Use the python flatbuffers library with the correct file paths

PiperOrigin-RevId: 334662368
Change-Id: I648738fc64997b4b21afffcf125732f0d13b45de

third_party/flatbuffers/BUILD.bazel

@@ -1,4 +1,5 @@
 load("@build_bazel_rules_android//android:rules.bzl", "android_library")
+load(":build_defs.bzl", "flatbuffer_py_strip_prefix_srcs")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -102,8 +103,8 @@ cc_library(
     visibility = ["//visibility:public"],
 )
 
-filegroup(
-    name = "runtime_py_srcs",
+flatbuffer_py_strip_prefix_srcs(
+    name = "flatbuffer_py_strip_prefix",
     srcs = [
         "python/flatbuffers/__init__.py",
         "python/flatbuffers/builder.py",
@@ -114,6 +115,21 @@ filegroup(
         "python/flatbuffers/table.py",
         "python/flatbuffers/util.py",
     ],
+    strip_prefix = "python/flatbuffers/",
+)
+
+filegroup(
+    name = "runtime_py_srcs",
+    srcs = [
+        "__init__.py",
+        "builder.py",
+        "compat.py",
+        "encode.py",
+        "number_types.py",
+        "packer.py",
+        "table.py",
+        "util.py",
+    ],
 )
 
 py_library(

third_party/flatbuffers/build_defs.bzl

@@ -361,18 +361,30 @@ _gen_flatbuffer_srcs = rule(
     output_to_genfiles = True,
 )
 
+def flatbuffer_py_strip_prefix_srcs(name, srcs = [], strip_prefix = ""):
+    """Strips path prefix.
+
+    Args:
+      name: Rule name. (required)
+      srcs: Source .py files. (required)
+      strip_prefix: Path that needs to be stripped from the srcs filepaths. (required)
+    """
+    for src in srcs:
+        native.genrule(
+            name = name + "_" + src.replace(".", "_").replace("/", "_"),
+            srcs = [src],
+            outs = [src.replace(strip_prefix, "")],
+            cmd = "cp $< $@",
+        )
+
 def _concat_flatbuffer_py_srcs_impl(ctx):
-    # Merge all generated python files. The files are concatenated and the
-    # import statements are removed. Finally we import the flatbuffer runtime
-    # library.
+    # Merge all generated python files.
+    command = "find '%s' -name '*.py' -exec cat {} + | sed '/import flatbuffers/d'"
+    command += " | sed '1s/^/import flatbuffers\\'$'\\n/' > %s"
     ctx.actions.run_shell(
         inputs = ctx.attr.deps[0].files,
         outputs = [ctx.outputs.out],
-        command = (
-            "find '%s' -name '*.py' -exec cat {} + |" +
-            "sed 's/from flatbuffers.compat import import_numpy/import numpy as np' |" +
-            "sed '/np = import_numpy()/d' > %s"
-        ) % (
+        command = command % (
             ctx.attr.deps[0].files.to_list()[0].path,
             ctx.outputs.out.path,
         ),