ClangCodeModel: Make use of clangd's "switchSourceHeader" extension

This allows us to switch between headers and sources with different base
names and/or locations, using symbol matching heuristics.

Task-number: QTCREATORBUG-16385
Change-Id: I2d9c07f412d70b75322ed65d491982d78674483d
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdclient.cpp

@@ -2255,6 +2255,28 @@ void ClangdClient::switchDeclDef(TextDocument *document, const QTextCursor &curs
     documentSymbolCache()->requestSymbols(d->switchDeclDefData->uri, Schedule::Now);
 }
 
+void ClangdClient::switchHeaderSource(const Utils::FilePath &filePath, bool inNextSplit)
+{
+    class SwitchSourceHeaderRequest : public Request<QJsonValue, std::nullptr_t, TextDocumentIdentifier>
+    {
+    public:
+        using Request::Request;
+        explicit SwitchSourceHeaderRequest(const Utils::FilePath &filePath)
+            : Request("textDocument/switchSourceHeader",
+                      TextDocumentIdentifier(DocumentUri::fromFilePath(filePath))) {}
+    };
+    SwitchSourceHeaderRequest req(filePath);
+    req.setResponseCallback([inNextSplit](const SwitchSourceHeaderRequest::Response &response) {
+        if (const Utils::optional<QJsonValue> result = response.result()) {
+            const DocumentUri uri = DocumentUri::fromProtocol(result->toString());
+            const Utils::FilePath filePath = uri.toFilePath();
+            if (!filePath.isEmpty())
+                CppEditor::openEditor(filePath, inNextSplit);
+        }
+    });
+    sendContent(req);
+}
+
 void ClangdClient::findLocalUsages(TextDocument *document, const QTextCursor &cursor,
         CppEditor::RenameCallback &&callback)
 {

src/plugins/clangcodemodel/clangdclient.h

@@ -75,6 +75,7 @@ public:
             const QTextCursor &cursor,
             CppEditor::CppEditorWidget *editorWidget,
             Utils::ProcessLinkCallback &&callback);
+    void switchHeaderSource(const Utils::FilePath &filePath, bool inNextSplit);
 
     void findLocalUsages(TextEditor::TextDocument *document, const QTextCursor &cursor,
                          CppEditor::RenameCallback &&callback);

src/plugins/clangcodemodel/clangmodelmanagersupport.cpp

@@ -248,6 +248,21 @@ void ClangModelManagerSupport::findUsages(const CppEditor::CursorInEditor &curso
     CppModelManager::findUsages(cursor, std::move(callback), CppModelManager::Backend::Builtin);
 }
 
+void ClangModelManagerSupport::switchHeaderSource(const Utils::FilePath &filePath, bool inNextSplit)
+{
+    if (ClangdClient * const client = clientForFile(filePath)) {
+        // The fast, synchronous approach works most of the time, so let's try that one first.
+        const auto otherFile = Utils::FilePath::fromString(
+                    correspondingHeaderOrSource(filePath.toString()));
+        if (!otherFile.isEmpty())
+            openEditor(otherFile, inNextSplit);
+        else
+            client->switchHeaderSource(filePath, inNextSplit);
+        return;
+    }
+    CppModelManager::switchHeaderSource(inNextSplit, CppModelManager::Backend::Builtin);
+}
+
 std::unique_ptr<CppEditor::AbstractOverviewModel> ClangModelManagerSupport::createOverviewModel()
 {
     return {};

src/plugins/clangcodemodel/clangmodelmanagersupport.h

@@ -97,6 +97,7 @@ private:
                       const QString &replacement) override;
     void findUsages(const CppEditor::CursorInEditor &cursor,
                     CppEditor::UsagesCallback &&callback) const override;
+    void switchHeaderSource(const Utils::FilePath &filePath, bool inNextSplit) override;
 
     void onEditorOpened(Core::IEditor *editor);
     void onCurrentEditorChanged(Core::IEditor *newCurrent);