shiboken6: Implement opaque containers for getters returning a const reference

Add a bool m_const member to the container helper template that
indicates a const container. Error out of the modification functions
if that is set.  Create an additional creation function for the const
case. A const opaque containers is then of same Python type as the
non-const version, requiring no further type checks.

Pick-to: 6.2
Task-number: PYSIDE-1605
Change-Id: I45faeb0d68e6144a9dfbe25497694b8acdd98c09
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

7 files changed, 84 insertions, 16 deletions

diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index a6abeb077..06299a2ab 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -197,8 +197,11 @@ static QString opaqueContainerCreationFunc(const AbstractMetaType &type)
         static_cast<const ContainerTypeEntry *>(type.typeEntry());
     const auto *instantiationTypeEntry =
         type.instantiations().constFirst().typeEntry();
-    return u"create"_qs
-           + containerTypeEntry->opaqueContainerName(instantiationTypeEntry->name());
+    QString result = u"create"_qs;
+    if (type.isConstant())
+        result += u"Const"_qs;
+    result += containerTypeEntry->opaqueContainerName(instantiationTypeEntry->name());
+    return result;
 }
 
 // Write declaration of the function to create PyObject wrapping a container
@@ -206,7 +209,7 @@ static void writeOpaqueContainerCreationFuncDecl(TextStream &s, const QString &n
                                                  AbstractMetaType type)
 {
     type.setReferenceType(NoReference);
-    type.setConstant(false);
+    // Maintain const
     s << "PyObject *" << name << '(' << type.cppSignature() << "*);\n";
 }
 
diff --git a/sources/shiboken6/generator/shiboken/cppgenerator_container.cpp b/sources/shiboken6/generator/shiboken/cppgenerator_container.cpp
index bc29e1d1e..eab57bcc0 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator_container.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator_container.cpp
@@ -73,6 +73,35 @@ static void writeSlot(TextStream &s, const QString &privateObjType,
       << "::" << methodName << ")},\n";
 }
 
+// Write creation function from C++ reference, used by field accessors
+// and getters which are within extern "C"
+static void writeContainerCreationFunc(TextStream &s,
+                                       const QString &funcName,
+                                       const QString &typeFName,
+                                       const QString &containerSignature,
+                                       bool isConst = false)
+{
+
+    // creation function from C++ reference, used by field accessors
+    // which are within extern "C"
+    s << "extern \"C\" PyObject *" << funcName << '(';
+    if (isConst)
+        s << "const ";
+    s << containerSignature << "* ct)\n{\n" << indent
+        << "auto *container = PyObject_New(ShibokenContainer, " << typeFName << "());\n"
+        << "auto *d = new ShibokenSequenceContainerPrivate<"
+        << containerSignature << ">();\n";
+    if (isConst) {
+        s << "d->m_list = const_cast<" << containerSignature << " *>(ct);\n"
+            << "d->m_const = true;\n";
+    } else {
+        s << "d->m_list = ct;\n";
+    }
+    s << "container->d = d;\n";
+    s << "return reinterpret_cast<PyObject *>(container);\n" << outdent
+        << "}\n\n";
+}
+
 // Generate code for a type wrapping a C++ container instantiation
 CppGenerator::OpaqueContainerData
    CppGenerator::writeOpaqueContainerConverterFunctions(TextStream &s,
@@ -184,17 +213,11 @@ CppGenerator::OpaqueContainerData
         << "static PyTypeObject *type = " << typeCreationFName
         << "();\nreturn type;\n" << outdent << "}\n\n";
 
-    // creation function from C++ reference, used by field accessors
-    // which are within extern "C"
-    const QString creationFunctionName =  u"create"_qs + result.name;
-    s << "extern \"C\" PyObject *" << creationFunctionName
-        << '(' << containerType.cppSignature() << "*ct)\n{\n" << indent
-        << "auto *container = PyObject_New(ShibokenContainer, " << typeFName << "());\n"
-        << "auto *d = new ShibokenSequenceContainerPrivate<"
-        << containerType.cppSignature() << ">();\n"
-        << "d->m_list = ct;\ncontainer->d = d;\n"
-        << "return reinterpret_cast<PyObject *>(container);\n" << outdent
-        << "}\n\n";
+    // creation functions from C++ references
+    writeContainerCreationFunc(s, u"create"_qs + result.name, typeFName,
+                               containerType.cppSignature());
+    writeContainerCreationFunc(s, u"createConst"_qs + result.name, typeFName,
+                               containerType.cppSignature(), true);
 
     // Check function
     result.checkFunctionName = result.name + u"_Check"_qs;
diff --git a/sources/shiboken6/libshiboken/sbkcontainer.h b/sources/shiboken6/libshiboken/sbkcontainer.h
index 284bf8c5c..97062a198 100644
--- a/sources/shiboken6/libshiboken/sbkcontainer.h
+++ b/sources/shiboken6/libshiboken/sbkcontainer.h
@@ -76,6 +76,9 @@ public:
 
