bpo-42426: IDLE: Fix reporting offset of the RE error in searchengine (pythonGH-23447)

Author: serhiy-storchaka

Lib/idlelib/NEWS.txt

@@ -3,6 +3,8 @@ Released on 2021-10-04?
 ======================================
 
 
+bpo-42426: Fix reporting offset of the RE error in searchengine.
+
 bpo-42416: Get docstrings for IDLE calltips more often
 by using inspect.getdoc.
 

Lib/idlelib/idle_test/test_searchengine.py

@@ -175,11 +175,13 @@ def test_getprog(self):
 
         engine.setpat('')
         Equal(engine.getprog(), None)
+        Equal(Mbox.showerror.message,
+              'Error: Empty regular expression')
         engine.setpat('+')
         engine.revar.set(1)
         Equal(engine.getprog(), None)
-        self.assertEqual(Mbox.showerror.message,
-                         'Error: nothing to repeat at position 0\nPattern: +')
+        Equal(Mbox.showerror.message,
+              'Error: nothing to repeat\nPattern: +\nOffset: 0')
 
     def test_report_error(self):
         showerror = Mbox.showerror

Lib/idlelib/searchengine.py

@@ -84,20 +84,17 @@ def getprog(self):
             flags = flags | re.IGNORECASE
         try:
             prog = re.compile(pat, flags)
-        except re.error as what:
-            args = what.args
-            msg = args[0]
-            col = args[1] if len(args) >= 2 else -1
-            self.report_error(pat, msg, col)
+        except re.error as e:
+            self.report_error(pat, e.msg, e.pos)
             return None
         return prog
 
-    def report_error(self, pat, msg, col=-1):
+    def report_error(self, pat, msg, col=None):
         # Derived class could override this with something fancier
         msg = "Error: " + str(msg)
         if pat:
             msg = msg + "\nPattern: " + str(pat)
-        if col >= 0:
+        if col is not None:
             msg = msg + "\nOffset: " + str(col)
         tkMessageBox.showerror("Regular expression error",
                                msg, master=self.root)

Misc/NEWS.d/next/IDLE/2020-11-21-17-21-21.bpo-42426.kNnPoC.rst

@@ -0,0 +1 @@
+Fix reporting offset of the RE error in searchengine.