Find libclang so that Python3 works, remove `PY2` annotations

We now require that Debian users install the `python3` and `python3-pip`
packages. This change lets the Python code search for `libclang.so`, which can
be located in different directories, depending on version, and is not found by
default otherwise.

Fixes #28

PiperOrigin-RevId: 254745872
Change-Id: Ia77680da2a3235c0a9518125676aa8a460e38e76

README.md

@@ -68,8 +68,9 @@ echo "deb http://storage.googleapis.com/bazel-apt stable jdk1.8" | \
   sudo tee /etc/apt/sources.list.d/bazel.list
 wget -qO - https://bazel.build/bazel-release.pub.gpg | sudo apt-key add -
 sudo apt-get update
-sudo apt-get install -qy python-typing python-clang-7 libclang-7-dev
-sudo apt-get install -qy build-essential linux-libc-dev bazel
+sudo apt-get install -qy build-essential linux-libc-dev bazel python3 \
+  python3-pip libclang-7-dev
+pip3 install clang
 ```
 
 Clone and run the build:

sandboxed_api/tools/generator2/BUILD

@@ -29,7 +29,6 @@ py_test(
         "code_test.py",
         "code_test_util.py",
     ],
-    python_version = "PY2",
     deps = [
         ":code",
         "@com_google_absl_py//absl/testing:absltest",
@@ -40,7 +39,6 @@ py_test(
 py_binary(
     name = "sapi_generator",
     srcs = ["sapi_generator.py"],
-    python_version = "PY2",
     visibility = ["//visibility:public"],
     deps = [
         ":code",

sandboxed_api/tools/generator2/code.py

@@ -17,6 +17,7 @@
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
+from ctypes import util
 import itertools
 import os
 from clang import cindex
@@ -32,6 +33,23 @@ _PARSE_OPTIONS = (cindex.TranslationUnit.PARSE_SKIP_FUNCTION_BODIES |
                   cindex.TranslationUnit.PARSE_DETAILED_PROCESSING_RECORD)
 
 
+def _init_libclang():
+  """Finds and initializes the libclang library."""
+  if cindex.Config.loaded:
+    return
+  # Try to find libclang in the standard location and a few versioned paths
+  # that are used on Debian (and others). If LD_LIBRARY_PATH is set, it is
+  # used as well.
+  for lib in [
+      'clang', 'clang-9', 'clang-8', 'clang-7', 'clang-6.0', 'clang-5.0',
+      'clang-4.0'
+  ]:
+    libclang = util.find_library(lib)
+    if libclang:
+      cindex.Config.set_library_file(libclang)
+      break
+
+
 def get_header_guard(path):
   # type: (Text) -> Text
   """Generates header guard string from path."""
@@ -610,6 +628,7 @@ class Analyzer(object):
   @staticmethod
   def process_files(input_paths, compile_flags):
     # type: (Text, List[Text]) -> List[_TranslationUnit]
+    _init_libclang()
     return [Analyzer._analyze_file_for_tu(path, compile_flags=compile_flags)
             for path in input_paths]
 
@@ -663,9 +682,9 @@ class Generator(object):
       facultative. If not given, then one is computed for each element of
       input_paths
     """
-
     self.translation_units = translation_units
     self.functions = None
+    _init_libclang()
 
   def generate(self, name, function_names, namespace=None, output_file=None,
                embed_dir=None, embed_name=None):