Split out Java proto compilation logic to a helper script.

This is just for clarity and should be a no-op.  Maintaining long shell
command lines embedded in genrules is not pretty.

--
MOS_MIGRATED_REVID=114967410

tools/build_rules/BUILD

@@ -1,5 +1,11 @@
 licenses(["notice"])  # Apache 2.0
 
+sh_binary(
+    name = "gensrcjar",
+    srcs = ["gensrcjar.sh"],
+    visibility = ["//visibility:public"],
+)
+
 filegroup(
     name = "srcs",
     srcs = glob(["**"]),

tools/build_rules/genproto.bzl

@@ -19,23 +19,20 @@ proto_filetype = FileType([".proto"])
 
 def gensrcjar_impl(ctx):
   out = ctx.outputs.srcjar
-  proto_output = out.path + ".proto_output"
-  proto_compiler = ctx.file._proto_compiler
-  sub_commands = [
-    "rm -rf " + proto_output,
-    "mkdir " + proto_output,
-    ' '.join([proto_compiler.path, "--java_out=" + proto_output,
-              ctx.file.src.path]),
-    "touch -t 198001010000 $(find " + proto_output + ")",
-    ctx.file._jar.path + " cMf " + out.path + " -C " + proto_output + " .",
-  ]
 
   ctx.action(
-    command=" && ".join(sub_commands),
-    inputs=[ctx.file.src, proto_compiler, ctx.file._jar] + ctx.files._jdk,
+    command=' '.join([
+        "JAR='%s'" % ctx.file._jar.path,
+        "OUTPUT='%s'" % out.path,
+        "PROTO_COMPILER='%s'" % ctx.file._proto_compiler.path,
+        "SOURCE='%s'" % ctx.file.src.path,
+        ctx.executable._gensrcjar.path,
+    ]),
+    inputs=([ctx.file.src] + ctx.files._gensrcjar + ctx.files._jar +
+            ctx.files._proto_compiler),
     outputs=[out],
     mnemonic="GenProtoSrcJar",
-    use_default_shell_env = True)
+    use_default_shell_env=True)
 
 gensrcjar = rule(
     gensrcjar_impl,
@@ -44,6 +41,11 @@ gensrcjar = rule(
             allow_files = proto_filetype,
             single_file = True,
         ),
+        "_gensrcjar": attr.label(
+            default = Label("@bazel_tools//tools/build_rules:gensrcjar"),
+            allow_files = True,
+            executable = True,
+        ),
         # TODO(bazel-team): this should be a hidden attribute with a default
         # value, but Skylark needs to support select first.
         "_proto_compiler": attr.label(
@@ -56,10 +58,6 @@ gensrcjar = rule(
             allow_files = True,
             single_file = True,
         ),
-        "_jdk": attr.label(
-            default = Label("@bazel_tools//tools/jdk:jdk"),
-            allow_files = True,
-        ),
     },
     outputs = {"srcjar": "lib%{name}.srcjar"},
 )

tools/build_rules/gensrcjar.sh

@@ -0,0 +1,64 @@
+#! /bin/sh
+# Copyright 2016 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# List of environment variables that must be defined as input.
+#
+# We use environment variables instead of positional arguments or flags for
+# clarity in the caller .bzl file and for simplicity of processing.  There is no
+# need to implement a full-blown argument parser for this simple script.
+INPUT_VARS="JAR OUTPUT PROTO_COMPILER SOURCE"
+
+# Basename of the script for error reporting purposes.
+PROGRAM_NAME="${0##*/}"
+
+# A timestamp to mark all generated files with to get deterministic JAR outputs.
+TIMESTAMP=198001010000
+
+# Prints an error and exits.
+#
+# Args:
+#   ...: list(str).  Parts of the message to print; all of them are joined
+#       with a single space in between.
+err() {
+  echo "${PROGRAM_NAME}: ${*}" 1>&2
+  exit 1
+}
+
+# Entry point.
+main() {
+  [ ${#} -eq 0 ] || err "No arguments allowed; set the following environment" \
+      "variables for configuration instead: ${INPUT_VARS}"
+  for var in ${INPUT_VARS}; do
+    local value
+    eval "value=\"\$${var}\""
+    [ -n "${value}" ] || err "Input environment variable ${var} is not set"
+  done
+
+  rm -f "${OUTPUT}"
+
+  local proto_output="${OUTPUT}.proto_output"
+  rm -rf "${proto_output}"
+  mkdir -p "${proto_output}"
+
+  "${PROTO_COMPILER}" --java_out="${proto_output}" "${SOURCE}" \
+      || err "proto_compiler failed"
+  find "${proto_output}" -exec touch -t "${TIMESTAMP}" '{}' \; \
+      || err "Failed to reset timestamps"
+  "${JAR}" cMf "${OUTPUT}.tmp" -C "${proto_output}" . \
+      || err "jar failed"
+  mv "${OUTPUT}.tmp" "${OUTPUT}"
+}
+
+main "${@}"