LanguageClient: Avoid calling throwing functions

Similar to with std::optional we want to avoid calling throwing
functions for std::variant, which includes std::get.
In many cases this also avoids the chain of `std::holds_alternative` +
`std::get` calls. And we never declare any `throws`.

Change-Id: I14f62ddef921b6bee90226ea34d1ffa62629bdc3
Reviewed-by: David Schulz <david.schulz@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>

10 files changed, 89 insertions, 100 deletions

diff --git a/src/plugins/languageclient/client.cpp b/src/plugins/languageclient/client.cpp
index 0d7826307a..f56538d6cb 100644
--- a/src/plugins/languageclient/client.cpp
+++ b/src/plugins/languageclient/client.cpp
@@ -903,7 +903,8 @@ void ClientPrivate::requestDocumentHighlightsNow(TextEditor::TextEditorWidget *w
             = m_serverCapabilities.documentHighlightProvider();
         if (!provider.has_value())
             return;
-        if (std::holds_alternative<bool>(*provider) && !std::get<bool>(*provider))
+        const auto boolvalue = std::get_if<bool>(&*provider);
+        if (boolvalue && !*boolvalue)
             return;
     }
 
@@ -935,7 +936,8 @@ void ClientPrivate::requestDocumentHighlightsNow(TextEditor::TextEditorWidget *w
             const QTextCharFormat &format =
                 widget->textDocument()->fontSettings().toTextCharFormat(TextEditor::C_OCCURRENCES);
             QTextDocument *document = widget->document();
-            for (const auto &highlight : std::get<QList<DocumentHighlight>>(*result)) {
+            const auto highlights = std::get_if<QList<DocumentHighlight>>(&*result);
+            for (const auto &highlight : *highlights) {
                 QTextEdit::ExtraSelection selection{widget->textCursor(), format};
                 const int &start = highlight.range().start().toPositionInDocument(document);
                 const int &end = highlight.range().end().toPositionInDocument(document);
@@ -1435,7 +1437,8 @@ void Client::requestCodeActions(const CodeActionRequest &request)
     } else {
         std::variant<bool, CodeActionOptions> provider
             = d->m_serverCapabilities.codeActionProvider().value_or(false);
-        if (!(std::holds_alternative<CodeActionOptions>(provider) || std::get<bool>(provider)))
+        const auto boolvalue = std::get_if<bool>(&provider);
+        if (boolvalue && !*boolvalue)
             return;
     }
 
@@ -1661,8 +1664,8 @@ bool Client::supportsDocumentSymbols(const TextEditor::TextDocument *doc) const
         = capabilities().documentSymbolProvider();
     if (!provider.has_value())
         return false;
-    if (std::holds_alternative<bool>(*provider))
-        return std::get<bool>(*provider);
+    if (const auto boolvalue = std::get_if<bool>(&*provider))
+        return *boolvalue;
     return true;
 }
 
@@ -2233,10 +2236,10 @@ bool ClientPrivate::sendWorkspceFolderChanges() const
         if (auto folder = workspace->workspaceFolders()) {
             if (folder->supported().value_or(false)) {
                 // holds either the Id for deregistration or whether it is registered
-                auto notification = folder->changeNotifications().value_or(false);
-                return std::holds_alternative<QString>(notification)
-                       || (std::holds_alternative<bool>(notification)
-                           && std::get<bool>(notification));
+                const std::variant<QString, bool> notification
+                    = folder->changeNotifications().value_or(false);
+                const auto boolvalue = std::get_if<bool>(&notification);
+                return !boolvalue || *boolvalue;
             }
         }
     }
diff --git a/src/plugins/languageclient/clientrequest.cpp b/src/plugins/languageclient/clientrequest.cpp
index 4e221f1b9d..3125b25a72 100644
--- a/src/plugins/languageclient/clientrequest.cpp
+++ b/src/plugins/languageclient/clientrequest.cpp
@@ -29,7 +29,8 @@ bool ClientWorkspaceSymbolRequest::preStartCheck()
         = client()->capabilities().workspaceSymbolProvider();
     if (!capability.has_value())
         return false;
-    if (std::holds_alternative<bool>(*capability) && !std::get<bool>(*capability))
+    const auto boolvalue = std::get_if<bool>(&*capability);
+    if (boolvalue && !boolvalue)
         return false;
 
