bpo-17535: IDLE editor line numbers (GH-14030)

Doc/library/idle.rst

@@ -290,22 +290,31 @@ Options menu (Shell and Editor)
 Configure IDLE
    Open a configuration dialog and change preferences for the following:
    fonts, indentation, keybindings, text color themes, startup windows and
-   size, additional help sources, and extensions.  On macOS,  open the
+   size, additional help sources, and extensions.  On macOS, open the
    configuration dialog by selecting Preferences in the application
-   menu. For more, see
+   menu. For more details, see
    :ref:`Setting preferences <preferences>` under Help and preferences.
 
+   Most configuration options apply to all windows or all future windows.
+   The option items below only apply to the active window.
+
 Show/Hide Code Context (Editor Window only)
    Open a pane at the top of the edit window which shows the block context
    of the code which has scrolled above the top of the window.  See
-   :ref:`Code Context <code-context>` in the Editing and Navigation section below.
+   :ref:`Code Context <code-context>` in the Editing and Navigation section
+   below.
+
+Show/Hide Line Numbers (Editor Window only)
+   Open a column to the left of the edit window which shows the number
+   of each line of text.  The default is off, which may be changed in the
+   preferences (see :ref:`Setting preferences <preferences>`).
 
 Zoom/Restore Height
    Toggles the window between normal size and maximum height. The initial size
    defaults to 40 lines by 80 chars unless changed on the General tab of the
    Configure IDLE dialog.  The maximum height for a screen is determined by
    momentarily maximizing a window the first time one is zoomed on the screen.
-   Changing screen settings may invalidate the saved height.  This toogle has
+   Changing screen settings may invalidate the saved height.  This toggle has
    no effect when a window is maximized.
 
 Window menu (Shell and Editor)

Doc/whatsnew/3.7.rst

@@ -1017,6 +1017,13 @@ by right-clicking the button.  (Contributed by Tal Einat in :issue:`1529353`.)
 
 The changes above have been backported to 3.6 maintenance releases.
 
+New in 3.7.5:
+
+Add optional line numbers for IDLE editor windows. Windows
+open without line numbers unless set otherwise in the General
+tab of the configuration dialog.
+(Contributed by Tal Einat and Saimadhav Heblikar in :issue:`17535`.)
+
 
 importlib
 ---------

Doc/whatsnew/3.8.rst

@@ -515,6 +515,11 @@ for certain types of invalid or corrupt gzip files.
 idlelib and IDLE
 ----------------
 
+Add optional line numbers for IDLE editor windows. Windows
+open without line numbers unless set otherwise in the General
+tab of the configuration dialog.
+(Contributed by Tal Einat and Saimadhav Heblikar in :issue:`17535`.)
+
 Output over N lines (50 by default) is squeezed down to a button.
 N can be changed in the PyShell section of the General page of the
 Settings dialog.  Fewer, but possibly extra long, lines can be squeezed by

Lib/idlelib/codecontext.py

@@ -13,7 +13,7 @@ import re
 from sys import maxsize as INFINITY
 
 import tkinter
-from tkinter.constants import TOP, X, SUNKEN
+from tkinter.constants import NSEW, SUNKEN
 
 from idlelib.config import idleConf
 
@@ -67,6 +67,7 @@ class CodeContext:
 
