Introduce a mechanism for sharing code across lldb/test and lldb/scripts

[zturner]

Summary

We have a lot of Python code in test and scripts that in theory could be reused amongst the two. Until now there is no mechanism to support this because Python's module / packaging system imposes some limitations on how and where your code must be in order to be re-used.

This patch addresses this by creating a new module lldb_shared which searches up the tree until it finds an lldb.root file. Then, it dynamically imports lldb_shared_base from that folder. lldb_shared_base is a module that exists only as a means to modify sys.path to add all of the shared module locations ot the path.

In order to make use of this, you need to copy the lldb_shared.py file into the root of each project that you wish to make use of this shared code.

The end result of this is that if you have a directory structure like this:

lldb
\__ test
\__ scripts
\__ common
     \__ useful_utility.py
\__ third_party
     \__ six
          \__ six.py

All you need to do is add lldb_shared.py to the root of lldb/test and lldb/scripts and then you can write

import lldb_shared
import useful_utility
import six

This patch is dependent on D13880

[tfiala]

Yep, like it.

lldb_shared_base.py

+import inspect
+import os
+import sys
+
+def add_third_party_module_dirs(lldb_root):
+    third_party_modules_dir = os.path.join(lldb_root, "third_party", "Python", "module")
+    if not os.path.isdir(third_party_modules_dir):
+        return
+
+    module_dirs = os.listdir(third_party_modules_dir)
+    for module_dir in module_dirs:
+        module_dir = os.path.join(third_party_modules_dir, module_dir)
+        sys.path.append(module_dir)
+lldb_root = os.path.dirname(inspect.getfile(inspect.currentframe()))
+add_third_party_module_dirs(lldb_root)

test/dotest.py

 
 from __future__ import print_function
 
+import lldb_shared
+
 import atexit
 import commands
 import importlib

 import unittest2
 import lldbtest_config
 
+import six
+
 
 def is_exe(fpath):
     """Returns true if fpath is an executable."""

test/lldb_shared.py

+import os
+import sys
+
+def find_lldb_root():
+    lldb_root = os.getcwd()
+    while True:
+        lldb_root = os.path.dirname(lldb_root)
+        if lldb_root is None:
+            return None
+
+        test_path = os.path.join(lldb_root, "lldb.root")
+        if os.path.isfile(test_path):
+            return lldb_root
+    return None
+
+lldb_root = find_lldb_root()
+if lldb_root is not None:
+    import imp
+    module = imp.find_module("lldb_shared_base", [lldb_root])
+    if module is not None:
+        imp.load_module("lldb_shared_base", *module)
 No newline at end of file