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.

Author: serhiy-storchaka

Lib/idlelib/pyshell.py

@@ -1061,8 +1061,10 @@ def begin(self):
  (sys.version, sys.platform, self.COPYRIGHT, nosub))
  self.text.focus_force()
  self.showprompt()
+ # User code should use separate default Tk root window
  import tkinter
- tkinter._default_root = None # 03Jan04 KBK What's this?
+ tkinter._support_default_root = True
+ tkinter._default_root = None
  return True
 
  def stop_readline(self):

Lib/test/test_idle.py

@@ -20,5 +20,5 @@
 if __name__ == '__main__':
  tk.NoDefaultRoot()
  unittest.main(exit=False)
- tk._support_default_root = 1
+ tk._support_default_root = True
  tk._default_root = None

Lib/tkinter/__init__.py

@@ -270,7 +270,7 @@ def __repr__(self):
  )
 
 
-_support_default_root = 1
+_support_default_root = True
 _default_root = None
 
 
@@ -280,13 +280,26 @@ def NoDefaultRoot():
  Call this function to inhibit that the first instance of
  Tk is used for windows without an explicit parent window.
  """
- global _support_default_root
- _support_default_root = 0
- global _default_root
+ global _support_default_root, _default_root
+ _support_default_root = False
+ # Delete, so any use of _default_root will immediately raise an exception.
+ # Rebind before deletion, so repeated calls will not fail.
  _default_root = None
  del _default_root
 
 
+def _get_default_root(what=None):
+ if not _support_default_root:
+ raise RuntimeError("No master specified and tkinter is "
+ "configured to not support default root")
+ if not _default_root:
+ if what:
+ raise RuntimeError(f"Too early to {what}: no default root window")
+ root = Tk()
+ assert _default_root is root
+ return _default_root
+
+
 def _tkerror(err):
  """Internal function."""
  pass
@@ -330,7 +343,7 @@ def __init__(self, master=None, value=None, name=None):
  raise TypeError("name must be a string")
  global _varnum
  if not master:
- master = _default_root
+ master = _get_default_root('create variable')
  self._root = master._root()
  self._tk = master.tk
  if name:
@@ -591,7 +604,7 @@ def get(self):
 
 def mainloop(n=0):
  """Run the main loop of Tcl."""
- _default_root.tk.mainloop(n)
+ _get_default_root('run the main loop').tk.mainloop(n)
 
 
 getint = int
@@ -600,9 +613,9 @@ def mainloop(n=0):
 
 
 def getboolean(s):
- """Convert true and false to integer values 1 and 0."""
+ """Convert Tcl object to True or False."""
  try:
- return _default_root.tk.getboolean(s)
+ return _get_default_root('use getboolean()').tk.getboolean(s)
  except TclError:
  raise ValueError("invalid literal for getboolean()")
 
@@ -2248,7 +2261,7 @@ def __init__(self, screenName=None, baseName=None, className='Tk',
  is the name of the widget class."""
  self.master = None
  self.children = {}
- self._tkloaded = 0
+ self._tkloaded = False
  # to avoid recursions in the getattr code in case of failure, we
  # ensure that self.tk is always _something_.
  self.tk = None
@@ -2272,7 +2285,7 @@ def loadtk(self):
  self._loadtk()
 
  def _loadtk(self):
- self._tkloaded = 1
+ self._tkloaded = True
  global _default_root
  # Version sanity checks
  tk_version = self.tk.getvar('tk_version')
@@ -2521,12 +2534,8 @@ class BaseWidget(Misc):
 
  def _setup(self, master, cnf):
  """Internal function. Sets up information about children."""
- if _support_default_root:
- global _default_root
- if not master:
- if not _default_root:
- _default_root = Tk()
- master = _default_root
+ if not master:
+ master = _get_default_root()
  self.master = master
  self.tk = master.tk
  name = None
@@ -3990,9 +3999,7 @@ class Image:
  def __init__(self, imgtype, name=None, cnf={}, master=None, **kw):
  self.name = None
  if not master:
- master = _default_root
- if not master:
- raise RuntimeError('Too early to create image')
+ master = _get_default_root('create image')
  self.tk = getattr(master, 'tk', master)
  if not name:
  Image._last_id += 1
@@ -4146,11 +4153,13 @@ def __init__(self, name=None, cnf={}, master=None, **kw):
 
 
 def image_names():
- return _default_root.tk.splitlist(_default_root.tk.call('image', 'names'))
+ tk = _get_default_root('use image_names()').tk
+ return tk.splitlist(tk.call('image', 'names'))
 
 
 def image_types():
- return _default_root.tk.splitlist(_default_root.tk.call('image', 'types'))
+ tk = _get_default_root('use image_types()').tk
+ return tk.splitlist(tk.call('image', 'types'))
 
 
 class Spinbox(Widget, XView):

