Add QtUiTools.loadUiType

This function will allow users to convert and load .ui files
at runtime.

A test case was added.

Change-Id: I64a220a07955e560f61f823d0ee2c3c9ff2209c1
Fixes: PYSIDE-1223
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>
Reviewed-by: Christian Tismer <tismer@stackless.com>

3 files changed, 249 insertions, 0 deletions

diff --git a/sources/pyside2/PySide2/QtUiTools/typesystem_uitools.xml b/sources/pyside2/PySide2/QtUiTools/typesystem_uitools.xml
index 7b27e8783..2ca12e788 100644
--- a/sources/pyside2/PySide2/QtUiTools/typesystem_uitools.xml
+++ b/sources/pyside2/PySide2/QtUiTools/typesystem_uitools.xml
@@ -139,4 +139,40 @@
       </add-function>
     </object-type>
 
+    <!--
+    After the removal of the 'pysideuic' Python module, many users were unable to generate and
+    load UI classes dynamically.
+    This function was created to provide an equivalent solution to the 'loadUiType' function from
+    Riverbank's PyQt.
+    -->
+    <add-function signature="loadUiType(const QString&amp; @uifile@)" return-type="PyObject*">
+      <inject-documentation format="target" mode="append">
+      This function will allow users to generate and load a `.ui` file at runtime, and it returns
+      a `tuple` containing the reference to the Python class, and the base class.
+
+      We don't recommend this approach since the workflow should be to generate a Python file
+      from the `.ui` file, and then import and load it to use it, but we do understand that
+      there are some corner cases when such functionality is required.
+
+      The internal process relies on `uic` being in the PATH, which is the same requirement for
+      the new `pyside2-uic` to work (which is just a wrapper around `uic -g python`)
+
+      A Simple use can be:
+
+      .. code-block:: python
+
+        from PySide2.QtUiTools import loadUiType
+
+        generated_class, base_class = loadUiType("themewidget.ui")
+        # the values will be:
+        #  (&lt;class '__main__.Ui_ThemeWidgetForm'&gt;, &lt;class 'PySide2.QtWidgets.QWidget'&gt;)
+
+
+      In that case, `generated_class` will be a reference to the Python class,
+      and `base_class` will be a reference to the base class.
+      </inject-documentation>
+      <inject-code file="../glue/qtuitools.cpp" snippet="loaduitype"/>
+    </add-function>
+
+
 </typesystem>
diff --git a/sources/pyside2/PySide2/glue/qtuitools.cpp b/sources/pyside2/PySide2/glue/qtuitools.cpp
index 00fc8e44a..668b512e4 100644
--- a/sources/pyside2/PySide2/glue/qtuitools.cpp
+++ b/sources/pyside2/PySide2/glue/qtuitools.cpp
@@ -109,3 +109,141 @@ registerCustomWidget(%PYARG_1);
 // Avoid calling the original function: %CPPSELF.%FUNCTION_NAME()
 %PYARG_0 = QUiLoaderLoadUiFromFileName(%CPPSELF, %1, %2);
 // @snippet quiloader-load-2
+
+// @snippet loaduitype
+/*
+Arguments:
+    %PYARG_1 (uifile)
+*/
+// 1. Generate the Python code from the UI file
+#ifdef IS_PY3K
+PyObject *strObj = PyUnicode_AsUTF8String(%PYARG_1);
+char *arg1 = PyBytes_AsString(strObj);
+QByteArray uiFileName(arg1);
+Py_DECREF(strObj);
+#else
+QByteArray uiFileName(PyBytes_AsString(%PYARG_1));
+#endif
+
+QFile uiFile(uiFileName);
+
+if (!uiFile.exists()) {
+    qCritical().noquote() << "File" << uiFileName << "does not exists";
+    Py_RETURN_NONE;
+}
+
+if (uiFileName.isEmpty()) {
+    qCritical() << "Error converting the UI filename to QByteArray";
+    Py_RETURN_NONE;
+}
+
+QString uicBin("uic");
+QStringList uicArgs = {"-g", "python", QString::fromUtf8(uiFileName)};
+
+QProcess uicProcess;
+uicProcess.start(uicBin, uicArgs);
+if (!uicProcess.waitForFinished()) {
+    qCritical() << "Cannot run 'uic': " << uicProcess.errorString() << " - "
+                << "Exit status " << uicProcess.exitStatus()
+                << " (" << uicProcess.exitCode() << ")\n"
+                << "Check if 'uic' is in PATH";
+    Py_RETURN_NONE;
+}
+QByteArray uiFileContent = uicProcess.readAllStandardOutput();
+QByteArray errorOutput = uicProcess.readAllStandardError();
+
+if (!errorOutput.isEmpty()) {
+    qCritical().noquote() << errorOutput;
+    Py_RETURN_NONE;
+}
+
+// 2. Obtain the 'classname' and the Qt base class.
+QByteArray className;
+QByteArray baseClassName;
+
+// Problem
+// The generated Python file doesn't have the Qt Base class information.
+
+// Solution
+// Use the XML file
+if (!uiFile.open(QIODevice::ReadOnly))
+    Py_RETURN_NONE;
+
+// This will look for the first <widget> tag, e.g.:
+//      <widget class="QWidget" name="ThemeWidgetForm">
+// and then extract the information from "class", and "name",
+// to get the baseClassName and className respectively
+QXmlStreamReader reader(&uiFile);
+while (!reader.atEnd() && baseClassName.isEmpty() && className.isEmpty()) {
+    auto token = reader.readNext();