     return true;
diff --git a/src/plugins/languageclient/languageclientcompletionassist.cpp b/src/plugins/languageclient/languageclientcompletionassist.cpp
index d6a2904fa4..7486ca102c 100644
--- a/src/plugins/languageclient/languageclientcompletionassist.cpp
+++ b/src/plugins/languageclient/languageclientcompletionassist.cpp
@@ -123,11 +123,11 @@ QString LanguageClientCompletionItem::detail() const
     if (auto _doc = m_item.documentation()) {
         auto doc = *_doc;
         QString detailDocText;
-        if (std::holds_alternative<QString>(doc)) {
-            detailDocText = std::get<QString>(doc);
-        } else if (std::holds_alternative<MarkupContent>(doc)) {
+        if (const auto s = std::get_if<QString>(&doc)) {
+            detailDocText = *s;
+        } else if (const auto m = std::get_if<MarkupContent>(&doc)) {
             // TODO markdown parser?
-            detailDocText = std::get<MarkupContent>(doc).content();
+            detailDocText = m->content();
         }
         if (!detailDocText.isEmpty())
             return detailDocText;
@@ -495,12 +495,10 @@ void LanguageClientCompletionAssistProcessor::handleCompletionResponse(
     }
 
     QList<CompletionItem> items;
-    if (std::holds_alternative<CompletionList>(*result)) {
-        const auto &list = std::get<CompletionList>(*result);
-        items = list.items().value_or(QList<CompletionItem>());
-    } else if (std::holds_alternative<QList<CompletionItem>>(*result)) {
-        items = std::get<QList<CompletionItem>>(*result);
-    }
+    if (const auto list = std::get_if<CompletionList>(&*result))
+        items = list->items().value_or(QList<CompletionItem>());
+    else if (const auto l = std::get_if<QList<CompletionItem>>(&*result))
+        items = *l;
     auto proposalItems = generateCompletionItems(items);
     if (!m_snippetsGroup.isEmpty()) {
         proposalItems << TextEditor::SnippetAssistCollector(m_snippetsGroup,
diff --git a/src/plugins/languageclient/languageclientformatter.cpp b/src/plugins/languageclient/languageclientformatter.cpp
index 52f35856af..acebc3184b 100644
--- a/src/plugins/languageclient/languageclientformatter.cpp
+++ b/src/plugins/languageclient/languageclientformatter.cpp
@@ -69,7 +69,8 @@ QFutureWatcher<ChangeSet> *LanguageClientFormatter::format(
             = m_client->capabilities().documentRangeFormattingProvider();
         if (!provider.has_value())
             return nullptr;
-        if (std::holds_alternative<bool>(*provider) && !std::get<bool>(*provider))
+        const auto boolvalue = std::get_if<bool>(&*provider);
+        if (boolvalue && !*boolvalue)
             return nullptr;
     }
     DocumentRangeFormattingParams params;
diff --git a/src/plugins/languageclient/languageclienthoverhandler.cpp b/src/plugins/languageclient/languageclienthoverhandler.cpp
index e878a62749..429c89e511 100644
--- a/src/plugins/languageclient/languageclienthoverhandler.cpp
+++ b/src/plugins/languageclient/languageclienthoverhandler.cpp
@@ -87,9 +87,8 @@ void HoverHandler::identifyMatch(TextEditor::TextEditorWidget *editorWidget,
 
