Add site.py site-packages tracing in verbose mode

Author: native-api

Lib/site.py

@@ -87,6 +87,10 @@
 USER_BASE = None
 
 
+def _trace(message):
+    if sys.flags.verbose:
+        print(message,file=sys.stderr)
+
 def makepath(*paths):
     dir = os.path.join(*paths)
     try:
@@ -155,6 +159,7 @@ def addpackage(sitedir, name, known_paths):
     else:
         reset = False
     fullname = os.path.join(sitedir, name)
+    _trace("Processing .pth file: %r" % fullname)
     try:
         f = open(fullname, "r")
     except OSError:
@@ -189,6 +194,7 @@ def addpackage(sitedir, name, known_paths):
 def addsitedir(sitedir, known_paths=None):
     """Add 'sitedir' argument to sys.path if missing and handle .pth files in
     'sitedir'"""
+    _trace("Adding directory: %r" % sitedir)
     if known_paths is None:
         known_paths = _init_pathinfo()
         reset = True
@@ -309,6 +315,7 @@ def addusersitepackages(known_paths):
     """
     # get the per user site-package path
     # this call will also make sure USER_BASE and USER_SITE are set
+    _trace("Processing user site-packages")
     user_site = getusersitepackages()
 
     if ENABLE_USER_SITE and os.path.isdir(user_site):
@@ -344,6 +351,7 @@ def getsitepackages(prefixes=None):
 
 def addsitepackages(known_paths, prefixes=None):
     """Add site-packages to sys.path"""
+    _trace("Processing global site-packages")
     for sitedir in getsitepackages(prefixes):
         if os.path.isdir(sitedir):
             addsitedir(sitedir, known_paths)

Lib/test/test_site.py

@@ -310,6 +310,15 @@ def test_no_home_directory(self):
             mock_addsitedir.assert_not_called()
             self.assertFalse(known_paths)
 
+    def test_trace(self):
+        import io
+        message="bla-bla-bla"
+        for verbose, out in (True, message+"\n"), (False, ""):
+            with mock.patch('sys.flags', mock.Mock(verbose=verbose)),\
+                    mock.patch('sys.stderr', io.StringIO()):
+                site._trace(message)
+                self.assertEqual(sys.stderr.getvalue(), out)
+
 
 class PthFile(object):
     """Helper class for handling testing of .pth files"""

Misc/NEWS.d/next/Library/2019-03-01-01-56-23.bpo-33944.-82Pkt.rst

@@ -0,0 +1 @@
+Added site.py site-packages tracing in verbose mode