signature: improve error handling for embedded applications

Entering something like

"""
mainWindow.setPointer(None)
"""

crashes in an old version of scriptableapplication, which
shows an omission in the signature interface. The error
shows up whenever a builtin module cannot be imported.

The error does not show up in PySide 6, because the
module is declared as a builtin via `PyImport_AppendInittab`.

* add registration of AppLib as a builtin (5.15)

* insert builtin modules per default into the mapping module

* simple recovery if a module cannot be found in sys.modules

[ChangeLog][shiboken6] Error handling was improved for embedded
applications and builtin modules are trusted as valid modules.

Change-Id: I722212a52a5e3aae924f0b965578485ecaf185a9
Fixes: PYSIDE-1710
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit 2149a45fddeedea317dccbfe5e5b14e13888e5c9)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 6 insertions, 5 deletions

diff --git a/sources/shiboken6/libshiboken/signature/signature.cpp b/sources/shiboken6/libshiboken/signature/signature.cpp
index 243f3e35f..a8a17ec14 100644
--- a/sources/shiboken6/libshiboken/signature/signature.cpp
+++ b/sources/shiboken6/libshiboken/signature/signature.cpp
@@ -512,9 +512,10 @@ static PyObject *adjustFuncName(const char *func_name)
         return nullptr;
 
     // Run `eval` on the type string to get the object.
+    // PYSIDE-1710: If the eval does not work, return the given string.
     AutoDecRef obtype(PyRun_String(_path, Py_eval_input, ns, ns));
     if (obtype.isNull())
-        return nullptr;
+        return String::fromCString(func_name);
 
     if (PyModule_Check(obtype.object())) {
         // This is a plain function. Return the unmangled name.
diff --git a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/errorhandler.py b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/errorhandler.py
index 0c1b72644..4c436eafd 100644
--- a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/errorhandler.py
+++ b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/errorhandler.py
@@ -104,8 +104,8 @@ def seterror_argument(args, func_name, info):
     try:
         func = eval(func_name, namespace)
     except Exception as e:
-        msg = f"Internal error evaluating {func_name}: " + str(e)
-        return TypeError, msg
+        msg = f"Error evaluating `{func_name}`: {e}"
+        return type(e), msg
     if info and type(info) is str:
         err = TypeError
         if info == "<":
diff --git a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/mapping.py b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/mapping.py
index adcbad3d9..77a61380f 100644
--- a/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/mapping.py
+++ b/sources/shiboken6/shibokenmodule/files.dir/shibokensupport/signature/mapping.py
@@ -54,7 +54,7 @@ import typing
 
 from pathlib import Path
 from typing import TypeVar, Generic
-from shibokensupport.signature.lib.tool import with_metaclass
+from _imp import is_builtin
 
 class ellipsis(object):
     def __repr__(self):
@@ -179,7 +179,7 @@ class Reloader(object):
         if getattr(mod, "__file__", None) and not Path(mod.__file__).is_dir():
             ending = Path(mod.__file__).suffix
             return ending not in (".py", ".pyc", ".pyo", ".pyi")
-        return False
+        return bool(is_builtin(mod.__name__))
 
     def update(self):
         """