Language server: Add completion support

This feature uncovered some sloppiness in our handling of QVariant types,
which has now been fixed.

Task-number: QBS-395
Change-Id: I687cef7470d97fe7887e4a7a1dbe672b2b9c79ec
Reviewed-by: Ivan Komissarov <ABBAPOH@gmail.com>
Reviewed-by: David Schulz <david.schulz@qt.io>

34 files changed, 480 insertions, 117 deletions

diff --git a/src/app/qbs/lspserver.cpp b/src/app/qbs/lspserver.cpp
index 807b6fb1d..c6cce6706 100644
--- a/src/app/qbs/lspserver.cpp
+++ b/src/app/qbs/lspserver.cpp
@@ -39,18 +39,25 @@
 
 #include "lspserver.h"
 
+#include <api/projectdata.h>
 #include <logging/translator.h>
 #include <lsp/basemessage.h>
+#include <lsp/completion.h>
 #include <lsp/initializemessages.h>
 #include <lsp/jsonrpcmessages.h>
 #include <lsp/messages.h>
+#include <lsp/servercapabilities.h>
 #include <lsp/textsynchronization.h>
+#include <parser/qmljsastvisitor_p.h>
+#include <parser/qmljslexer_p.h>
+#include <parser/qmljsparser_p.h>
 #include <tools/qbsassert.h>
 #include <tools/stlutils.h>
 
 #include <QBuffer>
 #include <QLocalServer>
 #include <QLocalSocket>
+#include <QMap>
 
 #include <unordered_map>
 #ifdef Q_OS_WINDOWS
@@ -103,6 +110,32 @@ static int posToOffset(const lsp::Position &pos, const QString &doc)
     return posToOffset(posFromLspPos(pos), doc);
 }
 
+class AstNodeLocator : public QbsQmlJS::AST::Visitor
+{
+public:
+    AstNodeLocator(int position, QbsQmlJS::AST::UiProgram &ast)
+        : m_position(position)
+    {
+        ast.accept(this);
+    }
+
+    QList<QbsQmlJS::AST::Node *> path() const { return m_path; }
+
+private:
+    bool preVisit(QbsQmlJS::AST::Node *node) override
+    {
+        if (int(node->firstSourceLocation().offset) > m_position)
+            return false;
+        if (int(node->lastSourceLocation().offset) < m_position)
+            return false;
+        m_path << node;
+        return true;
+    }
+
+    const int m_position;
+    QList<QbsQmlJS::AST::Node *> m_path;
+};
+
 class LspServer::Private
 {
 public:
@@ -119,6 +152,7 @@ public:
     void handleInitializeRequest();
     void handleInitializedNotification();
     void handleGotoDefinitionRequest();
+    void handleCompletionRequest();
     void handleShutdownRequest();
     void handleDidOpenNotification();
     void handleDidChangeNotification();
@@ -130,6 +164,7 @@ public:
     lsp::BaseMessage currentMessage;
     QJsonObject messageObject;
     QLocalSocket *socket = nullptr;
+    ProjectData projectData;
     CodeLinks codeLinks;
     std::unordered_map<QString, Document> documents;
 
@@ -153,8 +188,9 @@ LspServer::LspServer() : d(new Private)
 
 LspServer::~LspServer() { delete d; }
 
-void LspServer::updateProjectData(const CodeLinks &codeLinks)
+void LspServer::updateProjectData(const ProjectData &projectData, const CodeLinks &codeLinks)
 {
+    d->projectData = projectData;
     d->codeLinks = codeLinks;
 }
 
@@ -271,6 +307,8 @@ void LspServer::Private::handleCurrentMessage()
         return handleDidCloseNotification();
     if (method == "textDocument/definition")
         return handleGotoDefinitionRequest();
+    if (method == "textDocument/completion")
+        return handleCompletionRequest();
 
     sendErrorResponse(LspErrorResponse::MethodNotFound, Tr::tr("This server can do very little."));
 }
@@ -291,6 +329,9 @@ void LspServer::Private::handleInitializeRequest()
     lsp::ServerCapabilities capabilities; // TODO: hover
     capabilities.setDefinitionProvider(true);
     capabilities.setTextDocumentSync({int(lsp::TextDocumentSyncKind::Incremental)});
+    lsp::ServerCapabilities::CompletionOptions completionOptions;
+    completionOptions.setTriggerCharacters({"."});
+    capabilities.setCompletionProvider(completionOptions);
     result.setCapabilities(capabilities);
     sendResponse(result);
 }
@@ -353,6 +394,142 @@ void LspServer::Private::handleGotoDefinitionRequest()
     sendResponse(nullptr);
 }
 
