Implementation of maven_jar rule in Skylark.

**Experimental**

This is an initial implementation of the maven_jar rule in Skylark, targeted at
the FRs in issue #1410.

Implemented a wrapper around the maven binary to pull dependencies from
remote repositories into a directory under {output_base}/external.

Attributes `name`, `artifact`, `repository`, `sha1` have been implemented,
but not `server`.

Caveat: this rule assumes that the Maven dependency is installed in the
system. Hence, the maven_skylark_test integration tests are tagged with
"manual" and commented out because the Bazel CI isn't configured with
the Maven binary yet.

Added a serve_not_found helper for 404 response tests.

Usage:

```
load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")

maven_jar(
    name = "com_google_guava_guava",
    artifact = "com.google.guava:guava:18.0",
    sha1 = "cce0823396aa693798f8882e64213b1772032b09",
    repository = "http://uk.maven.org/maven2",
)
```

With regards to server, there are some limitations with retrieving a
maven_server's attribute at Loading Phase without the use of hacky macros
(issue #1704), and even if macros are used, the maven_server is not treated as
an actual dependency by maven_jar. There is a test (`test_unimplemented_server_attr`)
to ensure that the error message to shown to users if they use the server
attribute with this rule.

--
Change-Id: I167f9d13835c30be971928b4cc60167a8e396893
Reviewed-on: https://bazel-review.googlesource.com/c/5770
MOS_MIGRATED_REVID=133971809

WORKSPACE

@@ -52,3 +52,8 @@ bind(name = "xcrunwrapper", actual = "@bazel_tools//tools/objc:xcrunwrapper")
 
 bind(name = "protobuf/java_runtime", actual = "//third_party/protobuf:protobuf")
 bind(name = "protobuf/javalite_runtime", actual = "//third_party/protobuf:protobuf-lite")
+
+# For Skylark tests at //src/test/shell/bazel:maven_skylark_test
+# Uncomment the following lines, and the test in src/test/shell/bazel/BUILD to run it.
+# load("//tools/build_defs/repo:maven_rules.bzl", "maven_dependency_plugin")
+# maven_dependency_plugin()

src/test/shell/bazel/BUILD

@@ -279,6 +279,18 @@ sh_test(
     data = [":test-deps"],
 )
 
+# To run this test, ensure that the maven_dependency_plugin() in WORKSPACE is uncommented as well.
+sh_test(
+    name = "maven_skylark_test",
+    size = "medium",
+    srcs = ["maven_skylark_test.sh"],
+    data = [
+        ":test-deps",
+        "@m2//:files",
+    ],
+    tags = ["manual"],
+)
+
 sh_test(
     name = "generate_workspace_test",
     size = "large",

src/test/shell/bazel/external_integration_test.sh

@@ -349,15 +349,7 @@ EOF
 }
 
 function test_http_404() {
-  http_response=$TEST_TMPDIR/http_response
-  cat > $http_response <<EOF
-HTTP/1.0 404 Not Found
-
-Help, I'm lost!
-EOF
-  nc_port=$(pick_random_unused_tcp_port) || exit 1
-  nc_l $nc_port < $http_response &
-  nc_pid=$!
+  serve_not_found "Help, I'm lost!"
 
