Add map_to_output rule

rules/BUILD

@@ -16,6 +16,12 @@ bzl_library(
     deps = ["//rules/private:copy_file_private"],
 )
 
+bzl_library(
+    name = "map_to_output",
+    srcs = ["map_to_output.bzl"],
+    deps = ["//rules/private:map_to_output_private"],
+)
+
 bzl_library(
     name = "write_file",
     srcs = ["write_file.bzl"],

rules/map_to_output.bzl

@@ -0,0 +1,29 @@
+# Copyright 2019 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.
+
+"""A rule that copies a source file to bazel-bin at the same execroot path.
+Eg. <source_root>/foo/bar/a.txt -> <bazel-bin>/foo/bar/a.txt
+
+We cannot use genrule or copy_file rule to copy a source file to bazel-bin with
+the same execroot path, because both rules create label for the output
+artifact, which conflicts with the source file label. map_to_output rule
+achieves that by avoiding creating label for the output artifact.
+"""
+
+load(
+    "//rules/private:map_to_output_private.bzl",
+    _map_to_output = "map_to_output",
+)
+
+map_to_output = _map_to_output

rules/private/BUILD

@@ -8,6 +8,13 @@ bzl_library(
     visibility = ["//rules:__pkg__"],
 )
 
+bzl_library(
+    name = "map_to_output_private",
+    srcs = ["map_to_output_private.bzl"],
+    deps = [":copy_file_private"],
+    visibility = ["//rules:__pkg__"],
+)
+
 bzl_library(
     name = "write_file_private",
     srcs = ["write_file_private.bzl"],

rules/private/map_to_output_private.bzl

@@ -0,0 +1,61 @@
+# Copyright 2019 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.
+
+"""map_to_output() rule implementations.
+
+This rule copies a source file to bazel-bin at the same execroot path, we avoid
+label conflict with the source file by not creating label for the output
+artifact.
+"""
+
+load("//rules/private:copy_file_private.bzl", "copy_bash", "copy_cmd")
+
+def _map_to_output_impl(ctx):
+  src = ctx.file.src
+  if not src.is_source:
+    fail("A source file must be specified in map_to_output rule, %s is not a source file." % src.path)
+  dst = ctx.actions.declare_file(src.basename, sibling = src)
+  if ctx.attr.is_windows:
+    copy_cmd(ctx, src, dst)
+  else:
+    copy_bash(ctx, src, dst)
+  return DefaultInfo(files = depset([dst]), runfiles = ctx.runfiles(files = [dst]))
+
+_map_to_output = rule(
+  implementation = _map_to_output_impl,
+  attrs = {
+    "src": attr.label(mandatory = True, allow_single_file = True),
+    "is_windows": attr.bool(mandatory = True),
+  }
+)
+
+def map_to_output(name, src, **kwargs):
+  """Copies a source file to bazel-bin at the same execroot path.
+
+     Eg. <source_root>/foo/bar/a.txt -> <bazel-bin>/foo/bar/a.txt
+
+     Args:
+         name: Name of the rule.
+         src: A Label. The file to to copy.
+         **kwargs: further keyword arguments, e.g. `visibility`
+  """
+  _map_to_output(
+    name = name,
+    src = src,
+    is_windows = select({
+        "@bazel_tools//src/conditions:host_windows": True,
+        "//conditions:default": False,
+    }),
+    **kwargs
+  )

tests/map_to_output/BUILD

@@ -0,0 +1,20 @@
+load("//rules:map_to_output.bzl", "map_to_output")
+
+licenses(["notice"])
+
+package(default_testonly = 1)
+
+sh_test(
+    name = "map_to_output_tests",
+    srcs = ["map_to_output_tests.sh"],
+    data = [
+        ":a",
+        "//tests:unittest.bash",
+    ],
+    deps = ["@bazel_tools//tools/bash/runfiles"],
+)
+
+map_to_output(
+    name = "a",
+    src = "foo/bar/a.txt",
+)

tests/map_to_output/foo/bar/a.txt

@@ -0,0 +1,2 @@
+#!/bin/bash
+echo aaa

tests/map_to_output/map_to_output_tests.sh

@@ -0,0 +1,51 @@
+# Copyright 2019 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.
+
+# --- begin runfiles.bash initialization ---
+# Copy-pasted from Bazel's Bash runfiles library (tools/bash/runfiles/runfiles.bash).
+set -euo pipefail
+if [[ ! -d "${RUNFILES_DIR:-/dev/null}" && ! -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  if [[ -f "$0.runfiles_manifest" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles_manifest"
+  elif [[ -f "$0.runfiles/MANIFEST" ]]; then
+    export RUNFILES_MANIFEST_FILE="$0.runfiles/MANIFEST"
+  elif [[ -f "$0.runfiles/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+    export RUNFILES_DIR="$0.runfiles"
+  fi
+fi
+if [[ -f "${RUNFILES_DIR:-/dev/null}/bazel_tools/tools/bash/runfiles/runfiles.bash" ]]; then
+  source "${RUNFILES_DIR}/bazel_tools/tools/bash/runfiles/runfiles.bash"
+elif [[ -f "${RUNFILES_MANIFEST_FILE:-/dev/null}" ]]; then
+  source "$(grep -m1 "^bazel_tools/tools/bash/runfiles/runfiles.bash " \
+            "$RUNFILES_MANIFEST_FILE" | cut -d ' ' -f 2-)"
+else
+  echo >&2 "ERROR: cannot find @bazel_tools//tools/bash/runfiles:runfiles.bash"
+  exit 1
+fi
+# --- end runfiles.bash initialization ---
+
+source "$(rlocation bazel_skylib/tests/unittest.bash)" \
+  || { echo "Could not source bazel_skylib/tests/unittest.bash" >&2; exit 1; }
+
+function test_map_to_output() {
+  echo "$(rlocation bazel_skylib/tests/map_to_output/foo/bar/a.txt)" >"$TEST_log"
+  # Test the foo/bar/a.txt is copied to bazel-out/
+  expect_log 'bazel-out/'
+  cat "$(rlocation bazel_skylib/tests/map_to_output/foo/bar/a.txt)" >"$TEST_log"
+  # Test the content of foo/bar/a.txt is correct
+  expect_log '#!/bin/bash'
+  expect_log '^echo aaa$'
+}
+
+run_suite "map_to_output test suite"