+    if (token == QXmlStreamReader::StartElement && reader.name() == "widget") {
+        baseClassName = reader.attributes().value(QLatin1String("class")).toUtf8();
+        className = reader.attributes().value(QLatin1String("name")).toUtf8();
+    }
+}
+
+uiFile.close();
+
+if (className.isEmpty() || baseClassName.isEmpty() || reader.hasError()) {
+    qCritical() << "An error occurred when parsing the UI file while looking for the class info "
+                << reader.errorString();
+    Py_RETURN_NONE;
+}
+
+QByteArray pyClassName("Ui_"+className);
+
+PyObject *module = PyImport_ImportModule("__main__");
+PyObject *loc = PyModule_GetDict(module);
+
+// 3. exec() the code so the class exists in the context: exec(uiFileContent)
+// The context of PyRun_SimpleString is __main__.
+// 'Py_file_input' is the equivalent to using exec(), since it will execute
+// the code, without returning anything.
+Shiboken::AutoDecRef codeUi(Py_CompileString(uiFileContent.constData(), "<stdin>", Py_file_input));
+if (codeUi.isNull()) {
+    qCritical() << "Error while compiling the generated Python file";
+    Py_RETURN_NONE;
+}
+PyObject *uiObj = nullptr;
+#ifdef IS_PY3K
+uiObj = PyEval_EvalCode(codeUi, loc, loc);
+#else
+uiObj = PyEval_EvalCode(reinterpret_cast<PyCodeObject *>(codeUi.object()), loc, loc);
+#endif
+
+if (uiObj == nullptr) {
+    qCritical() << "Error while running exec() on the generated code";
+    Py_RETURN_NONE;
+}
+
+// 4. eval() the name of the class on a variable to return
+// 'Py_eval_input' is the equivalent to using eval(), since it will just
+// evaluate an expression.
+Shiboken::AutoDecRef codeClass(Py_CompileString(pyClassName.constData(),"<stdin>", Py_eval_input));
+if (codeClass.isNull()) {
+    qCritical() << "Error while compiling the Python class";
+    Py_RETURN_NONE;
+}
+
+Shiboken::AutoDecRef codeBaseClass(Py_CompileString(baseClassName.constData(), "<stdin>", Py_eval_input));
+if (codeBaseClass.isNull()) {
+    qCritical() << "Error while compiling the base class";
+    Py_RETURN_NONE;
+}
+
+#ifdef IS_PY3K
+PyObject *classObj = PyEval_EvalCode(codeClass, loc, loc);
+PyObject *baseClassObj = PyEval_EvalCode(codeBaseClass, loc, loc);
+#else
+PyObject *classObj = PyEval_EvalCode(reinterpret_cast<PyCodeObject *>(codeClass.object()), loc, loc);
+PyObject *baseClassObj = PyEval_EvalCode(reinterpret_cast<PyCodeObject *>(codeBaseClass.object()), loc, loc);
+#endif
+
+%PYARG_0  = PyTuple_New(2);
+if (%PYARG_0 == nullptr) {
+    qCritical() << "Error while creating the return Tuple";
+    Py_RETURN_NONE;
+}
+PyTuple_SET_ITEM(%PYARG_0, 0, classObj);
+PyTuple_SET_ITEM(%PYARG_0, 1, baseClassObj);
+// @snippet loaduitype
diff --git a/sources/pyside2/tests/QtUiTools/loadUiType_test.py b/sources/pyside2/tests/QtUiTools/loadUiType_test.py
new file mode 100644
index 000000000..9a3756376
--- /dev/null
+++ b/sources/pyside2/tests/QtUiTools/loadUiType_test.py
@@ -0,0 +1,75 @@
+#############################################################################
+##
+## Copyright (C) 2020 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the test suite of Qt for Python.
+##
+## $QT_BEGIN_LICENSE:GPL-EXCEPT$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 3 as published by the Free Software
+## Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import os
+import sys
+import unittest
+
+sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+from init_paths import init_test_paths
+init_test_paths(False)
+
+from helper.usesqapplication import UsesQApplication
+
+from PySide2.QtWidgets import QWidget, QFrame, QPushButton
+from PySide2.QtUiTools import loadUiType
+
+class loadUiTypeTester(UsesQApplication):
+    def testFunction(self):
+        filePath = os.path.join(os.path.dirname(__file__), "minimal.ui")
+        loaded = loadUiType(filePath)
+        self.assertNotEqual(loaded, None)
+
+        # (<class '__main__.Ui_Form'>, <class 'PySide2.QtWidgets.QFrame'>)
+        generated, base = loaded
+
+        # Generated class contains retranslateUi method
+        self.assertTrue("retranslateUi" in dir(generated))
+
+        # Base class instance will be QFrame for this example
+        self.assertTrue(isinstance(base(), QFrame))
+
+        anotherFileName = os.path.join(os.path.dirname(__file__), "test.ui")
+        another = loadUiType(anotherFileName)
+        self.assertNotEqual(another, None)
+
+        generated, base = another
+        # Base class instance will be QWidget for this example
+        self.assertTrue(isinstance(base(), QWidget))
+
+        w = base()
+        ui = generated()
+        ui.setupUi(w)
+
+        self.assertTrue(isinstance(ui.child_object, QFrame))
+        self.assertTrue(isinstance(ui.grandson_object, QPushButton))
+
+
+if __name__ == '__main__':
+    unittest.main()
+