Change proto_text generation so it will work when tensorflow is included as a

submodule.

When included as a submodule, the src paths come through as
external/tf/tensorflow/core/framework/tensor.proto instead of
tensorflow/core/framework/tensor.proto.

To work around this, introduce a known file into the SRCS list and use that to
infer the location of tensorflow.
Change: 122424014

tensorflow/tensorflow.bzl

@@ -667,7 +667,7 @@ def tf_generate_proto_text_sources(name, srcs_relative_dir, srcs):
   out_srcs = [p.replace(".proto", ".pb_text.cc") for p in srcs]
   native.genrule(
         name = name,
-        srcs = srcs,
+        srcs = srcs + ["//tensorflow/tools/proto_text:placeholder.txt"],
         outs = out_hdrs + out_srcs,
         cmd = "$(location //tensorflow/tools/proto_text:gen_proto_text_functions) " +
               "$(@D) " + srcs_relative_dir + " $(SRCS)",

tensorflow/tools/proto_text/BUILD

@@ -12,7 +12,10 @@ package(default_visibility = ["//visibility:private"])
 
 licenses(["notice"])  # Apache 2.0
 
-exports_files(["LICENSE"])
+exports_files([
+    "LICENSE",
+    "placeholder.txt",
+])
 
 load(
     "//tensorflow:tensorflow.bzl",

tensorflow/tools/proto_text/gen_proto_text_functions.cc

@@ -36,15 +36,33 @@ class CrashOnErrorCollector
                << column << " - " << message;
   }
 };
-}  // namespace
 
 static const char kTensorflowHeaderPrefix[] = "";
 
+static const char kPlaceholderFile[] =
+    "tensorflow/tools/proto_text/placeholder.txt";
+
+bool IsPlaceholderFile(const char* s) {
+  string ph(kPlaceholderFile);
+  string str(s);
+  return str.size() >= strlen(kPlaceholderFile) &&
+         ph == str.substr(str.size() - ph.size());
+}
+
+}  // namespace
+
 // Main program to take input protos and write output pb_text source files that
 // contain generated proto text input and output functions.
 //
-// Main expects the first argument to give the output path. This is followed by
-// pairs of arguments: <proto_name_relative_to_root, proto_file_path>.
+// Main expects:
+// - First argument is output path
+// - Second argument is the relative path of the protos to the root. E.g.,
+//   for protos built by a rule in tensorflow/core, this will be
+//   tensorflow/core.
+// - Then any number of source proto file names, plus one source name must be
+//   placeholder.txt from this gen tool's package.  placeholder.txt is
+//   ignored for proto resolution, but is used to determine the root at which
+//   the build tool has placed the source proto files.
 //
 // Note that this code doesn't use tensorflow's command line parsing, because of
 // circular dependencies between libraries if that were done.
@@ -59,26 +77,41 @@ int MainImpl(int argc, char** argv) {
   }
 
   const string output_root = argv[1];
-  const string relative_path = kTensorflowHeaderPrefix + string(argv[2]);
+  const string output_relative_path = kTensorflowHeaderPrefix + string(argv[2]);
+
+  string src_relative_path;
+  bool has_placeholder = false;
+  for (int i = 3; i < argc; ++i) {
+    if (IsPlaceholderFile(argv[i])) {
+      const string s(argv[i]);
+      src_relative_path = s.substr(0, s.size() - strlen(kPlaceholderFile));
+      has_placeholder = true;
+    }
+  }
+  if (!has_placeholder) {
+    LOG(ERROR) << kPlaceholderFile << " must be passed";
+    return -1;
+  }
 
   tensorflow::protobuf::compiler::DiskSourceTree source_tree;
 
-  // This requires all protos to be relative to the directory from which the
-  // genrule is invoked. If protos are generated in some other directory,
-  // then they may not be found.
-  source_tree.MapPath("", ".");
+  source_tree.MapPath("", src_relative_path.empty() ? "." : src_relative_path);
   CrashOnErrorCollector crash_on_error;
   tensorflow::protobuf::compiler::Importer importer(&source_tree,
                                                     &crash_on_error);
 
   for (int i = 3; i < argc; i++) {
-    const string proto_path = argv[i];
+    if (IsPlaceholderFile(argv[i])) continue;
+    const string proto_path = string(argv[i]).substr(src_relative_path.size());
+
     const tensorflow::protobuf::FileDescriptor* fd =
         importer.Import(proto_path);
 
     const int index = proto_path.find_last_of(".");
     string proto_path_no_suffix = proto_path.substr(0, index);
-    proto_path_no_suffix = proto_path_no_suffix.substr(relative_path.size());
+
+    proto_path_no_suffix =
+        proto_path_no_suffix.substr(output_relative_path.size());
 
     const auto code =
         tensorflow::GetProtoTextFunctionCode(*fd, kTensorflowHeaderPrefix);

tensorflow/tools/proto_text/placeholder.txt

@@ -0,0 +1 @@
+Contents are unused. See gen_proto_functions.cc for details.