feature-select: Implement a selectable feature framework

This is the framework for selectable features.
There are no real features implemented.

Planned is a maximum of 8 features.
They are all implemented as a dummy for now.

The decision depends of the following setting at the beginning of
a module after PySide2 import:

    from __feature__ import <feature name>

For more info, see the Jira issue, section

    The Principle Of Selectable Features In PySide

Task-number: PYSIDE-1019
Change-Id: If355e9294b5c16090b39d30422a90ea9c8523390
Reviewed-by: Christian Tismer <tismer@stackless.com>

9 files changed, 110 insertions, 59 deletions

diff --git a/sources/shiboken2/libshiboken/basewrapper.cpp b/sources/shiboken2/libshiboken/basewrapper.cpp
index 4c15582e9..5c2dc7807 100644
--- a/sources/shiboken2/libshiboken/basewrapper.cpp
+++ b/sources/shiboken2/libshiboken/basewrapper.cpp
@@ -95,12 +95,31 @@ void Sbk_object_dealloc(PyObject *self)
 static void SbkObjectTypeDealloc(PyObject *pyObj);
 static PyObject *SbkObjectTypeTpNew(PyTypeObject *metatype, PyObject *args, PyObject *kwds);
 
+static SelectableFeatureHook SelectFeatureSet = nullptr;
+
+void initSelectableFeature(SelectableFeatureHook func)
+{
+    SelectFeatureSet = func;
+}
+
+// PYSIDE-1019: Switch type's tp_dict to the currently active namespace.
+static PyObject *Sbk_TypeGet___dict__(PyTypeObject *type, void *context)
+{
+    auto dict = type->tp_dict;
+    if (dict == NULL)
+        Py_RETURN_NONE;
+    if (SelectFeatureSet != nullptr)
+        dict = SelectFeatureSet(type);
+    return PyDictProxy_New(dict);
+}
+
 // PYSIDE-908: The function PyType_Modified does not work in PySide, so we need to
 // explicitly pass __doc__. For __signature__ it _did_ actually work, because
 // it was not existing before. We add them both for clarity.
 static PyGetSetDef SbkObjectType_Type_getsetlist[] = {
     {const_cast<char *>("__signature__"), (getter)Sbk_TypeGet___signature__},
     {const_cast<char *>("__doc__"),       (getter)Sbk_TypeGet___doc__},
+    {const_cast<char *>("__dict__"),      (getter)Sbk_TypeGet___dict__},
     {nullptr}  // Sentinel
 };
 
@@ -121,8 +140,25 @@ static PyObject *SbkObjectType_repr(PyObject *type)
 
 #endif // PY_VERSION_HEX < 0x03000000
 
+// PYSIDE-1019: Switch type's tp_dict to the currently active namespace.
+static PyObject *(*type_getattro)(PyObject *type, PyObject *name);
+
+static PyObject *mangled_type_getattro(PyTypeObject *type, PyObject *name)
+{
+    /*
+     * Note: This `type_getattro` version is only the default that comes
+     * from `PyType_Type.tp_getattro`. This does *not* interfere in any way
+     * with the complex `tp_getattro` of `QObject` and other instances.
+     * What we change here is the meta class of `QObject`.
+     */
+    if (SelectFeatureSet != nullptr)
+        type->tp_dict = SelectFeatureSet(type);
+    return type_getattro(reinterpret_cast<PyObject *>(type), name);
+}
+
 static PyType_Slot SbkObjectType_Type_slots[] = {
     {Py_tp_dealloc, reinterpret_cast<void *>(SbkObjectTypeDealloc)},
+    {Py_tp_getattro, reinterpret_cast<void *>(mangled_type_getattro)},
     {Py_tp_setattro, reinterpret_cast<void *>(PyObject_GenericSetAttr)},
     {Py_tp_base, static_cast<void *>(&PyType_Type)},
     {Py_tp_alloc, reinterpret_cast<void *>(PyType_GenericAlloc)},
@@ -235,6 +271,9 @@ PyTypeObject *SbkObjectType_TypeF(void)
 {
     static PyTypeObject *type = nullptr;
     if (!type) {
+        // PYSIDE-1019: Insert the default tp_getattro explicitly here
+        //              so we can overwrite it a bit.
+        type_getattro = PyType_Type.tp_getattro;
         SbkObjectType_Type_spec.basicsize =
             PepHeapType_SIZE + sizeof(SbkObjectTypePrivate);
         type = reinterpret_cast<PyTypeObject *>(SbkType_FromSpec(&SbkObjectType_Type_spec));
diff --git a/sources/shiboken2/libshiboken/basewrapper.h b/sources/shiboken2/libshiboken/basewrapper.h
index 7248103cc..a4a8629fb 100644
--- a/sources/shiboken2/libshiboken/basewrapper.h
+++ b/sources/shiboken2/libshiboken/basewrapper.h
@@ -93,6 +93,9 @@ typedef void (*ObjectDestructor)(void *);
 
 typedef void (*SubTypeInitHook)(SbkObjectType *, PyObject *, PyObject *);
 