     def _reset(self):
         self.context = None
+        self.cell00 = None
         self.t1 = None
         self.topvisible = 1
         self.info = [(0, -1, "", False)]
@@ -105,25 +106,37 @@ class CodeContext:
             padx = 0
             border = 0
             for widget in widgets:
-                padx += widget.tk.getint(widget.pack_info()['padx'])
+                info = (widget.grid_info()
+                        if widget is self.editwin.text
+                        else widget.pack_info())
+                padx += widget.tk.getint(info['padx'])
                 padx += widget.tk.getint(widget.cget('padx'))
                 border += widget.tk.getint(widget.cget('border'))
             self.context = tkinter.Text(
-                self.editwin.top, font=self.text['font'],
+                self.editwin.text_frame,
                 height=1,
                 width=1,  # Don't request more than we get.
+                highlightthickness=0,
                 padx=padx, border=border, relief=SUNKEN, state='disabled')
+            self.update_font()
             self.update_highlight_colors()
             self.context.bind('<ButtonRelease-1>', self.jumptoline)
             # Get the current context and initiate the recurring update event.
             self.timer_event()
-            # Pack the context widget before and above the text_frame widget,
-            # thus ensuring that it will appear directly above text_frame.
-            self.context.pack(side=TOP, fill=X, expand=False,
-                              before=self.editwin.text_frame)
+            # Grid the context widget above the text widget.
+            self.context.grid(row=0, column=1, sticky=NSEW)
+
+            line_number_colors = idleConf.GetHighlight(idleConf.CurrentTheme(),
+                                                       'linenumber')
+            self.cell00 = tkinter.Frame(self.editwin.text_frame,
+                                        bg=line_number_colors['background'])
+            self.cell00.grid(row=0, column=0, sticky=NSEW)
             menu_status = 'Hide'
         else:
             self.context.destroy()
+            self.context = None
+            self.cell00.destroy()
+            self.cell00 = None
             self.text.after_cancel(self.t1)
             self._reset()
             menu_status = 'Show'
@@ -221,8 +234,9 @@ class CodeContext:
             self.update_code_context()
             self.t1 = self.text.after(self.UPDATEINTERVAL, self.timer_event)
 
-    def update_font(self, font):
+    def update_font(self):
         if self.context is not None:
+            font = idleConf.GetFont(self.text, 'main', 'EditorWindow')
             self.context['font'] = font
 
     def update_highlight_colors(self):
@@ -231,6 +245,11 @@ class CodeContext:
             self.context['background'] = colors['background']
             self.context['foreground'] = colors['foreground']
 
+        if self.cell00 is not None:
+            line_number_colors = idleConf.GetHighlight(idleConf.CurrentTheme(),
+                                                       'linenumber')
+            self.cell00.config(bg=line_number_colors['background'])
+
 
 CodeContext.reload()
 

Lib/idlelib/config-highlight.def

@@ -22,6 +22,10 @@ hit-foreground= #ffffff
 hit-background= #000000
 error-foreground= #000000
 error-background= #ff7777
+context-foreground= #000000
+context-background= lightgray
+linenumber-foreground= gray
+linenumber-background= #ffffff
 #cursor (only foreground can be set, restart IDLE)
 cursor-foreground= black
 #shell window
@@ -31,8 +35,6 @@ stderr-foreground= red
 stderr-background= #ffffff
 console-foreground= #770000
 console-background= #ffffff
-context-foreground= #000000
-context-background= lightgray
 
 [IDLE New]
 normal-foreground= #000000
@@ -55,6 +57,10 @@ hit-foreground= #ffffff
 hit-background= #000000
 error-foreground= #000000
 error-background= #ff7777
+context-foreground= #000000
+context-background= lightgray
+linenumber-foreground= gray
+linenumber-background= #ffffff
 #cursor (only foreground can be set, restart IDLE)
 cursor-foreground= black
 #shell window
@@ -64,8 +70,6 @@ stderr-foreground= red
 stderr-background= #ffffff
 console-foreground= #770000
 console-background= #ffffff
-context-foreground= #000000
-context-background= lightgray
 
 [IDLE Dark]
 comment-foreground = #dd0000
@@ -97,3 +101,5 @@ comment-background = #002240
 break-foreground = #FFFFFF
 context-foreground= #ffffff
 context-background= #454545
+linenumber-foreground= gray
+linenumber-background= #002240

Lib/idlelib/config-main.def

@@ -36,7 +36,7 @@
 # Additional help sources are listed in the [HelpFiles] section below
 # and should be viewable by a web browser (or the Windows Help viewer in
 # the case of .chm files). These sources will be listed on the Help
-# menu.  The pattern, and two examples, are
+# menu.  The pattern, and two examples, are:
 #
 # <sequence_number = menu item;/path/to/help/source>
 # 1 = IDLE;C:/Programs/Python36/Lib/idlelib/help.html
@@ -46,7 +46,7 @@
 # platform specific because of path separators, drive specs etc.
 #
 # The default files should not be edited except to add new sections to
-# config-extensions.def for added extensions .  The user files should be
+# config-extensions.def for added extensions.  The user files should be
 # modified through the Settings dialog.
 
