bpo-26806: transparently add 25 to the recursion limit in IDLE

This is done to compensate for the extra stack frames added by IDLE itself, which cause problems when setting the recursion limit to low values. This wraps sys.setrecursionlimit() and sys.getrecursionlimit() as invisibly as possible.
python · taleinat · Jul 6, 2019 · Jun 10, 2019 · Jun 10, 2019 · Jun 10, 2019
commit 062b111a695cd9f7e30f92b5d4862e4383031d43
diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
@@ -8,6 +8,7 @@
 import linecache
 import queue
 import sys
+import textwrap
 import time
 import traceback
 import _thread as thread
@@ -474,6 +475,44 @@ def __init__(self, rpchandler):
         self.calltip = calltip.Calltip()
         self.autocomplete = autocomplete.AutoComplete()
 
+        self._wrap_sys_setrecursionlimit()
+
+    def _wrap_sys_setrecursionlimit(self):
+        code = textwrap.dedent("""\
+            import sys
+            from functools import wraps
+
+            # add the delta to the default recursion limit, to compensate
+            sys.setrecursionlimit(sys.getrecursionlimit() + 25)
+
+            @wraps(sys.setrecursionlimit)
+            def setrecursionlimit(*args, **kwargs):
+                # mimic the original sys.setrecursionlimit()'s input handling
+                if kwargs:
+                    raise TypeError(
+                        "setrecursionlimit() takes no keyword arguments")
+                try:
+                    limit, = args
+                except ValueError:
+                    raise TypeError("setrecursionlimit() takes exactly one "
+                                    "argument ({} given)".format(len(args)))
+                if not limit > 0:
+                    raise ValueError(
+                        "recursion limit must be greater or equal than 1")
+
+                return setrecursionlimit.__wrapped__(limit + 25)
+            sys.setrecursionlimit = setrecursionlimit
+
+            @wraps(sys.getrecursionlimit)
+            def getrecursionlimit():
+                return getrecursionlimit.__wrapped__() - 25
+            sys.getrecursionlimit = getrecursionlimit
+
+            del sys
+            del wraps
+            """)
+        exec(code, self.locals)
+
     def runcode(self, code):
         global interruptable
         try:

diff --git a/Misc/NEWS.d/next/IDLE/2019-06-10-22-48-50.bpo-26806.Zltkum.rst b/Misc/NEWS.d/next/IDLE/2019-06-10-22-48-50.bpo-26806.Zltkum.rst
@@ -0,0 +1,2 @@
+Transparently add 25 to the recursion limit in IDLE's shell to compensate
+for stack frames added by IDLE.  Patch by Tal Einat.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Transparently add 25 to the recursion limit in IDLE's shell to compensate
		for stack frames added by IDLE. Patch by Tal Einat.