fix linecache

Author: picnixz

Lib/linecache.py

@@ -73,6 +73,15 @@ def checkcache(filename=None):
         except OSError:
             cache.pop(filename, None)
             continue
+        except ValueError:
+            # ValueError may happen on Windows platforms for long paths.
+            # In this case, we assume that we could not just read the file.
+            #
+            # See: https://github.com/python/cpython/issues/122170.
+            if os.name == 'nt':
+                cache.pop(filename, None)
+                continue
+            raise  # this should not happen on other platforms
         if size != stat.st_size or mtime != stat.st_mtime:
             cache.pop(filename, None)
 
@@ -137,8 +146,15 @@ def updatecache(filename, module_globals=None):
                 break
             except OSError:
                 pass
+            except ValueError:
+                if os.name != 'nt':
+                    raise  # this should not happen on other platforms
         else:
             return []
+    except ValueError:
+        if os.name != 'nt':
+            raise  # this should not happen on other platforms
+        return []
     try:
         with tokenize.open(fullname) as fp:
             lines = fp.readlines()

Lib/test/test_linecache.py

@@ -280,6 +280,28 @@ def test_loader(self):
         self.assertEqual(linecache.getlines(filename, module_globals),
                          ['source for x.y.z\n'])
 
+    def test_long_filename(self):
+        # For POSIX platforms, an OSError will be raised and will take
+        # the usual path handling. For Windows platforms, a ValueError
+        # is raised instead but linecache will handle it as if it were
+        # an OSError in this case.
+        #
+        # See: https://github.com/python/cpython/issues/122170
+
+        linecache.clearcache()
+        lines = linecache.updatecache('a' * 9999)
+        self.assertListEqual(lines, [])
+        self.assertNotIn('a' * 9999, linecache.cache)
+
+        # hack into the cache (it shouldn't be allowed
+        # but we never know what people do...)
+        linecache.cache['smallname'] = (0, 1234, [], 'a' * 9999)
+        linecache.checkcache('smallname')
+        self.assertNotIn('smallname', linecache.cache)
+
+        # just to be sure that we did not mess with cache
+        linecache.clearcache()
+
 
 class LineCacheInvalidationTests(unittest.TestCase):
     def setUp(self):