     const std::optional<std::variant<bool, WorkDoneProgressOptions>> &provider
         = m_client->capabilities().hoverProvider();
-    bool sendMessage = provider.has_value();
-    if (sendMessage && std::holds_alternative<bool>(*provider))
-        sendMessage = std::get<bool>(*provider);
+    const bool *boolvalue = provider.has_value() ? std::get_if<bool>(&*provider) : nullptr;
+    bool sendMessage = provider.has_value() && (!boolvalue || *boolvalue);
     if (std::optional<bool> registered = m_client->dynamicCapabilities().isRegistered(
             HoverRequest::methodName)) {
         sendMessage = *registered;
diff --git a/src/plugins/languageclient/languageclientoutline.cpp b/src/plugins/languageclient/languageclientoutline.cpp
index 8c45513ce9..504c915759 100644
--- a/src/plugins/languageclient/languageclientoutline.cpp
+++ b/src/plugins/languageclient/languageclientoutline.cpp
@@ -228,10 +228,10 @@ void LanguageClientOutlineWidget::handleResponse(const DocumentUri &uri,
 {
     if (uri != m_uri)
         return;
-    if (std::holds_alternative<QList<SymbolInformation>>(result))
-        m_model.setInfo(std::get<QList<SymbolInformation>>(result));
-    else if (std::holds_alternative<QList<DocumentSymbol>>(result))
-        m_model.setInfo(std::get<QList<DocumentSymbol>>(result));
+    if (const auto i = std::get_if<QList<SymbolInformation>>(&result))
+        m_model.setInfo(*i);
+    else if (const auto s = std::get_if<QList<DocumentSymbol>>(&result))
+        m_model.setInfo(*s);
     else
         m_model.clear();
 
@@ -369,10 +369,10 @@ void OutlineComboBox::updateModel(const DocumentUri &resultUri, const DocumentSy
 {
     if (m_uri != resultUri)
         return;
-    if (std::holds_alternative<QList<SymbolInformation>>(result))
-        m_model.setInfo(std::get<QList<SymbolInformation>>(result));
-    else if (std::holds_alternative<QList<DocumentSymbol>>(result))
-        m_model.setInfo(std::get<QList<DocumentSymbol>>(result));
+    if (const auto i = std::get_if<QList<SymbolInformation>>(&result))
+        m_model.setInfo(*i);
+    else if (const auto s = std::get_if<QList<DocumentSymbol>>(&result))
+        m_model.setInfo(*i);
     else
         m_model.clear();
 
diff --git a/src/plugins/languageclient/languageclientsymbolsupport.cpp b/src/plugins/languageclient/languageclientsymbolsupport.cpp
index 9bc7cd1027..71b41bbcbf 100644
--- a/src/plugins/languageclient/languageclientsymbolsupport.cpp
+++ b/src/plugins/languageclient/languageclientsymbolsupport.cpp
@@ -100,9 +100,8 @@ static MessageId sendTextDocumentPositionParamsRequest(Client *client,
             sendMessage = supportedFile;
     } else {
         const auto provider = std::mem_fn(member)(serverCapability);
-        sendMessage = provider.has_value();
-        if (sendMessage && std::holds_alternative<bool>(*provider))
-            sendMessage = std::get<bool>(*provider);
+        const bool *boolvalue = provider.has_value() ? std::get_if<bool>(&*provider) : nullptr;
+        sendMessage = provider.has_value() && (!boolvalue || *boolvalue);
     }
     if (sendMessage) {
         client->sendMessage(request);
@@ -191,9 +190,8 @@ bool SymbolSupport::supportsFindLink(TextEditor::TextDocument *document, LinkTar
         else
             supported = m_client->isSupportedUri(uri);
     } else {
-        supported = provider.has_value();
-        if (supported && std::holds_alternative<bool>(*provider))
-            supported = std::get<bool>(*provider);
+        const bool *boolvalue = provider.has_value() ? std::get_if<bool>(&*provider) : nullptr;
+        supported = provider.has_value() && (!boolvalue || *boolvalue);
     }
     return supported;
 }
@@ -259,8 +257,8 @@ bool SymbolSupport::supportsFindUsages(TextEditor::TextDocument *document) const
             return false;
         }
     } else if (auto referencesProvider = m_client->capabilities().referencesProvider()) {
-        if (std::holds_alternative<bool>(*referencesProvider)) {
-            if (!std::get<bool>(*referencesProvider))
+        if (const auto b = std::get_if<bool>(&*referencesProvider)) {
+            if (!*b)
                 return false;
         }
     } else {
@@ -447,13 +445,11 @@ static bool supportsRename(Client *client,
         }
     }
     if (auto renameProvider = client->capabilities().renameProvider()) {
-        if (std::holds_alternative<bool>(*renameProvider)) {
-            if (!std::get<bool>(*renameProvider))
+        if (const auto b = std::get_if<bool>(&*renameProvider)) {
+            if (!*b)
                 return false;
-        } else if (std::holds_alternative<ServerCapabilities::RenameOptions>(*renameProvider)) {
-            prepareSupported = std::get<ServerCapabilities::RenameOptions>(*renameProvider)
-                                   .prepareProvider()
-                                   .value_or(false);
+        } else if (const auto opt = std::get_if<ServerCapabilities::RenameOptions>(&*renameProvider)) {
+            prepareSupported = opt->prepareProvider().value_or(false);
         }
     } else {
         return false;
@@ -524,19 +520,17 @@ void SymbolSupport::requestPrepareRename(TextEditor::TextDocument *document,
 