 [General]
@@ -65,6 +65,7 @@ font= TkFixedFont
 font-size= 10
 font-bold= 0
 encoding= none
+line-numbers-default= 0
 
 [PyShell]
 auto-squeeze-min-lines= 50

Lib/idlelib/config.py

@@ -319,6 +319,10 @@ class IdleConf:
                 'hit-background':'#000000',
                 'error-foreground':'#ffffff',
                 'error-background':'#000000',
+                'context-foreground':'#000000',
+                'context-background':'#ffffff',
+                'linenumber-foreground':'#000000',
+                'linenumber-background':'#ffffff',
                 #cursor (only foreground can be set)
                 'cursor-foreground':'#000000',
                 #shell window
@@ -328,11 +332,11 @@ class IdleConf:
                 'stderr-background':'#ffffff',
                 'console-foreground':'#000000',
                 'console-background':'#ffffff',
-                'context-foreground':'#000000',
-                'context-background':'#ffffff',
                 }
         for element in theme:
-            if not cfgParser.has_option(themeName, element):
+            if not (cfgParser.has_option(themeName, element) or
+                    # Skip warning for new elements.
+                    element.startswith(('context-', 'linenumber-'))):
                 # Print warning that will return a default color
                 warning = ('\n Warning: config.IdleConf.GetThemeDict'
                            ' -\n problem retrieving theme element %r'

Lib/idlelib/configdialog.py

@@ -819,6 +819,7 @@ class HighPage(Frame):
             'Shell Error Text': ('error', '12'),
             'Shell Stdout Text': ('stdout', '13'),
             'Shell Stderr Text': ('stderr', '14'),
+            'Line Number': ('linenumber', '16'),
             }
         self.builtin_name = tracers.add(
                 StringVar(self), self.var_changed_builtin_name)
@@ -866,6 +867,11 @@ class HighPage(Frame):
             ('stderr', 'stderr'), ('\n\n', 'normal'))
         for texttag in text_and_tags:
             text.insert(END, texttag[0], texttag[1])
+        n_lines = len(text.get('1.0', END).splitlines())
+        for lineno in range(1, n_lines + 1):
+            text.insert(f'{lineno}.0',
+                        f'{lineno:{len(str(n_lines))}d} ',
+                        'linenumber')
         for element in self.theme_elements:
             def tem(event, elem=element):
                 # event.widget.winfo_top_level().highlight_target.set(elem)
@@ -1827,6 +1833,9 @@ class GenPage(Frame):
                 frame_format: Frame
                     format_width_title: Label
                     (*)format_width_int: Entry - format_width
+                frame_line_numbers_default: Frame
+                    line_numbers_default_title: Label
+                    (*)line_numbers_default_bool: Checkbutton - line_numbers_default
                 frame_context: Frame
                     context_title: Label
                     (*)context_int: Entry - context_lines
@@ -1866,6 +1875,9 @@ class GenPage(Frame):
                 IntVar(self), ('main', 'General', 'autosave'))
         self.format_width = tracers.add(
                 StringVar(self), ('extensions', 'FormatParagraph', 'max-width'))
+        self.line_numbers_default = tracers.add(
+                BooleanVar(self),
+                ('main', 'EditorWindow', 'line-numbers-default'))
         self.context_lines = tracers.add(
                 StringVar(self), ('extensions', 'CodeContext', 'maxlines'))
 
@@ -1944,6 +1956,14 @@ class GenPage(Frame):
                 validatecommand=self.digits_only, validate='key',
         )
 
+        frame_line_numbers_default = Frame(frame_editor, borderwidth=0)
+        line_numbers_default_title = Label(
+            frame_line_numbers_default, text='Show line numbers in new windows')
+        self.line_numbers_default_bool = Checkbutton(
+                frame_line_numbers_default,
+                variable=self.line_numbers_default,
+                width=1)
+
         frame_context = Frame(frame_editor, borderwidth=0)
         context_title = Label(frame_context, text='Max Context Lines :')
         self.context_int = Entry(
@@ -2021,6 +2041,10 @@ class GenPage(Frame):
         frame_format.pack(side=TOP, padx=5, pady=0, fill=X)
         format_width_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
         self.format_width_int.pack(side=TOP, padx=10, pady=5)
+        # frame_line_numbers_default.
+        frame_line_numbers_default.pack(side=TOP, padx=5, pady=0, fill=X)
+        line_numbers_default_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
+        self.line_numbers_default_bool.pack(side=LEFT, padx=5, pady=5)
         # frame_context.
         frame_context.pack(side=TOP, padx=5, pady=0, fill=X)
         context_title.pack(side=LEFT, anchor=W, padx=5, pady=5)
@@ -2063,6 +2087,8 @@ class GenPage(Frame):
                 'main', 'General', 'autosave', default=0, type='bool'))
         self.format_width.set(idleConf.GetOption(
                 'extensions', 'FormatParagraph', 'max-width', type='int'))
+        self.line_numbers_default.set(idleConf.GetOption(
+                'main', 'EditorWindow', 'line-numbers-default', type='bool'))
         self.context_lines.set(idleConf.GetOption(
                 'extensions', 'CodeContext', 'maxlines', type='int'))
 