+// We operate under the assumption that the client has basic QML support.
+// Therefore, we only provide completion for qbs modules and their properties.
+// Only a simple prefix match is implemented, with no regard to the contents after the cursor.
+void LspServer::Private::handleCompletionRequest()
+{
+    if (!projectData.isValid())
+        return sendResponse(nullptr);
+
+    const lsp::CompletionParams params(messageObject.value(lsp::paramsKey));
+    const QString sourceFile = params.textDocument().uri().toLocalFile();
+    const Document *sourceDoc = nullptr;
+    if (const auto it = documents.find(sourceFile); it != documents.end())
+        sourceDoc = &it->second;
+    if (!sourceDoc)
+        return sendResponse(nullptr);
+
+    // If there are products corresponding to this file, check only these when looking for modules.
+    // Otherwise, check all products.
+    const QList<ProductData> allProducts = projectData.allProducts();
+    if (allProducts.isEmpty())
+        return sendResponse(nullptr);
+    QList<ProductData> relevantProducts;
+    for (const ProductData &p : allProducts) {
+        if (p.location().filePath() == sourceFile)
+            relevantProducts << p;
+    }
+    if (relevantProducts.isEmpty())
+        relevantProducts = allProducts;
+
+    QString identifierPrefix;
+    QStringList modulePrefixes;
+    const int offset = posToOffset(params.position(), sourceDoc->currentContent) - 1;
+    if (offset < 0 || offset >= sourceDoc->currentContent.length())
+        return sendResponse(nullptr);
+    const auto collectFromRawString = [&] {
+        int currentPos = offset;
+        const auto constructIdentifier = [&] {
+            QString id;
+            while (currentPos >= 0) {
+                const QChar c = sourceDoc->currentContent.at(currentPos);
+                if (!c.isLetterOrNumber() && c != '_')
+                    break;
+                id.prepend(c);
+                --currentPos;
+            }
+            return id;
+        };
+        identifierPrefix = constructIdentifier();
+        while (true) {
+            if (currentPos <= 0 || sourceDoc->currentContent.at(currentPos) != '.')
+                return;
+            --currentPos;
+            const QString modulePrefix = constructIdentifier();
+            if (modulePrefix.isEmpty())
+                return;
+            modulePrefixes.prepend(modulePrefix);
+        }
+    };
+
+    // Parse the current file. Note that completion usually happens on invalid code, which
+    // often confuses the parser so much that it yields unusable results. Therefore, we always
+    // gather our input parameters from the raw string. We only use the parse result to skip
+    // completion in contexts where it is undesirable.
+    QbsQmlJS::Engine engine;
+    QbsQmlJS::Lexer lexer(&engine);
+    lexer.setCode(sourceDoc->currentContent, 1);
+    QbsQmlJS::Parser parser(&engine);
+    parser.parse();
+    if (parser.ast()) {
+        AstNodeLocator locator(offset, *parser.ast());
+        const QList<QbsQmlJS::AST::Node *> &astPath = locator.path();
+        if (!astPath.isEmpty()) {
+            switch (astPath.last()->kind) {
+            case QbsQmlJS::AST::Node::Kind_FieldMemberExpression:
+            case QbsQmlJS::AST::Node::Kind_UiObjectDefinition:
+            case QbsQmlJS::AST::Node::Kind_UiQualifiedId:
+            case QbsQmlJS::AST::Node::Kind_UiScriptBinding:
+                break;
+            default:
+                return sendResponse(nullptr);
+            }
+        }
+    }
+
+    collectFromRawString();
+    if (modulePrefixes.isEmpty() && identifierPrefix.isEmpty())
+        return sendResponse(nullptr); // We do not want to start completion from nothing.
+
+    QJsonArray results;
+    QMap<QString, QString> namesAndTypes;
+    for (const ProductData &product : std::as_const(relevantProducts)) {
+        const PropertyMap &moduleProps = product.moduleProperties();
+        const QStringList allModules = moduleProps.allModules();
+        const QString moduleNameOrPrefix = modulePrefixes.join('.');
+
+        // Case 1: Prefixes match a module name. Identifier can only expand to the name
+        // of a module property.
+        // Example: "Qt.core.a^" -> "Qt.core.availableBuildVariants"
+        if (!modulePrefixes.isEmpty() && allModules.contains(moduleNameOrPrefix)) {
+            for (const PropertyMap::PropertyInfo &info :
+                 moduleProps.allPropertiesForModule(moduleNameOrPrefix)) {
+                if (info.isBuiltin)
+                    continue;
+                if (!identifierPrefix.isEmpty() && !info.name.startsWith(identifierPrefix))
+                    continue;
+                namesAndTypes.insert(info.name, info.type);
+            }
+            continue;
+        }
+
+        // Case 2: Isolated identifier. Can only expand to a module name.
+        //     Example: "Q^" -> "Qt.core", "Qt.widgets", ...
+        // Case 3: Prefixes match a module prefix. Identifier can only expand to a module name.
+        //     Example: "Qt.c^" -> "Qt.core", "Qt.concurrent", ...
+        QString fullPrefix = identifierPrefix;
+        int nameOffset = 0;
+        if (!modulePrefixes.isEmpty()) {
+            fullPrefix.prepend(moduleNameOrPrefix + '.');
+            nameOffset = moduleNameOrPrefix.length() + 1;
+        }
+        for (const QString &module : allModules) {
+            if (module.startsWith(fullPrefix))
+                namesAndTypes.insert(module.mid(nameOffset), {});
+        }
+    }
+
+    for (auto it = namesAndTypes.cbegin(); it != namesAndTypes.cend(); ++it) {
+        lsp::CompletionItem item;
+        item.setLabel(it.key());
+        if (!it.value().isEmpty())
+            item.setDetail(it.value());
+        results.append(QJsonObject(item));
+    };
+    sendResponse(results);
+}
+
 void LspServer::Private::handleShutdownRequest()
 {
     state = State::Shutdown;
@@ -425,14 +602,13 @@ void LspServer::Private::handleDidCloseNotification()
 static int posToOffset(const CodePosition &pos, const QString &doc)
 {
     int offset = 0;
-    int next = 0;
-    for (int newlines = 0; newlines < pos.line() - 1; ++newlines) {
+    for (int newlines = 0, next = 0; newlines < pos.line() - 1; ++newlines) {
         offset = doc.indexOf('\n', next);
         if (offset == -1)
             return -1;
         next = offset + 1;
     }
-    return offset + pos.column() - 1;
+    return offset + pos.column();
 }
 
 bool Document::isPositionUpToDate(const CodePosition &pos) const
diff --git a/src/app/qbs/lspserver.h b/src/app/qbs/lspserver.h
index 2538789ca..566808309 100644
--- a/src/app/qbs/lspserver.h
+++ b/src/app/qbs/lspserver.h
@@ -43,7 +43,9 @@
 
 #include <QString>
 
-namespace qbs::Internal {
+namespace qbs {
+class ProjectData;
+namespace Internal {
 
 class LspServer
 {
@@ -51,7 +53,7 @@ public:
     LspServer();
     ~LspServer();
 
-    void updateProjectData(const CodeLinks &codeLinks);
+    void updateProjectData(const ProjectData &projectData, const CodeLinks &codeLinks);
     QString socketPath() const;
 
 private:
@@ -59,4 +61,5 @@ private:
     Private * const d;
 };
 
-} // namespace qbs::Internal
+} // namespace Internal
+} // namespace qbs
diff --git a/src/app/qbs/session.cpp b/src/app/qbs/session.cpp
index d69a11b24..ebc9015b2 100644
--- a/src/app/qbs/session.cpp
+++ b/src/app/qbs/session.cpp
@@ -288,7 +288,7 @@ void Session::setupProject(const QJsonObject &request)
         const ProjectData oldProjectData = m_projectData;
         m_project = setupJob->project();
         m_projectData = m_project.projectData();
-        m_lspServer.updateProjectData(m_project.codeLinks());
+        m_lspServer.updateProjectData(m_projectData, m_project.codeLinks());
         QJsonObject reply;
         reply.insert(StringConstants::type(), QLatin1String("project-resolved"));
         if (success)
diff --git a/src/lib/corelib/api/projectdata.cpp b/src/lib/corelib/api/projectdata.cpp
index 11469ee18..34e679d6d 100644
--- a/src/lib/corelib/api/projectdata.cpp
+++ b/src/lib/corelib/api/projectdata.cpp
@@ -40,6 +40,7 @@
 
 #include "projectdata_p.h"
 #include "propertymap_p.h"
+#include <language/builtindeclarations.h>
 #include <language/language.h>
 #include <language/propertymapinternal.h>
 #include <loader/loaderutils.h>
@@ -49,7 +50,6 @@
 #include <tools/qttools.h>
 #include <tools/stlutils.h>
 #include <tools/stringconstants.h>
-#include <tools/stringconstants.h>
 
 #include <QtCore/qdir.h>
 #include <QtCore/qjsonarray.h>
@@ -732,21 +732,16 @@ bool operator==(const ProductData &lhs, const ProductData &rhs)
     if (!lhs.isValid() && !rhs.isValid())
         return true;
 