         const std::optional<PrepareRenameResult> &result = response.result();
         if (result.has_value()) {
-            if (std::holds_alternative<PlaceHolderResult>(*result)) {
-                auto placeHolderResult = std::get<PlaceHolderResult>(*result);
-                startRenameSymbol(params,
-                                  placeholder.isEmpty() ? placeHolderResult.placeHolder()
-                                                        : placeholder,
-                                  oldSymbolName,
-                                  callback,
-                                  preferLowerCaseFileNames);
-            } else if (std::holds_alternative<Range>(*result)) {
-                auto range = std::get<Range>(*result);
+            if (const auto placeHolderResult = std::get_if<PlaceHolderResult>(&*result)) {
+                startRenameSymbol(
+                    params,
+                    placeholder.isEmpty() ? placeHolderResult->placeHolder() : placeholder,
+                    oldSymbolName,
+                    callback,
+                    preferLowerCaseFileNames);
+            } else if (const auto range = std::get_if<Range>(&*result)) {
                 if (document) {
-                    const int start = range.start().toPositionInDocument(document->document());
-                    const int end = range.end().toPositionInDocument(document->document());
+                    const int start = range->start().toPositionInDocument(document->document());
+                    const int end = range->end().toPositionInDocument(document->document());
                     const QString reportedSymbolName = document->textAt(start, end - start);
                     startRenameSymbol(params,
                                       derivePlaceholder(reportedSymbolName, placeholder),
@@ -586,28 +580,24 @@ Utils::SearchResultItems generateReplaceItems(const WorkspaceEdit &edits,
     const DocumentUri::PathMapper &pathMapper = client->hostPathMapper();
     if (!documentChanges.isEmpty()) {
         for (const DocumentChange &documentChange : std::as_const(documentChanges)) {
-            if (std::holds_alternative<TextDocumentEdit>(documentChange)) {
-                const TextDocumentEdit edit = std::get<TextDocumentEdit>(documentChange);
-                rangesInDocument[edit.textDocument().uri().toFilePath(pathMapper)] = convertEdits(
-                    edit.edits());
+            if (const auto edit = std::get_if<TextDocumentEdit>(&documentChange)) {
+                rangesInDocument[edit->textDocument().uri().toFilePath(pathMapper)] = convertEdits(
+                    edit->edits());
             } else {
                 Utils::SearchResultItem item;
 
