Introduce const-signal-or-slot, to find getters unintentionally marked as slots

Warns for:
- non-void const method marked as slot
- const method marked as signal
- connecting to a method which isn't marked as slot, is const and returns non-void

3 files changed, 151 insertions, 0 deletions

diff --git a/src/checks/level1/README-const-signal-or-slot.md b/src/checks/level1/README-const-signal-or-slot.md
new file mode 100644
index 00000000..9a3e71b2
--- /dev/null
+++ b/src/checks/level1/README-const-signal-or-slot.md
@@ -0,0 +1,14 @@
+# const-signal-or-slot
+
+Warns when a signal or non-void slot is const.
+
+This aims to prevent unintentionally marking a getter as slot, or connecting to
+the wrong method. For signals, it's just pointless to mark them as const.
+
+Warns for the following cases:
+
+- non-void const method marked as slot
+- const method marked as signal
+- connecting to a method which isn't marked as slot, is const and returns non-void
+
+For exposing methods to QML prefer either Q_PROPERTY or Q_INVOKABLE.
diff --git a/src/checks/level1/const-signal-or-slot.cpp b/src/checks/level1/const-signal-or-slot.cpp
new file mode 100644
index 00000000..faa580ae
--- /dev/null
+++ b/src/checks/level1/const-signal-or-slot.cpp
@@ -0,0 +1,98 @@
+/*
+  This file is part of the clazy static checker.
+
+  Copyright (C) 2017 Sergio Martins <smartins@kde.org>
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Library General Public
+  License as published by the Free Software Foundation; either
+  version 2 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Library General Public License for more details.
+
+  You should have received a copy of the GNU Library General Public License
+  along with this library; see the file COPYING.LIB.  If not, write to
+  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+  Boston, MA 02110-1301, USA.
+*/
+
+#include "const-signal-or-slot.h"
+#include "Utils.h"
+#include "HierarchyUtils.h"
+#include "QtUtils.h"
+#include "TypeUtils.h"
+#include "checkmanager.h"
+#include "ClazyContext.h"
+#include "AccessSpecifierManager.h"
+
+#include <clang/AST/AST.h>
+
+using namespace clang;
+using namespace std;
+
+
+ConstSignalOrSlot::ConstSignalOrSlot(const std::string &name, ClazyContext *context)
+    : CheckBase(name, context)
+{
+    context->enableAccessSpecifierManager();
+}
+
+void ConstSignalOrSlot::VisitStmt(clang::Stmt *stmt)
+{
+    auto call = dyn_cast<CallExpr>(stmt);
+    AccessSpecifierManager *accessSpecifierManager = m_context->accessSpecifierManager;
+    if (!call || !accessSpecifierManager)
+        return;
+
+    FunctionDecl *func = call->getDirectCallee();
+    if (!QtUtils::isConnect(func) || !QtUtils::connectHasPMFStyle(func))
+        return;
+
+    CXXMethodDecl *slot = QtUtils::pmfFromConnect(call, 2);
+    if (!slot) // The slot is either third or fourth argument
+        slot = QtUtils::pmfFromConnect(call, 3);
+
+    if (!slot || !slot->isConst() || slot->getReturnType()->isVoidType()) // const and returning void must do something, so not a getter
+        return;
+
+    QtAccessSpecifierType specifierType = accessSpecifierManager->qtAccessSpecifierType(slot);
+    if (specifierType == QtAccessSpecifier_Slot || specifierType == QtAccessSpecifier_Signal)
+        return; // For stuff explicitly marked as slots or signals we use VisitDecl
+
+
+    // Here the user is connecting to a const method, which isn't marked as slot or signal and returns non-void
+    // Looks like a getter!
+
+    emitWarning(stmt, slot->getQualifiedNameAsString() + " is not a slot, and is possibly a getter");
+}
+
+void ConstSignalOrSlot::VisitDecl(Decl *decl)
+{
+    auto method = dyn_cast<CXXMethodDecl>(decl);
+    if (!method || !method->isConst())
+        return;
+
+    AccessSpecifierManager *a = m_context->accessSpecifierManager;
+    if (!a)
+        return;
+
+    if (method->isThisDeclarationADefinition() && !method->hasInlineBody()) // Don't warn twice
+        return;
+
+    CXXRecordDecl *record = method->getParent();
+    if (TypeUtils::derivesFrom(record, "QDBusAbstractInterface"))
+        return;
+
+    QtAccessSpecifierType specifierType = a->qtAccessSpecifierType(method);
+
+    if (specifierType == QtAccessSpecifier_Slot && !method->getReturnType()->isVoidType()) {
+        emitWarning(decl, "getter " + method->getQualifiedNameAsString() + " possibly mismarked as a slot");
+    } else if (specifierType == QtAccessSpecifier_Signal) {
+        emitWarning(decl, "signal " + method->getQualifiedNameAsString() + " shouldn't be const");
+    }
+}
+
+REGISTER_CHECK("const-signal-or-slot", ConstSignalOrSlot, CheckLevel1)
diff --git a/src/checks/level1/const-signal-or-slot.h b/src/checks/level1/const-signal-or-slot.h
new file mode 100644
index 00000000..294a6b73
--- /dev/null
+++ b/src/checks/level1/const-signal-or-slot.h
@@ -0,0 +1,39 @@
+/*
+  This file is part of the clazy static checker.
+
+  Copyright (C) 2017 Sergio Martins <smartins@kde.org>
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Library General Public
+  License as published by the Free Software Foundation; either
+  version 2 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Library General Public License for more details.
+
+  You should have received a copy of the GNU Library General Public License
+  along with this library; see the file COPYING.LIB.  If not, write to
+  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+  Boston, MA 02110-1301, USA.
+*/
+
+#ifndef CLAZY_CONST_SIGNAL_OR_SLOT_H
+#define CLAZY_CONST_SIGNAL_OR_SLOT_H
+
+#include "checkbase.h"
+
+
+/**
+ * See README-const-signal-or-slot.md for more info.
+ */
+class ConstSignalOrSlot : public CheckBase
+{
+public:
+    explicit ConstSignalOrSlot(const std::string &name, ClazyContext *context);
+    void VisitStmt(clang::Stmt *stmt) override;
+    void VisitDecl(clang::Decl *decl) override;
+};
+
+#endif