-    return lhs.isValid() == rhs.isValid()
-            && lhs.name() == rhs.name()
-            && lhs.targetName() == rhs.targetName()
-            && lhs.type() == rhs.type()
-            && lhs.version() == rhs.version()
-            && lhs.dependencies() == rhs.dependencies()
-            && lhs.profile() == rhs.profile()
-            && lhs.multiplexConfigurationId() == rhs.multiplexConfigurationId()
-            && lhs.location() == rhs.location()
-            && lhs.groups() == rhs.groups()
-            && lhs.generatedArtifacts() == rhs.generatedArtifacts()
-            && lhs.properties() == rhs.properties()
-            && lhs.moduleProperties() == rhs.moduleProperties()
-            && lhs.isEnabled() == rhs.isEnabled()
-            && lhs.isMultiplexed() == rhs.isMultiplexed();
+    return lhs.isValid() == rhs.isValid() && lhs.name() == rhs.name()
+           && lhs.targetName() == rhs.targetName() && lhs.type() == rhs.type()
+           && lhs.version() == rhs.version() && lhs.dependencies() == rhs.dependencies()
+           && lhs.profile() == rhs.profile()
+           && lhs.multiplexConfigurationId() == rhs.multiplexConfigurationId()
+           && lhs.location() == rhs.location() && lhs.groups() == rhs.groups()
+           && lhs.generatedArtifacts() == rhs.generatedArtifacts()
+           && qVariantMapsEqual(lhs.properties(), rhs.properties())
+           && lhs.moduleProperties() == rhs.moduleProperties() && lhs.isEnabled() == rhs.isEnabled()
+           && lhs.isMultiplexed() == rhs.isMultiplexed();
 }
 
 bool operator!=(const ProductData &lhs, const ProductData &rhs)
@@ -954,6 +949,52 @@ QStringList PropertyMap::allProperties() const
 }
 
 /*!
+ * \brief Returns the names of all modules whose properties can be requested.
+ */
+QStringList PropertyMap::allModules() const
+{
+    QStringList modules;
+    for (auto it = d->m_map->value().constBegin(); it != d->m_map->value().constEnd(); ++it) {
+        if (it.value().canConvert<QVariantMap>())
+            modules << it.key();
+    }
+    return modules;
+}
+
+/*!
+ * \brief Returns information about all properties of the given module.
+ */
+QList<PropertyMap::PropertyInfo> PropertyMap::allPropertiesForModule(const QString &module) const
+{
+    const QVariantMap moduleProps = d->m_map->value().value(module).toMap();
+    QList<PropertyInfo> properties;
+    const auto builtinProps = transformed<QStringList>(
+        BuiltinDeclarations::instance().declarationsForType(ItemType::Module).properties(),
+        [](const PropertyDeclaration &decl) { return decl.name(); });
+    for (auto it = moduleProps.begin(); it != moduleProps.end(); ++it) {
+        static const auto getType = [](const QVariant &v) -> QString {
+            switch (qVariantType(v)) {
+            case QMetaType::Bool:
+                return PropertyDeclaration::typeString(PropertyDeclaration::Boolean);
+            case QMetaType::Int:
+                return PropertyDeclaration::typeString(PropertyDeclaration::Integer);
+            case QMetaType::QVariantList:
+                return PropertyDeclaration::typeString(PropertyDeclaration::VariantList);
+            case QMetaType::QString:
+                return PropertyDeclaration::typeString(PropertyDeclaration::String);
+            case QMetaType::QStringList:
+                return PropertyDeclaration::typeString(PropertyDeclaration::StringList);
+            default:
+                return PropertyDeclaration::typeString(PropertyDeclaration::Variant);
+            }
+        };
+        properties << PropertyInfo{
+            it.key(), getType(it.value()), it.value(), builtinProps.contains(it.key())};
+    }
+    return properties;
+}
+
+/*!
  * \brief Returns the value of the given property of a product or group.
  */
 QVariant PropertyMap::getProperty(const QString &name) const
diff --git a/src/lib/corelib/api/projectdata.h b/src/lib/corelib/api/projectdata.h
index 9fe6445c7..4b7bc2803 100644
--- a/src/lib/corelib/api/projectdata.h
+++ b/src/lib/corelib/api/projectdata.h
@@ -74,6 +74,14 @@ class QBS_EXPORT PropertyMap
     friend QBS_EXPORT bool operator!=(const PropertyMap &, const PropertyMap &);
 
 public:
+    struct PropertyInfo
+    {
+        QString name;
+        QString type;
+        QVariant value;
+        bool isBuiltin = false;
+    };
+
     PropertyMap();
     PropertyMap(const PropertyMap &other);
     PropertyMap(PropertyMap &&other) Q_DECL_NOEXCEPT;
@@ -83,6 +91,8 @@ public:
     PropertyMap &operator =(PropertyMap &&other) Q_DECL_NOEXCEPT;
 
     QStringList allProperties() const;
+    QStringList allModules() const;
+    QList<PropertyInfo> allPropertiesForModule(const QString &module) const;
     QVariant getProperty(const QString &name) const;
 
     QStringList getModulePropertiesAsStringList(const QString &moduleName,
diff --git a/src/lib/corelib/buildgraph/buildgraph.cpp b/src/lib/corelib/buildgraph/buildgraph.cpp
index d641627e7..10aae5991 100644
--- a/src/lib/corelib/buildgraph/buildgraph.cpp
+++ b/src/lib/corelib/buildgraph/buildgraph.cpp
@@ -710,7 +710,7 @@ void updateArtifactFromSourceArtifact(const ResolvedProductPtr &product,
     const QVariantMap oldModuleProperties = artifact->properties->value();
     setArtifactData(artifact, sourceArtifact);
     if (oldFileTags != artifact->fileTags()
-            || oldModuleProperties != artifact->properties->value()) {
+        || !qVariantMapsEqual(oldModuleProperties, artifact->properties->value())) {
         invalidateArtifactAsRuleInputIfNecessary(artifact);
     }
 }
@@ -766,7 +766,7 @@ void updateGeneratedArtifacts(ResolvedProduct *product)
             provideFullFileTagsAndProperties(artifact);
             applyPerArtifactProperties(artifact);
             if (oldFileTags != artifact->fileTags()
-                    || oldModuleProperties != artifact->properties->value()) {
+                || !qVariantMapsEqual(oldModuleProperties, artifact->properties->value())) {
                 invalidateArtifactAsRuleInputIfNecessary(artifact);
             }
         }
diff --git a/src/lib/corelib/buildgraph/buildgraphloader.cpp b/src/lib/corelib/buildgraph/buildgraphloader.cpp
index 023931e5c..6488ce9fd 100644
--- a/src/lib/corelib/buildgraph/buildgraphloader.cpp
+++ b/src/lib/corelib/buildgraph/buildgraphloader.cpp
@@ -755,10 +755,11 @@ bool BuildGraphLoader::checkProductForInstallInfoChanges(const ResolvedProductPt
             << StringConstants::installDirProperty() << StringConstants::installPrefixProperty()
             << StringConstants::installRootProperty();
     for (const QString &key : specialProperties) {
-        if (restoredProduct->moduleProperties->qbsPropertyValue(key)
-                != newlyResolvedProduct->moduleProperties->qbsPropertyValue(key)) {
+        if (!qVariantsEqual(
+                restoredProduct->moduleProperties->qbsPropertyValue(key),
+                newlyResolvedProduct->moduleProperties->qbsPropertyValue(key))) {
             qCDebug(lcBuildGraph).noquote().nospace()
-                    << "Product property 'qbs." << key << "' changed.";
+                << "Product property 'qbs." << key << "' changed.";
             return true;
         }
     }
@@ -850,7 +851,8 @@ bool BuildGraphLoader::checkConfigCompatibility()
     }
     if (!m_parameters.overrideBuildGraphData()) {
         if (!m_parameters.overriddenValues().empty()
-                && m_parameters.overriddenValues() != restoredProject->overriddenValues) {
+            && !qVariantMapsEqual(
+                m_parameters.overriddenValues(), restoredProject->overriddenValues)) {
             const auto toUserOutput = [](const QVariantMap &propMap) {
                 QString o;
                 for (auto it = propMap.begin(); it != propMap.end(); ++it) {
@@ -868,7 +870,7 @@ bool BuildGraphLoader::checkConfigCompatibility()
                                    "you really want to rebuild with the new properties.")
                             .arg(toUserOutput(restoredProject->overriddenValues),
                                      toUserOutput(m_parameters.overriddenValues())));
-            }
+        }
         m_parameters.setOverriddenValues(restoredProject->overriddenValues);
         if (m_parameters.topLevelProfile() != restoredProject->profile()) {
             throw ErrorInfo(Tr::tr("The current profile is '%1', but profile '%2' was used "
@@ -883,7 +885,8 @@ bool BuildGraphLoader::checkConfigCompatibility()
     }
     if (!m_parameters.overrideBuildGraphData())
         return true;
-    if (m_parameters.finalBuildConfigurationTree() != restoredProject->buildConfiguration())
+    if (!qVariantMapsEqual(
+            m_parameters.finalBuildConfigurationTree(), restoredProject->buildConfiguration()))
         return false;
     Settings settings(m_parameters.settingsDirectory());
     const QVariantMap profileConfigsTree = restoredProject->fullProfileConfigsTree();
diff --git a/src/lib/corelib/buildgraph/rulecommands.cpp b/src/lib/corelib/buildgraph/rulecommands.cpp
index 6acd1d68c..73d05eaca 100644
--- a/src/lib/corelib/buildgraph/rulecommands.cpp
+++ b/src/lib/corelib/buildgraph/rulecommands.cpp
@@ -99,15 +99,11 @@ AbstractCommand::~AbstractCommand() = default;
 
