Enable absolute imports in lldbsuite

[zturner]

Summary

Enable absolute imports in lldbsuite.

Absolute imports were introduced in Python 2.5 as a feature
(e.g. from __future__ import absolute_import), and made default
in Python 3.

When absolute imports are enabled, the import system changes in
a couple of ways:

1) The `import foo` syntax will *only* search sys.path.  If `foo`
   isn't in sys.path, it won't be found.  Period.  Without absolute
   imports, the import system will also search the same directory
   that the importing file resides in, so that you can easily
   import from the same folder.

2) From inside a package, you can use a dot syntax to refer to higher
   levels of the current package.  For example, if you are in the
   package lldbsuite.test.utility, then ..foo refers to
   lldbsuite.test.foo.  You can use this notation with the
   `from X import Y` syntax to write intra-package references.  For
   example, using the previous locationa s a starting point, writing
   `from ..support import seven` would import lldbsuite.support.seven

Since this is now the default behavior in Python 3, this means that
importing from the same directory with `import foo` *no longer works*.
As a result, the only way to have portable code is to force absolute
imports for all versions of Python.

See PEP 0328 [https://www.python.org/dev/peps/pep-0328/] for more
information about absolute and relative imports.

[tfiala]

Does this mean that if we import third party modules, and since you have embedded them into our package, that we would have to change third party code to adhere to our packaging structure? If not, fine. If so, this was one of the areas I mentioned that I was concerned about with the monolithic packaging structure.

[zturner]

In D14342#282346, @tfiala wrote:

Does this mean that if we import third party modules, and since you have embedded them into our package, that we would have to change third party code to adhere to our packaging structure? If not, fine. If so, this was one of the areas I mentioned that I was concerned about with the monolithic packaging structure.

No. I actually explicitly went out of my way to remove the third party packages from our package. That's why they are all in lldb/third_party now. use_lldb_suite adds all the third_party directories to sys.path up front, so you can still use absolute import syntax for this. i.e. import six will still just work, because it's in sys.path.

That said, the only place you have to use relative import syntax is to import stuff from within the same package. Plus, even in the hypothetical case where we did have that, as long as we don't write from future import absolute_import at the top of those packages' modules, they would still continue to work as they normally do.

It took me a while to wrap my head around this PEP, but now that I understand it, I think it's a good thing in principle, since it solves name collisions between your own modules and third-party / system modules by forcing you to make it explicit which one you want. Either you want a system / third-party module (e.g. import foo) or you want a module from within your current package (e.g. from . import foo)

[tfiala]

Okay, looks good then. Thanks, Zachary!

packages/Python/lldbsuite/test/__init__.py

 # Module level initialization for the `lldbsuite.test` module.
 
-import dotest
+from __future__ import absolute_import
+
+from . import dotest
 run_suite = dotest.run_suite

packages/Python/lldbsuite/test/bench.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
 import os, sys
 import re

packages/Python/lldbsuite/test/curses_results.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
+# System modules
 import curses
 import datetime
-import lldbcurses
 import math
 import sys
 import test_results
 import time
 
+# Third-party modules
+
+# LLDB modules
+from . import lldbcurses
+
 class Curses(test_results.ResultsFormatter):
     """Receives live results from tests that are running and reports them to the terminal in a curses GUI"""
 

packages/Python/lldbsuite/test/dosep.py

 """
 
 from __future__ import print_function
-
-
+from __future__ import absolute_import
 
 # system packages and modules
 import asyncore

 
 from six.moves import queue
 
-# Add our local test_runner/lib dir to the python path.
-sys.path.append(os.path.join(os.path.dirname(__file__), "test_runner", "lib"))
-
 # Our packages and modules
-import dotest_channels
-import dotest_args
+import lldbsuite.support.seven as seven
+
+from . import dotest_channels
+from . import dotest_args
+
+# Todo: Convert this folder layout to be relative-import friendly and don't hack up
+# sys.path like this
+sys.path.append(os.path.join(os.path.dirname(__file__), "test_runner", "lib"))
 import lldb_utils
 import process_control
-import lldbsuite.support.seven as seven
 
 # Status codes for running command with timeout.
 eTimedOut, ePassed, eFailed = 124, 0, 1

packages/Python/lldbsuite/test/dotest.py

 for available options.
 """
 
+from __future__ import absolute_import
 from __future__ import print_function
-import sys
-
-import lldbsuite
-import lldbtest_config
 
+# System modules
+import sys
 import atexit
 import importlib
 import os
-import dotest_args
 import errno
 import platform
 import progress

 import socket
 import subprocess
 import sys
-import test_results
-from test_results import EventBuilder
 import inspect
-import unittest2
-import test_categories
 
+# Third-party modules
 import six
-import lldbsuite.support.seven as seven
+import unittest2
+
+# LLDB Modules
+import lldbsuite
+from . import dotest_args
+from . import lldbtest_config
+from . import test_categories
+from . import test_results
+from .test_results import EventBuilder
+from ..support import seven
 
 def is_exe(fpath):
     """Returns true if fpath is an executable."""

