bpo-42630: Improve error reporting in Tkinter for absent default root (GH-23781)

* Tkinter functions and constructors which need a default root window
  raise now RuntimeError with descriptive message instead of obscure
  AttributeError or NameError if it is not created yet or cannot
  be created automatically.

* Add tests for all functions which use default root window.

* Fix import in the pynche script.

Lib/tkinter/test/test_tkinter/test_font.py

@@ -2,7 +2,7 @@ import unittest
 import tkinter
 from tkinter import font
 from test.support import requires, run_unittest, gc_collect, ALWAYS_EQ
-from tkinter.test.support import AbstractTkTest
+from tkinter.test.support import AbstractTkTest, AbstractDefaultRootTest
 
 requires('gui')
 
@@ -107,7 +107,37 @@ class FontTest(AbstractTkTest, unittest.TestCase):
         )
 
 
-tests_gui = (FontTest, )
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_families(self):
+        self.assertRaises(RuntimeError, font.families)
+        root = tkinter.Tk()
+        families = font.families()
+        self.assertIsInstance(families, tuple)
+        self.assertTrue(families)
+        for family in families:
+            self.assertIsInstance(family, str)
+            self.assertTrue(family)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, font.families)
+
+    def test_names(self):
+        self.assertRaises(RuntimeError, font.names)
+        root = tkinter.Tk()
+        names = font.names()
+        self.assertIsInstance(names, tuple)
+        self.assertTrue(names)
+        for name in names:
+            self.assertIsInstance(name, str)
+            self.assertTrue(name)
+        self.assertIn(fontname, names)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, font.names)
+
+
+tests_gui = (FontTest, DefaultRootTest)
 
 if __name__ == "__main__":
     run_unittest(*tests_gui)

Lib/tkinter/test/test_tkinter/test_images.py

@@ -2,7 +2,7 @@ import unittest
 import tkinter
 from test import support
 from test.support import os_helper
-from tkinter.test.support import AbstractTkTest, requires_tcl
+from tkinter.test.support import AbstractTkTest, AbstractDefaultRootTest, requires_tcl
 
 support.requires('gui')
 
@@ -20,6 +20,47 @@ class MiscTest(AbstractTkTest, unittest.TestCase):
         self.assertIsInstance(image_names, tuple)
 
 
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_image_types(self):
+        self.assertRaises(RuntimeError, tkinter.image_types)
+        root = tkinter.Tk()
+        image_types = tkinter.image_types()
+        self.assertIsInstance(image_types, tuple)
+        self.assertIn('photo', image_types)
+        self.assertIn('bitmap', image_types)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.image_types)
+
+    def test_image_names(self):
+        self.assertRaises(RuntimeError, tkinter.image_names)
+        root = tkinter.Tk()
+        image_names = tkinter.image_names()
+        self.assertIsInstance(image_names, tuple)
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.image_names)
+
+    def test_image_create_bitmap(self):
+        self.assertRaises(RuntimeError, tkinter.BitmapImage)
+        root = tkinter.Tk()
+        image = tkinter.BitmapImage()
+        self.assertIn(image.name, tkinter.image_names())
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.BitmapImage)
+
+    def test_image_create_photo(self):
+        self.assertRaises(RuntimeError, tkinter.PhotoImage)
+        root = tkinter.Tk()
+        image = tkinter.PhotoImage()
+        self.assertIn(image.name, tkinter.image_names())
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.PhotoImage)
+
+
 class BitmapImageTest(AbstractTkTest, unittest.TestCase):
 
     @classmethod
@@ -331,7 +372,7 @@ class PhotoImageTest(AbstractTkTest, unittest.TestCase):
         self.assertEqual(image.transparency_get(4, 6), False)
 
 
-tests_gui = (MiscTest, BitmapImageTest, PhotoImageTest,)
+tests_gui = (MiscTest, DefaultRootTest, BitmapImageTest, PhotoImageTest,)
 
 if __name__ == "__main__":
     support.run_unittest(*tests_gui)

Lib/tkinter/test/test_tkinter/test_misc.py

@@ -1,7 +1,7 @@
 import unittest
 import tkinter
 from test import support
-from tkinter.test.support import AbstractTkTest
+from tkinter.test.support import AbstractTkTest, AbstractDefaultRootTest
 
 support.requires('gui')
 
@@ -241,7 +241,85 @@ class MiscTest(AbstractTkTest, unittest.TestCase):
                          " num=3 delta=-1 focus=True"
                          " x=10 y=20 width=300 height=200>")
 