 bool AbstractCommand::equals(const AbstractCommand *other) const
 {
-    return type() == other->type()
-            && m_description == other->m_description
-            && m_extendedDescription == other->m_extendedDescription
-            && m_highlight == other->m_highlight
-            && m_ignoreDryRun == other->m_ignoreDryRun
-            && m_silent == other->m_silent
-            && m_jobPool == other->m_jobPool
-            && m_timeout == other->m_timeout
-            && m_properties == other->m_properties;
+    return type() == other->type() && m_description == other->m_description
+           && m_extendedDescription == other->m_extendedDescription
+           && m_highlight == other->m_highlight && m_ignoreDryRun == other->m_ignoreDryRun
+           && m_silent == other->m_silent && m_jobPool == other->m_jobPool
+           && m_timeout == other->m_timeout && qVariantMapsEqual(m_properties, other->m_properties);
 }
 
 void AbstractCommand::fillFromScriptValue(JSContext *ctx, const JSValue *scriptValue,
diff --git a/src/lib/corelib/buildgraph/rulesapplicator.cpp b/src/lib/corelib/buildgraph/rulesapplicator.cpp
index 5cc4be96e..e07abd74a 100644
--- a/src/lib/corelib/buildgraph/rulesapplicator.cpp
+++ b/src/lib/corelib/buildgraph/rulesapplicator.cpp
@@ -293,8 +293,9 @@ void RulesApplicator::doApply(const ArtifactSet &inputArtifacts, JSValue prepare
             }
             outputArtifact->properties->setValue(artifactModulesCfg);
             if (!outputInfo.newlyCreated
-                    && (outputArtifact->fileTags() != outputInfo.oldFileTags
-                        || outputArtifact->properties->value() != outputInfo.oldProperties)) {
+                && (outputArtifact->fileTags() != outputInfo.oldFileTags
+                    || !qVariantMapsEqual(
+                        outputArtifact->properties->value(), outputInfo.oldProperties))) {
                 invalidateArtifactAsRuleInputIfNecessary(outputArtifact);
             }
         }
@@ -664,8 +665,10 @@ Artifact *RulesApplicator::createOutputArtifactFromScriptValue(const JSValue &ob
             connect(outputInfo.artifact, dependency);
     }
     ArtifactBindingsExtractor().apply(engine(), outputInfo.artifact, obj);
-    if (!outputInfo.newlyCreated && (outputInfo.artifact->fileTags() != outputInfo.oldFileTags
-            || outputInfo.artifact->properties->value() != outputInfo.oldProperties)) {
+    if (!outputInfo.newlyCreated
+        && (outputInfo.artifact->fileTags() != outputInfo.oldFileTags
+            || !qVariantMapsEqual(
+                outputInfo.artifact->properties->value(), outputInfo.oldProperties))) {
         invalidateArtifactAsRuleInputIfNecessary(outputInfo.artifact);
     }
     return outputInfo.artifact;
diff --git a/src/lib/corelib/buildgraph/transformerchangetracking.cpp b/src/lib/corelib/buildgraph/transformerchangetracking.cpp
index f0b8986f4..ae43e8219 100644
--- a/src/lib/corelib/buildgraph/transformerchangetracking.cpp
+++ b/src/lib/corelib/buildgraph/transformerchangetracking.cpp
@@ -158,7 +158,7 @@ bool TrafoChangeTracker::checkForPropertyChange(const Property &restoredProperty
     case Property::PropertyInArtifact:
         QBS_CHECK(false);
     }
-    if (restoredProperty.value != v) {
+    if (!qVariantsEqual(restoredProperty.value, v)) {
         qCDebug(lcBuildGraph).noquote().nospace()
                 << "Value for property '" << restoredProperty.moduleName << "."
                 << restoredProperty.propertyName << "' has changed.\n"
diff --git a/src/lib/corelib/language/language.cpp b/src/lib/corelib/language/language.cpp
index d2c213999..1f491814a 100644
--- a/src/lib/corelib/language/language.cpp
+++ b/src/lib/corelib/language/language.cpp
@@ -939,7 +939,7 @@ bool operator==(const ExportedProperty &p1, const ExportedProperty &p2)
 
 bool operator==(const ExportedModuleDependency &d1, const ExportedModuleDependency &d2)
 {
-    return d1.name == d2.name && d1.moduleProperties == d2.moduleProperties;
+    return d1.name == d2.name && qVariantMapsEqual(d1.moduleProperties, d2.moduleProperties);
 }
 
 bool equals(const std::vector<ExportedItemPtr> &l1, const std::vector<ExportedItemPtr> &l2)
@@ -966,20 +966,19 @@ bool operator==(const ExportedModule &m1, const ExportedModule &m2)
         for (auto it1 = m1.cbegin(), it2 = m2.cbegin(); it1 != m1.cend(); ++it1, ++it2) {
             if (it1.key()->name != it2.key()->name)
                 return false;
-            if (it1.value() != it2.value())
+            if (!qVariantMapsEqual(it1.value(), it2.value()))
                 return false;
         }
         return true;
     };
 