Lib/idlelib/editor.py

@@ -53,6 +53,7 @@ class EditorWindow(object):
     from idlelib.autoexpand import AutoExpand
     from idlelib.calltip import Calltip
     from idlelib.codecontext import CodeContext
+    from idlelib.sidebar import LineNumbers
     from idlelib.format import FormatParagraph, FormatRegion, Indents, Rstrip
     from idlelib.parenmatch import ParenMatch
     from idlelib.squeezer import Squeezer
@@ -61,7 +62,8 @@ class EditorWindow(object):
     filesystemencoding = sys.getfilesystemencoding()  # for file names
     help_url = None
 
-    allow_codecontext = True
+    allow_code_context = True
+    allow_line_numbers = True
 
     def __init__(self, flist=None, filename=None, key=None, root=None):
         # Delay import: runscript imports pyshell imports EditorWindow.
@@ -198,12 +200,14 @@ class EditorWindow(object):
             text.bind("<<open-turtle-demo>>", self.open_turtle_demo)
 
         self.set_status_bar()
+        text_frame.pack(side=LEFT, fill=BOTH, expand=1)
+        text_frame.rowconfigure(1, weight=1)
+        text_frame.columnconfigure(1, weight=1)
         vbar['command'] = self.handle_yview
-        vbar.pack(side=RIGHT, fill=Y)
+        vbar.grid(row=1, column=2, sticky=NSEW)
         text['yscrollcommand'] = vbar.set
         text['font'] = idleConf.GetFont(self.root, 'main', 'EditorWindow')
-        text_frame.pack(side=LEFT, fill=BOTH, expand=1)
-        text.pack(side=TOP, fill=BOTH, expand=1)
+        text.grid(row=1, column=1, sticky=NSEW)
         text.focus_set()
 
         # usetabs true  -> literal tab characters are used by indent and
@@ -250,7 +254,8 @@ class EditorWindow(object):
         self.good_load = False
         self.set_indentation_params(False)
         self.color = None # initialized below in self.ResetColorizer
-        self.codecontext = None
+        self.code_context = None # optionally initialized later below
+        self.line_numbers = None # optionally initialized later below
         if filename:
             if os.path.exists(filename) and not os.path.isdir(filename):
                 if io.loadfile(filename):
@@ -316,10 +321,20 @@ class EditorWindow(object):
         text.bind("<<refresh-calltip>>", ctip.refresh_calltip_event)
         text.bind("<<force-open-calltip>>", ctip.force_open_calltip_event)
         text.bind("<<zoom-height>>", self.ZoomHeight(self).zoom_height_event)
-        if self.allow_codecontext:
-            self.codecontext = self.CodeContext(self)
+        if self.allow_code_context:
+            self.code_context = self.CodeContext(self)
             text.bind("<<toggle-code-context>>",
-                      self.codecontext.toggle_code_context_event)
+                      self.code_context.toggle_code_context_event)
+        else:
+            self.update_menu_state('options', '*Code Context', 'disabled')
+        if self.allow_line_numbers:
+            self.line_numbers = self.LineNumbers(self)
+            if idleConf.GetOption('main', 'EditorWindow',
+                                  'line-numbers-default', type='bool'):
+                self.toggle_line_numbers_event()
+            text.bind("<<toggle-line-numbers>>", self.toggle_line_numbers_event)
+        else:
+            self.update_menu_state('options', '*Line Numbers', 'disabled')
 
     def _filename_to_unicode(self, filename):
         """Return filename as BMP unicode so displayable in Tk."""
@@ -779,8 +794,11 @@ class EditorWindow(object):
         self._addcolorizer()
         EditorWindow.color_config(self.text)
 
