1 files changed, 62 insertions, 0 deletions
diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
index 6b3928b..c6ed76b 100644
--- a/Lib/idlelib/run.py
+++ b/Lib/idlelib/run.py
@@ -4,10 +4,12 @@ Simplified, pyshell.ModifiedInterpreter spawns a subprocess with
 f'''{sys.executable} -c "__import__('idlelib.run').run.main()"'''
 '.run' is needed because __import__ returns idlelib, not idlelib.run.
 """
+import functools
 import io
 import linecache
 import queue
 import sys
+import textwrap
 import time
 import traceback
 import _thread as thread
@@ -305,6 +307,64 @@ def fix_scaling(root):
                 font['size'] = round(-0.75*size)
 
 
+RECURSIONLIMIT_DELTA = 30
+def install_recursionlimit_wrappers():
+    """Install wrappers to always add 30 to the recursion limit."""
+    # see: bpo-26806
+
+    @functools.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(f"setrecursionlimit() takes exactly one "
+                            f"argument ({len(args)} given)")
+        if not limit > 0:
+            raise ValueError(
+                "recursion limit must be greater or equal than 1")
+
+        return setrecursionlimit.__wrapped__(limit + RECURSIONLIMIT_DELTA)
+
+    setrecursionlimit.__doc__ += "\n\n" + textwrap.fill(textwrap.dedent(f"""\
+        This IDLE wrapper adds {RECURSIONLIMIT_DELTA} to prevent possible
+        uninterruptible loops.
+        """).strip())
+
+    @functools.wraps(sys.getrecursionlimit)
+    def getrecursionlimit():
+        return getrecursionlimit.__wrapped__() - RECURSIONLIMIT_DELTA
+
+    getrecursionlimit.__doc__ += "\n\n" + textwrap.fill(textwrap.dedent(f"""\
+        This IDLE wrapper subtracts {RECURSIONLIMIT_DELTA} to compensate for
+        the {RECURSIONLIMIT_DELTA} IDLE adds when setting the limit.
+        """).strip())
+
+    # add the delta to the default recursion limit, to compensate
+    sys.setrecursionlimit(sys.getrecursionlimit() + RECURSIONLIMIT_DELTA)
+
+    sys.setrecursionlimit = setrecursionlimit
+    sys.getrecursionlimit = getrecursionlimit
+
+
+def uninstall_recursionlimit_wrappers():
+    """Uninstall the recursion limit wrappers from the sys module.
+
+    IDLE only uses this for tests. Users can import run and call
+    this to remove the wrapping.
+    """
+    if (
+            getattr(sys.setrecursionlimit, '__wrapped__', None) and
+            getattr(sys.getrecursionlimit, '__wrapped__', None)
+    ):
+        sys.setrecursionlimit = sys.setrecursionlimit.__wrapped__
+        sys.getrecursionlimit = sys.getrecursionlimit.__wrapped__
+        sys.setrecursionlimit(sys.getrecursionlimit() - RECURSIONLIMIT_DELTA)
+
+
 class MyRPCServer(rpc.RPCServer):
 
     def handle_error(self, request, client_address):
@@ -448,6 +508,8 @@ class MyHandler(rpc.RPCHandler):
         # sys.stdin gets changed from within IDLE's shell. See issue17838.
         self._keep_stdin = sys.stdin
 
+        install_recursionlimit_wrappers()
+
         self.interp = self.get_remote_proxy("interp")
         rpc.RPCHandler.getresponse(self, myseq=None, wait=0.05)