LSP: Add support for activeParameter of SignatureInformation

Task-number: QTCREATORBUG-26346
Change-Id: Ieab18f08e4f1b9fa6cacfae0a18310af4bc35165
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/languageserverprotocol/clientcapabilities.h

@@ -336,6 +336,12 @@ public:
             Utils::optional<QList<MarkupKind>> documentationFormat() const;
             void setDocumentationFormat(const QList<MarkupKind> &documentationFormat);
             void clearDocumentationFormat() { remove(documentationFormatKey); }
+
+            Utils::optional<bool> activeParameterSupport() const
+            { return optionalValue<bool>(activeParameterSupportKey); }
+            void setActiveParameterSupport(bool activeParameterSupport)
+            { insert(activeParameterSupportKey, activeParameterSupport); }
+            void clearActiveParameterSupport() { remove(activeParameterSupportKey); }
         };
 
         // The client supports the following `SignatureInformation` specific properties.

src/libs/languageserverprotocol/jsonkeys.h

@@ -29,6 +29,7 @@ namespace LanguageServerProtocol {
 
 constexpr char actionsKey[] = "actions";
 constexpr char activeParameterKey[] = "activeParameter";
+constexpr char activeParameterSupportKey[] = "activeParameterSupport";
 constexpr char activeSignatureKey[] = "activeSignature";
 constexpr char addedKey[] = "added";
 constexpr char additionalTextEditsKey[] = "additionalTextEdits";

src/libs/languageserverprotocol/languagefeatures.h

@@ -145,6 +145,10 @@ public:
     void setParameters(const QList<ParameterInformation> &parameters)
     { insertArray(parametersKey, parameters); }
     void clearParameters() { remove(parametersKey); }
+
+    Utils::optional<int> activeParameter() const { return optionalValue<int>(activeParameterKey); }
+    void setActiveParameter(int activeParameter) { insert(activeParameterKey, activeParameter); }
+    void clearActiveParameter() { remove(activeParameterKey); }
 };
 
 /**

src/plugins/languageclient/client.cpp

@@ -248,6 +248,7 @@ static ClientCapabilities generateClientCapabilities()
     signatureHelp.setDynamicRegistration(true);
     TextDocumentClientCapabilities::SignatureHelpCapabilities::SignatureInformationCapabilities info;
     info.setDocumentationFormat({MarkupKind::markdown, MarkupKind::plaintext});
+    info.setActiveParameterSupport(true);
     signatureHelp.setSignatureInformation(info);
     documentCapabilities.setSignatureHelp(signatureHelp);
 

src/plugins/languageclient/languageclientfunctionhint.cpp

@@ -61,11 +61,12 @@ QString FunctionHintProposalModel::text(int index) const
     if (index < 0 || m_sigis.signatures().size() <= index)
         return {};
     const SignatureInformation signature = m_sigis.signatures().at(index);
+    int parametersIndex = signature.activeParameter().value_or(-1);
+    if (parametersIndex < 0) {
+        if (index == m_sigis.activeSignature().value_or(-1))
+            parametersIndex = m_sigis.activeParameter().value_or(-1);
+    }
     QString label = signature.label();
-    if (index != m_sigis.activeSignature().value_or(-1))
-        return label;
-
-    const int parametersIndex = m_sigis.activeParameter().value_or(-1);
     if (parametersIndex < 0)
         return label;