-        if self.codecontext is not None:
-            self.codecontext.update_highlight_colors()
+        if self.code_context is not None:
+            self.code_context.update_highlight_colors()
+
+        if self.line_numbers is not None:
+            self.line_numbers.update_colors()
 
     IDENTCHARS = string.ascii_letters + string.digits + "_"
 
@@ -799,11 +817,16 @@ class EditorWindow(object):
         "Update the text widgets' font if it is changed"
         # Called from configdialog.py
 
-        new_font = idleConf.GetFont(self.root, 'main', 'EditorWindow')
         # Update the code context widget first, since its height affects
         # the height of the text widget.  This avoids double re-rendering.
-        if self.codecontext is not None:
-            self.codecontext.update_font(new_font)
+        if self.code_context is not None:
+            self.code_context.update_font()
+        # Next, update the line numbers widget, since its width affects
+        # the width of the text widget.
+        if self.line_numbers is not None:
+            self.line_numbers.update_font()
+        # Finally, update the main text widget.
+        new_font = idleConf.GetFont(self.root, 'main', 'EditorWindow')
         self.text['font'] = new_font
 
     def RemoveKeybindings(self):
@@ -1467,6 +1490,19 @@ class EditorWindow(object):
             indentsmall = indentlarge = 0
         return indentlarge - indentsmall
 
+    def toggle_line_numbers_event(self, event=None):
+        if self.line_numbers is None:
+            return
+
+        if self.line_numbers.is_shown:
+            self.line_numbers.hide_sidebar()
+            menu_label = "Show"
+        else:
+            self.line_numbers.show_sidebar()
+            menu_label = "Hide"
+        self.update_menu_label(menu='options', index='*Line Numbers',
+                               label=f'{menu_label} Line Numbers')
+
 # "line.col" -> line, as an int
 def index2line(index):
     return int(float(index))

Lib/idlelib/help.html

@@ -271,10 +271,15 @@ fonts, indentation, keybindings, text color themes, startup windows and
 size, additional help sources, and extensions.  On macOS,  open the
 configuration dialog by selecting Preferences in the application
 menu. For more, see
-<a class="reference internal" href="#preferences"><span class="std std-ref">Setting preferences</span></a> under Help and preferences.</dd>
+<a class="reference internal" href="#preferences"><span class="std std-ref">Setting preferences</span></a> under Help and preferences.
+Most configuration options apply to all windows or all future windows.
+The option items below only apply to the active window.</dd>
 <dt>Show/Hide Code Context (Editor Window only)</dt><dd>Open a pane at the top of the edit window which shows the block context
 of the code which has scrolled above the top of the window.  See
 <a class="reference internal" href="#code-context"><span class="std std-ref">Code Context</span></a> in the Editing and Navigation section below.</dd>
+<dt>Line Numbers (Editor Window only)</dt><dd>Open a column to the left of the edit window which shows the linenumber
+of each line of text.  The default is off unless configured on
+(see <a class="reference internal" href="#preferences"><span class="std std-ref">Setting preferences</span></a>).</dd>
 <dt>Zoom/Restore Height</dt><dd>Toggles the window between normal size and maximum height. The initial size
 defaults to 40 lines by 80 chars unless changed on the General tab of the
 Configure IDLE dialog.  The maximum height for a screen is determined by
@@ -607,7 +612,7 @@ IDLE should be started in a command line window.  The secondary subprocess
 will then be attached to that window for input and output.</p>
 <p>The IDLE code running in the execution process adds frames to the call stack
 that would not be there otherwise.  IDLE wraps <code class="docutils literal notranslate"><span class="pre">sys.getrecursionlimit</span></code> and
-<code class="docutils literal notranslate"><span class="pre">sys.setrecursionlimit</span></code> to reduce their visibility.</p>
+<code class="docutils literal notranslate"><span class="pre">sys.setrecursionlimit</span></code> to reduce the effect of the additional stack frames.</p>
 <p>If <code class="docutils literal notranslate"><span class="pre">sys</span></code> is reset by user code, such as with <code class="docutils literal notranslate"><span class="pre">importlib.reload(sys)</span></code>,
 IDLE’s changes are lost and input from the keyboard and output to the screen
 will not work correctly.</p>
@@ -895,7 +900,7 @@ also used for testing.</p>
 <br />
     <br />
 
