Normalize debugger temp file paths on Windows

ipykernel/compiler.py

@@ -1,6 +1,7 @@
 from IPython.core.compilerop import CachingCompiler
 import tempfile
 import os
+import sys
 
 
 def murmur2_x86(data, seed):
@@ -36,11 +37,35 @@ def murmur2_x86(data, seed):
 
     return h
 
+convert_to_long_pathname = lambda filename:filename
+
+if sys.platform == 'win32':
+    try:
+        import ctypes
+        from ctypes.wintypes import MAX_PATH, LPCWSTR, LPWSTR, DWORD
+
+        _GetLongPathName = ctypes.windll.kernel32.GetLongPathNameW
+        _GetLongPathName.argtypes = [LPCWSTR, LPWSTR, DWORD]
+        _GetLongPathName.restype = DWORD
+
+        def _convert_to_long_pathname(filename):
+            buf = ctypes.create_unicode_buffer(MAX_PATH)
+            rv = _GetLongPathName(filename, buf, MAX_PATH)
+            if rv != 0 and rv <= MAX_PATH:
+                filename = buf.value
+            return filename
+
+        # test that it works so if there are any issues we fail just once here
+        _convert_to_long_pathname(__file__)
+    except:
+        pass
+    else:
+        convert_to_long_pathname = _convert_to_long_pathname
 
 def get_tmp_directory():
-    tmp_dir = tempfile.gettempdir()
+    tmp_dir = convert_to_long_pathname(tempfile.gettempdir())
     pid = os.getpid()
-    return tmp_dir + '/ipykernel_' + str(pid)
+    return tmp_dir + os.sep + 'ipykernel_' + str(pid)
 
 
 def get_tmp_hash_seed():
@@ -52,7 +77,7 @@ def get_file_name(code):
     cell_name = os.environ.get("IPYKERNEL_CELL_NAME")
     if cell_name is None:
         name = murmur2_x86(code, get_tmp_hash_seed())
-        cell_name = get_tmp_directory() + '/' + str(name) + '.py'
+        cell_name = get_tmp_directory() + os.sep + str(name) + '.py'
     return cell_name
 
 

ipykernel/debugger.py

@@ -507,7 +507,7 @@ async def debugInfo(self, message):
                 'isStarted': self.is_started,
                 'hashMethod': 'Murmur2',
                 'hashSeed': get_tmp_hash_seed(),
-                'tmpFilePrefix': get_tmp_directory() + '/',
+                'tmpFilePrefix': get_tmp_directory() + os.sep,
                 'tmpFileSuffix': '.py',
                 'breakpoints': breakpoint_list,
                 'stoppedThreads': self.stopped_threads,

ipykernel/tests/test_debugger.py

@@ -271,3 +271,9 @@ def test_rich_inspect_at_breakpoint(kernel_with_debug):
     )
 
     assert reply["body"]["data"] == {"text/plain": locals_[0]["value"]}
+
+
+def test_convert_to_long_pathname():
+    if sys.platform == 'win32':
+        from ipykernel.compiler import _convert_to_long_pathname
+        _convert_to_long_pathname(__file__)