ClangCodeModel: Let user decide how to do the header/source switch

While clangd's AST matching can find source files at any location, it also
has a number of annoying bugs that break the functionality for some
users. This patch brings back the previous "try built-in first" logic, but
also lets users choose their preferred backend.

Task-number: QTCREATORBUG-29175
Change-Id: I6b854ed05652e6468509e5748a83a8f9bf76fc20
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

4 files changed, 66 insertions, 4 deletions

diff --git a/src/plugins/clangcodemodel/clangmodelmanagersupport.cpp b/src/plugins/clangcodemodel/clangmodelmanagersupport.cpp
index 1dd66db3cd..8aea72ce0e 100644
--- a/src/plugins/clangcodemodel/clangmodelmanagersupport.cpp
+++ b/src/plugins/clangcodemodel/clangmodelmanagersupport.cpp
@@ -352,10 +352,24 @@ void ClangModelManagerSupport::findUsages(const CursorInEditor &cursor) const
 
 void ClangModelManagerSupport::switchHeaderSource(const FilePath &filePath, bool inNextSplit)
 {
-    if (ClangdClient * const client = clientForFile(filePath))
-        client->switchHeaderSource(filePath, inNextSplit);
-    else
-        CppModelManager::switchHeaderSource(inNextSplit, CppModelManager::Backend::Builtin);
+    if (ClangdClient * const client = clientForFile(filePath)) {
+        switch (ClangdProjectSettings(client->project()).settings().headerSourceSwitchMode) {
+        case ClangdSettings::HeaderSourceSwitchMode::BuiltinOnly:
+            CppModelManager::switchHeaderSource(inNextSplit, CppModelManager::Backend::Builtin);
+            return;
+        case ClangdSettings::HeaderSourceSwitchMode::ClangdOnly:
+            client->switchHeaderSource(filePath, inNextSplit);
+            return;
+        case ClangdSettings::HeaderSourceSwitchMode::Both:
+            const FilePath otherFile = correspondingHeaderOrSource(filePath);
+            if (!otherFile.isEmpty())
+                openEditor(otherFile, inNextSplit);
+            else
+                client->switchHeaderSource(filePath, inNextSplit);
+            return;
+        }
+    }
+    CppModelManager::switchHeaderSource(inNextSplit, CppModelManager::Backend::Builtin);
 }
 
 void ClangModelManagerSupport::checkUnused(const Link &link, SearchResult *search,
diff --git a/src/plugins/cppeditor/cppcodemodelsettings.cpp b/src/plugins/cppeditor/cppcodemodelsettings.cpp
index 5919a97b84..2f4fdffab2 100644
--- a/src/plugins/cppeditor/cppcodemodelsettings.cpp
+++ b/src/plugins/cppeditor/cppcodemodelsettings.cpp
@@ -64,6 +64,9 @@ static QString useClangdKey() { return QLatin1String("UseClangdV7"); }
 static QString clangdPathKey() { return QLatin1String("ClangdPath"); }
 static QString clangdIndexingKey() { return QLatin1String("ClangdIndexing"); }
 static QString clangdIndexingPriorityKey() { return QLatin1String("ClangdIndexingPriority"); }
+static QString clangdHeaderSourceSwitchModeKey() {
+    return QLatin1String("ClangdHeaderSourceSwitchMode");
+}
 static QString clangdHeaderInsertionKey() { return QLatin1String("ClangdHeaderInsertion"); }
 static QString clangdThreadLimitKey() { return QLatin1String("ClangdThreadLimit"); }
 static QString clangdDocumentThresholdKey() { return QLatin1String("ClangdDocumentThreshold"); }
@@ -229,6 +232,16 @@ QString ClangdSettings::priorityToDisplayString(const IndexingPriority &priority
     return {};
 }
 