     # If we are running as the multiprocess test runner, kick off the
     # multiprocess test runner here.
     if isMultiprocessTestRunner():
-        import dosep
+        from . import dosep
         dosep.main(output_on_success, num_threads, multiprocess_test_subdir,
                    test_runner_name, results_formatter_object)
         raise Exception("should never get here")

packages/Python/lldbsuite/test/dotest_args.py

 from __future__ import print_function
+from __future__ import absolute_import
 
+# System modules
 import argparse
 import sys
 import multiprocessing
 import os
 import textwrap
 
+# Third-party modules
+
+# LLDB modules
+
 class ArgParseNamespace(object):
     pass
 

packages/Python/lldbsuite/test/dotest_channels.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
 
-
+# System modules
 import asyncore
 import socket
 
+# Third-party modules
 from six.moves import cPickle
 
+# LLDB modules
+
 class UnpicklingForwardingReaderChannel(asyncore.dispatcher):
     """Provides an unpickling, forwarding asyncore dispatch channel reader.
 

packages/Python/lldbsuite/test/lldb_pylint_helper.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
+# System modules
 import os
 import platform
 import subprocess
 import sys
 
+# Third-party modules
+
+# LLDB modules
+
 
 def add_lldb_test_paths(check_dir):
     # pylint: disable=line-too-long

packages/Python/lldbsuite/test/lldbbench.py

+from __future__ import absolute_import
+
+# System modules
 import time
-#import numpy
-from lldbtest import *
+
+# Third-party modules
+
+# LLDB modules
+from .lldbtest import *
 
 class Stopwatch(object):
     """Stopwatch provides a simple utility to start/stop your stopwatch multiple

packages/Python/lldbsuite/test/lldbcurses.py

+from __future__ import absolute_import
 
-
-import curses, curses.panel
+# System modules
+import curses
+import curses.panel
 import sys
-import six
 import time 
 
+# Third-party modules
+import six
+
+# LLDB modules
+
 class Point(object):
     def __init__(self, x, y):
         self.x = x

packages/Python/lldbsuite/test/lldbinline.py

 from __future__ import print_function
+from __future__ import absolute_import
 
-import lldb
-from lldbtest import *
-import lldbutil
+# System modules
 import os
 import sys
 
+# Third-party modules
+
+# LLDB modules
+import lldb
+from .lldbtest import *
+from . import lldbutil
+
 def source_type(filename):
     _, extension = os.path.splitext(filename)
     return {

packages/Python/lldbsuite/test/lldbpexpect.py

 from __future__ import print_function
+from __future__ import absolute_import
 
-
-
-import lldb
-from lldbtest import *
-import lldbutil
+# System modules
 import os
 import sys
+
+# Third-party modules
 import pexpect
 
+# LLDB Modules
+import lldb
+from .lldbtest import *
+from . import lldbutil
+
 class PExpectTest(TestBase):
     
     mydir = TestBase.compute_mydir(__file__)

packages/Python/lldbsuite/test/lldbplatformutil.py

 """ This module contains functions used by the test cases to hide the
 architecture and/or the platform dependent nature of the tests. """
 
+from __future__ import absolute_import
+
+# System modules
+
+# Third-party modules
+
+# LLDB modules
+
 def check_first_register_readable(test_case):
     if test_case.getArchitecture() in ['x86_64', 'i386']:
         test_case.expect("register read eax", substrs = ['eax = 0x'])

packages/Python/lldbsuite/test/lldbtest.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
-
-
+# System modules
 import abc
+import collections
 import gc
 import glob
 import os, sys, traceback

 from subprocess import *
 import time
 import types
-import unittest2
-import lldb
-import lldbtest_config
-import  lldbutil
-import test_categories
 
+# Third-party modules
+import unittest2
 from six import add_metaclass
 from six import StringIO as SixStringIO
 from six.moves.urllib import parse as urlparse
 import six
-import collections
+
+# LLDB modules
+import lldb
+from . import lldbtest_config
+from . import lldbutil
+from . import test_categories
 
 # dosep.py starts lots and lots of dotest instances
 # This option helps you find if two (or more) dotest instances are using the same

         """ Returns a string that represents the compiler version.
             Supports: llvm, clang.
         """
-        from lldbutil import which
+        from .lldbutil import which
         version = 'unknown'
 
         compiler = self.getCompilerBinary()

         Run the 'thread list' command, and select the thread with stop reason as
         'stop_reason'.  If no such thread exists, no select action is done.
         """
-        from lldbutil import stop_reason_to_str
+        from .lldbutil import stop_reason_to_str
         self.runCmd('thread list')
         output = self.res.GetOutput()
         thread_line_pattern = re.compile("^[ *] thread #([0-9]+):.*stop reason = %s" %

 
     def DebugSBValue(self, val):
         """Debug print a SBValue object, if traceAlways is True."""
-        from lldbutil import value_type_to_str
+        from .lldbutil import value_type_to_str
 
         if not traceAlways:
             return

packages/Python/lldbsuite/test/lldbutil.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
-
-
-import lldb
-import os, sys
+# System modules
+import collections
+import os
 import re
+import sys
 
+# Third-party modules
 from six import StringIO as SixStringIO
 import six
-import collections
+
+# LLDB modules
+import lldb
+
 
 # ===================================================
 # Utilities for locating/checking executable programs

packages/Python/lldbsuite/test/test_categories.py

 Provides definitions for various lldb test categories
 """
 
+from __future__ import absolute_import
+
+# System modules
 import sys
 
+# Third-party modules
+
+# LLDB modules
+
 all_categories = {
     'dataformatters': 'Tests related to the type command and the data formatters subsystem',
     'expression'    : 'Tests related to the expression parser',

packages/Python/lldbsuite/test/test_results.py

 """
 
 from __future__ import print_function
+from __future__ import absolute_import
 
-
-
+# System modules
 import argparse
 import inspect
 import os

 import traceback
 import xml.sax.saxutils
 
+# Third-party modules
 import six
 from six.moves import cPickle
 
+# LLDB modules
 
 class EventBuilder(object):
     """Helper class to build test result event dictionaries."""