qmllint: Warn about unintentional empty blocksHEADdev

If a property binding is a js block without any statements, it could
mean that the user intended to create an object literal instead of an
empty block that returns undefined.

Task-number: QTBUG-129307
Change-Id: If242ddac140cce6479062194b785096ba1f6c0a6
Reviewed-by: Fabian Kosmale <[email protected]>

5 files changed, 23 insertions, 1 deletions

diff --git a/src/qmlcompiler/qqmljsimportvisitor_p.h b/src/qmlcompiler/qqmljsimportvisitor_p.h
index 32f6915b32..c13f09f112 100644
--- a/src/qmlcompiler/qqmljsimportvisitor_p.h
+++ b/src/qmlcompiler/qqmljsimportvisitor_p.h
@@ -305,7 +305,7 @@ protected:
 
     enum class BindingExpressionParseResult { Invalid, Script, Literal, Translation };
     enum class BindingForPropertyDefintion { Yes, No };
-    BindingExpressionParseResult parseBindingExpression(
+    virtual BindingExpressionParseResult parseBindingExpression(
             const QString &name, const QQmlJS::AST::Statement *statement,
             const QQmlJS::AST::UiPublicMember *associatedPropertyDefinition = nullptr);
     bool isImportPrefix(QString prefix) const;
diff --git a/src/qmlcompiler/qqmljslintervisitor.cpp b/src/qmlcompiler/qqmljslintervisitor.cpp
index b5d254a00c..540ba6c535 100644
--- a/src/qmlcompiler/qqmljslintervisitor.cpp
+++ b/src/qmlcompiler/qqmljslintervisitor.cpp
@@ -416,6 +416,22 @@ bool LinterVisitor::visit(ExpressionStatement *ast)
     return true;
 }
 
+QQmlJSImportVisitor::BindingExpressionParseResult LinterVisitor::parseBindingExpression(
+        const QString &name, const QQmlJS::AST::Statement *statement,
+        const QQmlJS::AST::UiPublicMember *associatedPropertyDefinition)
+{
+    if (statement && statement->kind == (int)AST::Node::Kind::Kind_Block) {
+        const auto *block = static_cast<const AST::Block *>(statement);
+        if (!block->statements && associatedPropertyDefinition) {
+            m_logger->log("Unintentional empty block, use ({}) for empty object literal"_L1,
+                          qmlUnintentionalEmptyBlock,
+                          combine(block->lbraceToken, block->rbraceToken));
+        }
+    }
+
+    return QQmlJSImportVisitor::parseBindingExpression(name, statement, associatedPropertyDefinition);
+}
+
 void LinterVisitor::handleLiteralBinding(const QQmlJSMetaPropertyBinding &binding,
                                          const UiPublicMember *associatedPropertyDefinition)
 {
diff --git a/src/qmlcompiler/qqmljslintervisitor_p.h b/src/qmlcompiler/qqmljslintervisitor_p.h
index 416dc972c1..efec9b3abf 100644
--- a/src/qmlcompiler/qqmljslintervisitor_p.h
+++ b/src/qmlcompiler/qqmljslintervisitor_p.h
@@ -92,6 +92,9 @@ private:
     void warnCaseNoFlowControl(QQmlJS::SourceLocation caseToken) const;
     void checkCaseFallthrough(QQmlJS::AST::StatementList *statements, SourceLocation errorLoc,
                               SourceLocation nextLoc);
+    BindingExpressionParseResult parseBindingExpression(
+            const QString &name, const QQmlJS::AST::Statement *statement,
+            const QQmlJS::AST::UiPublicMember *associatedPropertyDefinition = nullptr) override;
     void handleLiteralBinding(const QQmlJSMetaPropertyBinding &binding,
                               const AST::UiPublicMember *associatedPropertyDefinition) override;
 };
diff --git a/src/qmlcompiler/qqmljslogger.cpp b/src/qmlcompiler/qqmljslogger.cpp
index d3cf05fb1d..40bdd9c48d 100644
--- a/src/qmlcompiler/qqmljslogger.cpp
+++ b/src/qmlcompiler/qqmljslogger.cpp
@@ -131,6 +131,8 @@ using namespace Qt::StringLiterals;
       false, false)                                                                                \
     X(qmlUncreatableType, "uncreatable-type", "UncreatableType",                                   \
       "Warn if uncreatable types are created", QtWarningMsg, false, false)                         \
+    X(qmlUnintentionalEmptyBlock, "unintentional-empty-block", "UnintentionalEmptyBlock",          \
+      "Warn about bindings that contain only an empty block", QtWarningMsg, false, false)          \
     X(qmlUnqualified, "unqualified", "UnqualifiedAccess",                                          \
       "Warn about unqualified identifiers and how to fix them", QtWarningMsg, false, false)        \
     X(qmlUnreachableCode, "unreachable-code", "UnreachableCode", "Warn about unreachable code.",   \
diff --git a/src/qmlcompiler/qqmljsloggingutils.h b/src/qmlcompiler/qqmljsloggingutils.h
index c33fe5a407..05067c7d64 100644
--- a/src/qmlcompiler/qqmljsloggingutils.h
+++ b/src/qmlcompiler/qqmljsloggingutils.h
@@ -88,6 +88,7 @@ extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlSyntaxIdQuotation;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlTopLevelComponent;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlTranslationFunctionMismatch;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUncreatableType;
+extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnintentionalEmptyBlock;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnqualified;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnreachableCode;
 extern const Q_QMLCOMPILER_EXPORT QQmlSA::LoggerWarningId qmlUnresolvedAlias;