Make the bash completion generation easier to customize per product, take 2.

Refactor the code to generate the bash completions file by moving the
logic to a separate script and keeping the genrule as a dumb invocation
of this script.  This allows us to more easily customize the rules
for Blaze.

--
PiperOrigin-RevId: 146362379
MOS_MIGRATED_REVID=146362379

2 files changed, 85 insertions, 7 deletions

diff --git a/scripts/BUILD b/scripts/BUILD
index decf702cfc..7c782cc760 100644
--- a/scripts/BUILD
+++ b/scripts/BUILD
@@ -8,15 +8,16 @@ genrule(
     name = "bash_completion",
     srcs = ["bazel-complete-template.bash"],
     outs = ["bazel-complete.bash"],
-    cmd = "cat $(SRCS) > $@\n" +
-          "touch err.log\n" +
-          "TMP=`mktemp -d $${TMPDIR:-/tmp}/tmp.XXXXXXXXXX`\n" +
-          "trap \"rm -fr err.log $${TMP}\" EXIT\n" +
-          "$(location //src:bazel) " +
-          "    --batch --output_user_root=$${TMP} --host_javabase=$(JAVABASE) " +
-          "    help completion 2>err.log >>$@ || { cat err.log; exit 1; }",
+    cmd = " ".join([
+        "$(location :generate_bash_completion.sh)",
+        "--bazel=$(location //src:bazel)",
+        "--javabase=$(JAVABASE)",
+        "--output=$@",
+        "--prepend=$(location bazel-complete-template.bash)",
+    ]),
     output_to_bindir = 1,
     tools = [
+        ":generate_bash_completion.sh",
         "//src:bazel",
         "//tools/defaults:jdk",
     ],
diff --git a/scripts/generate_bash_completion.sh b/scripts/generate_bash_completion.sh
new file mode 100755
index 0000000000..83851e39ff
--- /dev/null
+++ b/scripts/generate_bash_completion.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+#
+# Copyright 2017 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#
+# Generates the Bash completion script for Bazel.
+#
+# At a minimum, you must pass the --bazel and --output flags to specify the path
+# to the Bazel binary to use and the output file to generate.
+#
+# Callers can customize the completion script by passing additional files with
+# the --prepend and --append flags, which are stitched together to generate the
+# final completion script.  Prepended files can override built-in variables and
+# appended files can override built-in functions.
+#
+
+set -e
+
+die() {
+  echo "${@}" 1>&2
+  exit 1
+}
+
+get_optarg() {
+  expr "${1}" : "[^=]*=\\(.*\\)"
+}
+
+append=
+bazel=
+javabase=
+output=
+prepend=
+while [ ${#} -gt 0 ]; do
+  case "${1}" in
+    --append=*) append="${append} $(get_optarg "${1}")" ;;
+    --bazel=*) bazel="$(get_optarg "${1}")" ;;
+    --javabase=*) javabase="$(get_optarg "${1}")" ;;
+    --output=*) output="$(get_optarg "${1}")" ;;
+    --prepend=*) prepend="${prepend} $(get_optarg "${1}")" ;;
+    --*) die "Unknown option ${1}" ;;
+    *) break ;;
+  esac
+  shift
+done
+[ ${#} -eq 0 ] || die "No arguments allowed"
+[ -n "${bazel}" ] || die "--bazel required but not provided"
+[ -n "${output}" ] || die "--output required but not provided"
+
+tempdir="$(mktemp -d "${TMPDIR:-/tmp}/generate_bash_completion.XXXXXXXX")"
+trap "rm -rf '${tempdir}'" EXIT
+
+touch "${tempdir}/WORKSPACE"
+mkdir "${tempdir}/root"
+
+[ -z "${prepend}" ] || cat ${prepend} >>"${tempdir}/output"
+
+host_javabase_flag=
+[ -z "${javabase}" ] || host_javabase_flag="--host_javabase=${javabase}"
+"${bazel}" --output_user_root="${tempdir}/root" ${host_javabase_flag} \
+    help completion >>"${tempdir}/output"
+
+[ -z "${append}" ] || cat ${append} >>"${tempdir}/output"
+
+rm -f "${output}"
+mv "${tempdir}/output" "${output}"