-    return m1.propertyValues == m2.propertyValues
-            && m1.modulePropertyValues == m2.modulePropertyValues
-            && equals(m1.children, m2.children)
-            && m1.m_properties == m2.m_properties
-            && m1.importStatements == m2.importStatements
-            && m1.productDependencies.size() == m2.productDependencies.size()
-            && m1.productDependencies == m2.productDependencies
-            && depMapsEqual(m1.dependencyParameters, m2.dependencyParameters);
+    return qVariantMapsEqual(m1.propertyValues, m2.propertyValues)
+           && qVariantMapsEqual(m1.modulePropertyValues, m2.modulePropertyValues)
+           && equals(m1.children, m2.children) && m1.m_properties == m2.m_properties
+           && m1.importStatements == m2.importStatements
+           && m1.productDependencies.size() == m2.productDependencies.size()
+           && m1.productDependencies == m2.productDependencies
+           && depMapsEqual(m1.dependencyParameters, m2.dependencyParameters);
 }
 
 JSValue PrivateScriptFunction::getFunction(ScriptEngine *engine, const QString &errorMessage) const
diff --git a/src/lib/corelib/language/propertydeclaration.cpp b/src/lib/corelib/language/propertydeclaration.cpp
index 9b1b890f4..d56ab3bb0 100644
--- a/src/lib/corelib/language/propertydeclaration.cpp
+++ b/src/lib/corelib/language/propertydeclaration.cpp
@@ -308,6 +308,26 @@ QVariant PropertyDeclaration::convertToPropertyType(const QVariant &v, Type t,
     return c;
 }
 
+QVariant PropertyDeclaration::typedNullValue() const
+{
+    switch (type()) {
+    case PropertyDeclaration::Boolean:
+        return typedNullVariant<bool>();
+    case PropertyDeclaration::Integer:
+        return typedNullVariant<int>();
+    case PropertyDeclaration::VariantList:
+        return typedNullVariant<QVariantList>();
+    case PropertyDeclaration::String:
+    case PropertyDeclaration::Path:
+        return typedNullVariant<QString>();
+    case PropertyDeclaration::StringList:
+    case PropertyDeclaration::PathList:
+        return typedNullVariant<QStringList>();
+    default:
+        return {};
+    }
+}
+
 bool PropertyDeclaration::shouldCheckAllowedValues() const
 {
     return isValid()
diff --git a/src/lib/corelib/language/propertydeclaration.h b/src/lib/corelib/language/propertydeclaration.h
index a64094af8..79a39ecbd 100644
--- a/src/lib/corelib/language/propertydeclaration.h
+++ b/src/lib/corelib/language/propertydeclaration.h
@@ -128,6 +128,7 @@ public:
 
     static QVariant convertToPropertyType(
             const QVariant &v, Type t, const QStringList &namePrefix, const QString &key);
+    QVariant typedNullValue() const;
 
     bool shouldCheckAllowedValues() const;
     void checkAllowedValues(
diff --git a/src/lib/corelib/language/propertymapinternal.h b/src/lib/corelib/language/propertymapinternal.h
index 83e18ba48..af551cf6f 100644
--- a/src/lib/corelib/language/propertymapinternal.h
+++ b/src/lib/corelib/language/propertymapinternal.h
@@ -77,7 +77,7 @@ private:
 
 inline bool operator==(const PropertyMapInternal &lhs, const PropertyMapInternal &rhs)
 {
-    return lhs.m_value == rhs.m_value;
+    return qVariantsEqual(lhs.m_value, rhs.m_value);
 }
 
 QVariant QBS_AUTOTEST_EXPORT moduleProperty(const QVariantMap &properties,
diff --git a/src/lib/corelib/language/scriptengine.cpp b/src/lib/corelib/language/scriptengine.cpp
index d655c0073..7847cb24d 100644
--- a/src/lib/corelib/language/scriptengine.cpp
+++ b/src/lib/corelib/language/scriptengine.cpp
@@ -488,6 +488,8 @@ void ScriptEngine::addInternalExtension(const char *name, JSValue ext)
 
 JSValue ScriptEngine::asJsValue(const QVariant &v, quintptr id, bool frozen)
 {
+    if (v.isNull())
+        return JS_UNDEFINED;
     switch (static_cast<QMetaType::Type>(v.userType())) {
     case QMetaType::QByteArray:
         return asJsValue(v.toByteArray());
diff --git a/src/lib/corelib/loader/dependenciesresolver.cpp b/src/lib/corelib/loader/dependenciesresolver.cpp
index e49af1600..5df47217f 100644
--- a/src/lib/corelib/loader/dependenciesresolver.cpp
+++ b/src/lib/corelib/loader/dependenciesresolver.cpp
@@ -751,7 +751,7 @@ void DependenciesResolver::adjustDependsItemForMultiplexing(Item *dependsItem)
         for (auto lhsProperty = lhs.constBegin(); lhsProperty != lhs.constEnd(); lhsProperty++) {
             const auto rhsProperty = rhs.find(lhsProperty.key());
             const bool isCommonProperty = rhsProperty != rhs.constEnd();
-            if (isCommonProperty && lhsProperty.value() != rhsProperty.value())
+            if (isCommonProperty && !qVariantsEqual(lhsProperty.value(), rhsProperty.value()))
                 return false;
         }
         return true;
diff --git a/src/lib/corelib/loader/loaderutils.cpp b/src/lib/corelib/loader/loaderutils.cpp
index a78b3b4c5..a6105ee50 100644
--- a/src/lib/corelib/loader/loaderutils.cpp
+++ b/src/lib/corelib/loader/loaderutils.cpp
@@ -943,7 +943,7 @@ void DependencyParametersMerger::merge(QVariantMap &current, const QVariantMap &
             currentValue = mdst;
         } else {
             if (m_currentPrio == nextPrio) {
-                if (currentValue.isValid() && currentValue != newValue)
+                if (currentValue.isValid() && !qVariantsEqual(currentValue, newValue))
                     m_conflicts.emplace_back(m_path, currentValue, newValue, m_currentPrio);
             } else {
                 removeIf(m_conflicts, [this](const Conflict &conflict) {
diff --git a/src/lib/corelib/loader/probesresolver.cpp b/src/lib/corelib/loader/probesresolver.cpp
index b38366900..efca2854c 100644
--- a/src/lib/corelib/loader/probesresolver.cpp
+++ b/src/lib/corelib/loader/probesresolver.cpp
@@ -212,7 +212,7 @@ void ProbesResolver::resolveProbe(ProductContext &productContext, Item *parent,
                 newValue = initialProperties.value(b.first);
             }
         }
-        if (newValue != getJsVariant(ctx, b.second)) {
+        if (!qVariantsEqual(newValue, getJsVariant(ctx, b.second))) {
             if (!resolvedProbe)
                 storedValue = VariantValue::createStored(newValue);
             else
@@ -281,10 +281,10 @@ bool ProbesResolver::probeMatches(const ProbeConstPtr &probe, bool condition,
         CompareScript compareScript) const
 {
     return probe->condition() == condition
-            && probe->initialProperties() == initialProperties
-            && (compareScript == CompareScript::No
-                || (probe->configureScript() == configureScript
-                    && !probe->needsReconfigure(m_loaderState.topLevelProject().lastResolveTime())));
+           && qVariantMapsEqual(probe->initialProperties(), initialProperties)
+           && (compareScript == CompareScript::No
+               || (probe->configureScript() == configureScript
+                   && !probe->needsReconfigure(m_loaderState.topLevelProject().lastResolveTime())));
 }
 
