Bug 1575135 - Make configure sandbox open() look more like python 3's. r=nalexander

As a consequence, we can replace the encoded_open function that did the
same in an opt-in manner.

Differential Revision: https://phabricator.services.mozilla.com/D42605

--HG--
extra : moz-landing-system : lando

build/moz.configure/old.configure

@@ -5,13 +5,6 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 
-@imports('codecs')
-@imports('sys')
-@imports(_from='mozbuild.util', _import='system_encoding')
-def encoded_open(path, mode):
-    return codecs.open(path, mode, system_encoding)
-
-
 option(env='AUTOCONF', nargs=1, help='Path to autoconf 2.13')
 
 
@@ -148,7 +141,7 @@ def prepare_configure(old_configure, mozconfig, autoconf, build_env, shell,
                 die('Failed re-creating old-configure: %s' % e.message)
 
     cmd = [shell, old_configure]
-    with encoded_open('old-configure.vars', 'w') as out:
+    with open('old-configure.vars', 'w') as out:
         log.debug('Injecting the following to old-configure:')
 
         def inject(command):
@@ -351,7 +344,7 @@ def old_configure(prepare_configure, prepare_configure_options, altered_path):
     if ret:
         with log.queue_debug():
             if config_log:
-                with encoded_open(config_log.baseFilename, 'r') as fh:
+                with open(config_log.baseFilename, 'r') as fh:
                     fh.seek(log_size)
                     for line in fh:
                         log.debug(line.rstrip())
@@ -368,7 +361,7 @@ def old_configure(prepare_configure, prepare_configure_options, altered_path):
         'split': split,
         'unique_list': unique_list,
     }
-    with encoded_open('config.data', 'r') as fh:
+    with open('config.data', 'r') as fh:
         code = compile(fh.read(), 'config.data', 'exec')
         # Every variation of the exec() function I tried led to:
         # SyntaxError: unqualified exec is not allowed in function 'main' it

config/mozunit/mozunit/mozunit.py

@@ -170,7 +170,8 @@ class MockedOpen(object):
         for name, content in files.items():
             self.files[normcase(os.path.abspath(name))] = content
 
-    def __call__(self, name, mode='r'):
+    def __call__(self, name, mode='r', buffering=None):
+        # buffering is ignored.
         absname = normcase(os.path.abspath(name))
         if 'w' in mode:
             file = MockedFile(self, absname)

python/mozbuild/mozbuild/configure/__init__.py

@@ -4,6 +4,7 @@
 
 from __future__ import absolute_import, print_function, unicode_literals
 
+import codecs
 import inspect
 import logging
 import os
@@ -35,6 +36,7 @@ from mozbuild.util import (
     memoized_property,
     ReadOnlyDict,
     ReadOnlyNamespace,
+    system_encoding,
 )
 
 import mozpack.path as mozpath
@@ -899,9 +901,21 @@ class ConfigureSandbox(dict):
             return self
         # Special case for the open() builtin, because otherwise, using it
         # fails with "IOError: file() constructor not accessible in
-        # restricted mode"
+        # restricted mode". We also make open() look more like python 3's,
+        # decoding to unicode strings unless the mode says otherwise.
         if what == '__builtin__.open':
-            return lambda *args, **kwargs: open(*args, **kwargs)
+            def wrapped_open(name, mode=None, buffering=None):
+                args = (name,)
+                kwargs = {}
+                if buffering is not None:
+                    kwargs['buffering'] = buffering
+                if mode is not None:
+                    args += (mode,)
+                    if 'b' in mode:
+                        return open(*args, **kwargs)
+                kwargs['encoding'] = system_encoding
+                return codecs.open(*args, **kwargs)
+            return wrapped_open
         # Special case os and os.environ so that os.environ is our copy of
         # the environment.
         if what == 'os.environ':

python/mozbuild/mozbuild/test/configure/data/subprocess.configure

@@ -15,7 +15,7 @@ def dies_when_logging(_):
     if getpreferredencoding().lower() == 'utf-8':
         quote_char = '\u00B4'.encode('utf-8')
     try:
-        with open(test_file, 'w+') as fh:
+        with open(test_file, 'w+b') as fh:
             fh.write(quote_char)
         out = check_cmd_output('cat', 'test.txt')
         log.info(out)