prefixOffset
-                                                                  + versionPrefix.length()));
-        }
         if (clangdVersion.isNull()) {
             labelSetter.setWarning(tr("Failed to retrieve clangd version: "
                                       "Unexpected clangd output."));
             return;
         }
         if (clangdVersion < QVersionNumber(13)) {
-            labelSetter.setWarning(tr("The clangd version is %1, but %2 or greater is "
+            labelSetter.setWarning(tr("The clangd version is %1, but %2 or greater is required.")
-                                      "recommended for full functionality.")
                                    .arg(clangdVersion.toString()).arg(13));
             return;
         }