 } // namespace Internal
diff --git a/src/lib/corelib/loader/productresolver.cpp b/src/lib/corelib/loader/productresolver.cpp
index 9944fc56f..fd2f044a7 100644
--- a/src/lib/corelib/loader/productresolver.cpp
+++ b/src/lib/corelib/loader/productresolver.cpp
@@ -1589,7 +1589,13 @@ void PropertiesEvaluator::evaluateProperty(
         } else if (pd.type() == PropertyDeclaration::VariantList) {
             v = v.toList();
         }
+
+        // Enforce proper type for undefined values (note that path degrades to string).
+        if (!v.isValid())
+            v = pd.typedNullValue();
+
         pd.checkAllowedValues(v, propValue->location(), propName, m_loaderState);
+
         result[propName] = v;
         break;
     }
diff --git a/src/lib/corelib/parser/qmljsastvisitor_p.h b/src/lib/corelib/parser/qmljsastvisitor_p.h
index bec174c65..4b7911aa4 100644
--- a/src/lib/corelib/parser/qmljsastvisitor_p.h
+++ b/src/lib/corelib/parser/qmljsastvisitor_p.h
@@ -58,7 +58,7 @@
 namespace QbsQmlJS {
 namespace AST {
 
-class QBS_AUTOTEST_EXPORT Visitor
+class QML_PARSER_EXPORT Visitor
 {
 public:
     Visitor();
diff --git a/src/lib/corelib/parser/qmljsengine_p.h b/src/lib/corelib/parser/qmljsengine_p.h
index 2a616126d..9c603ee5c 100644
--- a/src/lib/corelib/parser/qmljsengine_p.h
+++ b/src/lib/corelib/parser/qmljsengine_p.h
@@ -93,7 +93,7 @@ public:
     QString message;
 };
 
-class QBS_AUTOTEST_EXPORT Engine
+class QML_PARSER_EXPORT Engine
 {
     Lexer *_lexer{nullptr};
     Directives *_directives{nullptr};
diff --git a/src/lib/corelib/parser/qmljsglobal_p.h b/src/lib/corelib/parser/qmljsglobal_p.h
index c3d198ea5..02e0b38e4 100644
--- a/src/lib/corelib/parser/qmljsglobal_p.h
+++ b/src/lib/corelib/parser/qmljsglobal_p.h
@@ -41,31 +41,14 @@
 
 #include <QtCore/qglobal.h>
 
-// Force QML_PARSER_EXPORT to be always empty.
-#ifndef QT_CREATOR
-#   define QT_CREATOR
-#endif
-#ifdef QML_BUILD_STATIC_LIB
-#   undef QML_BUILD_STATIC_LIB
-#endif
-#define QML_BUILD_STATIC_LIB 1
-
-#ifdef QT_CREATOR
-#  ifdef QMLJS_BUILD_DIR
-#    define QML_PARSER_EXPORT Q_DECL_EXPORT
-#  elif QML_BUILD_STATIC_LIB
-#    define QML_PARSER_EXPORT
-#  else
-#    define QML_PARSER_EXPORT Q_DECL_IMPORT
-#  endif // QMLJS_BUILD_DIR
-
-#else // !QT_CREATOR
-#  if defined(QT_BUILD_QMLDEVTOOLS_LIB) || defined(QT_QMLDEVTOOLS_LIB)
-     // QmlDevTools is a static library
-#    define QML_PARSER_EXPORT
-#  else
-#    define QML_PARSER_EXPORT Q_AUTOTEST_EXPORT
-#  endif
-#endif // QT_CREATOR
+#ifdef QBS_STATIC_LIB
+#define QML_PARSER_EXPORT
+#else
+#ifdef QBS_LIBRARY
+#define QML_PARSER_EXPORT Q_DECL_EXPORT
+#else
+#define QML_PARSER_EXPORT Q_DECL_IMPORT
+#endif // QBS_LIBRARY
+#endif // QBS_STATIC_LIB
 
 #endif // QMLJSGLOBAL_P_H
diff --git a/src/lib/corelib/parser/qmljslexer_p.h b/src/lib/corelib/parser/qmljslexer_p.h
index aef68e0c5..c9801c0f5 100644
--- a/src/lib/corelib/parser/qmljslexer_p.h
+++ b/src/lib/corelib/parser/qmljslexer_p.h
@@ -86,7 +86,7 @@ public:
     }
 };
 
-class QBS_AUTOTEST_EXPORT Lexer: public QmlJSGrammar
+class QML_PARSER_EXPORT Lexer : public QmlJSGrammar
 {
 public:
     enum {
diff --git a/src/lib/corelib/parser/qmljsparser_p.h b/src/lib/corelib/parser/qmljsparser_p.h
index c761bb25b..9744a7eb6 100644
--- a/src/lib/corelib/parser/qmljsparser_p.h
+++ b/src/lib/corelib/parser/qmljsparser_p.h
@@ -70,7 +70,7 @@ namespace QbsQmlJS {
 
 class Engine;
 
-class QBS_AUTOTEST_EXPORT Parser: protected QmlJSGrammar
+class QML_PARSER_EXPORT Parser : protected QmlJSGrammar
 {
 public:
     union Value {
diff --git a/src/lib/corelib/tools/persistence.cpp b/src/lib/corelib/tools/persistence.cpp
index 44090dee2..0e545377a 100644
--- a/src/lib/corelib/tools/persistence.cpp
+++ b/src/lib/corelib/tools/persistence.cpp
@@ -140,6 +140,11 @@ void PersistentPool::finalizeWriteStream()
 
 void PersistentPool::storeVariant(const QVariant &variant)
 {
+    if (variant.isNull()) {
+        m_stream << quint32(QMetaType::User);
+        m_stream << variant;
+        return;
+    }
     const auto type = static_cast<quint32>(variant.userType());
     m_stream << type;
     switch (type) {
@@ -231,8 +236,5 @@ void PersistentPool::doStoreValue(const QProcessEnvironment &env)
         store(env.value(key));
 }
 
-const PersistentPool::PersistentObjectId PersistentPool::ValueNotFoundId;
-const PersistentPool::PersistentObjectId PersistentPool::EmptyValueId;
-
 } // namespace Internal
 } // namespace qbs
diff --git a/src/lib/corelib/tools/persistence.h b/src/lib/corelib/tools/persistence.h
index b7aa543a4..86365c993 100644
--- a/src/lib/corelib/tools/persistence.h
+++ b/src/lib/corelib/tools/persistence.h
@@ -145,8 +145,9 @@ private:
     template<typename T> QHash<T, PersistentObjectId> &idMap();
     template<typename T> PersistentObjectId &lastStoredId();
 
