Readability

tools/distrib/python/grpcio_tools/grpc_tools/protoc.py

@@ -28,6 +28,9 @@ import sys
 
 from grpc_tools import _protoc_compiler
 
+_PROTO_MODULE_SUFFIX = "_pb2"
+_SERVICE_MODULE_SUFFIX = "_pb2_grpc"
+
 def main(command_arguments):
     """Run the protocol buffer compiler with the given command-line arguments.
 
@@ -65,7 +68,7 @@ def _augmented_syspath(new_paths):
 def get_protos(protobuf_path, include_paths=None):
   with _augmented_syspath(include_paths):
     # TODO: Pull these strings out to module-level constants.
-    module_name = _proto_file_to_module_name("_pb2", protobuf_path)
+    module_name = _proto_file_to_module_name(_PROTO_MODULE_SUFFIX, protobuf_path)
     module = importlib.import_module(module_name)
     return module
 
@@ -73,7 +76,7 @@ def get_protos(protobuf_path, include_paths=None):
 def get_services(protobuf_path, include_paths=None):
   get_protos(protobuf_path, include_paths)
   with _augmented_syspath(include_paths):
-    module_name = _proto_file_to_module_name("_pb2_grpc", protobuf_path)
+    module_name = _proto_file_to_module_name(_SERVICE_MODULE_SUFFIX, protobuf_path)
     module = importlib.import_module(module_name)
     return module
 
@@ -83,13 +86,12 @@ def get_protos_and_services(protobuf_path, include_paths=None):
           get_services(protobuf_path, include_paths=include_paths))
 
 
-
 _proto_code_cache = {}
 
 class ProtoLoader(importlib.abc.Loader):
-  def __init__(self, suffix, code_fn, module_name, protobuf_path, proto_root):
+  def __init__(self, suffix, codegen_fn, module_name, protobuf_path, proto_root):
     self._suffix = suffix
-    self._code_fn = code_fn
+    self._codegen_fn = codegen_fn
     self._module_name = module_name
     self._protobuf_path = protobuf_path
     self._proto_root = proto_root
@@ -98,7 +100,7 @@ class ProtoLoader(importlib.abc.Loader):
     return None
 
   def _generated_file_to_module_name(self, filepath):
-    components = filepath.split("/")
+    components = filepath.split(os.path.sep)
     return ".".join(components[:-1] + [os.path.splitext(components[-1])[0]])
 
   def exec_module(self, module):
@@ -108,7 +110,12 @@ class ProtoLoader(importlib.abc.Loader):
       code = _proto_code_cache[self._module_name]
       six.exec_(code, module.__dict__)
     else:
-      files = self._code_fn(self._protobuf_path.encode('ascii'), [path.encode('ascii') for path in sys.path])
+      files = self._codegen_fn(self._protobuf_path.encode('ascii'), [path.encode('ascii') for path in sys.path])
+      # NOTE: The files are returned in topological order of dependencies. Each
+      # entry is guaranteed to depend only on the modules preceding it in the
+      # list and the last entry is guaranteed to be our requested module. We
+      # cache the code from the first invocation at module-scope so that we
+      # don't have to regenerate code that has already been generated by protoc.
       for f in files[:-1]:
         module_name = self._generated_file_to_module_name(f[0].decode('ascii'))
         if module_name not in sys.modules:
@@ -119,9 +126,9 @@ class ProtoLoader(importlib.abc.Loader):
 
 
 class ProtoFinder(importlib.abc.MetaPathFinder):
-  def __init__(self, suffix, code_fn):
+  def __init__(self, suffix, codegen_fn):
     self._suffix = suffix
-    self._code_fn = code_fn
+    self._codegen_fn = codegen_fn
 
   def find_spec(self, fullname, path, target=None):
     filepath = _module_name_to_proto_file(self._suffix, fullname)
@@ -133,9 +140,10 @@ class ProtoFinder(importlib.abc.MetaPathFinder):
         continue
       else:
         # TODO: Use a stdlib helper function to construct this.
-        return importlib.machinery.ModuleSpec(fullname, ProtoLoader(self._suffix, self._code_fn, fullname, filepath, search_path))
+        return importlib.machinery.ModuleSpec(fullname, ProtoLoader(self._suffix, self._codegen_fn, fullname, filepath, search_path))
 
-sys.meta_path.extend([ProtoFinder("_pb2", _protoc_compiler.get_protos), ProtoFinder("_pb2_grpc", _protoc_compiler.get_services)])
+sys.meta_path.extend([ProtoFinder(_PROTO_MODULE_SUFFIX, _protoc_compiler.get_protos),
+                      ProtoFinder(_SERVICE_MODULE_SUFFIX, _protoc_compiler.get_services)])
 
 if __name__ == '__main__':
     proto_include = pkg_resources.resource_filename('grpc_tools', '_proto')