Extract sandboxing context as a series of encapsulated contexts.

setuptools/sandbox.py

@@ -5,6 +5,7 @@ import operator
 import functools
 import itertools
 import re
+import contextlib
 
 import pkg_resources
 
@@ -42,20 +43,95 @@ def _execfile(filename, globals, locals=None):
     code = compile(script, filename, 'exec')
     exec(code, globals, locals)
 
+
+@contextlib.contextmanager
+def save_argv():
+    saved = sys.argv[:]
+    try:
+        yield saved
+    finally:
+        sys.argv[:] = saved
+
+
+@contextlib.contextmanager
+def save_path():
+    saved = sys.path[:]
+    try:
+        yield saved
+    finally:
+        sys.path[:] = saved
+
+
+@contextlib.contextmanager
+def override_temp(replacement):
+    """
+    Monkey-patch tempfile.tempdir with replacement, ensuring it exists
+    """
+    if not os.path.isdir(replacement):
+        os.makedirs(replacement)
+
+    saved = tempfile.tempdir
+
+    tempfile.tempdir = replacement
+
+    try:
+        yield
+    finally:
+        tempfile.tempdir = saved
+
+
+@contextlib.contextmanager
+def pushd(target):
+    saved = os.getcwd()
+    os.chdir(target)
+    try:
+        yield saved
+    finally:
+        os.chdir(saved)
+
+
+@contextlib.contextmanager
+def save_modules():
+    saved = sys.modules.copy()
+    try:
+        yield saved
+    finally:
+        sys.modules.update(saved)
+        # remove any modules imported since
+        del_modules = [
+            mod_name for mod_name in sys.modules
+            if mod_name not in saved
+            # exclude any encodings modules. See #285
+            and not mod_name.startswith('encodings.')
+        ]
+        list(map(sys.modules.__delitem__, del_modules))
+
+
+@contextlib.contextmanager
+def save_pkg_resources_state():
+    saved = pkg_resources.__getstate__()
+    try:
+        yield saved
+    finally:
+        pkg_resources.__setstate__(saved)
+
+
+@contextlib.contextmanager
+def setup_context(setup_dir):
+    temp_dir = os.path.join(setup_dir, 'temp')
+    with save_pkg_resources_state():
+        with save_modules():
+            with save_path():
+                with save_argv():
+                    with override_temp(temp_dir):
+                        with pushd(setup_dir):
+                            yield
+
+
 def run_setup(setup_script, args):
     """Run a distutils setup script, sandboxed in its directory"""
-    old_dir = os.getcwd()
-    save_argv = sys.argv[:]
-    save_path = sys.path[:]
     setup_dir = os.path.abspath(os.path.dirname(setup_script))
-    temp_dir = os.path.join(setup_dir,'temp')
-    if not os.path.isdir(temp_dir): os.makedirs(temp_dir)
-    save_tmp = tempfile.tempdir
-    save_modules = sys.modules.copy()
-    pr_state = pkg_resources.__getstate__()
-    try:
-        tempfile.tempdir = temp_dir
-        os.chdir(setup_dir)
+    with setup_context(setup_dir):
         try:
             sys.argv[:] = [setup_script]+list(args)
             sys.path.insert(0, setup_dir)
@@ -71,21 +147,6 @@ def run_setup(setup_script, args):
             if v.args and v.args[0]:
                 raise
             # Normal exit, just return
-    finally:
-        pkg_resources.__setstate__(pr_state)
-        sys.modules.update(save_modules)
-        # remove any modules imported within the sandbox
-        del_modules = [
-            mod_name for mod_name in sys.modules
-            if mod_name not in save_modules
-            # exclude any encodings modules. See #285
-            and not mod_name.startswith('encodings.')
-        ]
-        list(map(sys.modules.__delitem__, del_modules))
-        os.chdir(old_dir)
-        sys.path[:] = save_path
-        sys.argv[:] = save_argv
-        tempfile.tempdir = save_tmp
 
 
 class AbstractSandbox: