bpo-38636: Fix IDLE tab toggle and file indent width (GH-17008)

These Format menu functions (default shortcuts Alt-T and Alt-U)
were mistakenly disabled in 3.7.5 and 3.8.0.
(cherry picked from commit b8462477bf)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/idlelib/NEWS.txt

@@ -3,6 +3,10 @@ Released on 2019-12-16?
 ======================================
 
 
+bpo-38636: Fix IDLE Format menu tab toggle and file indent width. These
+functions (default shortcuts Alt-T and Alt-U) were mistakenly disabled
+in 3.7.5 and 3.8.0.
+
 bpo-4360: Add an option to toggle IDLE's cursor blink for shell,
 editor, and output windows.  See Settings, General, Window Preferences,
 Cursor Blink.  Patch by Zachary Spytz.

Lib/idlelib/editor.py

@@ -186,8 +186,9 @@ class EditorWindow(object):
         text.bind("<<uncomment-region>>", fregion.uncomment_region_event)
         text.bind("<<tabify-region>>", fregion.tabify_region_event)
         text.bind("<<untabify-region>>", fregion.untabify_region_event)
-        text.bind("<<toggle-tabs>>", self.Indents.toggle_tabs_event)
-        text.bind("<<change-indentwidth>>", self.Indents.change_indentwidth_event)
+        indents = self.Indents(self)
+        text.bind("<<toggle-tabs>>", indents.toggle_tabs_event)
+        text.bind("<<change-indentwidth>>", indents.change_indentwidth_event)
         text.bind("<Left>", self.move_at_edge_if_selection(0))
         text.bind("<Right>", self.move_at_edge_if_selection(1))
         text.bind("<<del-word-left>>", self.del_word_left)

Lib/idlelib/format.py

@@ -353,8 +353,7 @@ class FormatRegion:
             maxvalue=16)
 
 
-# With mixed indents not allowed, these are semi-useless and not unittested.
-class Indents:  # pragma: no cover
+class Indents:
     "Change future indents."
 
     def __init__(self, editwin):

Lib/idlelib/idle_test/test_format.py

@@ -417,7 +417,7 @@ class FormatRegionTest(unittest.TestCase):
         self.text.delete('1.0', 'end')
 
     code_sample = """\
-
+# WS line needed for test.
 class C1():
     # Class comment.
     def __init__(self, a, b):
@@ -574,7 +574,42 @@ class C1():
         self.assertEqual(ask(), 10)
 
 
-class rstripTest(unittest.TestCase):
+class IndentsTest(unittest.TestCase):
+
+    @mock.patch.object(ft, "askyesno")
+    def test_toggle_tabs(self, askyesno):
+        editor = DummyEditwin(None, None)  # usetabs == False.
+        indents = ft.Indents(editor)
+        askyesno.return_value = True
+
+        indents.toggle_tabs_event(None)
+        self.assertEqual(editor.usetabs, True)
+        self.assertEqual(editor.indentwidth, 8)
+
+        indents.toggle_tabs_event(None)
+        self.assertEqual(editor.usetabs, False)
+        self.assertEqual(editor.indentwidth, 8)
+
+    @mock.patch.object(ft, "askinteger")
+    def test_change_indentwidth(self, askinteger):
+        editor = DummyEditwin(None, None)  # indentwidth == 4.
+        indents = ft.Indents(editor)
+
+        askinteger.return_value = None
+        indents.change_indentwidth_event(None)
+        self.assertEqual(editor.indentwidth, 4)
+
+        askinteger.return_value = 3
+        indents.change_indentwidth_event(None)
+        self.assertEqual(editor.indentwidth, 3)
+
+        askinteger.return_value = 5
+        editor.usetabs = True
+        indents.change_indentwidth_event(None)
+        self.assertEqual(editor.indentwidth, 3)
+
+
+class RstripTest(unittest.TestCase):
 
     def test_rstrip_line(self):
         editor = MockEditor()

Misc/NEWS.d/next/IDLE/2019-10-30-22-11-16.bpo-38636.hUhDeB.rst

@@ -0,0 +1,3 @@
+Fix IDLE Format menu tab toggle and file indent width. These functions
+(default shortcuts Alt-T and Alt-U) were mistakenly disabled in 3.7.5
+and 3.8.0.