bpo-39781: Do not jump when select in IDLE codecontext

Lib/idlelib/NEWS.txt

@@ -3,6 +3,8 @@ Released on 2020-10-05?
 ======================================
 
 
+bpo-39781: Selecting code context lines no longer causes a jump.
+
 bpo-39663: Add tests for pyparse find_good_parse_start().
 
 bpo-39600: Remove duplicate font names from configuration list.

Lib/idlelib/codecontext.py

@@ -7,7 +7,6 @@
 enclosing block.  The number of hint lines is determined by the maxlines
 variable in the codecontext section of config-extensions.def. Lines which do
 not open blocks are not shown in the context hints pane.
-
 """
 import re
 from sys import maxsize as INFINITY
@@ -17,8 +16,8 @@
 
 from idlelib.config import idleConf
 
-BLOCKOPENERS = {"class", "def", "elif", "else", "except", "finally", "for",
-                "if", "try", "while", "with", "async"}
+BLOCKOPENERS = {'class', 'def', 'if', 'elif', 'else', 'while', 'for',
+                 'try', 'except', 'finally', 'with', 'async'}
 
 
 def get_spaces_firstword(codeline, c=re.compile(r"^(\s*)(\w*)")):
@@ -84,7 +83,7 @@ def __del__(self):
         if self.t1 is not None:
             try:
                 self.text.after_cancel(self.t1)
-            except tkinter.TclError:
+            except tkinter.TclError:  # pragma: no cover
                 pass
             self.t1 = None
 
@@ -112,19 +111,19 @@ def toggle_code_context_event(self, event=None):
                 padx += widget.tk.getint(info['padx'])
                 padx += widget.tk.getint(widget.cget('padx'))
                 border += widget.tk.getint(widget.cget('border'))
-            self.context = tkinter.Text(
+            context = self.context = tkinter.Text(
                 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)
+            context.bind('<ButtonRelease-1>', self.jumptoline)
             # Get the current context and initiate the recurring update event.
             self.timer_event()
             # Grid the context widget above the text widget.
-            self.context.grid(row=0, column=1, sticky=NSEW)
+            context.grid(row=0, column=1, sticky=NSEW)
 
             line_number_colors = idleConf.GetHighlight(idleConf.CurrentTheme(),
                                                        'linenumber')
@@ -215,18 +214,25 @@ def update_code_context(self):
         self.context['state'] = 'disabled'
 
     def jumptoline(self, event=None):
-        "Show clicked context line at top of editor."
-        lines = len(self.info)
-        if lines == 1:  # No context lines are showing.
-            newtop = 1
-        else:
-            # Line number clicked.
-            contextline = int(float(self.context.index('insert')))
-            # Lines not displayed due to maxlines.
-            offset = max(1, lines - self.context_depth) - 1
-            newtop = self.info[offset + contextline][0]
-        self.text.yview(f'{newtop}.0')
-        self.update_code_context()
+        """ Show clicked context line at top of editor.
+
+        If a selection was made, don't jump; allow copying.
+        If no visible context, show the top line of the file.
+        """
+        try:
+            self.context.index("sel.first")
+        except tkinter.TclError:
+            lines = len(self.info)
+            if lines == 1:  # No context lines are showing.
+                newtop = 1
+            else:
+                # Line number clicked.
+                contextline = int(float(self.context.index('insert')))
+                # Lines not displayed due to maxlines.
+                offset = max(1, lines - self.context_depth) - 1
+                newtop = self.info[offset + contextline][0]
+            self.text.yview(f'{newtop}.0')
+            self.update_code_context()
 
     def timer_event(self):
         "Event on editor text widget triggered every UPDATEINTERVAL ms."

Lib/idlelib/idle_test/test_codecontext.py

@@ -332,6 +332,14 @@ def test_jumptoline(self):
         jump()
         eq(cc.topvisible, 8)
 
+        # Context selection stops jump.
+        cc.text.yview('5.0')
+        cc.update_code_context()
+        cc.context.tag_add('sel', '1.0', '2.0')
+        cc.context.mark_set('insert', '1.0')
+        jump()  # Without selection, to line 2.
+        eq(cc.topvisible, 5)
+
     @mock.patch.object(codecontext.CodeContext, 'update_code_context')
     def test_timer_event(self, mock_update):
         # Ensure code context is not active.

Misc/NEWS.d/next/IDLE/2020-02-27-22-17-09.bpo-39781.bbYBeL.rst

@@ -0,0 +1 @@
+Selecting code context lines no longer causes a jump.