issue #217: initial module scanner code.

This is sketch code, it's being done separately from mitogen.master.* to
begin with to avoid breaking what's there.

ansible_mitogen/module_finder.py

@@ -0,0 +1,137 @@
+
+import imp
+import os
+import sys
+import mitogen.master
+
+
+class Name(object):
+    def __str__(self):
+        return self.identifier
+
+    def __repr__(self):
+        return 'Name(%r)' % (self.identifier,)
+
+    def __init__(self, identifier):
+        self.identifier = identifier
+
+    def head(self):
+        head, _, tail = self.identifier.partition('.')
+        return head
+
+    def tail(self):
+        head, _, tail = self.identifier.partition('.')
+        return tail
+
+    def pop_n(self, level):
+        name = self.identifier
+        for _ in xrange(level):
+            if '.' not in name:
+                return None
+            name, _, _ = self.identifier.rpartition('.')
+        return Name(name)
+
+    def append(self, part):
+        return Name('%s.%s' % (self.identifier, part))
+
+
+class Module(object):
+    def __init__(self, name, path, kind=imp.PY_SOURCE, parent=None):
+        self.name = Name(name)
+        self.path = path
+        if kind == imp.PKG_DIRECTORY:
+            self.path = os.path.join(self.path, '__init__.py')
+        self.kind = kind
+        self.parent = parent
+
+    def fullname(self):
+        bits = [str(self.name)]
+        while self.parent:
+            bits.append(str(self.parent.name))
+            self = self.parent
+        return '.'.join(reversed(bits))
+
+    def __repr__(self):
+        return 'Module(%r, path=%r, parent=%r)' % (
+            self.name,
+            self.path,
+            self.parent,
+        )
+
+    def dirname(self):
+        return os.path.dirname(self.path)
+
+    def code(self):
+        fp = open(self.path)
+        try:
+            return compile(fp.read(), str(self.name), 'exec')
+        finally:
+            fp.close()
+
+
+def find(name, path=(), parent=None):
+    """
+    (Name, search path) -> Module instance or None.
+    """
+    try:
+        tup = imp.find_module(name.head(), list(path))
+    except ImportError:
+        return parent
+
+    fp, path, (suffix, mode, kind) = tup
+    if fp:
+        fp.close()
+
+    module = Module(name.head(), path, kind, parent)
+    if name.tail():
+        return find_relative(module, Name(name.tail()), path)
+    return module
+
+
+def find_relative(parent, name, path=()):
+    path = [parent.dirname()] + list(path)
+    return find(name, path, parent=parent)
+
+
+def path_pop(s, n):
+    return os.pathsep.join(s.split(os.pathsep)[-n:])
+
+
+def scan(module, path):
+    scanner = mitogen.master.scan_code_imports(module.code())
+    for level, modname_s, fromlist in scanner:
+        modname = Name(modname_s)
+        if level == -1:
+            imported = find_relative(module, modname, path)
+        elif level:
+            subpath = [path_pop(module.dirname(), level)] + list(path)
+            imported = find(modname.pop_n(level), subpath)
+        else:
+            imported = find(modname.pop_n(level), path)
+
+        if imported and mitogen.master.is_stdlib_path(imported.path):
+            continue
+
+        if imported and fromlist:
+            have = False
+            for fromname_s in fromlist:
+                fromname = modname.append(fromname_s)
+                f_imported = find_relative(imported, fromname, path)
+                if f_imported and f_imported.fullname() == fromname.identifier:
+                    have = True
+                    yield fromname, f_imported, None
+            if have:
+                continue
+
+        if imported:
+            yield modname, imported
+
+
+module = Module(name='ansible_module_apt', path='/Users/dmw/src/mitogen/.venv/lib/python2.7/site-packages/ansible/modules/packaging/os/apt.py')
+path = tuple(sys.path)
+path = ('/Users/dmw/src/ansible/lib',) + path
+
+
+from pprint import pprint
+for name, imported in scan(module, sys.path):
+    print '%s: %s' % (name, imported and (str(name) == imported.fullname()))