bpo-38715: Fix compileall.compile_dir() ddir regression

Lib/compileall.py

@@ -16,12 +16,11 @@
 import py_compile
 import struct
 
-from functools import partial
 from pathlib import Path
 
 __all__ = ["compile_dir","compile_file","compile_path"]
 
-def _walk_dir(dir, maxlevels, quiet=0):
+def _walk_dir(dir, maxlevels, ddir=None, quiet=0):
     if quiet < 2 and isinstance(dir, os.PathLike):
         dir = os.fspath(dir)
     if not quiet:
@@ -37,12 +36,18 @@ def _walk_dir(dir, maxlevels, quiet=0):
         if name == '__pycache__':
             continue
         fullname = os.path.join(dir, name)
+
+        if ddir is not None:
+            dfile = os.path.join(ddir, name)
+        else:
+            dfile = None
+
         if not os.path.isdir(fullname):
-            yield fullname
+            yield fullname, ddir
         elif (maxlevels > 0 and name != os.curdir and name != os.pardir and
               os.path.isdir(fullname) and not os.path.islink(fullname)):
             yield from _walk_dir(fullname, maxlevels=maxlevels - 1,
-                                 quiet=quiet)
+                                 ddir=dfile, quiet=quiet)
 
 def compile_dir(dir, maxlevels=None, ddir=None, force=False,
                 rx=None, quiet=0, legacy=False, optimize=-1, workers=1,
@@ -83,25 +88,29 @@ def compile_dir(dir, maxlevels=None, ddir=None, force=False,
             workers = 1
     if maxlevels is None:
         maxlevels = sys.getrecursionlimit()
-    files = _walk_dir(dir, quiet=quiet, maxlevels=maxlevels)
+    walk_result = _walk_dir(dir, quiet=quiet, maxlevels=maxlevels,
+                            ddir=ddir)
     success = True
     if workers != 1 and ProcessPoolExecutor is not None:
+        def compile(args):
+            file, ddir = args
+            return compile_file(file,
+                                ddir=ddir, force=force,
+                                rx=rx, quiet=quiet,
+                                legacy=legacy,
+                                optimize=optimize,
+                                invalidation_mode=invalidation_mode,
+                                stripdir=stripdir,
+                                prependdir=prependdir,
+                                limit_sl_dest=limit_sl_dest)
+
         # If workers == 0, let ProcessPoolExecutor choose
         workers = workers or None
         with ProcessPoolExecutor(max_workers=workers) as executor:
-            results = executor.map(partial(compile_file,
-                                           ddir=ddir, force=force,
-                                           rx=rx, quiet=quiet,
-                                           legacy=legacy,
-                                           optimize=optimize,
-                                           invalidation_mode=invalidation_mode,
-                                           stripdir=stripdir,
-                                           prependdir=prependdir,
-                                           limit_sl_dest=limit_sl_dest),
-                                   files)
+            results = executor.map(compile, walk_result)
             success = min(results, default=True)
     else:
-        for file in files:
+        for file, ddir in walk_result:
             if not compile_file(file, ddir, force, rx, quiet,
                                 legacy, optimize, invalidation_mode,
                                 stripdir=stripdir, prependdir=prependdir,