-    static const PersistentObjectId ValueNotFoundId = -1;
-    static const PersistentObjectId EmptyValueId = -2;
+    static const inline PersistentObjectId ValueNotFoundId = -1;
+    static const inline PersistentObjectId EmptyValueId = -2;
+    static const inline PersistentObjectId NullValueId = -3;
 
     std::unique_ptr<QIODevice> m_file;
     QDataStream m_stream;
@@ -271,8 +272,13 @@ template<typename T> inline T PersistentPool::idLoadValue()
 {
     int id;
     m_stream >> id;
-    if (id == EmptyValueId)
+    if (id == NullValueId)
         return T();
+    if (id == EmptyValueId) {
+        if constexpr (std::is_same_v<T, QString>)
+            return QString(0, QChar());
+        return T();
+    }
     QBS_CHECK(id >= 0);
     if (id >= static_cast<int>(idStorage<T>().size())) {
         T value;
@@ -287,6 +293,12 @@ template<typename T> inline T PersistentPool::idLoadValue()
 template<typename T>
 void PersistentPool::idStoreValue(const T &value)
 {
+    if constexpr (std::is_same_v<T, QString>) {
+        if (value.isNull()) {
+            m_stream << NullValueId;
+            return;
+        }
+    }
     if (value.isEmpty()) {
         m_stream << EmptyValueId;
         return;
diff --git a/src/lib/corelib/tools/qttools.h b/src/lib/corelib/tools/qttools.h
index 88ada73d4..029948be4 100644
--- a/src/lib/corelib/tools/qttools.h
+++ b/src/lib/corelib/tools/qttools.h
@@ -199,6 +199,51 @@ inline bool qVariantConvert(QVariant &variant, int typeId)
 #endif
 }
 
+inline QMetaType::Type qVariantType(const QVariant &v)
+{
+    return static_cast<QMetaType::Type>(
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+        v.metaType().id()
+#else
+        v.type()
+#endif
+    );
+}
+
+template<typename T>
+inline QVariant typedNullVariant()
+{
+    const auto metaType = QMetaType::fromType<T>();
+#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
+    return QVariant(metaType, nullptr);
+#else
+    return QVariant(static_cast<QVariant::Type>(metaType.id()));
+#endif
+}
+
+inline bool qVariantsEqual(const QVariant &v1, const QVariant &v2)
+{
+    return v1.isNull() == v2.isNull() && v1 == v2;
+}
+
+inline bool qVariantMapsEqual(const QVariantMap &m1, const QVariantMap &m2)
+{
+    if (m1.size() != m2.size())
+        return false;
+    if (m1.isSharedWith(m2))
+        return true;
+
+    auto it1 = m1.cbegin();
+    auto it2 = m2.cbegin();
+    while (it1 != m1.cend()) {
+        if (it1.key() != it2.key() || !qVariantsEqual(it1.value(), it2.value()))
+            return false;
+        ++it2;
+        ++it1;
+    }
+    return true;
+}
+
 } // namespace qbs
 
 #endif // QBSQTTOOLS_H
diff --git a/src/lib/corelib/tools/setupprojectparameters.cpp b/src/lib/corelib/tools/setupprojectparameters.cpp
index 28ad745ce..185323c09 100644
--- a/src/lib/corelib/tools/setupprojectparameters.cpp
+++ b/src/lib/corelib/tools/setupprojectparameters.cpp
@@ -47,6 +47,7 @@
 #include <tools/jsonhelper.h>
 #include <tools/profile.h>
 #include <tools/qbsassert.h>
+#include <tools/qttools.h>
 #include <tools/scripttools.h>
 #include <tools/settings.h>
 #include <tools/stringconstants.h>
@@ -517,7 +518,7 @@ ErrorInfo SetupProjectParameters::expandBuildConfiguration()
     QVariantMap expandedConfig = expandedBuildConfiguration(profile, configurationName(), &err);
     if (err.hasError())
         return err;
-    if (d->buildConfiguration != expandedConfig) {
+    if (!qVariantMapsEqual(d->buildConfiguration, expandedConfig)) {
         d->buildConfigurationTree.clear();
         d->buildConfiguration = expandedConfig;
     }
diff --git a/tests/auto/api/tst_api.cpp b/tests/auto/api/tst_api.cpp
index d3141ce59..7726cee15 100644
--- a/tests/auto/api/tst_api.cpp
+++ b/tests/auto/api/tst_api.cpp
@@ -1925,7 +1925,8 @@ struct ProductDataSelector
     bool qbsPropertiesMatch(const qbs::ProductData &p) const
     {
         for (auto it = qbsProperties.begin(); it != qbsProperties.end(); ++it) {
-            if (it.value() != p.moduleProperties().getModuleProperty("qbs", it.key()))
+            if (!qbs::qVariantsEqual(
+                    it.value(), p.moduleProperties().getModuleProperty("qbs", it.key())))
                 return false;
         }
         return true;
diff --git a/tests/auto/blackbox/testdata/lsp/lsp.qbs b/tests/auto/blackbox/testdata/lsp/lsp.qbs
index 2e30ad930..24479e0ec 100644
--- a/tests/auto/blackbox/testdata/lsp/lsp.qbs
+++ b/tests/auto/blackbox/testdata/lsp/lsp.qbs
@@ -3,6 +3,7 @@ Project {
         name: "dep"
         Depends { name: "m" }
         Depends { name: "Prefix"; submodules: ["m1", "m2", "m3"] }
+
     }
     Product {
         Depends { name: "dep" }
diff --git a/tests/auto/blackbox/testdata/lsp/modules/Prefix/m1/m1.qbs b/tests/auto/blackbox/testdata/lsp/modules/Prefix/m1/m1.qbs
index 84957060c..09bac2dc2 100644
--- a/tests/auto/blackbox/testdata/lsp/modules/Prefix/m1/m1.qbs
+++ b/tests/auto/blackbox/testdata/lsp/modules/Prefix/m1/m1.qbs
@@ -1,2 +1,5 @@
 Module {
+    property bool p1
+    property string p2
+    property bool x
 }
diff --git a/tests/auto/blackbox/tst_blackbox.cpp b/tests/auto/blackbox/tst_blackbox.cpp
index 11a4078ea..8ba6e2fa5 100644
--- a/tests/auto/blackbox/tst_blackbox.cpp
+++ b/tests/auto/blackbox/tst_blackbox.cpp
@@ -6369,20 +6369,33 @@ void TestBlackbox::qbsLanguageServer_data()
             << ((testDataDir + "/lsp/modules/Prefix/m1/m1.qbs:1:1\n")
                 + (testDataDir + "/lsp/modules/Prefix/m2/m2.qbs:1:1\n")
                 + (testDataDir + "/lsp/modules/Prefix/m3/m3.qbs:1:1"));
-    QTest::addRow("follow to product") << "--goto-def"
-                                       << (testDataDir + "/lsp/lsp.qbs:8:19")
-                                       << QString() << QString()
-                                       << (testDataDir + "/lsp/lsp.qbs:2:5");
+    QTest::addRow("follow to product")
+        << "--goto-def" << (testDataDir + "/lsp/lsp.qbs:9:19") << QString() << QString()
+        << (testDataDir + "/lsp/lsp.qbs:2:5");
     QTest::addRow("follow to module, non-invalidating insert")
-            << "--goto-def"
-            << (testDataDir + "/lsp/lsp.qbs:4:9")
-            << "5:9" << QString("property bool dummy\n")
-            << (testDataDir + "/lsp/modules/m/m.qbs:1:1");
+        << "--goto-def" << (testDataDir + "/lsp/lsp.qbs:4:9") << "5:9"
+        << QString("property bool dummy\n") << (testDataDir + "/lsp/modules/m/m.qbs:1:1");
     QTest::addRow("follow to module, invalidating insert")
-            << "--goto-def"
-            << (testDataDir + "/lsp/lsp.qbs:4:9")
-            << QString() << QString("property bool dummy\n")
-            << QString();
+        << "--goto-def" << (testDataDir + "/lsp/lsp.qbs:4:9") << QString()
+        << QString("property bool dummy\n") << QString();
+    QTest::addRow("completion: LHS, module prefix")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString() << QString("P")
+        << QString("Prefix.m1\nPrefix.m2\nPrefix.m3");
+    QTest::addRow("completion: LHS, module name")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString() << QString("Prefix.m")
+        << QString("m1\nm2\nm3");
+    QTest::addRow("completion: LHS, module property right after dot")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString()
+        << QString("Prefix.m1.") << QString("p1 bool\np2 string\nx bool");
+    QTest::addRow("completion: LHS, module property with identifier prefix")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString()
+        << QString("Prefix.m1.p") << QString("p1 bool\np2 string");
+    QTest::addRow("completion: simple RHS, module property")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString()
+        << QString("property bool dummy: Prefix.m1.p") << QString("p1 bool\np2 string");
+    QTest::addRow("completion: complex RHS, module property")
+        << "--completion" << (testDataDir + "/lsp/lsp.qbs:7:1") << QString()
+        << QString("property bool dummy: { return Prefix.m1.p") << QString("p1 bool\np2 string");
 }
 