-tests_gui = (MiscTest, )
+    def test_getboolean(self):
+        for v in 'true', 'yes', 'on', '1', 't', 'y', 1, True:
+            self.assertIs(self.root.getboolean(v), True)
+        for v in 'false', 'no', 'off', '0', 'f', 'n', 0, False:
+            self.assertIs(self.root.getboolean(v), False)
+        self.assertRaises(ValueError, self.root.getboolean, 'yea')
+        self.assertRaises(ValueError, self.root.getboolean, '')
+        self.assertRaises(TypeError, self.root.getboolean, None)
+        self.assertRaises(TypeError, self.root.getboolean, ())
+
+    def test_mainloop(self):
+        log = []
+        def callback():
+            log.append(1)
+            self.root.after(100, self.root.quit)
+        self.root.after(100, callback)
+        self.root.mainloop(1)
+        self.assertEqual(log, [])
+        self.root.mainloop(0)
+        self.assertEqual(log, [1])
+        self.assertTrue(self.root.winfo_exists())
+
+
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_default_root(self):
+        self.assertIs(tkinter._support_default_root, True)
+        self.assertIsNone(tkinter._default_root)
+        root = tkinter.Tk()
+        root2 = tkinter.Tk()
+        root3 = tkinter.Tk()
+        self.assertIs(tkinter._default_root, root)
+        root2.destroy()
+        self.assertIs(tkinter._default_root, root)
+        root.destroy()
+        self.assertIsNone(tkinter._default_root)
+        root3.destroy()
+        self.assertIsNone(tkinter._default_root)
+
+    def test_no_default_root(self):
+        self.assertIs(tkinter._support_default_root, True)
+        self.assertIsNone(tkinter._default_root)
+        root = tkinter.Tk()
+        self.assertIs(tkinter._default_root, root)
+        tkinter.NoDefaultRoot()
+        self.assertIs(tkinter._support_default_root, False)
+        self.assertFalse(hasattr(tkinter, '_default_root'))
+        # repeated call is no-op
+        tkinter.NoDefaultRoot()
+        self.assertIs(tkinter._support_default_root, False)
+        self.assertFalse(hasattr(tkinter, '_default_root'))
+        root.destroy()
+        self.assertIs(tkinter._support_default_root, False)
+        self.assertFalse(hasattr(tkinter, '_default_root'))
+        root = tkinter.Tk()
+        self.assertIs(tkinter._support_default_root, False)
+        self.assertFalse(hasattr(tkinter, '_default_root'))
+        root.destroy()
+
+    def test_getboolean(self):
+        self.assertRaises(RuntimeError, tkinter.getboolean, '1')
+        root = tkinter.Tk()
+        self.assertIs(tkinter.getboolean('1'), True)
+        self.assertRaises(ValueError, tkinter.getboolean, 'yea')
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.getboolean, '1')
+
+    def test_mainloop(self):
+        self.assertRaises(RuntimeError, tkinter.mainloop)
+        root = tkinter.Tk()
+        root.after_idle(root.quit)
+        tkinter.mainloop()
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, tkinter.mainloop)
+
+
+tests_gui = (MiscTest, DefaultRootTest)
 
 if __name__ == "__main__":
     support.run_unittest(*tests_gui)

Lib/tkinter/test/test_tkinter/test_simpledialog.py

@@ -0,0 +1,25 @@
+import unittest
+import tkinter
+from test.support import requires, run_unittest, swap_attr
+from tkinter.test.support import AbstractDefaultRootTest
+from tkinter.simpledialog import Dialog, askinteger
+
+requires('gui')
+
+
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_askinteger(self):
+        self.assertRaises(RuntimeError, askinteger, "Go To Line", "Line number")
+        root = tkinter.Tk()
+        with swap_attr(Dialog, 'wait_window', lambda self, w: w.destroy()):
+            askinteger("Go To Line", "Line number")
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, askinteger, "Go To Line", "Line number")
+
+
+tests_gui = (DefaultRootTest,)
+
+if __name__ == "__main__":
+    run_unittest(*tests_gui)

Lib/tkinter/test/test_tkinter/test_variables.py

@@ -1,8 +1,10 @@
 import unittest
 import gc
+import tkinter
 from tkinter import (Variable, StringVar, IntVar, DoubleVar, BooleanVar, Tcl,
                      TclError)
 from test.support import ALWAYS_EQ
+from tkinter.test.support import AbstractDefaultRootTest
 
 
 class Var(Variable):
@@ -308,8 +310,21 @@ class TestBooleanVar(TestBase):
             v.get()
 
 
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_variable(self):
+        self.assertRaises(RuntimeError, Variable)
+        root = tkinter.Tk()
+        v = Variable()
+        v.set("value")
+        self.assertEqual(v.get(), "value")
+        root.destroy()
+        tkinter.NoDefaultRoot()
+        self.assertRaises(RuntimeError, Variable)
+
+
 tests_gui = (TestVariable, TestStringVar, TestIntVar,
-             TestDoubleVar, TestBooleanVar)
+             TestDoubleVar, TestBooleanVar, DefaultRootTest)
 
 
 if __name__ == "__main__":

Lib/tkinter/test/test_tkinter/test_widgets.py

@@ -5,7 +5,8 @@ import os
 from test.support import requires
 
 from tkinter.test.support import (tcl_version, requires_tcl,
-                                  get_tk_patchlevel, widget_eq)
+                                  get_tk_patchlevel, widget_eq,
+                                  AbstractDefaultRootTest)
 from tkinter.test.widget_tests import (
     add_standard_options, noconv, pixels_round,
     AbstractWidgetTest, StandardOptionsTests, IntegerSizeTests, PixelSizeTests,
@@ -1295,12 +1296,21 @@ class MessageTest(AbstractWidgetTest, unittest.TestCase):
         self.checkIntegerParam(widget, 'aspect', 250, 0, -300)
 
 
+class DefaultRootTest(AbstractDefaultRootTest, unittest.TestCase):
+
+    def test_frame(self):
+        self._test_widget(tkinter.Frame)
+
+    def test_label(self):
+        self._test_widget(tkinter.Label)
+
+
 tests_gui = (
         ButtonTest, CanvasTest, CheckbuttonTest, EntryTest,
         FrameTest, LabelFrameTest,LabelTest, ListboxTest,
         MenubuttonTest, MenuTest, MessageTest, OptionMenuTest,
         PanedWindowTest, RadiobuttonTest, ScaleTest, ScrollbarTest,
-        SpinboxTest, TextTest, ToplevelTest,
+        SpinboxTest, TextTest, ToplevelTest, DefaultRootTest,
 )
 
 if __name__ == '__main__':