   cd ${WORKSPACE_DIR}
   cat > WORKSPACE <<EOF

src/test/shell/bazel/maven_skylark_test.sh

@@ -0,0 +1,194 @@
+#!/bin/bash
+#
+# 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.
+#
+# Test the Skylark implementation of the maven_jar() rule.
+
+# Load test environment
+src=$(cd "$(dirname ${BASH_SOURCE[0]})" && pwd)
+source $src/test-setup.sh \
+  || { echo "test-setup.sh not found!" >&2; exit 1; }
+source $src/remote_helpers.sh \
+  || { echo "remote_helpers.sh not found!" >&2; exit 1; }
+
+function setup_zoo() {
+  mkdir -p zoo
+  cat > zoo/BUILD <<EOF
+java_binary(
+    name = "ball-pit",
+    srcs = ["BallPit.java"],
+    main_class = "BallPit",
+    deps = ["//external:mongoose"],
+)
+EOF
+
+  cat > zoo/BallPit.java <<EOF
+import carnivore.Mongoose;
+
+public class BallPit {
+    public static void main(String args[]) {
+        Mongoose.frolic();
+    }
+}
+EOF
+}
+
+function tear_down() {
+  shutdown_server
+}
+
+function test_maven_jar_skylark() {
+  setup_zoo
+  version="1.21"
+  serve_artifact com.example.carnivore carnivore $version
+
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")
+maven_jar(
+    name = 'endangered',
+    artifact = "com.example.carnivore:carnivore:$version",
+    repository = 'http://localhost:$fileserver_port/',
+    sha1 = '$sha1',
+    local_repository = "@m2//:BUILD",
+)
+
+# Make use of the pre-downloaded maven-dependency-plugin because there's no
+# internet connection at this stage.
+local_repository(
+  name = "m2",
+  path = "$TEST_SRCDIR/m2",
+)
+
+bind(name = 'mongoose', actual = '@endangered//jar')
+EOF
+
+  bazel run //zoo:ball-pit >& $TEST_log || fail "Expected run to succeed"
+  expect_log "Tra-la!"
+}
+
+# Same as test_maven_jar, except omit sha1 implying "we don't care".
+function test_maven_jar_no_sha1_skylark() {
+  setup_zoo
+  version="1.22"
+  serve_artifact com.example.carnivore carnivore $version
+
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")
+
+maven_jar(
+    name = 'endangered',
+    artifact = "com.example.carnivore:carnivore:$version",
+    repository = 'http://localhost:$fileserver_port/',
+    local_repository = "@m2//:BUILD",
+)
+
+local_repository(
+  name = "m2",
+  path = "$TEST_SRCDIR/m2",
+)
+
+bind(name = 'mongoose', actual = '@endangered//jar')
+EOF
+
+  bazel run //zoo:ball-pit >& $TEST_log || fail "Expected run to succeed"
+  expect_log "Tra-la!"
+}
+
+function test_maven_jar_404_skylark() {
+  setup_zoo
+  version="1.23"
+  serve_not_found
+
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")
+maven_jar(
+    name = 'endangered',
+    artifact = "com.example.carnivore:carnivore:$version",
+    repository = 'http://localhost:$nc_port/',
+    local_repository = "@m2//:BUILD",
+)
+
+local_repository(
+  name = "m2",
+  path = "$TEST_SRCDIR/m2",
+)
+
+bind(name = 'mongoose', actual = '@endangered//jar')
+EOF
+
+  bazel clean --expunge
+  bazel build //zoo:ball-pit >& $TEST_log && echo "Expected build to fail"
+  kill_nc
+  expect_log "Failed to fetch Maven dependency"
+}
+
+function test_maven_jar_mismatched_sha1_skylark() {
+  setup_zoo
+  version="1.24"
+  serve_artifact com.example.carnivore carnivore 1.24
+
+  wrong_sha1="0123456789012345678901234567890123456789"
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")
+
+maven_jar(
+    name = 'endangered',
+    artifact = "com.example.carnivore:carnivore:1.24",
+    repository = 'http://localhost:$fileserver_port/',
+    sha1 = '$wrong_sha1',
+    local_repository = "@m2//:BUILD",
+)
+
+local_repository(
+  name = "m2",
+  path = "$TEST_SRCDIR/m2",
+)
+
+bind(name = 'mongoose', actual = '@endangered//jar')
+EOF
+
+  bazel fetch //zoo:ball-pit >& $TEST_log && echo "Expected fetch to fail"
+  expect_log "has SHA-1 of $sha1, does not match expected SHA-1 ($wrong_sha1)"
+}
+
+function test_unimplemented_server_attr_skylark() {
+  setup_zoo
+  version="1.25"
+  serve_jar
+
+  cat > WORKSPACE <<EOF
+load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")
+
+maven_jar(
+    name = 'endangered',
+    artifact = "com.example.carnivore:carnivore:$version",
+    server = "attr_not_implemented",
+    local_repository = "@m2//:BUILD"
+)
+
+local_repository(
+  name = "m2",
+  path = "$TEST_SRCDIR/m2",
+)
+
+bind(name = 'mongoose', actual = '@endangered//jar')
+EOF
+
+  bazel build //zoo:ball-pit >& $TEST_log && echo "Expected build to fail"
+  kill_nc
+  expect_log "specifies a 'server' attribute which is currently not supported."
+}
+
+run_suite "maven skylark tests"

src/test/shell/bazel/maven_test.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 #
-# Copyright 2015 The Bazel Authors. All rights reserved.
+# 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.
@@ -87,14 +87,8 @@ EOF
 
 function test_maven_jar_404() {
   setup_zoo
-  http_response=$TEST_TMPDIR/http_response
-  cat > $http_response <<EOF
-HTTP/1.0 404 Not Found
+  serve_not_found
 
-EOF
-  nc_port=$(pick_random_unused_tcp_port) || exit 1
-  nc_l $nc_port < $http_response &
-  nc_pid=$!
   cat > WORKSPACE <<EOF
 maven_jar(
     name = 'endangered',
@@ -112,21 +106,20 @@ EOF
 
 function test_maven_jar_mismatched_sha1() {
   setup_zoo
-  serve_jar
+  serve_artifact com.example.carnivore carnivore 1.23
 
   wrong_sha1="0123456789012345678901234567890123456789"
   cat > WORKSPACE <<EOF
 maven_jar(
     name = 'endangered',
     artifact = "com.example.carnivore:carnivore:1.23",
-    repository = 'http://localhost:$nc_port/',
+    repository = 'http://localhost:$fileserver_port/',
     sha1 = '$wrong_sha1',
 )
 bind(name = 'mongoose', actual = '@endangered//jar')
 EOF
 
   bazel fetch //zoo:ball-pit >& $TEST_log && echo "Expected fetch to fail"
-  kill_nc
   expect_log "has SHA-1 of $sha1, does not match expected SHA-1 ($wrong_sha1)"
 }
 

src/test/shell/bazel/remote_helpers.sh

@@ -94,6 +94,21 @@ EOF
   redirect_pid=$!
 }
 
+# Serves a HTTP 404 Not Found response with an optional parameter for the
+# response body.
+function serve_not_found() {
+  RESPONSE_BODY=${1:-}
+  http_response=$TEST_TMPDIR/http_response
+  cat > $http_response <<EOF
+HTTP/1.0 404 Not Found
+
+$RESPONSE_BODY
+EOF
+  nc_port=$(pick_random_unused_tcp_port) || exit 1
+  nc_l $nc_port < $http_response &
+  nc_pid=$!
+}
+
 # Waits for the SimpleHTTPServer to actually start up before the test is run.
 # Otherwise the entire test can run before the server starts listening for
 # connections, which causes flakes.