 void TestBlackbox::qbsLanguageServer()
diff --git a/tests/auto/language/tst_language.cpp b/tests/auto/language/tst_language.cpp
index 7af4356cb..456e8b9d0 100644
--- a/tests/auto/language/tst_language.cpp
+++ b/tests/auto/language/tst_language.cpp
@@ -1928,7 +1928,7 @@ void TestLanguage::moduleParameters()
             };
             const QVariantMap actual = findInProduct(it.key());
             const QVariantMap expected = it.value().toMap();
-            const bool same = actual == expected;
+            const bool same = qVariantMapsEqual(actual, expected);
             if (!same) {
                 qDebug().noquote() << "---" << expected;
                 qDebug().noquote() << "+++" << actual;
diff --git a/tests/lspclient/lspclient.cpp b/tests/lspclient/lspclient.cpp
index 8574161da..40adc9288 100644
--- a/tests/lspclient/lspclient.cpp
+++ b/tests/lspclient/lspclient.cpp
@@ -27,6 +27,7 @@
 ****************************************************************************/
 
 #include <lsp/clientcapabilities.h>
+#include <lsp/completion.h>
 #include <lsp/initializemessages.h>
 #include <lsp/languagefeatures.h>
 #include <lsp/textsynchronization.h>
@@ -40,7 +41,10 @@
 #include <cstdlib>
 #include <iostream>
 
-enum class Command { GotoDefinition, };
+enum class Command {
+    GotoDefinition,
+    Completion,
+};
 
 class LspClient : public QObject
 {
@@ -65,6 +69,8 @@ private:
     void handleResponse();
     void sendGotoDefinitionRequest();
     void handleGotoDefinitionResponse();
+    void sendCompletionRequest();
+    void handleCompletionResponse();
     lsp::DocumentUri uri() const;
     lsp::DocumentUri::PathMapper mapper() const;
 
@@ -93,6 +99,8 @@ int main(int argc, char *argv[])
                                           "socket");
     const QCommandLineOption gotoDefinitionOption(
                 {"goto-def", "g"}, "Go to definition from the specified location.");
+    const QCommandLineOption completionOption(
+        {"completion", "c"}, "Request completion at the specified location.");
     const QCommandLineOption insertCodeOption("insert-code",
                                           "A piece of code to insert before doing the actual "
                                           "operation.",
@@ -101,7 +109,12 @@ int main(int argc, char *argv[])
                                                 "The location at which to insert the code.",
                                                 "<line>:<column>");
     QCommandLineParser parser;
-    parser.addOptions({socketOption, insertCodeOption, insertLocationOption, gotoDefinitionOption});
+    parser.addOptions(
+        {socketOption,
+         insertCodeOption,
+         insertLocationOption,
+         gotoDefinitionOption,
+         completionOption});
     parser.addHelpOption();
     parser.addPositionalArgument("location", "The location at which to operate.",
                                  "<file>:<line>:<column>");
@@ -120,6 +133,8 @@ int main(int argc, char *argv[])
 
     if (parser.isSet(gotoDefinitionOption))
         command = Command::GotoDefinition;
+    else if (parser.isSet(completionOption))
+        command = Command::Completion;
     else
         complainAndExit("Don't know what to do.");
 
@@ -339,6 +354,8 @@ void LspClient::sendRequest()
     switch (m_command) {
     case Command::GotoDefinition:
         return sendGotoDefinitionRequest();
+    case Command::Completion:
+        return sendCompletionRequest();
     }
 }
 
@@ -352,6 +369,8 @@ void LspClient::handleResponse()
     switch (m_command) {
     case Command::GotoDefinition:
         return handleGotoDefinitionResponse();
+    case Command::Completion:
+        return handleCompletionResponse();
     }
 }
 
@@ -380,6 +399,29 @@ void LspClient::handleGotoDefinitionResponse()
     exit(EXIT_SUCCESS);
 }
 
+void LspClient::sendCompletionRequest()
+{
+    const lsp::TextDocumentIdentifier doc(uri());
+    const lsp::Position pos(m_line - 1, m_column - 1);
+    sendMessage(lsp::CompletionRequest({doc, pos}));
+}
+
+void LspClient::handleCompletionResponse()
+{
+    const lsp::CompletionResult result(lsp::CompletionRequest::Response(m_messageObject)
+                                           .result()
+                                           .value_or(lsp::CompletionResult()));
+    if (const auto items = std::get_if<QList<lsp::CompletionItem>>(&result)) {
+        for (const lsp::CompletionItem &item : *items) {
+            std::cout << qPrintable(item.label());
+            if (item.detail())
+                std::cout << ' ' << qPrintable(*item.detail());
+            std::cout << std::endl;
+        }
+    }
+    exit(EXIT_SUCCESS);
+}
+
 lsp::DocumentUri LspClient::uri() const
 {
     return lsp::DocumentUri::fromFilePath(lsp::Utils::FilePath::fromUserInput(m_filePath),