-    Last updated on Jul 04, 2019.
+    Last updated on Jul 23, 2019.
     <a href="https://docs.python.org/3/bugs.html">Found a bug</a>?
     <br />
 

Lib/idlelib/idle_test/htest.py

@@ -67,6 +67,7 @@ outwin.OutputWindow (indirectly being tested with grep test)
 
 import idlelib.pyshell  # Set Windows DPI awareness before Tk().
 from importlib import import_module
+import textwrap
 import tkinter as tk
 from tkinter.ttk import Scrollbar
 tk.NoDefaultRoot()
@@ -205,6 +206,19 @@ _io_binding_spec = {
            "Check that changes were saved by opening the file elsewhere."
     }
 
+_linenumbers_drag_scrolling_spec = {
+    'file': 'sidebar',
+    'kwds': {},
+    'msg': textwrap.dedent("""\
+        Click on the line numbers and drag down below the edge of the
+        window, moving the mouse a bit and then leaving it there for a while.
+        The text and line numbers should gradually scroll down, with the
+        selection updated continuously.
+        Do the same as above, dragging to above the window. The text and line
+        numbers should gradually scroll up, with the selection updated
+        continuously."""),
+    }
+
 _multi_call_spec = {
     'file': 'multicall',
     'kwds': {},

Lib/idlelib/idle_test/test_codecontext.py

@@ -4,7 +4,7 @@ from idlelib import codecontext
 import unittest
 import unittest.mock
 from test.support import requires
-from tkinter import Tk, Frame, Text, TclError
+from tkinter import NSEW, Tk, Frame, Text, TclError
 
 from unittest import mock
 import re
@@ -62,7 +62,7 @@ class CodeContextTest(unittest.TestCase):
         text.insert('1.0', code_sample)
         # Need to pack for creation of code context text widget.
         frame.pack(side='left', fill='both', expand=1)
-        text.pack(side='top', fill='both', expand=1)
+        text.grid(row=1, column=1, sticky=NSEW)
         cls.editor = DummyEditwin(root, frame, text)
         codecontext.idleConf.userCfg = testcfg
 
@@ -77,6 +77,7 @@ class CodeContextTest(unittest.TestCase):
 
     def setUp(self):
         self.text.yview(0)
+        self.text['font'] = 'TkFixedFont'
         self.cc = codecontext.CodeContext(self.editor)
 
         self.highlight_cfg = {"background": '#abcdef',
@@ -86,10 +87,18 @@ class CodeContextTest(unittest.TestCase):
             if element == 'context':
                 return self.highlight_cfg
             return orig_idleConf_GetHighlight(theme, element)
-        patcher = unittest.mock.patch.object(
+        GetHighlight_patcher = unittest.mock.patch.object(
             codecontext.idleConf, 'GetHighlight', mock_idleconf_GetHighlight)
-        patcher.start()
-        self.addCleanup(patcher.stop)
+        GetHighlight_patcher.start()
+        self.addCleanup(GetHighlight_patcher.stop)
+
+        self.font_override = 'TkFixedFont'
+        def mock_idleconf_GetFont(root, configType, section):
+            return self.font_override
+        GetFont_patcher = unittest.mock.patch.object(
+            codecontext.idleConf, 'GetFont', mock_idleconf_GetFont)
+        GetFont_patcher.start()
+        self.addCleanup(GetFont_patcher.stop)
 
     def tearDown(self):
         if self.cc.context:
@@ -339,69 +348,59 @@ class CodeContextTest(unittest.TestCase):
     def test_font(self):
         eq = self.assertEqual
         cc = self.cc
-        save_font = cc.text['font']
+
+        orig_font = cc.text['font']
         test_font = 'TkTextFont'
+        self.assertNotEqual(orig_font, test_font)
 
         # Ensure code context is not active.
         if cc.context is not None:
             cc.toggle_code_context_event()
 
+        self.font_override = test_font
         # Nothing breaks or changes with inactive code context.
-        cc.update_font(test_font)
+        cc.update_font()
 
