Temporary prefix for installing build dependencies

pip/wheel.py

@@ -14,6 +14,7 @@ import re
 import shutil
 import stat
 import sys
+import sysconfig
 import tempfile
 import warnings
 
@@ -631,6 +632,55 @@ class Wheel(object):
         return bool(set(tags).intersection(self.file_tags))
 
 
+class BuildEnvironment(object):
+    """Context manager to install build deps in a simple temporary environment
+    """
+    def __init__(self):
+        self.prefix = tempfile.mkdtemp('pip-build-env-')
+
+    def __enter__(self):
+        self.save_path = os.environ.get('PATH', None)
+        self.save_pythonpath = os.environ.get('PYTHONPATH', None)
+
+        install_scheme = 'nt' if (os.name == 'nt') else 'posix_prefix'
+        install_dirs = sysconfig.get_paths(install_scheme, vars={
+            'base': self.prefix,
+            'platbase': self.prefix,
+        })
+
+        scripts = install_dirs['scripts']
+        if self.save_path:
+            os.environ['PATH'] = scripts + os.pathsep + self.save_path
+        else:
+            os.environ['PATH'] = scripts + os.pathsep + os.defpath
+
+        if install_dirs['purelib'] == install_dirs['platlib']:
+            lib_dirs = install_dirs['purelib']
+        else:
+            lib_dirs = install_dirs['purelib'] + os.pathsep + install_dirs['platlib']
+        if self.save_pythonpath:
+            os.environ['PYTHONPATH'] = lib_dirs + os.pathsep + self.save_pythonpath
+        else:
+            os.environ['PYTHONPATH'] = lib_dirs
+
+        return self.prefix
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if self.save_path is None:
+            os.environ.pop('PATH', None)
+        else:
+            os.environ['PATH'] = self.save_path
+
+        if self.save_pythonpath is None:
+            os.environ.pop('PYTHONPATH', None)
+        else:
+            os.environ['PYTHONPATH'] = self.save_pythonpath
+
+        rmtree(self.prefix)
+
+        return False  # Do not suppress exceptions
+
+
 class WheelBuilder(object):
     """Build wheels from a RequirementSet."""