     SequenceContainer *m_list{};
     bool m_ownsList = false;
+    bool m_const = false;
+    static constexpr const char *msgModifyConstContainer =
+        "Attempt to modify a constant container.";
 
     static PyObject *tpNew(PyTypeObject *subtype, PyObject * /* args */, PyObject * /* kwds */)
     {
@@ -137,12 +140,16 @@ public:
 
     static PyObject *push_back(PyObject *self, PyObject *pyArg)
     {
+        auto *d = get(self);
         if (!ShibokenContainerValueConverter<value_type>::checkValue(pyArg)) {
             PyErr_SetString(PyExc_TypeError, "wrong type passed to append.");
             return nullptr;
         }
+        if (d->m_const) {
+            PyErr_SetString(PyExc_TypeError, msgModifyConstContainer);
+            return nullptr;
+        }
 
-        auto *d = get(self);
         OptionalValue value = ShibokenContainerValueConverter<value_type>::convertValueToCpp(pyArg);
         if (!value.has_value())
             return nullptr;
@@ -152,12 +159,16 @@ public:
 
     static PyObject *push_front(PyObject *self, PyObject *pyArg)
     {
+        auto *d = get(self);
         if (!ShibokenContainerValueConverter<value_type>::checkValue(pyArg)) {
             PyErr_SetString(PyExc_TypeError, "wrong type passed to append.");
             return nullptr;
         }
+        if (d->m_const) {
+            PyErr_SetString(PyExc_TypeError, msgModifyConstContainer);
+            return nullptr;
+        }
 
-        auto *d = get(self);
         OptionalValue value = ShibokenContainerValueConverter<value_type>::convertValueToCpp(pyArg);
         if (!value.has_value())
             return nullptr;
@@ -168,6 +179,11 @@ public:
     static PyObject *clear(PyObject *self)
     {
         auto *d = get(self);
+        if (d->m_const) {
+            PyErr_SetString(PyExc_TypeError, msgModifyConstContainer);
+            return nullptr;
+        }
+
         d->m_list->clear();
         Py_RETURN_NONE;
     }
@@ -175,6 +191,11 @@ public:
     static PyObject *pop_back(PyObject *self)
     {
         auto *d = get(self);
+        if (d->m_const) {
+            PyErr_SetString(PyExc_TypeError, msgModifyConstContainer);
+            return nullptr;
+        }
+
         d->m_list->pop_back();
         Py_RETURN_NONE;
     }
@@ -182,6 +203,11 @@ public:
     static PyObject *pop_front(PyObject *self)
     {
         auto *d = get(self);
+        if (d->m_const) {
+            PyErr_SetString(PyExc_TypeError, msgModifyConstContainer);
+            return nullptr;
+        }
+
         d->m_list->pop_front();
         Py_RETURN_NONE;
     }
diff --git a/sources/shiboken6/tests/libminimal/listuser.cpp b/sources/shiboken6/tests/libminimal/listuser.cpp
index 5ad570faa..6a0230d60 100644
--- a/sources/shiboken6/tests/libminimal/listuser.cpp
+++ b/sources/shiboken6/tests/libminimal/listuser.cpp
@@ -128,3 +128,8 @@ std::list<int> &ListUser::getIntList()
 {
     return m_stdIntList;
 }
+
+const std::list<int> &ListUser::getConstIntList() const
+{
+    return m_stdIntList;
+}
diff --git a/sources/shiboken6/tests/libminimal/listuser.h b/sources/shiboken6/tests/libminimal/listuser.h
index e3b38049c..0eae69ae1 100644
--- a/sources/shiboken6/tests/libminimal/listuser.h
+++ b/sources/shiboken6/tests/libminimal/listuser.h
@@ -72,6 +72,7 @@ struct LIBMINIMAL_API ListUser
 
     void setStdIntList(const std::list<int> &l);
     std::list<int> &getIntList();
+    const std::list<int> &getConstIntList() const;
 
     std::list<int> m_stdIntList;
 };
diff --git a/sources/shiboken6/tests/minimalbinding/listuser_test.py b/sources/shiboken6/tests/minimalbinding/listuser_test.py
index 7bb65d359..a1fc48c08 100644
--- a/sources/shiboken6/tests/minimalbinding/listuser_test.py
+++ b/sources/shiboken6/tests/minimalbinding/listuser_test.py
@@ -351,6 +351,11 @@ class ListOfIntListConversionTest(unittest.TestCase):
         self.assertEqual(len(lu.m_stdIntList), 4)
         self.assertEqual(lu.m_stdIntList[3], 6)
 
+        # Access a const list via getter and verify that it cannot be modified
+        const_l = lu.getConstIntList()
+        self.assertEqual(len(const_l), 4)
+        self.assertRaises(TypeError, const_l.append, 6)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/sources/shiboken6/tests/minimalbinding/typesystem_minimal.xml b/sources/shiboken6/tests/minimalbinding/typesystem_minimal.xml
index 94ec4a649..9bb7e7b7e 100644
--- a/sources/shiboken6/tests/minimalbinding/typesystem_minimal.xml
+++ b/sources/shiboken6/tests/minimalbinding/typesystem_minimal.xml
@@ -53,6 +53,11 @@
                 <replace-type modified-type="StdIntList"/>
             </modify-argument>
         </modify-function>
+        <modify-function signature="getConstIntList()const">
+            <modify-argument index="return">
+                <replace-type modified-type="StdIntList"/>
+            </modify-argument>
+        </modify-function>
     </value-type>
     <value-type name="MinBoolUser"/>