LSP: fix hover request result

According to the protocol a hover request can also return a Null as a
result. Reflect this in the protocol implementation and adapt usages.

Change-Id: I14ce71639c64b6de00e9c1198617083c1a3de9eb
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/languageserverprotocol/languagefeatures.cpp

@@ -403,4 +403,19 @@ Utils::optional<QJsonValue> CodeLens::data() const
     return contains(dataKey) ? Utils::make_optional(value(dataKey)) : Utils::nullopt;
 }
 
+HoverResult::HoverResult(const QJsonValue &value)
+{
+    if (value.isObject())
+        emplace<Hover>(Hover(value.toObject()));
+    else
+        emplace<std::nullptr_t>(nullptr);
+}
+
+bool HoverResult::isValid() const
+{
+    if (auto hover = Utils::get_if<Hover>(this))
+        return hover->isValid();
+    return true;
+}
+
 } // namespace LanguageServerProtocol

src/libs/languageserverprotocol/languagefeatures.h

@@ -101,8 +101,17 @@ public:
     bool isValid() const override { return contains(contentsKey); }
 };
 
+class LANGUAGESERVERPROTOCOL_EXPORT HoverResult : public Utils::variant<Hover, std::nullptr_t>
+{
+public:
+    HoverResult() : variant(nullptr) {}
+    explicit HoverResult(const Hover &hover) : variant(hover) {}
+    explicit HoverResult(const QJsonValue &value);
+    bool isValid() const;
+};
+
 class LANGUAGESERVERPROTOCOL_EXPORT HoverRequest
-    : public Request<Hover, std::nullptr_t, TextDocumentPositionParams>
+    : public Request<HoverResult, std::nullptr_t, TextDocumentPositionParams>
 {
 public:
     explicit HoverRequest(const TextDocumentPositionParams &params);

src/plugins/clangcodemodel/clangdclient.cpp

@@ -2344,9 +2344,10 @@ void ClangdClient::findLocalUsages(TextDocument *document, const QTextCursor &cu
 void ClangdClient::gatherHelpItemForTooltip(const HoverRequest::Response &hoverResponse,
                                             const DocumentUri &uri)
 {
-    if (const Utils::optional<Hover> result = hoverResponse.result()) {
-        const HoverContent content = result->content();
-        const MarkupContent * const markup = Utils::get_if<MarkupContent>(&content);
+    if (const Utils::optional<HoverResult> result = hoverResponse.result()) {
+        if (auto hover = Utils::get_if<Hover>(&(*result))) {
+            const HoverContent content = hover->content();
+            const MarkupContent *const markup = Utils::get_if<MarkupContent>(&content);
             if (markup) {
                 const QString markupString = markup->content();
 
@@ -2370,19 +2371,25 @@ void ClangdClient::gatherHelpItemForTooltip(const HoverRequest::Response &hoverR
                 if (!lines.isEmpty()) {
                     const auto filePath = Utils::FilePath::fromUserInput(lines.last().simplified());
                     if (filePath.exists()) {
-                    d->setHelpItemForTooltip(hoverResponse.id(), filePath.fileName(),
+                        d->setHelpItemForTooltip(hoverResponse.id(),
+                                                 filePath.fileName(),
                                                  HelpItem::Brief);
                         return;
                     }
                 }
             }
         }
+    }
 
     const TextDocument * const doc = documentForFilePath(uri.toFilePath());
     QTC_ASSERT(doc, return);
     const auto astHandler = [this, uri, hoverResponse](const AstNode &ast, const MessageId &) {
         const MessageId id = hoverResponse.id();
-        const Range range = hoverResponse.result()->range().value_or(Range());
+        Range range;
+        if (const Utils::optional<HoverResult> result = hoverResponse.result()) {
+            if (auto hover = Utils::get_if<Hover>(&(*result)))
+                range = hover->range().value_or(Range());
+        }
         const QList<AstNode> path = getAstPath(ast, range);
         if (path.isEmpty()) {
             d->setHelpItemForTooltip(id);

src/plugins/languageclient/languageclienthoverhandler.cpp

@@ -58,8 +58,10 @@ void HoverHandler::setHelpItem(const LanguageServerProtocol::MessageId &msgId,
                                const Core::HelpItem &help)
 {
     if (msgId == m_response.id()) {
-        if (Utils::optional<Hover> result = m_response.result())
-            setContent(result->content());
+        if (Utils::optional<HoverResult> result = m_response.result()) {
+            if (auto hover = Utils::get_if<Hover>(&(*result)))
+                setContent(hover->content());
+        }
         m_response = {};
         setLastHelpItemIdentified(help);
         m_report(priority());
@@ -129,13 +131,15 @@ void HoverHandler::handleResponse(const HoverRequest::Response &response)
         if (m_client)
             m_client->log(*error);
     }
-    if (Utils::optional<Hover> result = response.result()) {
+    if (Utils::optional<HoverResult> result = response.result()) {
+        if (auto hover = Utils::get_if<Hover>(&(*result))) {
             if (m_helpItemProvider) {
                 m_response = response;
                 m_helpItemProvider(response, m_uri);
                 return;
             }
-        setContent(result->content());
+            setContent(hover->content());
+        }
     }
     m_report(priority());
 }