+QString ClangdSettings::headerSourceSwitchModeToDisplayString(HeaderSourceSwitchMode mode)
+{
+    switch (mode) {
+    case HeaderSourceSwitchMode::BuiltinOnly: return Tr::tr("Use Built-in Only");
+    case HeaderSourceSwitchMode::ClangdOnly: return Tr::tr("Use Clangd Only");
+    case HeaderSourceSwitchMode::Both: return Tr::tr("Try Both");
+    }
+    return {};
+}
+
 ClangdSettings &ClangdSettings::instance()
 {
     static ClangdSettings settings;
@@ -528,6 +541,7 @@ QVariantMap ClangdSettings::Data::toMap() const
                                                               : QString());
     map.insert(clangdIndexingKey(), indexingPriority != IndexingPriority::Off);
     map.insert(clangdIndexingPriorityKey(), int(indexingPriority));
+    map.insert(clangdHeaderSourceSwitchModeKey(), int(headerSourceSwitchMode));
     map.insert(clangdHeaderInsertionKey(), autoIncludeHeaders);
     map.insert(clangdThreadLimitKey(), workerThreadLimit);
     map.insert(clangdDocumentThresholdKey(), documentUpdateThreshold);
@@ -549,6 +563,8 @@ void ClangdSettings::Data::fromMap(const QVariantMap &map)
     const auto it = map.find(clangdIndexingKey());
     if (it != map.end() && !it->toBool())
         indexingPriority = IndexingPriority::Off;
+    headerSourceSwitchMode = HeaderSourceSwitchMode(map.value(clangdHeaderSourceSwitchModeKey(),
+                                                              int(headerSourceSwitchMode)).toInt());
     autoIncludeHeaders = map.value(clangdHeaderInsertionKey(), false).toBool();
     workerThreadLimit = map.value(clangdThreadLimitKey(), 0).toInt();
     documentUpdateThreshold = map.value(clangdDocumentThresholdKey(), 500).toInt();
diff --git a/src/plugins/cppeditor/cppcodemodelsettings.h b/src/plugins/cppeditor/cppcodemodelsettings.h
index 7bfdc2e85e..c22fb88faa 100644
--- a/src/plugins/cppeditor/cppcodemodelsettings.h
+++ b/src/plugins/cppeditor/cppcodemodelsettings.h
@@ -84,9 +84,11 @@ class CPPEDITOR_EXPORT ClangdSettings : public QObject
     Q_OBJECT
 public:
     enum class IndexingPriority { Off, Background, Normal, Low, };
+    enum class HeaderSourceSwitchMode { BuiltinOnly, ClangdOnly, Both };
 
     static QString priorityToString(const IndexingPriority &priority);
     static QString priorityToDisplayString(const IndexingPriority &priority);
+    static QString headerSourceSwitchModeToDisplayString(HeaderSourceSwitchMode mode);
 