+typedef PyObject *(*SelectableFeatureHook)(PyTypeObject *);
+LIBSHIBOKEN_API void initSelectableFeature(SelectableFeatureHook func);
+
 extern LIBSHIBOKEN_API PyTypeObject *SbkObjectType_TypeF(void);
 extern LIBSHIBOKEN_API SbkObjectType *SbkObject_TypeF(void);
 
diff --git a/sources/shiboken2/libshiboken/pep384impl.cpp b/sources/shiboken2/libshiboken/pep384impl.cpp
index 5e0053e2e..4149bbcbf 100644
--- a/sources/shiboken2/libshiboken/pep384impl.cpp
+++ b/sources/shiboken2/libshiboken/pep384impl.cpp
@@ -78,14 +78,20 @@ static PyGetSetDef probe_getseters[] = {
     {nullptr}  /* Sentinel */
 };
 
+static PyMemberDef probe_members[] = {
+    {nullptr}  /* Sentinel */
+};
+
 #define probe_tp_dealloc    make_dummy(1)
 #define probe_tp_repr       make_dummy(2)
 #define probe_tp_call       make_dummy(3)
+#define probe_tp_getattro   make_dummy(16)
 #define probe_tp_str        make_dummy(4)
 #define probe_tp_traverse   make_dummy(5)
 #define probe_tp_clear      make_dummy(6)
 #define probe_tp_iternext   make_dummy(7)
 #define probe_tp_methods    probe_methoddef
+#define probe_tp_members    probe_members
 #define probe_tp_getset     probe_getseters
 #define probe_tp_descr_get  make_dummy(10)
 #define probe_tp_init       make_dummy(11)
@@ -101,11 +107,13 @@ static PyType_Slot typeprobe_slots[] = {
     {Py_tp_dealloc,     probe_tp_dealloc},
     {Py_tp_repr,        probe_tp_repr},
     {Py_tp_call,        probe_tp_call},
+    {Py_tp_getattro,    probe_tp_getattro},
     {Py_tp_str,         probe_tp_str},
     {Py_tp_traverse,    probe_tp_traverse},
     {Py_tp_clear,       probe_tp_clear},
     {Py_tp_iternext,    probe_tp_iternext},
     {Py_tp_methods,     probe_tp_methods},
+    {Py_tp_members,     probe_tp_members},
     {Py_tp_getset,      probe_tp_getset},
     {Py_tp_descr_get,   probe_tp_descr_get},
     {Py_tp_init,        probe_tp_init},
@@ -144,6 +152,7 @@ check_PyTypeObject_valid()
         || probe_tp_dealloc         != check->tp_dealloc
         || probe_tp_repr            != check->tp_repr
         || probe_tp_call            != check->tp_call
+        || probe_tp_getattro        != check->tp_getattro
         || probe_tp_str             != check->tp_str
         || probe_tp_traverse        != check->tp_traverse
         || probe_tp_clear           != check->tp_clear
@@ -427,27 +436,6 @@ PyRun_String(const char *str, int start, PyObject *globals, PyObject *locals)
 
 #endif // Py_LIMITED_API
 
-// This is only a simple local helper that returns a computed variable.
-// Used also in Python 2.
-#if defined(Py_LIMITED_API) || defined(IS_PY2)
-static PyObject *
-PepRun_GetResult(const char *command)
-{
-    PyObject *d, *v, *res;
-
-    d = PyDict_New();
-    if (d == nullptr
-        || PyDict_SetItem(d, Shiboken::PyMagicName::builtins(), PyEval_GetBuiltins()) < 0) {
-        return nullptr;
-    }
-    v = PyRun_String(command, Py_file_input, d, d);
-    res = v ? PyDict_GetItem(d, Shiboken::PyName::result()) : nullptr;
-    Py_XDECREF(v);
-    Py_DECREF(d);
-    return res;
-}
-#endif // defined(Py_LIMITED_API) || defined(IS_PY2)
-
 /*****************************************************************************
  *
  * Support for classobject.h
@@ -669,6 +657,29 @@ PyImport_GetModule(PyObject *name)
 