-                if (std::holds_alternative<CreateFileOperation>(documentChange)) {
-                    auto op = std::get<CreateFileOperation>(documentChange);
-                    item.setLineText(op.message(pathMapper));
-                    item.setFilePath(op.uri().toFilePath(pathMapper));
-                    item.setUserData(QVariant(op));
-                } else if (std::holds_alternative<RenameFileOperation>(documentChange)) {
-                    auto op = std::get<RenameFileOperation>(documentChange);
-                    item.setLineText(op.message(pathMapper));
-                    item.setFilePath(op.oldUri().toFilePath(pathMapper));
-                    item.setUserData(QVariant(op));
-                } else if (std::holds_alternative<DeleteFileOperation>(documentChange)) {
-                    auto op = std::get<DeleteFileOperation>(documentChange);
-                    item.setLineText(op.message(pathMapper));
-                    item.setFilePath(op.uri().toFilePath(pathMapper));
-                    item.setUserData(QVariant(op));
+                if (const auto op = std::get_if<CreateFileOperation>(&documentChange)) {
+                    item.setLineText(op->message(pathMapper));
+                    item.setFilePath(op->uri().toFilePath(pathMapper));
+                    item.setUserData(QVariant(*op));
+                } else if (const auto op = std::get_if<RenameFileOperation>(&documentChange)) {
+                    item.setLineText(op->message(pathMapper));
+                    item.setFilePath(op->oldUri().toFilePath(pathMapper));
+                    item.setUserData(QVariant(*op));
+                } else if (const auto op = std::get_if<DeleteFileOperation>(&documentChange)) {
+                    item.setLineText(op->message(pathMapper));
+                    item.setFilePath(op->uri().toFilePath(pathMapper));
+                    item.setUserData(QVariant(*op));
                 }
 
                 items << item;
diff --git a/src/plugins/languageclient/languageclientutils.cpp b/src/plugins/languageclient/languageclientutils.cpp
index 3df7622548..4924654ffc 100644
--- a/src/plugins/languageclient/languageclientutils.cpp
+++ b/src/plugins/languageclient/languageclientutils.cpp
@@ -349,13 +349,12 @@ bool applyDocumentChange(const Client *client, const DocumentChange &change)
     if (!client)
         return false;
 