     class CPPEDITOR_EXPORT Data
     {
@@ -103,6 +105,7 @@ public:
                     && s1.diagnosticConfigId == s2.diagnosticConfigId
                     && s1.workerThreadLimit == s2.workerThreadLimit
                     && s1.indexingPriority == s2.indexingPriority
+                    && s1.headerSourceSwitchMode == s2.headerSourceSwitchMode
                     && s1.autoIncludeHeaders == s2.autoIncludeHeaders
                     && s1.documentUpdateThreshold == s2.documentUpdateThreshold
                     && s1.sizeThresholdEnabled == s2.sizeThresholdEnabled
@@ -123,6 +126,7 @@ public:
         qint64 sizeThresholdInKb = 1024;
         bool useClangd = true;
         IndexingPriority indexingPriority = IndexingPriority::Low;
+        HeaderSourceSwitchMode headerSourceSwitchMode = HeaderSourceSwitchMode::Both;
         bool autoIncludeHeaders = false;
         bool sizeThresholdEnabled = false;
         bool haveCheckedHardwareReqirements = false;
@@ -143,6 +147,7 @@ public:
     static void setCustomDiagnosticConfigs(const ClangDiagnosticConfigs &configs);
     Utils::FilePath clangdFilePath() const;
     IndexingPriority indexingPriority() const { return m_data.indexingPriority; }
+    HeaderSourceSwitchMode headerSourceSwitchMode() const { return m_data.headerSourceSwitchMode; }
     bool autoIncludeHeaders() const { return m_data.autoIncludeHeaders; }
     int workerThreadLimit() const { return m_data.workerThreadLimit; }
     int documentUpdateThreshold() const { return m_data.documentUpdateThreshold; }
diff --git a/src/plugins/cppeditor/cppcodemodelsettingspage.cpp b/src/plugins/cppeditor/cppcodemodelsettingspage.cpp
index 00224f5d90..88f5bf0de8 100644
--- a/src/plugins/cppeditor/cppcodemodelsettingspage.cpp
+++ b/src/plugins/cppeditor/cppcodemodelsettingspage.cpp
@@ -192,6 +192,7 @@ class ClangdSettingsWidget::Private
 public:
     QCheckBox useClangdCheckBox;
     QComboBox indexingComboBox;
+    QComboBox headerSourceSwitchComboBox;
     QCheckBox autoIncludeHeadersCheckBox;
     QCheckBox sizeThresholdCheckBox;
     QSpinBox threadLimitSpinBox;
@@ -220,6 +221,12 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
         "cores unused.</p>"
         "<p>Normal Priority: Reduced priority compared to interactive work.</p>"
         "Low Priority: Same priority as other clangd work.");
+    const QString headerSourceSwitchToolTip = Tr::tr(
+        "<p>Which C/C++ backend to use when switching between header and source file."
+        "<p>The clangd implementation has more capabilities, but also has some bugs not present "
+        "in the built-in variant."
+        "<p>When \"Try Both\" is selected, clangd will be employed only if the built-in variant "
+        "does not find anything.");
     const QString workerThreadsToolTip = Tr::tr(
         "Number of worker threads used by clangd. Background indexing also uses this many "
         "worker threads.");
@@ -249,6 +256,15 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
             d->indexingComboBox.setCurrentIndex(d->indexingComboBox.count() - 1);
     }
     d->indexingComboBox.setToolTip(indexingToolTip);
+    using SwitchMode = ClangdSettings::HeaderSourceSwitchMode;
+    for (SwitchMode mode : {SwitchMode::BuiltinOnly, SwitchMode::ClangdOnly, SwitchMode::Both}) {
+        d->headerSourceSwitchComboBox.addItem(
+            ClangdSettings::headerSourceSwitchModeToDisplayString(mode), int(mode));
+        if (mode == settings.headerSourceSwitchMode())
+            d->headerSourceSwitchComboBox.setCurrentIndex(
+                d->headerSourceSwitchComboBox.count() - 1);
+    }
+    d->headerSourceSwitchComboBox.setToolTip(headerSourceSwitchToolTip);
     d->autoIncludeHeadersCheckBox.setText(Tr::tr("Insert header files on completion"));
     d->autoIncludeHeadersCheckBox.setChecked(settings.autoIncludeHeaders());
     d->autoIncludeHeadersCheckBox.setToolTip(autoIncludeToolTip);
@@ -294,6 +310,13 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
     indexingPriorityLabel->setToolTip(indexingToolTip);
     formLayout->addRow(indexingPriorityLabel, indexingPriorityLayout);
 
+    const auto headerSourceSwitchLayout = new QHBoxLayout;
+    headerSourceSwitchLayout->addWidget(&d->headerSourceSwitchComboBox);
+    headerSourceSwitchLayout->addStretch(1);
+    const auto headerSourceSwitchLabel = new QLabel(Tr::tr("Header/source switch mode:"));
+    headerSourceSwitchLabel->setToolTip(headerSourceSwitchToolTip);
+    formLayout->addRow(headerSourceSwitchLabel, headerSourceSwitchLayout);
+
     const auto threadLimitLayout = new QHBoxLayout;
     threadLimitLayout->addWidget(&d->threadLimitSpinBox);
     threadLimitLayout->addStretch(1);
@@ -449,6 +472,8 @@ ClangdSettingsWidget::ClangdSettingsWidget(const ClangdSettings::Data &settingsD
             this, &ClangdSettingsWidget::settingsDataChanged);
     connect(&d->indexingComboBox, &QComboBox::currentIndexChanged,
             this, &ClangdSettingsWidget::settingsDataChanged);
+    connect(&d->headerSourceSwitchComboBox, &QComboBox::currentIndexChanged,
+            this, &ClangdSettingsWidget::settingsDataChanged);
     connect(&d->autoIncludeHeadersCheckBox, &QCheckBox::toggled,
             this, &ClangdSettingsWidget::settingsDataChanged);
     connect(&d->threadLimitSpinBox, &QSpinBox::valueChanged,
@@ -479,6 +504,8 @@ ClangdSettings::Data ClangdSettingsWidget::settingsData() const
     data.executableFilePath = d->clangdChooser.filePath();
     data.indexingPriority = ClangdSettings::IndexingPriority(
         d->indexingComboBox.currentData().toInt());
+    data.headerSourceSwitchMode = ClangdSettings::HeaderSourceSwitchMode(
+        d->headerSourceSwitchComboBox.currentData().toInt());
     data.autoIncludeHeaders = d->autoIncludeHeadersCheckBox.isChecked();
     data.workerThreadLimit = d->threadLimitSpinBox.value();
     data.documentUpdateThreshold = d->documentUpdateThreshold.value();