 #endif // PY_VERSION_HEX < 0x03070000 || defined(Py_LIMITED_API)
 
+// 2020-06-16: For simplicity of creating arbitrary things, this function
+// is now made public.
+
+PyObject *
+PepRun_GetResult(const char *command)
+{
+    /*
+     * Evaluate a string and return the variable `result`
+     */
+    PyObject *d, *v, *res;
+
+    d = PyDict_New();
+    if (d == nullptr
+        || PyDict_SetItem(d, Shiboken::PyMagicName::builtins(), PyEval_GetBuiltins()) < 0) {
+        return nullptr;
+    }
+    v = PyRun_String(command, Py_file_input, d, d);
+    res = v ? PyDict_GetItem(d, Shiboken::PyName::result()) : nullptr;
+    Py_XDECREF(v);
+    Py_DECREF(d);
+    return res;
+}
+
 /*****************************************************************************
  *
  * Python 2 incompatibilities
diff --git a/sources/shiboken2/libshiboken/pep384impl.h b/sources/shiboken2/libshiboken/pep384impl.h
index 2bfe52254..2a14d6543 100644
--- a/sources/shiboken2/libshiboken/pep384impl.h
+++ b/sources/shiboken2/libshiboken/pep384impl.h
@@ -98,7 +98,7 @@ typedef struct _typeobject {
     void *X13; // hashfunc tp_hash;
     ternaryfunc tp_call;
     reprfunc tp_str;
-    void *X16; // getattrofunc tp_getattro;
+    getattrofunc tp_getattro;
     void *X17; // setattrofunc tp_setattro;
     void *X18; // PyBufferProcs *tp_as_buffer;
     unsigned long tp_flags;
@@ -110,7 +110,7 @@ typedef struct _typeobject {
     void *X25; // getiterfunc tp_iter;
     iternextfunc tp_iternext;
     struct PyMethodDef *tp_methods;
-    void *X28; // struct PyMemberDef *tp_members;
+    struct PyMemberDef *tp_members;
     struct PyGetSetDef *tp_getset;
     struct _typeobject *tp_base;
     PyObject *tp_dict;
@@ -531,6 +531,9 @@ extern LIBSHIBOKEN_API PyTypeObject *PepMethodDescr_TypePtr;
 LIBSHIBOKEN_API PyObject *PyImport_GetModule(PyObject *name);
 #endif // PY_VERSION_HEX < 0x03070000 || defined(Py_LIMITED_API)
 
+// Evaluate a script and return the variable `result`
+LIBSHIBOKEN_API PyObject *PepRun_GetResult(const char *command);
+
 /*****************************************************************************
  *
  * Python 2 incompatibilities
diff --git a/sources/shiboken2/libshiboken/sbkstaticstrings.cpp b/sources/shiboken2/libshiboken/sbkstaticstrings.cpp
index 541d74918..9dd98eef3 100644
--- a/sources/shiboken2/libshiboken/sbkstaticstrings.cpp
+++ b/sources/shiboken2/libshiboken/sbkstaticstrings.cpp
@@ -52,9 +52,11 @@ namespace Shiboken
 {
 namespace PyName {
 // exported:
+STATIC_STRING_IMPL(dict_ring, "dict_ring")
 STATIC_STRING_IMPL(dumps, "dumps")
 STATIC_STRING_IMPL(loads, "loads")
 STATIC_STRING_IMPL(result, "result")
+STATIC_STRING_IMPL(select_id, "select_id")
 STATIC_STRING_IMPL(value, "value")
 STATIC_STRING_IMPL(values, "values")
 
