# HG changeset patch
# Parent  c445746d08461dc146afcb34116b8d2731da853d
Check for negative workers even if ProcessPoolExecutor unavailable

This matches the documentation, and passes the test suite when multithreading
is disabled.

diff -r c445746d0846 Lib/compileall.py
--- a/Lib/compileall.py	Wed Oct 19 19:37:20 2016 +0300
+++ b/Lib/compileall.py	Thu Oct 20 07:34:39 2016 +0000
@@ -66,13 +66,13 @@
     optimize:  optimization level or -1 for level of the interpreter
     workers:   maximum number of parallel workers
     """
+    if workers is not None and workers < 0:
+        raise ValueError('workers must be greater or equal to 0')
+
     files = _walk_dir(dir, quiet=quiet, maxlevels=maxlevels,
                       ddir=ddir)
     success = 1
     if workers is not None and workers != 1 and ProcessPoolExecutor is not None:
-        if workers < 0:
-            raise ValueError('workers must be greater or equal to 0')
-
         workers = workers or None
         with ProcessPoolExecutor(max_workers=workers) as executor:
             results = executor.map(partial(compile_file,
diff -r c445746d0846 Misc/NEWS
--- a/Misc/NEWS	Wed Oct 19 19:37:20 2016 +0300
+++ b/Misc/NEWS	Thu Oct 20 07:34:39 2016 +0000
@@ -110,6 +110,10 @@
 Library
 -------
 
+- Issue #NNNNN: Always raise ValueError for negative
+  compileall.compile_dir(workers=...) parameter, even when multithreading is
+  unavailable.
+
 - Issue #24452: Make webbrowser support Chrome on Mac OS X.
 
 - Issue #20766: Fix references leaked by pdb in the handling of SIGINT