ClangCodeModel: Use project-specific clangd client, if possible

If we open a file that does not belong to a currently open project, there
is a good chance that the current project's parse context is a better fit
for the file than the fallback client's.

Fixes: QTCREATORBUG-26697
Change-Id: I6c17e275b047602c51364f3203b3f0a3e74a49fc
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -58,6 +58,7 @@
 #include <projectexplorer/buildsystem.h>
 #include <projectexplorer/project.h>
 #include <projectexplorer/projectnodes.h>
+#include <projectexplorer/projecttree.h>
 #include <projectexplorer/session.h>
 #include <projectexplorer/target.h>
 
@@ -85,6 +86,13 @@ static CppEditor::CppModelManager *cppModelManager()
     return CppEditor::CppModelManager::instance();
 }
 
+static ProjectExplorer::Project *fallbackProject()
+{
+    if (ProjectExplorer::Project * const p = ProjectExplorer::ProjectTree::currentProject())
+        return p;
+    return ProjectExplorer::SessionManager::startupProject();
+}
+
 static const QList<TextEditor::BaseTextEditor *> allCppEditors()
 {
     QList<TextEditor::BaseTextEditor *> cppEditors;
@@ -148,10 +156,7 @@ ClangModelManagerSupport::ClangModelManagerSupport()
     connect(sessionManager, &ProjectExplorer::SessionManager::aboutToRemoveProject,
             this, &ClangModelManagerSupport::onAboutToRemoveProject);
     connect(sessionManager, &ProjectExplorer::SessionManager::projectRemoved,
-            this, [this] {
-        if (ClangdClient * const fallbackClient = clientForProject(nullptr))
-            claimNonProjectSources(fallbackClient);
-    });
+            this, [this] { claimNonProjectSources(clientForProject(fallbackProject())); });
 
     CppEditor::ClangdSettings::setDefaultClangdPath(Core::ICore::clangdExecutable(CLANG_BINDIR));
     connect(&CppEditor::ClangdSettings::instance(), &CppEditor::ClangdSettings::changed,
@@ -369,13 +374,16 @@ void ClangModelManagerSupport::updateLanguageClient(
             // Acquaint the client with all open C++ documents for this project.
             bool hasDocuments = false;
             for (TextEditor::BaseTextEditor * const editor : allCppEditors()) {
-                const Utils::FilePath filePath = editor->textDocument()->filePath();
-                if (!project->isKnownFile(filePath))
-                    continue;
+                TextEditor::TextDocument * const doc = editor->textDocument();
+                const Client * const currentClient = LanguageClientManager::clientForDocument(doc);
+                if (!currentClient || !currentClient->project()
+                        || currentClient->state() != Client::Initialized
+                        || project->isKnownFile(doc->filePath())) {
                     LanguageClientManager::openDocumentWithClient(editor->textDocument(), client);
-                ClangEditorDocumentProcessor::clearTextMarks(filePath);
+                    ClangEditorDocumentProcessor::clearTextMarks(doc->filePath());
                     hasDocuments = true;
                 }
+            }
 
             if (client->state() == Client::Initialized)
                 updateParserConfig();
@@ -443,7 +451,7 @@ ClangdClient *ClangModelManagerSupport::clientForProject(
 
 ClangdClient *ClangModelManagerSupport::clientForFile(const Utils::FilePath &file) const
 {
-    return clientForProject(ProjectExplorer::SessionManager::projectForFile(file));
+    return qobject_cast<ClangdClient *>(LanguageClientManager::clientForFilePath(file));
 }
 
 ClangdClient *ClangModelManagerSupport::createClient(ProjectExplorer::Project *project,
@@ -454,15 +462,19 @@ ClangdClient *ClangModelManagerSupport::createClient(ProjectExplorer::Project *p
     return client;
 }
 
-void ClangModelManagerSupport::claimNonProjectSources(ClangdClient *fallbackClient)
+void ClangModelManagerSupport::claimNonProjectSources(ClangdClient *client)
 {
+    if (!client)
+        return;
     for (TextEditor::BaseTextEditor * const editor : allCppEditors()) {
-        if (ProjectExplorer::SessionManager::projectForFile(editor->textDocument()->filePath()))
+        if (Client * const currentClient = LanguageClientManager::clientForDocument(
+                    editor->textDocument());
+                currentClient && currentClient->state() == Client::Initialized
+                && (currentClient == client || currentClient->project())) {
             continue;
-        if (!fallbackClient->documentOpen(editor->textDocument())) {
-            ClangEditorDocumentProcessor::clearTextMarks(editor->textDocument()->filePath());
-            fallbackClient->openDocument(editor->textDocument());
         }
+        ClangEditorDocumentProcessor::clearTextMarks(editor->textDocument()->filePath());
+        client->openDocument(editor->textDocument());
     }
 }
 
@@ -562,8 +574,10 @@ void ClangModelManagerSupport::onEditorOpened(Core::IEditor *editor)
 
         // TODO: Ensure that not fully loaded documents are updated?
 
-        ProjectExplorer::Project * const project
+        ProjectExplorer::Project * project
                 = ProjectExplorer::SessionManager::projectForFile(document->filePath());
+        if (!project)
+            project = fallbackProject();
         if (ClangdClient * const client = clientForProject(project))
             LanguageClientManager::openDocumentWithClient(textDocument, client);
     }

src/plugins/clangcodemodel/clangmodelmanagersupport.h

@@ -134,7 +134,7 @@ private:
     void updateLanguageClient(ProjectExplorer::Project *project,
                               const CppEditor::ProjectInfo::ConstPtr &projectInfo);
     ClangdClient *createClient(ProjectExplorer::Project *project, const Utils::FilePath &jsonDbDir);
-    void claimNonProjectSources(ClangdClient *fallbackClient);
+    void claimNonProjectSources(ClangdClient *client);
     void watchForExternalChanges();
     void watchForInternalChanges();
 

src/plugins/clangcodemodel/test/clangdtests.cpp

@@ -2036,7 +2036,7 @@ void ClangdTestExternalChanges::test()
     QVERIFY(waitForSignalOrTimeout(ClangModelManagerSupport::instance(),
                                    &ClangModelManagerSupport::createdClient, timeOutInMs()));
     ClangdClient * const newClient = ClangModelManagerSupport::instance()
-            ->clientForFile(filePath("main.cpp"));
+            ->clientForProject(project());
     QVERIFY(newClient);
     QVERIFY(newClient != oldClient);
     newClient->enableTesting();