@@ -75,6 +77,7 @@ STATIC_STRING_IMPL(staticmethod, "staticmethod")
 namespace PyMagicName {
 // exported:
 STATIC_STRING_IMPL(class_, "__class__")
+STATIC_STRING_IMPL(dict, "__dict__")
 STATIC_STRING_IMPL(ecf, "__ecf__")
 STATIC_STRING_IMPL(file, "__file__")
 STATIC_STRING_IMPL(members, "__members__")
diff --git a/sources/shiboken2/libshiboken/sbkstaticstrings.h b/sources/shiboken2/libshiboken/sbkstaticstrings.h
index 4078d163c..ebb64579c 100644
--- a/sources/shiboken2/libshiboken/sbkstaticstrings.h
+++ b/sources/shiboken2/libshiboken/sbkstaticstrings.h
@@ -49,11 +49,13 @@ namespace Shiboken
 namespace PyName
 {
 LIBSHIBOKEN_API PyObject *co_name();
+LIBSHIBOKEN_API PyObject *dict_ring();
 LIBSHIBOKEN_API PyObject *dumps();
 LIBSHIBOKEN_API PyObject *f_code();
 LIBSHIBOKEN_API PyObject *f_lineno();
 LIBSHIBOKEN_API PyObject *loads();
 LIBSHIBOKEN_API PyObject *result();
+LIBSHIBOKEN_API PyObject *select_id();
 LIBSHIBOKEN_API PyObject *value();
 LIBSHIBOKEN_API PyObject *values();
 } // namespace PyName
@@ -61,6 +63,7 @@ LIBSHIBOKEN_API PyObject *values();
 namespace PyMagicName
 {
 LIBSHIBOKEN_API PyObject *class_();
+LIBSHIBOKEN_API PyObject *dict();
 LIBSHIBOKEN_API PyObject *ecf();
 LIBSHIBOKEN_API PyObject *file();
 LIBSHIBOKEN_API PyObject *members();
diff --git a/sources/shiboken2/libshiboken/shiboken.h b/sources/shiboken2/libshiboken/shiboken.h
index 0d2d6b0a6..3e1df5235 100644
--- a/sources/shiboken2/libshiboken/shiboken.h
+++ b/sources/shiboken2/libshiboken/shiboken.h
@@ -55,6 +55,7 @@
 #include "sbkstaticstrings.h"
 #include "shibokenmacros.h"
 #include "shibokenbuffer.h"
+#include "signature.h"
 
 #endif // SHIBOKEN_H
 
diff --git a/sources/shiboken2/libshiboken/signature.cpp b/sources/shiboken2/libshiboken/signature.cpp
index b09b68d47..4614a131e 100644
--- a/sources/shiboken2/libshiboken/signature.cpp
+++ b/sources/shiboken2/libshiboken/signature.cpp
@@ -74,8 +74,8 @@ typedef struct safe_globals_struc {
     PyObject *helper_module;
     PyObject *arg_dict;
     PyObject *map_dict;
-    PyObject *value_dict;   // for writing signatures
-    PyObject *feature_dict;  // registry for PySide.__feature__
+    PyObject *value_dict;       // for writing signatures
+    PyObject *feature_dict;     // registry for PySide.support.__feature__
     // init part 2: run module
     PyObject *pyside_type_init_func;
     PyObject *create_signature_func;
@@ -653,22 +653,17 @@ _fixup_getset(PyTypeObject *type, const char *name, PyGetSetDef *new_gsp)
             }
         }
     }
-    PyMemberDef *md = type->tp_members;
-    if (md != nullptr)
-        for (; md->name != nullptr; md++)
-            if (strcmp(md->name, name) == 0)
-                return 1;
-    // staticmethod has just a `__doc__` in the class
-    assert(strcmp(type->tp_name, "staticmethod") == 0 && strcmp(name, "__doc__") == 0);
+    // staticmethod has just a __doc__ in the class
+    assert(strcmp(type->tp_name, "staticmethod") == 0);
     return 0;
 }
 
 static int
-add_more_getsets(PyTypeObject *type, PyGetSetDef *gsp, PyObject **doc_descr)
+add_more_getsets(PyTypeObject *type, PyGetSetDef *gsp, PyObject **old_descr)
 {
     /*
-     * This function is used to assign a new `__signature__` attribute,
-     * and also to override a `__doc__` or `__name__` attribute.
+     * This function is used to assign a new __signature__ attribute,
+     * and also to override a __doc__ attribute.
      */
     assert(PyType_Check(type));
     PyType_Ready(type);
@@ -676,11 +671,9 @@ add_more_getsets(PyTypeObject *type, PyGetSetDef *gsp, PyObject **doc_descr)
     for (; gsp->name != nullptr; gsp++) {
         PyObject *have_descr = PyDict_GetItemString(dict, gsp->name);
         if (have_descr != nullptr) {
+            assert(strcmp(gsp->name, "__doc__") == 0);
             Py_INCREF(have_descr);
-            if (strcmp(gsp->name, "__doc__") == 0)
-                *doc_descr = have_descr;
-            else
-                assert(false);
+            *old_descr = have_descr;
             if (!_fixup_getset(type, gsp->name, gsp))
                 continue;
         }
@@ -831,7 +824,7 @@ static PyGetSetDef new_PyWrapperDescr_getsets[] = {
 //
 // Additionally to the interface via __signature__, we also provide
 // a general function, which allows for different signature layouts.
-// The "modifier" argument is a string that is passed in from 'loader.py'.
+// The "modifier" argument is a string that is passed in from loader.py .
 // Configuration what the modifiers mean is completely in Python.
 //
 