Lib/tkinter/commondialog.py

@@ -18,10 +18,10 @@ class Dialog:
  command = None
 
  def __init__(self, master=None, **options):
+ if not master:
+ master = options.get('parent')
  self.master = master
  self.options = options
- if not master and options.get('parent'):
- self.master = options['parent']
 
  def _fixoptions(self):
  pass # hook

Lib/tkinter/font.py

@@ -69,7 +69,7 @@ def _mkdict(self, args):
  def __init__(self, root=None, font=None, name=None, exists=False,
  **options):
  if not root:
- root = tkinter._default_root
+ root = tkinter._get_default_root('use font')
  tk = getattr(root, 'tk', root)
  if font:
  # get actual settings corresponding to the given font
@@ -184,7 +184,7 @@ def metrics(self, *options, **kw):
 def families(root=None, displayof=None):
  "Get font families (as a tuple)"
  if not root:
- root = tkinter._default_root
+ root = tkinter._get_default_root('use font.families()')
  args = ()
  if displayof:
  args = ('-displayof', displayof)
@@ -194,7 +194,7 @@ def families(root=None, displayof=None):
 def names(root=None):
  "Get names of defined fonts (as a tuple)"
  if not root:
- root = tkinter._default_root
+ root = tkinter._get_default_root('use font.names()')
  return root.tk.splitlist(root.tk.call("font", "names"))
 
 

Lib/tkinter/simpledialog.py

@@ -24,9 +24,7 @@
 """
 
 from tkinter import *
-from tkinter import messagebox
-
-import tkinter # used at _QueryDialog for tkinter._default_root
+from tkinter import messagebox, _get_default_root
 
 
 class SimpleDialog:
@@ -128,13 +126,17 @@ def __init__(self, parent, title = None):
 
  title -- the dialog title
  '''
- Toplevel.__init__(self, parent)
+ master = parent
+ if not master:
+ master = _get_default_root('create dialog window')
+
+ Toplevel.__init__(self, master)
 
  self.withdraw() # remain invisible for now
- # If the master is not viewable, don't
+ # If the parent is not viewable, don't
  # make the child transient, or else it
  # would be opened withdrawn
- if parent.winfo_viewable():
+ if parent is not None and parent.winfo_viewable():
  self.transient(parent)
 
  if title:
@@ -155,7 +157,7 @@ def __init__(self, parent, title = None):
 
  self.protocol("WM_DELETE_WINDOW", self.cancel)
 
- if self.parent is not None:
+ if parent is not None:
  self.geometry("+%d+%d" % (parent.winfo_rootx()+50,
  parent.winfo_rooty()+50))
 
@@ -259,9 +261,6 @@ def __init__(self, title, prompt,
  minvalue = None, maxvalue = None,
  parent = None):
 
- if not parent:
- parent = tkinter._default_root
-
  self.prompt = prompt
  self.minvalue = minvalue
  self.maxvalue = maxvalue

Lib/tkinter/test/support.py

@@ -36,6 +36,33 @@ def tearDown(self):
  w.destroy()
  self.root.withdraw()
 
+
+class AbstractDefaultRootTest:
+
+ def setUp(self):
+ self._old_support_default_root = tkinter._support_default_root
+ destroy_default_root()
+ tkinter._support_default_root = True
+ self.wantobjects = tkinter.wantobjects
+
+ def tearDown(self):
+ destroy_default_root()
+ tkinter._default_root = None
+ tkinter._support_default_root = self._old_support_default_root
+
+ def _test_widget(self, constructor):
+ # no master passing
+ x = constructor()
+ self.assertIsNotNone(tkinter._default_root)
+ self.assertIs(x.master, tkinter._default_root)
+ self.assertIs(x.tk, tkinter._default_root.tk)
+ x.destroy()
+ destroy_default_root()
+ tkinter.NoDefaultRoot()
+ self.assertRaises(RuntimeError, constructor)
+ self.assertFalse(hasattr(tkinter, '_default_root'))
+
+
 def destroy_default_root():
  if getattr(tkinter, '_default_root', None):
  tkinter._default_root.update_idletasks()

Lib/tkinter/test/test_tkinter/test_font.py

@@ -2,7 +2,7 @@
 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 @@ def test_repr(self):
  )
 
 
-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 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 @@ def test_image_names(self):
  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 @@ def test_transparency(self):
  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)