Inspect compiled CFFI extension members

To use a CFFI extension, its "lib" symbol gives access to the exported
C symbols and its "ffi" symbol gives access to low-level utilities.
An import such as the following is required:

  from _compiled_extension_module import ffi
  from _compiled_extension_module import lib

Then in the code, these objects are used to access the C symbols:

  pp = ffi.cast('struct mystruct *', p)
  lib.exported_c_function(pp)

Even if "_compiled_extension_module" is added to
AstroidManager.extension_package_whitelist, the "ffi" and "lib" objects
are not analyzed properly since they do not fall into any of the
supported categories of objects. A dummy "builtin.module" node is
inserted in their place preventing tools like pylint to properly detect
object membership. Thus producing invalid errors:

  Instance of 'module' has no 'cast' member [no-member]
  Instance of 'module' has no 'exported_c_function' member [no-member]

Both these objects define __all__ attributes which lists their exported
symbols. The presence of __all__ means that dir(member) will work and
that object_build may be called recursively on that member.

Insert a Module node to represent these objects and add their members to
the built AST.

Link: https://cffi.readthedocs.io/en/latest/overview.html#main-mode-of-usage
Signed-off-by: Robin Jarry <robin.jarry@6wind.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 515fd656..9b400d5f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -192,6 +192,8 @@ Release Date: TBA
 
   Close #755
 
+* Properly analyze CFFI compiled extensions.
+
 What's New in astroid 2.3.2?
 ============================
 Release Date: TBA
diff --git a/astroid/raw_building.py b/astroid/raw_building.py
index d94f9240..c852485e 100644
--- a/astroid/raw_building.py
+++ b/astroid/raw_building.py
@@ -354,6 +354,11 @@ class InspectBuilder:
                 # This should be called for Jython, where some builtin
                 # methods aren't caught by isbuiltin branch.
                 _build_from_function(node, name, member, self._module)
+            elif hasattr(member, '__all__'):
+                module = build_module(name)
+                _attach_local_node(node, module, name)
+                # recursion
+                self.object_build(module, member)
             else:
                 # create an empty node so that the name is actually defined
                 attach_dummy_node(node, name, member)