@@ -916,25 +909,13 @@ PySide_PatchTypes(void)
                                         reinterpret_cast<PyObject *>(&PyString_Type), "split"));
         Shiboken::AutoDecRef wrap_descr(PyObject_GetAttrString(
                                         reinterpret_cast<PyObject *>(Py_TYPE(Py_True)), "__add__"));
-        // abbreviations for readability
-        auto md_gs = new_PyMethodDescr_getsets;
-        auto md_doc = &old_md_doc_descr;
-        auto cf_gs = new_PyCFunction_getsets;
-        auto cf_doc = &old_cf_doc_descr;
-        auto sm_gs = new_PyStaticMethod_getsets;
-        auto sm_doc = &old_sm_doc_descr;
-        auto tp_gs = new_PyType_getsets;
-        auto tp_doc = &old_tp_doc_descr;
-        auto wd_gs = new_PyWrapperDescr_getsets;
-        auto wd_doc = &old_wd_doc_descr;
-
         if (meth_descr.isNull() || wrap_descr.isNull()
             || PyType_Ready(Py_TYPE(meth_descr)) < 0
-            || add_more_getsets(PepMethodDescr_TypePtr,  md_gs, md_doc) < 0
-            || add_more_getsets(&PyCFunction_Type,       cf_gs, cf_doc) < 0
-            || add_more_getsets(PepStaticMethod_TypePtr, sm_gs, sm_doc) < 0
-            || add_more_getsets(&PyType_Type,            tp_gs, tp_doc) < 0
-            || add_more_getsets(Py_TYPE(wrap_descr),     wd_gs, wd_doc) < 0
+            || add_more_getsets(PepMethodDescr_TypePtr,  new_PyMethodDescr_getsets,  &old_md_doc_descr) < 0
+            || add_more_getsets(&PyCFunction_Type,       new_PyCFunction_getsets,    &old_cf_doc_descr) < 0
+            || add_more_getsets(PepStaticMethod_TypePtr, new_PyStaticMethod_getsets, &old_sm_doc_descr) < 0
+            || add_more_getsets(&PyType_Type,            new_PyType_getsets,         &old_tp_doc_descr) < 0
+            || add_more_getsets(Py_TYPE(wrap_descr),     new_PyWrapperDescr_getsets, &old_wd_doc_descr) < 0
             )
             return -1;
 #ifndef _WIN32
@@ -1233,8 +1214,8 @@ FinishSignatureInitialization(PyObject *module, const char *signatures[])
      * Still, it is not possible to call init phase 2 from here,
      * because the import is still running. Do it from Python!
      */
-    if (   PySide_PatchTypes() < 0
-        || PySide_FinishSignatures(module, signatures) < 0) {
+    PySide_PatchTypes();
+    if (PySide_FinishSignatures(module, signatures) < 0) {
         PyErr_Print();
         PyErr_SetNone(PyExc_ImportError);
     }
@@ -1285,4 +1266,10 @@ PyObject *Sbk_TypeGet___doc__(PyObject *ob)
     return pyside_tp_get___doc__(ob);
 }
 
+PyObject *GetFeatureDict()
+{
+    init_module_1();
+    return pyside_globals->feature_dict;
+}
+
 } //extern "C"
diff --git a/sources/shiboken2/libshiboken/signature.h b/sources/shiboken2/libshiboken/signature.h
index b22a78497..2a69df9cf 100644
--- a/sources/shiboken2/libshiboken/signature.h
+++ b/sources/shiboken2/libshiboken/signature.h
@@ -50,6 +50,7 @@ LIBSHIBOKEN_API void FinishSignatureInitialization(PyObject *, const char *[]);
 LIBSHIBOKEN_API void SetError_Argument(PyObject *, const char *);
 LIBSHIBOKEN_API PyObject *Sbk_TypeGet___signature__(PyObject *, PyObject *);
 LIBSHIBOKEN_API PyObject *Sbk_TypeGet___doc__(PyObject *);
+LIBSHIBOKEN_API PyObject *GetFeatureDict();
 
 } // extern "C"