copy_file: add rule and tests (#123)

This PR adds two new rules: copy_file and
copy_xfile.

Both rules solve a common problem: to copy one
file to another location. The problem is routinely
solved using a genrule. That however requires
Bash, since genrules execute Bash commands.
Requiring Bash is a problem on Windows.

The new rules do not require Bash on Windows (only
on other platforms).

The only difference between the rules is that
copy_xfile creates an executable file while
copy_file doesn't.

See https://github.com/bazelbuild/bazel/issues/4319

4 files changed, 189 insertions, 0 deletions

diff --git a/tests/BUILD b/tests/BUILD
index e4b67aa..13b496d 100644
--- a/tests/BUILD
+++ b/tests/BUILD
@@ -16,6 +16,11 @@ load(":versions_tests.bzl", "versions_test_suite")
 
 licenses(["notice"])
 
+exports_files(
+    ["unittest.bash"],
+    visibility = ["//tests:__subpackages__"],
+)
+
 build_test_test_suite()
 
 collections_test_suite()
diff --git a/tests/copy_file/BUILD b/tests/copy_file/BUILD
new file mode 100644
index 0000000..47d7887
--- /dev/null
+++ b/tests/copy_file/BUILD
@@ -0,0 +1,119 @@
+# This package aids testing the 'copy_file' rule.
+#
+# The package contains 4 copy_file rules:
+# - 'copy_src' and 'copy_gen' copy a source file and a generated file
+#   respectively
+# - 'copy_xsrc' and 'copy_xgen' copy a source file and a generated file
+#   respectively (both are shell scripts), and mark their output as executable
+#
+# The generated file is the output of the 'gen' genrule.
+#
+# The 'bin_src' and 'bin_gen' rules are sh_binary rules. They use the
+# 'copy_xsrc' and 'copy_xgen' rules respectively. The sh_binary rule requires
+# its source to be executable, so building these two rules successfully means
+# that 'copy_file' managed to make its output executable.
+#
+# The 'run_executables' genrule runs the 'bin_src' and 'bin_gen' binaries,
+# partly to ensure they can be run, and partly so we can observe their output
+# and assert the contents in the 'copy_file_tests' test.
+#
+# The 'file_deps' filegroup depends on 'copy_src'. The filegroup rule uses the
+# DefaultInfo.files field from its dependencies. When we data-depend on the
+# filegroup from 'copy_file_tests', we transitively data-depend on the
+# DefaultInfo.files of the 'copy_src' rule.
+#
+# The 'copy_file_tests' test is the actual integration test. It data-depends
+# on:
+# - the 'run_executables' rule, to get the outputs of 'bin_src' and 'bin_gen'
+# - the 'file_deps' rule, and by nature of using a filegroup, we get the files
+#   from the DefaultInfo.files of the 'copy_file' rule, and thereby assert that
+#   that field contains the output file of the rule
+# - the 'copy_nonempty_text' rule, and thereby on the DefaultInfo.runfiles field
+#   of it, so we assert that that field contains the output file of the rule
+
+load("//rules:copy_file.bzl", "copy_file")
+
+package(default_testonly = 1)
+
+sh_test(
+    name = "copy_file_tests",
+    srcs = ["copy_file_tests.sh"],
+    data = [
+        ":run_executables",
+        # Use DefaultInfo.files from 'copy_src' (via 'file_deps').
+        ":file_deps",
+        # Use DefaultInfo.runfiles from 'copy_gen'.
+        ":copy_gen",
+        "//tests:unittest.bash",
+    ],
+    deps = ["@bazel_tools//tools/bash/runfiles"],
+)
+
+filegroup(
+    name = "file_deps",
+    # Use DefaultInfo.files from 'copy_src'.
+    srcs = [
+        ":copy_src",
+    ],
+)
+
+# If 'run_executables' is built, then 'bin_gen' and 'bin_src' are
+# executable, asserting that copy_file makes the output executable.
+genrule(
+    name = "run_executables",
+    outs = [
+        "xsrc-out.txt",
+        "xgen-out.txt",
+    ],
+    cmd = ("$(location :bin_src) > $(location xsrc-out.txt) && " +
+           "$(location :bin_gen) > $(location xgen-out.txt)"),
+    output_to_bindir = 1,
+    tools = [
+        ":bin_gen",
+        ":bin_src",
+    ],
+)
+
+# If 'bin_src' is built, then 'copy_xsrc' made its output executable.
+sh_binary(
+    name = "bin_src",
+    srcs = [":copy_xsrc"],
+)
+
+# If 'bin_gen' is built, then 'copy_xgen' made its output executable.
+sh_binary(
+    name = "bin_gen",
+    srcs = [":copy_xgen"],
+)
+
+copy_file(
+    name = "copy_src",
+    src = "a.txt",
+    out = "out/a-out.txt",
+)
+
+copy_file(
+    name = "copy_gen",
+    src = ":gen",
+    out = "out/gen-out.txt",
+)
+
+copy_file(
+    name = "copy_xsrc",
+    src = "a.txt",
+    out = "xout/a-out.sh",
+    is_executable = True,
+)
+
+copy_file(
+    name = "copy_xgen",
+    src = ":gen",
+    out = "xout/gen-out.sh",
+    is_executable = True,
+)
+
+genrule(
+    name = "gen",
+    outs = ["b.txt"],
+    cmd = "echo -e '#!/bin/bash\necho potato' > $@",
+)
diff --git a/tests/copy_file/a.txt b/tests/copy_file/a.txt
new file mode 100644
index 0000000..acd332a
--- /dev/null
+++ b/tests/copy_file/a.txt
@@ -0,0 +1,2 @@
+#!/bin/bash
+echo aaa
diff --git a/tests/copy_file/copy_file_tests.sh b/tests/copy_file/copy_file_tests.sh
new file mode 100755
index 0000000..23f45d5
--- /dev/null
+++ b/tests/copy_file/copy_file_tests.sh
@@ -0,0 +1,63 @@
+# Copyright 2019 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# --- begin runfiles.bash initialization ---
+# Copy-pasted from Bazel's Bash runfiles library (tools/bash/runfiles/runfiles.bash).
+set -euo pipefail
+if [[ ! -d "${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 "$(rlocation bazel_skylib/tests/unittest.bash)" \
+  || { echo "Could not source bazel_skylib/tests/unittest.bash" >&2; exit 1; }
+
+function test_copy_src() {
+  cat "$(rlocation bazel_skylib/tests/copy_file/out/a-out.txt)" >"$TEST_log"
+  expect_log '^#!/bin/bash$'
+  expect_log '^echo aaa$'
+}
+
+function test_copy_gen() {
+  cat "$(rlocation bazel_skylib/tests/copy_file/out/gen-out.txt)" >"$TEST_log"
+  expect_log '^#!/bin/bash$'
+  expect_log '^echo potato$'
+}
+
+function test_copy_xsrc() {
+  cat "$(rlocation bazel_skylib/tests/copy_file/xsrc-out.txt)" >"$TEST_log"
+  expect_log '^aaa$'
+}
+
+function test_copy_xgen() {
+  cat "$(rlocation bazel_skylib/tests/copy_file/xgen-out.txt)" >"$TEST_log"
+  expect_log '^potato$'
+}
+
+run_suite "copy_file_tests test suite"