-        # Activate code context, but no change to font.
-        cc.toggle_code_context_event()
-        eq(cc.context['font'], save_font)
-        # Call font update with the existing font.
-        cc.update_font(save_font)
-        eq(cc.context['font'], save_font)
+        # Activate code context, previous font change is immediately effective.
         cc.toggle_code_context_event()
-
-        # Change text widget font and activate code context.
-        cc.text['font'] = test_font
-        cc.toggle_code_context_event(test_font)
         eq(cc.context['font'], test_font)
 
-        # Just call the font update.
-        cc.update_font(save_font)
-        eq(cc.context['font'], save_font)
-        cc.text['font'] = save_font
+        # Call the font update, change is picked up.
+        self.font_override = orig_font
+        cc.update_font()
+        eq(cc.context['font'], orig_font)
 
     def test_highlight_colors(self):
         eq = self.assertEqual
         cc = self.cc
-        save_colors = dict(self.highlight_cfg)
+
+        orig_colors = dict(self.highlight_cfg)
         test_colors = {'background': '#222222', 'foreground': '#ffff00'}
 
+        def assert_colors_are_equal(colors):
+            eq(cc.context['background'], colors['background'])
+            eq(cc.context['foreground'], colors['foreground'])
+
         # Ensure code context is not active.
         if cc.context:
             cc.toggle_code_context_event()
 
+        self.highlight_cfg = test_colors
         # Nothing breaks with inactive code context.
         cc.update_highlight_colors()
 
-        # Activate code context, but no change to colors.
+        # Activate code context, previous colors change is immediately effective.
         cc.toggle_code_context_event()
-        eq(cc.context['background'], save_colors['background'])
-        eq(cc.context['foreground'], save_colors['foreground'])
+        assert_colors_are_equal(test_colors)
 
-        # Call colors update, but no change to font.
+        # Call colors update with no change to the configured colors.
         cc.update_highlight_colors()
-        eq(cc.context['background'], save_colors['background'])
-        eq(cc.context['foreground'], save_colors['foreground'])
-        cc.toggle_code_context_event()
-
-        # Change colors and activate code context.
-        self.highlight_cfg = test_colors
-        cc.toggle_code_context_event()
-        eq(cc.context['background'], test_colors['background'])
-        eq(cc.context['foreground'], test_colors['foreground'])
+        assert_colors_are_equal(test_colors)
 
-        # Change colors and call highlight colors update.
-        self.highlight_cfg = save_colors
+        # Call the colors update with code context active, change is picked up.
+        self.highlight_cfg = orig_colors
         cc.update_highlight_colors()
-        eq(cc.context['background'], save_colors['background'])
-        eq(cc.context['foreground'], save_colors['foreground'])
+        assert_colors_are_equal(orig_colors)
 
 
 class HelperFunctionText(unittest.TestCase):

Lib/idlelib/mainmenu.py

@@ -100,7 +100,8 @@ menudefs = [
    ('Configure _IDLE', '<<open-config-dialog>>'),
    None,
    ('Show _Code Context', '<<toggle-code-context>>'),
-   ('Zoom Height', '<<zoom-height>>'),
+   ('Show _Line Numbers', '<<toggle-line-numbers>>'),
+   ('_Zoom Height', '<<zoom-height>>'),
    ]),
 
  ('window', [

Lib/idlelib/outwin.py

@@ -74,13 +74,11 @@ class OutputWindow(EditorWindow):
         ("Go to file/line", "<<goto-file-line>>", None),
     ]
 
-    allow_codecontext = False
+    allow_code_context = False
 
     def __init__(self, *args):
         EditorWindow.__init__(self, *args)
         self.text.bind("<<goto-file-line>>", self.goto_file_line)
-        self.text.unbind("<<toggle-code-context>>")
-        self.update_menu_state('options', '*Code Context', 'disabled')
 
     # Customize EditorWindow
     def ispythonsource(self, filename):

Lib/idlelib/pyshell.py

@@ -861,6 +861,8 @@ class PyShell(OutputWindow):
         ("Squeeze", "<<squeeze-current-text>>"),
     ]
 
+    allow_line_numbers = False
+
     # New classes
     from idlelib.history import History
 

Misc/NEWS.d/next/IDLE/2019-06-13-01-07-20.bpo-17535.K8i2St.rst

+Add optional line numbers for IDLE editor windows.  Windows
+open without line numbers unless set otherwise in the General
+tab of the configuration dialog. 
+