Allow disabling of the sys.path rewrite technique using an environment variable.

2 files changed, 17 insertions, 1 deletions

diff --git a/CHANGES.txt b/CHANGES.txt
index 10027a90..2ad565bc 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -3,6 +3,21 @@ CHANGES
 =======
 
 ----
+18.3
+----
+
+* Setuptools now allows disabling of the manipulation of the sys.path
+  during the processing of the easy-install.pth file. To do so, set
+  the environment variable ``SETUPTOOLS_SYS_PATH_TECHNIQUE`` to
+  anything but "rewrite" (consider "raw"). During any install operation
+  with manipulation disabled, setuptools packages will be appended to
+  sys.path naturally.
+
+  Future versions may change the default behavior to disable
+  manipulation. If so, the default behavior can be retained by setting
+  the variable to "rewrite".
+
+----
 18.2
 ----
 
diff --git a/setuptools/command/easy_install.py b/setuptools/command/easy_install.py
index 2b639c1b..7c0dfa99 100755
--- a/setuptools/command/easy_install.py
+++ b/setuptools/command/easy_install.py
@@ -1612,7 +1612,8 @@ class RewritePthDistributions(PthDistributions):
         """)
 
 
-PthDistributions = RewritePthDistributions
+if os.environ.get('SETUPTOOLS_SYS_PATH_TECHNIQUE', 'rewrite') == 'rewrite':
+    PthDistributions = RewritePthDistributions
 
 
 def _first_line_re():