-    if (std::holds_alternative<TextDocumentEdit>(change)) {
-        return applyTextDocumentEdit(client, std::get<TextDocumentEdit>(change));
-    } else if (std::holds_alternative<CreateFileOperation>(change)) {
-        const auto createOperation = std::get<CreateFileOperation>(change);
-        const FilePath filePath = createOperation.uri().toFilePath(client->hostPathMapper());
+    if (const auto e = std::get_if<TextDocumentEdit>(&change)) {
+        return applyTextDocumentEdit(client, *e);
+    } else if (const auto createOperation = std::get_if<CreateFileOperation>(&change)) {
+        const FilePath filePath = createOperation->uri().toFilePath(client->hostPathMapper());
         if (filePath.exists()) {
-            if (const std::optional<CreateFileOptions> options = createOperation.options()) {
+            if (const std::optional<CreateFileOptions> options = createOperation->options()) {
                 if (options->overwrite().value_or(false)) {
                     if (!filePath.removeFile())
                         return false;
@@ -365,16 +364,15 @@ bool applyDocumentChange(const Client *client, const DocumentChange &change)
             }
         }
         return filePath.ensureExistingFile();
-    } else if (std::holds_alternative<RenameFileOperation>(change)) {
-        const RenameFileOperation renameOperation = std::get<RenameFileOperation>(change);
-        const FilePath oldPath = renameOperation.oldUri().toFilePath(client->hostPathMapper());
+    } else if (const auto renameOperation = std::get_if<RenameFileOperation>(&change)) {
+        const FilePath oldPath = renameOperation->oldUri().toFilePath(client->hostPathMapper());
         if (!oldPath.exists())
             return false;
-        const FilePath newPath = renameOperation.newUri().toFilePath(client->hostPathMapper());
+        const FilePath newPath = renameOperation->newUri().toFilePath(client->hostPathMapper());
         if (oldPath == newPath)
             return true;
         if (newPath.exists()) {
-            if (const std::optional<CreateFileOptions> options = renameOperation.options()) {
+            if (const std::optional<CreateFileOptions> options = renameOperation->options()) {
                 if (options->overwrite().value_or(false)) {
                     if (!newPath.removeFile())
                         return false;
@@ -384,10 +382,9 @@ bool applyDocumentChange(const Client *client, const DocumentChange &change)
             }
         }
         return oldPath.renameFile(newPath);
-    } else if (std::holds_alternative<DeleteFileOperation>(change)) {
-        const auto deleteOperation = std::get<DeleteFileOperation>(change);
-        const FilePath filePath = deleteOperation.uri().toFilePath(client->hostPathMapper());
-        if (const std::optional<DeleteFileOptions> options = deleteOperation.options()) {
+    } else if (const auto deleteOperation = std::get_if<DeleteFileOperation>(&change)) {
+        const FilePath filePath = deleteOperation->uri().toFilePath(client->hostPathMapper());
+        if (const std::optional<DeleteFileOptions> options = deleteOperation->options()) {
             if (!filePath.exists())
                 return options->ignoreIfNotExists().value_or(false);
             if (filePath.isDir() && options->recursive().value_or(false))
diff --git a/src/plugins/languageclient/progressmanager.cpp b/src/plugins/languageclient/progressmanager.cpp
index 6b82d289df..4ef7d0b60d 100644
--- a/src/plugins/languageclient/progressmanager.cpp
+++ b/src/plugins/languageclient/progressmanager.cpp
@@ -69,10 +69,10 @@ bool ProgressManager::isProgressEndMessage(const LanguageServerProtocol::Progres
 Utils::Id languageClientProgressId(const ProgressToken &token)
 {
     constexpr char k_LanguageClientProgressId[] = "LanguageClient.ProgressId.";
-    auto toString = [](const ProgressToken &token){
-        if (std::holds_alternative<int>(token))
-            return QString::number(std::get<int>(token));
-        return std::get<QString>(token);
+    auto toString = [](const ProgressToken &token) {
+        if (const auto i = std::get_if<int>(&token))
+            return QString::number(*i);
+        return *std::get_if<QString>(&token);
     };
     return Utils::Id(k_LanguageClientProgressId).withSuffix(toString(token));
 }
diff --git a/src/plugins/languageclient/snippet.cpp b/src/plugins/languageclient/snippet.cpp
index 7a0fd21131..b401123ef8 100644
--- a/src/plugins/languageclient/snippet.cpp
+++ b/src/plugins/languageclient/snippet.cpp
@@ -251,11 +251,11 @@ void SnippetParsingTest::testSnippetParsing()
     QFETCH(Parts, parts);
 
     SnippetParseResult result = LanguageClient::parseSnippet(input);
-    QCOMPARE(std::holds_alternative<ParsedSnippet>(result), success);
+    const auto snippet = std::get_if<ParsedSnippet>(&result);
+    QCOMPARE(snippet != nullptr, success);
     if (!success)
         return;
 
-    ParsedSnippet snippet = std::get<ParsedSnippet>(result);
 
     auto rangesCompare = [&](const ParsedSnippet::Part &actual, const SnippetPart &expected) {
         QCOMPARE(actual.text, expected.text);
@@ -264,10 +264,10 @@ void SnippetParsingTest::testSnippetParsing()
         QCOMPARE(manglerId, expected.manglerId);
     };
 
-    QCOMPARE(snippet.parts.count(), parts.count());
+    QCOMPARE(snippet->parts.count(), parts.count());
 
     for (int i = 0; i < parts.count(); ++i)
-        rangesCompare(snippet.parts.at(i), parts.at(i));
+        rangesCompare(snippet->parts.at(i), parts.at(i));
 }
 
 QObject *createSnippetParsingTest()